Monday, May 31, 2010

Electrical Relays


Electrical Relays



Relays are electrically operated switches that open and close under the control of another electrical circuit. The current that flows through the coil of the relay leads to creation of a magnetic field that attracts a lever and changes the switch contacts. Relay switches have two switch positions as the coil current can be on or off.

A relay can also be considered as an electrical amplifier because it is able to control an output circuit of higher power than the input circuit.

Types of Electrical Relay
There are different types of relay available in the market depending on the end use. These are:

* Latching Relay
* Reed Relay
* Polarized Relay
* Mercury-Wetted Relay
* Machine tool Relay
* Relay Circuit
* Contactor Relay
* Solid-state contactor Relay
* Solid state Relay
* Overload protector Relay

Pole and Throw Configurations
Relay is a type of switch and thus can have the following configurations:

* SPST - Single Pole Single Throw
* SPDT - Single Pole Double Throw
* DPST - Double Pole Single Throw
* DPDT - Double Pole Double Throw
* QPDT - Quadruple Pole Double Throw

Specifications to be Considered
There are certain important specifications that must be considered while selecting an appropriate relay for a particular application. These are: Selection of an appropriate relay for a particular application requires evaluation of many different factors:

* Number and type of contacts: These can be normally open, normally closed, or changeover (double-throw).

* Rating of contacts: While small relays switch a few amperes, there are large contactors that are rated for up to 3000 amperes.

* Voltage rating of contacts: This can vary depending on the type of relay. While control relays are rated 300 VAC or 600 VAC, automotive types to 50 VDC, special high-voltage relays to about 15,000 V.

* Package/enclosure: The packing or enclosures of relay can be open, touch-safe, double-voltage for isolation between circuits, outdoor, oil-splash resistant and explosion proof.

* Mounting: This can be plug board, rail mount, panel mount, through-panel mount, enclosure for mounting on walls or equipment.

* Regulatory approvals: Relays approved from agencies assure high quality to customers.

Electrical Relays Applications
Relays are used in numerous applications including:

* Modem
* Automobiles
* Aerospace
* Telecommunications

Electrical Fuse


Electrical Fuse



A fuse is used for protecting electrical devices and components from over currents and short circuits. A electrical fuse works by interrupting the flow of current through the melting of an internal element.

General specifications
Listed below are common specifications that apply to electric fuses are:

* Fuse types: These include:
o Miniature: These fuses are available in dimensions of 5x20mm and 6.3x32mm.

o Subminiature or micro: Also known as micro fuses, these have very small dimensions (no principal dimension greater than 10 mm) and aresuitable for compact circuit board layouts.

o Midget: These refer to fuses that have 13/32" diameter.

o Automotive: These fuses are only used in automotive.

o Blade type: These fuses are typically used in low voltage, high current applications.

o PC board: These fuses are specifically used on PC boards.

o Protective: These fuses are used for protecting secondary circuits or low voltage ICs.

* Mounting: These include:
o Solderable or surface mount
o Solderable with leads
o Replaceable with holder or clips

o Performance Ratings
There are certain performance criteria that one must consider while selecting fuses. These are:
+ Voltage rating: It is the maximum voltage, up to which a safe fault current interruption will occur.

+ Current rating: It is the maximum continuous operating current of the circuit.

+ Rated breaking capacity: It is the short circuit current at which the fuse can blow without being destructed.

+ Interrupt rating: These can be high interrupt, medium interrupt, or low interrupt.

o Performance Characteristics
There are certain performance characteristics that one must consider while selecting fuses. These are:
+ Fast acting: These fuses are used in circuits that have inrush currents or where the over current must be quickly interrupted.

+ Time lag: These fuses are used in circuits where high starting inrush currents occur and decay gradually.
Operating temperature of fuse is another environmental parameter that must be considered.

* Material of construction: These include:
o Ceramic
o Sand

Circuit Breakers


Circuit Breakers



The circuit breaker is a popular and most important electrical device to ensure safety in the modern world. The circuit breaker is used to cut the power supply when an electrical wire has too much current flowing through it. Without these simple devices, household electricity would not be possible because of the chances for fire and short circuit resulting from simple wiring problems and equipment failures.

The device serves in the course of normal system operation to energize or de-energize loads. In case of conditions where excessive current develops, a circuit breaker opens for protecting equipment and surroundings from possible damage due to excess flow of current.

This automatically-operated electrical switch, unlike a fuse, can be reset (either manually or automatically) for resuming normal operation. These devices are made in varying sizes, right from small devices for protecting an individual household appliance up to large switchgear designed for protecting high voltage circuits feeding an entire city.

Circuit breakerCircuit breaker

Types of Circuit Breakers
There are different technologies being used for manufacturing different circuit breakers and it is difficult to categorize them into distinct categories. Different circuit breakers are used in domestic, commercial and light industrial applications at low voltage (less than 1000 V). These include:

* MCB (Miniature Circuit Breaker): The rated current of the device is not more than 100 A. These have thermal or thermal-magnetic operation... more

* MCCB (Moulded Case Circuit Breaker): The rated current of the device is up to 1000 A. These have thermal or thermal-magnetic operation.

Circuit Breaker Variants

* Magnetic Circuit Breakers: These are a type of circuit breakers that make use of a magnetic actuator to trip the circuit. These circuit breakers allow the current to flow through the electrical device and then pass through an electromagnetic actuator. When the current flow reaches a preset or pre-determined level, the magnetic field in the electromagnet is strong enough to trip the breaker and allow the contacts to open. A magnetic breaker needs to be manually set.

* Hydraulic Circuit Breakers: These are a popular type of circuit breakers designed for those applications requiring higher amperage and voltage handling capability.

* Thermal Circuit Breakers: A simple thermal circuit breaker allows the current to flow from a battery terminal, through the bi-metal strip and then to the other terminal. The bi-metal strip is made of two different types of metals, having different coefficients of expansion. This results in one metal expanding more than the other, in case of same rise of temperature. In this circuit breaker, when one metallic strips expands more than the other, and thus disconnects the contacts.
*


* Auto Reset Circuit Breakers: These circuit breakers re set automatically in case of a faulty load or circuit. These circuit breakers are widely used in case of leakage, short - circuit, surge or overload etc. Auto reset circuit breakers do not require manual assistance for re setting and cut off power supply in case of power trip. This power is than again restored after auto resetting.

High Voltage Circuit Breakers
There are electric power systems requiring the breaking of higher currents at higher voltages. It is such systems that high-voltage AC circuit breakers are used.

* Vacuum Circuit Breaker: The rated current of the device is up to 3000 A. These specialty circuit breakers interrupt the current by creating and extinguishing the arc in a vacuum container. These devices can only be practically used for voltages up to about 35,000 V, which corresponds to the medium-voltage range of power systems. These circuit breakers have longer life expectancies between overhaul than do air circuit breakers.
*


* Air Circuit Breaker: The rated current of the device is up to 10,000 A. Some of them are electronically controlled, while others are microprocessor controlled. These circuit breakers are used for main power distribution in large industrial plants.

Switchgears


Switchgears



Switchgear are a type of electrical distribution devices used for converting incoming electrical power into several smaller circuits. They are also used for providing overload protection in the form of fuses or circuit breakers. The term is also used for both de-energizing equipment to allow work to be done and for clearing faults downstream. Switchgear vary in different parameters including number of panels, mounting style, and electrical specifications.

Switchgear

Switchgear Types
Switchgear can be of different types including:

* A simple open air circuit breaker
* Gas insulated switchgear (GIS)
* Oil insulated switchgear
* Vacuum circuit breakers

Switchgear Locations
These electrical distribution devices can be anywhere that isolation and protection may be required. These include generators, transformers, substations, motors, and high or medium voltage distribution networks. Different types of switchgear are often used by the power utility as protection against line to ground, phase to phase, or line to neutral faults. They are also used for heavy industry purposes.

Fuse and Circuit Breakers
A fuse contains a metallic element, which melts if the current exceeds a specific amperage. Circuit breaker is a mechanical switching device, which breaks currents under specific, abnormal circuit conditions.

Switchgears Applications
Switchgears are used in diverse applications and industries. Some of them are: For example, some devices are used to

* Power lighting systems
* UPS
* Inverter applications

Other Types

* Circuit Breakers
* Electrical Fuse
* Electrical Relays
* Electrical Switches

3M™ Scotchlok™ Hand Crimping Tool E-9R


3M™ Scotchlok™ Hand Crimping Tool E-9R


The 3M™ Crimping Tool E-9R is the latest innovation in industry-leading 3M™ Scotchlok™ cable connection technology for telecom applications.

Enameled Wires



Enameled Wires


Enameled wire is a thin wire insulated with the help of coating. The core material used in it is copper and it is covered with a thin layer of enamel. It is primarily used in electric motor coils. It produces magnetic flux when electricity passes through it. Though enameled wire is insulated but there is no need of stripping off the insulation as for other insulated wires. These wires can be soldered as well.



Enameled Wires

Uses of Enameled wires

* Enameled wire is used in motor coils.
* Enameled wire is used in the construction of electromagnets.
* Enameled wire is also used in construction of transformers and inductors.

Properties of Enameled Wires

* Enameled wires have excellent resistance to heat. That's why they are used in making electric coils. They are also resistant to heat shock.
* They are also resistant to wearing and tearing.
* They offer especially magnificent resistance to refrigerant materials.
* They are smooth, hard, and durable.
* They are chemically resistant, and cannot burn.

Application of Enameled Wires

* Enameled wires are appropriate to be used in compressor motors of freezer, refrigerator and air conditioner.
* They are also best suited to be used in the motors which operate at high temperature, high speed. They are also suitable for those motors which require repeated starting.
* They are applied in hermetical motors and coils of electrical devices.
* They are suitable for those applications where high speed automatic winding is needed.


Types of Enameled Wires
On the basis of materials used in making the core of the wire the enameled wire can be divided into two types. Mainly aluminum and copper is used as the major material for these wires. Sometimes copper-clad aluminum wire is also used.

* Enameled Aluminum Wires: In this category of enameled wires the core material used in the conductor is aluminum. They have very good electric conductivity and are low weight. These wires have high hot impact performance. The enameled aluminum wires are ideal for electric machinery with short and periodic workloads.

* Enameled Copper Wires: The material used in making conductor in this type of wire is copper. These enameled wires have high thermal resistance and are thermally stable. They are resistance to freon. They are resistant to high overload and can bear high heat shock. They are used for smoke and heat exhaust motors and inverter-driven motors.

Classification of Enameled Wires
Enameled wires are classified on three basis. They are classified by

* Diameter
* Temperature
* Isolation

3M / Dymo Industrial Form Strategic Alliance


3M / Dymo Industrial Form Strategic Alliance



The 3M Electrical Markets Division and DYMO Industrial, the industrial division of DYMO, a Newell Rubbermaid company (NYSE: NWL), have announced the formation of a strategic alliance. Beginning June 1, 2010, 3M will offer a line of portable industrial strength labelers through its distribution channels serving electrical markets in North America and key countries in Latin America and Europe. The products will be co-branded under the 3M and DYMO names.

Electrical engineering



Electrical engineering



Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical power supply. It now covers a range of subtopics including power, electronics, control systems, signal processing and telecommunications.

Electrical engineering may or may not include electronic engineering. Where a distinction is made, usually outside of the United States, electrical engineering is considered to deal with the problems associated with large-scale electrical systems such as power transmission and motor control, whereas electronic engineering deals with the study of small-scale electronic systems including computers and integrated circuits.[1] Alternatively, electrical engineers are usually concerned with using electricity to transmit energy, while electronic engineers are concerned with using electricity to transmit information. More recently, the distinction has become blurred by the growth of power electronics.
Contents
[hide]

* 1 History
o 1.1 Modern developments
* 2 Education
* 3 Practicing engineers
* 4 Tools and work
* 5 Sub-disciplines
o 5.1 Power
o 5.2 Control
o 5.3 Electronics
o 5.4 Microelectronics
o 5.5 Signal processing
o 5.6 Telecommunications
o 5.7 Instrumentation
o 5.8 Computers
* 6 Related disciplines
* 7 See also
* 8 Note
* 9 References
* 10 External links

History
Main article: History of electrical engineering
The discoveries of Michael Faraday formed the foundation of electric motor technology

Electricity has been a subject of scientific interest since at least the early 17th century. The first electrical engineer was probably William Gilbert who designed the versorium: a device that detected the presence of statically charged objects. He was also the first to draw a clear distinction between magnetism and static electricity and is credited with establishing the term electricity.[2] In 1775 Alessandro Volta's scientific experimentations devised the electrophorus, a device that produced a static electric charge, and by 1800 Volta developed the voltaic pile, a forerunner of the electric battery.[3]

However, it was not until the 19th century that research into the subject started to intensify. Notable developments in this century include the work of Georg Ohm, who in 1827 quantified the relationship between the electric current and potential difference in a conductor, Michael Faraday, the discoverer of electromagnetic induction in 1831, and James Clerk Maxwell, who in 1873 published a unified theory of electricity and magnetism in his treatise Electricity and Magnetism.[4]
Thomas Edison built the world's first large-scale electrical supply network

During these years, the study of electricity was largely considered to be a subfield of physics. It was not until the late 19th century that universities started to offer degrees in electrical engineering. The Darmstadt University of Technology founded the first chair and the first faculty of electrical engineering worldwide in 1882. In the same year, under Professor Charles Cross, the Massachusetts Institute of Technology began offering the first option of Electrical Engineering within a physics department.[5] In 1883 Darmstadt University of Technology and Cornell University introduced the world's first courses of study in electrical engineering, and in 1885 the University College London founded the first chair of electrical engineering in the United Kingdom.[6] The University of Missouri subsequently established the first department of electrical engineering in the United States in 1886.[7]
Nikola Tesla made long-distance electrical transmission networks possible.

During this period, the work concerning electrical engineering increased dramatically. In 1882, Edison switched on the world's first large-scale electrical supply network that provided 110 volts direct current to fifty-nine customers in lower Manhattan. In 1884 Sir Charles Parsons invented the steam turbine which today generates about 80 percent of the electric power in the world using a variety of heat sources. In 1887, Nikola Tesla filed a number of patents related to a competing form of power distribution known as alternating current. In the following years a bitter rivalry between Tesla and Edison, known as the "War of Currents", took place over the preferred method of distribution. AC eventually replaced DC for generation and power distribution, enormously extending the range and improving the safety and efficiency of power distribution.

The efforts of the two did much to further electrical engineering—Tesla's work on induction motors and polyphase systems influenced the field for years to come, while Edison's work on telegraphy and his development of the stock ticker proved lucrative for his company, which ultimately became General Electric. However, by the end of the 19th century, other key figures in the progress of electrical engineering were beginning to emerge.[8]
Modern developments

During the development of radio, many scientists and inventors contributed to radio technology and electronics. In his classic UHF experiments of 1888, Heinrich Hertz transmitted (via a spark-gap transmitter) and detected radio waves using electrical equipment. In 1895, Nikola Tesla was able to detect signals from the transmissions of his New York lab at West Point (a distance of 80.4 km / 49.95 miles).[9] In 1897, Karl Ferdinand Braun introduced the cathode ray tube as part of an oscilloscope, a crucial enabling technology for electronic television.[10] John Fleming invented the first radio tube, the diode, in 1904. Two years later, Robert von Lieben and Lee De Forest independently developed the amplifier tube, called the triode.[11] In 1895, Guglielmo Marconi furthered the art of hertzian wireless methods. Early on, he sent wireless signals over a distance of one and a half miles. In December 1901, he sent wireless waves that were not affected by the curvature of the Earth. Marconi later transmitted the wireless signals across the Atlantic between Poldhu, Cornwall, and St. John's, Newfoundland, a distance of 2,100 miles (3,400 km).[12] In 1920 Albert Hull developed the magnetron which would eventually lead to the development of the microwave oven in 1946 by Percy Spencer.[13][14] In 1934 the British military began to make strides toward radar (which also uses the magnetron) under the direction of Dr Wimperis, culminating in the operation of the first radar station at Bawdsey in August 1936.[15]

In 1941 Konrad Zuse presented the Z3, the world's first fully functional and programmable computer.[16] In 1946 the ENIAC (Electronic Numerical Integrator and Computer) of John Presper Eckert and John Mauchly followed, beginning the computing era. The arithmetic performance of these machines allowed engineers to develop completely new technologies and achieve new objectives, including the Apollo missions and the NASA moon landing.[17]

The invention of the transistor in 1947 by William B. Shockley, John Bardeen and Walter Brattain opened the door for more compact devices and led to the development of the integrated circuit in 1958 by Jack Kilby and independently in 1959 by Robert Noyce.[18] Starting in 1968, Ted Hoff and a team at Intel invented the first commercial microprocessor, which presaged the personal computer. The Intel 4004 was a 4-bit processor released in 1971, but in 1973 the Intel 8080, an 8-bit processor, made the first personal computer, the Altair 8800, possible.[19]
Education
Main article: Education and training of electrical and electronics engineers

Electrical engineers typically possess an academic degree with a major in electrical engineering. The length of study for such a degree is usually four or five years and the completed degree may be designated as a Bachelor of Engineering, Bachelor of Science, Bachelor of Technology or Bachelor of Applied Science depending upon the university. The degree generally includes units covering physics, mathematics, computer science, project management and specific topics in electrical engineering. Initially such topics cover most, if not all, of the sub-disciplines of electrical engineering. Students then choose to specialize in one or more sub-disciplines towards the end of the degree.

Some electrical engineers also choose to pursue a postgraduate degree such as a Master of Engineering/Master of Science (MEng/MSc), a Master of Engineering Management, a Doctor of Philosophy (PhD) in Engineering, an Engineering Doctorate (EngD), or an Engineer's degree. The Master and Engineer's degree may consist of either research, coursework or a mixture of the two. The Doctor of Philosophy and Engineering Doctorate degrees consist of a significant research component and are often viewed as the entry point to academia. In the United Kingdom and various other European countries, the Master of Engineering is often considered an undergraduate degree of slightly longer duration than the Bachelor of Engineering.[20]
Practicing engineers

In most countries, a Bachelor's degree in engineering represents the first step towards professional certification and the degree program itself is certified by a professional body. After completing a certified degree program the engineer must satisfy a range of requirements (including work experience requirements) before being certified. Once certified the engineer is designated the title of Professional Engineer (in the United States, Canada and South Africa ), Chartered Engineer (in India, the United Kingdom, Ireland and Zimbabwe), Chartered Professional Engineer (in Australia and New Zealand) or European Engineer (in much of the European Union).

The advantages of certification vary depending upon location. For example, in the United States and Canada "only a licensed engineer may seal engineering work for public and private clients".[21] This requirement is enforced by state and provincial legislation such as Quebec's Engineers Act.[22] In other countries, no such legislation exists. Practically all certifying bodies maintain a code of ethics that they expect all members to abide by or risk expulsion.[23] In this way these organizations play an important role in maintaining ethical standards for the profession. Even in jurisdictions where certification has little or no legal bearing on work, engineers are subject to contract law. In cases where an engineer's work fails he or she may be subject to the tort of negligence and, in extreme cases, the charge of criminal negligence. An engineer's work must also comply with numerous other rules and regulations such as building codes and legislation pertaining to environmental law.

Professional bodies of note for electrical engineers include the Institute of Electrical and Electronics Engineers (IEEE) and the Institution of Engineering and Technology (IET). The IEEE claims to produce 30% of the world's literature in electrical engineering, has over 360,000 members worldwide and holds over 3,000 conferences annually.[24] The IET publishes 21 journals, has a worldwide membership of over 150,000, and claims to be the largest professional engineering society in Europe.[25][26] Obsolescence of technical skills is a serious concern for electrical engineers. Membership and participation in technical societies, regular reviews of periodicals in the field and a habit of continued learning are therefore essential to maintaining proficiency.[27]

In Australia, Canada and the United States electrical engineers make up around 0.25% of the labor force (see note). Outside of Europe and North America, engineering graduates per-capita, and hence probably electrical engineering graduates also, are most numerous in Taiwan, Japan, and South Korea.[28]
Tools and work

From the Global Positioning System to electric power generation, electrical engineers have contributed to the development of a wide range of technologies. They design, develop, test and supervise the deployment of electrical systems and electronic devices. For example, they may work on the design of telecommunication systems, the operation of electric power stations, the lighting and wiring of buildings, the design of household appliances or the electrical control of industrial machinery.[29]
Satellite communications is one of many projects an electrical engineer might work on

Fundamental to the discipline are the sciences of physics and mathematics as these help to obtain both a qualitative and quantitative description of how such systems will work. Today most engineering work involves the use of computers and it is commonplace to use computer-aided design programs when designing electrical systems. Nevertheless, the ability to sketch ideas is still invaluable for quickly communicating with others.

Although most electrical engineers will understand basic circuit theory (that is the interactions of elements such as resistors, capacitors, diodes, transistors and inductors in a circuit), the theories employed by engineers generally depend upon the work they do. For example, quantum mechanics and solid state physics might be relevant to an engineer working on VLSI (the design of integrated circuits), but are largely irrelevant to engineers working with macroscopic electrical systems. Even circuit theory may not be relevant to a person designing telecommunication systems that use off-the-shelf components. Perhaps the most important technical skills for electrical engineers are reflected in university programs, which emphasize strong numerical skills, computer literacy and the ability to understand the technical language and concepts that relate to electrical engineering.

For many engineers, technical work accounts for only a fraction of the work they do. A lot of time may also be spent on tasks such as discussing proposals with clients, preparing budgets and determining project schedules.[30] Many senior engineers manage a team of technicians or other engineers and for this reason project management skills are important. Most engineering projects involve some form of documentation and strong written communication skills are therefore very important.

The workplaces of electrical engineers are just as varied as the types of work they do. Electrical engineers may be found in the pristine lab environment of a fabrication plant, the offices of a consulting firm or on site at a mine. During their working life, electrical engineers may find themselves supervising a wide range of individuals including scientists, electricians, computer programmers and other engineers.
Sub-disciplines

Electrical engineering has many sub-disciplines, the most popular of which are listed below. Although there are electrical engineers who focus exclusively on one of these sub-disciplines, many deal with a combination of them. Sometimes certain fields, such as electronic engineering and computer engineering, are considered separate disciplines in their own right.
Power
Main article: Power engineering
Power pole

Power engineering deals with the generation, transmission and distribution of electricity as well as the design of a range of related devices. These include transformers, electric generators, electric motors, high voltage engineering and power electronics. In many regions of the world, governments maintain an electrical network called a power grid that connects a variety of generators together with users of their energy. Users purchase electrical energy from the grid, avoiding the costly exercise of having to generate their own. Power engineers may work on the design and maintenance of the power grid as well as the power systems that connect to it. Such systems are called on-grid power systems and may supply the grid with additional power, draw power from the grid or do both. Power engineers may also work on systems that do not connect to the grid, called off-grid power systems, which in some cases are preferable to on-grid systems. The future includes Satellite controlled power systems, with feedback in real time to prevent power surges and prevent blackouts.
Control
Main article: Control engineering
Control systems play a critical role in space flight

Control engineering focuses on the modeling of a diverse range of dynamic systems and the design of controllers that will cause these systems to behave in the desired manner. To implement such controllers electrical engineers may use electrical circuits, digital signal processors, microcontrollers and PLCs (Programmable Logic Controllers). Control engineering has a wide range of applications from the flight and propulsion systems of commercial airliners to the cruise control present in many modern automobiles. It also plays an important role in industrial automation.

Control engineers often utilize feedback when designing control systems. For example, in an automobile with cruise control the vehicle's speed is continuously monitored and fed back to the system which adjusts the motor's power output accordingly. Where there is regular feedback, control theory can be used to determine how the system responds to such feedback.
Electronics
Main article: Electronic engineering
Circuit board

Electronic engineering involves the design and testing of electronic circuits that use the properties of components such as resistors, capacitors, inductors, diodes and transistors to achieve a particular functionality. The tuned circuit, which allows the user of a radio to filter out all but a single station, is just one example of such a circuit. Another example (of a pneumatic signal conditioner) is shown in the adjacent photograph.

Prior to the second world war, the subject was commonly known as radio engineering and basically was restricted to aspects of communications and radar, commercial radio and early television. Later, in post war years, as consumer devices began to be developed, the field grew to include modern television, audio systems, computers and microprocessors. In the mid to late 1950s, the term radio engineering gradually gave way to the name electronic engineering.

Before the invention of the integrated circuit in 1959, electronic circuits were constructed from discrete components that could be manipulated by humans. These discrete circuits consumed much space and power and were limited in speed, although they are still common in some applications. By contrast, integrated circuits packed a large number—often millions—of tiny electrical components, mainly transistors, into a small chip around the size of a coin. This allowed for the powerful computers and other electronic devices we see today.
Microelectronics
Main article: Microelectronics
Microprocessor

Microelectronics engineering deals with the design and microfabrication of very small electronic circuit components for use in an integrated circuit or sometimes for use on their own as a general electronic component. The most common microelectronic components are semiconductor transistors, although all main electronic components (resistors, capacitors, inductors) can be created at a microscopic level. Nanoelectronics is the further scaling of devices down to nanometer levels.

Microelectronic components are created by chemically fabricating wafers of semiconductors such as silicon (at higher frequencies, compound semiconductors like gallium arsenide and indium phosphide) to obtain the desired transport of electronic charge and control of current. The field of microelectronics involves a significant amount of chemistry and material science and requires the electronic engineer working in the field to have a very good working knowledge of the effects of quantum mechanics.
Signal processing
Main article: Signal processing
A Bayer filter on a CCD requires signal processing to get a red, green, and blue value at each pixel

Signal processing deals with the analysis and manipulation of signals. Signals can be either analog, in which case the signal varies continuously according to the information, or digital, in which case the signal varies according to a series of discrete values representing the information. For analog signals, signal processing may involve the amplification and filtering of audio signals for audio equipment or the modulation and demodulation of signals for telecommunications. For digital signals, signal processing may involve the compression, error detection and error correction of digitally sampled signals.

Signal Processing is a very mathematically oriented and intensive area forming the core of digital signal processing and it is rapidly expanding with new applications in every field of electrical engineering such as communications, control, radar, TV/Audio/Video engineering, power electronics and bio-medical engineering as many already existing analog systems are replaced with their digital counterparts.

Although in the classical era, analog signal processing only provided a mathematical description of a system to be designed, which is actually implemented by the analog hardware engineers, Digital Signal Processing both provides a mathematical description of the systems to be designed and also actually implements them (either by software programming or by hardware embedding) without much dependency on hardware issues, which exponentiates the importance and success of DSP engineering.

The deep and strong relations between signals and the information they carry makes signal processing equivalent of information processing. Which is the reason why the field finds so many diversified applications. DSP processor ICs are found in every type of modern electronic systems and products including, SDTV | HDTV sets, radios and mobile communication devices, Hi-Fi audio equipments, Dolby noise reduction algorithms, GSM mobile phones, mp3 multimedia players, camcorders and digital cameras, automobile control systems, noise cancelling headphones, digital spectrum analyzers, intelligent missile guidance, radar, GPS based cruise control systems and all kinds of image processing, video processing, audio processing and speech processing systems.
Telecommunications
Main article: Telecommunications engineering
Milstar

Telecommunications engineering focuses on the transmission of information across a channel such as a coax cable, optical fiber or free space. Transmissions across free space require information to be encoded in a carrier wave in order to shift the information to a carrier frequency suitable for transmission, this is known as modulation. Popular analog modulation techniques include amplitude modulation and frequency modulation. The choice of modulation affects the cost and performance of a system and these two factors must be balanced carefully by the engineer.

Once the transmission characteristics of a system are determined, telecommunication engineers design the transmitters and receivers needed for such systems. These two are sometimes combined to form a two-way communication device known as a transceiver. A key consideration in the design of transmitters is their power consumption as this is closely related to their signal strength. If the signal strength of a transmitter is insufficient the signal's information will be corrupted by noise.
Instrumentation
Main article: Instrumentation engineering
Radar gun

Instrumentation engineering deals with the design of devices to measure physical quantities such as pressure, flow and temperature. The design of such instrumentation requires a good understanding of physics that often extends beyond electromagnetic theory. For example, radar guns use the Doppler effect to measure the speed of oncoming vehicles. Similarly, thermocouples use the Peltier-Seebeck effect to measure the temperature difference between two points.

Often instrumentation is not used by itself, but instead as the sensors of larger electrical systems. For example, a thermocouple might be used to help ensure a furnace's temperature remains constant. For this reason, instrumentation engineering is often viewed as the counterpart of control engineering.
Computers
Main article: Computer engineering
Personal digital assistant

Computer engineering deals with the design of computers and computer systems. This may involve the design of new hardware, the design of PDAs or the use of computers to control an industrial plant. Computer engineers may also work on a system's software. However, the design of complex software systems is often the domain of software engineering, which is usually considered a separate discipline. Desktop computers represent a tiny fraction of the devices a computer engineer might work on, as computer-like architectures are now found in a range of devices including video game consoles and DVD players.
Related disciplines

Mechatronics is an engineering discipline which deals with the convergence of electrical and mechanical systems. Such combined systems are known as electromechanical systems and have widespread adoption. Examples include automated manufacturing systems, heating, ventilation and air-conditioning systems and various subsystems of aircraft and automobiles.

The term mechatronics is typically used to refer to macroscopic systems but futurists have predicted the emergence of very small electromechanical devices. Already such small devices, known as Microelectromechanical systems (MEMS), are used in automobiles to tell airbags when to deploy, in digital projectors to create sharper images and in inkjet printers to create nozzles for high definition printing. In the future it is hoped the devices will help build tiny implantable medical devices and improve optical communication.[31]

Biomedical engineering is another related discipline, concerned with the design of medical equipment. This includes fixed equipment such as ventilators, MRI scanners and electrocardiograph monitors as well as mobile equipment such as cochlear implants, artificial pacemakers and artificial hearts.

Electrical engineering


Electrical engineering



Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical power supply. It now covers a range of subtopics including power, electronics, control systems, signal processing and telecommunications.

Electrical engineering may or may not include electronic engineering. Where a distinction is made, usually outside of the United States, electrical engineering is considered to deal with the problems associated with large-scale electrical systems such as power transmission and motor control, whereas electronic engineering deals with the study of small-scale electronic systems including computers and integrated circuits.[1] Alternatively, electrical engineers are usually concerned with using electricity to transmit energy, while electronic engineers are concerned with using electricity to transmit information. More recently, the distinction has become blurred by the growth of power electronics.
Contents
[hide]

* 1 History
o 1.1 Modern developments
* 2 Education
* 3 Practicing engineers
* 4 Tools and work
* 5 Sub-disciplines
o 5.1 Power
o 5.2 Control
o 5.3 Electronics
o 5.4 Microelectronics
o 5.5 Signal processing
o 5.6 Telecommunications
o 5.7 Instrumentation
o 5.8 Computers
* 6 Related disciplines
* 7 See also
* 8 Note
* 9 References
* 10 External links

History
Main article: History of electrical engineering
The discoveries of Michael Faraday formed the foundation of electric motor technology

Electricity has been a subject of scientific interest since at least the early 17th century. The first electrical engineer was probably William Gilbert who designed the versorium: a device that detected the presence of statically charged objects. He was also the first to draw a clear distinction between magnetism and static electricity and is credited with establishing the term electricity.[2] In 1775 Alessandro Volta's scientific experimentations devised the electrophorus, a device that produced a static electric charge, and by 1800 Volta developed the voltaic pile, a forerunner of the electric battery.[3]

However, it was not until the 19th century that research into the subject started to intensify. Notable developments in this century include the work of Georg Ohm, who in 1827 quantified the relationship between the electric current and potential difference in a conductor, Michael Faraday, the discoverer of electromagnetic induction in 1831, and James Clerk Maxwell, who in 1873 published a unified theory of electricity and magnetism in his treatise Electricity and Magnetism.[4]
Thomas Edison built the world's first large-scale electrical supply network

During these years, the study of electricity was largely considered to be a subfield of physics. It was not until the late 19th century that universities started to offer degrees in electrical engineering. The Darmstadt University of Technology founded the first chair and the first faculty of electrical engineering worldwide in 1882. In the same year, under Professor Charles Cross, the Massachusetts Institute of Technology began offering the first option of Electrical Engineering within a physics department.[5] In 1883 Darmstadt University of Technology and Cornell University introduced the world's first courses of study in electrical engineering, and in 1885 the University College London founded the first chair of electrical engineering in the United Kingdom.[6] The University of Missouri subsequently established the first department of electrical engineering in the United States in 1886.[7]
Nikola Tesla made long-distance electrical transmission networks possible.

During this period, the work concerning electrical engineering increased dramatically. In 1882, Edison switched on the world's first large-scale electrical supply network that provided 110 volts direct current to fifty-nine customers in lower Manhattan. In 1884 Sir Charles Parsons invented the steam turbine which today generates about 80 percent of the electric power in the world using a variety of heat sources. In 1887, Nikola Tesla filed a number of patents related to a competing form of power distribution known as alternating current. In the following years a bitter rivalry between Tesla and Edison, known as the "War of Currents", took place over the preferred method of distribution. AC eventually replaced DC for generation and power distribution, enormously extending the range and improving the safety and efficiency of power distribution.

The efforts of the two did much to further electrical engineering—Tesla's work on induction motors and polyphase systems influenced the field for years to come, while Edison's work on telegraphy and his development of the stock ticker proved lucrative for his company, which ultimately became General Electric. However, by the end of the 19th century, other key figures in the progress of electrical engineering were beginning to emerge.[8]
Modern developments

During the development of radio, many scientists and inventors contributed to radio technology and electronics. In his classic UHF experiments of 1888, Heinrich Hertz transmitted (via a spark-gap transmitter) and detected radio waves using electrical equipment. In 1895, Nikola Tesla was able to detect signals from the transmissions of his New York lab at West Point (a distance of 80.4 km / 49.95 miles).[9] In 1897, Karl Ferdinand Braun introduced the cathode ray tube as part of an oscilloscope, a crucial enabling technology for electronic television.[10] John Fleming invented the first radio tube, the diode, in 1904. Two years later, Robert von Lieben and Lee De Forest independently developed the amplifier tube, called the triode.[11] In 1895, Guglielmo Marconi furthered the art of hertzian wireless methods. Early on, he sent wireless signals over a distance of one and a half miles. In December 1901, he sent wireless waves that were not affected by the curvature of the Earth. Marconi later transmitted the wireless signals across the Atlantic between Poldhu, Cornwall, and St. John's, Newfoundland, a distance of 2,100 miles (3,400 km).[12] In 1920 Albert Hull developed the magnetron which would eventually lead to the development of the microwave oven in 1946 by Percy Spencer.[13][14] In 1934 the British military began to make strides toward radar (which also uses the magnetron) under the direction of Dr Wimperis, culminating in the operation of the first radar station at Bawdsey in August 1936.[15]

In 1941 Konrad Zuse presented the Z3, the world's first fully functional and programmable computer.[16] In 1946 the ENIAC (Electronic Numerical Integrator and Computer) of John Presper Eckert and John Mauchly followed, beginning the computing era. The arithmetic performance of these machines allowed engineers to develop completely new technologies and achieve new objectives, including the Apollo missions and the NASA moon landing.[17]

The invention of the transistor in 1947 by William B. Shockley, John Bardeen and Walter Brattain opened the door for more compact devices and led to the development of the integrated circuit in 1958 by Jack Kilby and independently in 1959 by Robert Noyce.[18] Starting in 1968, Ted Hoff and a team at Intel invented the first commercial microprocessor, which presaged the personal computer. The Intel 4004 was a 4-bit processor released in 1971, but in 1973 the Intel 8080, an 8-bit processor, made the first personal computer, the Altair 8800, possible.[19]
Education
Main article: Education and training of electrical and electronics engineers

Electrical engineers typically possess an academic degree with a major in electrical engineering. The length of study for such a degree is usually four or five years and the completed degree may be designated as a Bachelor of Engineering, Bachelor of Science, Bachelor of Technology or Bachelor of Applied Science depending upon the university. The degree generally includes units covering physics, mathematics, computer science, project management and specific topics in electrical engineering. Initially such topics cover most, if not all, of the sub-disciplines of electrical engineering. Students then choose to specialize in one or more sub-disciplines towards the end of the degree.

Some electrical engineers also choose to pursue a postgraduate degree such as a Master of Engineering/Master of Science (MEng/MSc), a Master of Engineering Management, a Doctor of Philosophy (PhD) in Engineering, an Engineering Doctorate (EngD), or an Engineer's degree. The Master and Engineer's degree may consist of either research, coursework or a mixture of the two. The Doctor of Philosophy and Engineering Doctorate degrees consist of a significant research component and are often viewed as the entry point to academia. In the United Kingdom and various other European countries, the Master of Engineering is often considered an undergraduate degree of slightly longer duration than the Bachelor of Engineering.[20]
Practicing engineers

In most countries, a Bachelor's degree in engineering represents the first step towards professional certification and the degree program itself is certified by a professional body. After completing a certified degree program the engineer must satisfy a range of requirements (including work experience requirements) before being certified. Once certified the engineer is designated the title of Professional Engineer (in the United States, Canada and South Africa ), Chartered Engineer (in India, the United Kingdom, Ireland and Zimbabwe), Chartered Professional Engineer (in Australia and New Zealand) or European Engineer (in much of the European Union).

The advantages of certification vary depending upon location. For example, in the United States and Canada "only a licensed engineer may seal engineering work for public and private clients".[21] This requirement is enforced by state and provincial legislation such as Quebec's Engineers Act.[22] In other countries, no such legislation exists. Practically all certifying bodies maintain a code of ethics that they expect all members to abide by or risk expulsion.[23] In this way these organizations play an important role in maintaining ethical standards for the profession. Even in jurisdictions where certification has little or no legal bearing on work, engineers are subject to contract law. In cases where an engineer's work fails he or she may be subject to the tort of negligence and, in extreme cases, the charge of criminal negligence. An engineer's work must also comply with numerous other rules and regulations such as building codes and legislation pertaining to environmental law.

Professional bodies of note for electrical engineers include the Institute of Electrical and Electronics Engineers (IEEE) and the Institution of Engineering and Technology (IET). The IEEE claims to produce 30% of the world's literature in electrical engineering, has over 360,000 members worldwide and holds over 3,000 conferences annually.[24] The IET publishes 21 journals, has a worldwide membership of over 150,000, and claims to be the largest professional engineering society in Europe.[25][26] Obsolescence of technical skills is a serious concern for electrical engineers. Membership and participation in technical societies, regular reviews of periodicals in the field and a habit of continued learning are therefore essential to maintaining proficiency.[27]

In Australia, Canada and the United States electrical engineers make up around 0.25% of the labor force (see note). Outside of Europe and North America, engineering graduates per-capita, and hence probably electrical engineering graduates also, are most numerous in Taiwan, Japan, and South Korea.[28]
Tools and work

From the Global Positioning System to electric power generation, electrical engineers have contributed to the development of a wide range of technologies. They design, develop, test and supervise the deployment of electrical systems and electronic devices. For example, they may work on the design of telecommunication systems, the operation of electric power stations, the lighting and wiring of buildings, the design of household appliances or the electrical control of industrial machinery.[29]
Satellite communications is one of many projects an electrical engineer might work on

Fundamental to the discipline are the sciences of physics and mathematics as these help to obtain both a qualitative and quantitative description of how such systems will work. Today most engineering work involves the use of computers and it is commonplace to use computer-aided design programs when designing electrical systems. Nevertheless, the ability to sketch ideas is still invaluable for quickly communicating with others.

Although most electrical engineers will understand basic circuit theory (that is the interactions of elements such as resistors, capacitors, diodes, transistors and inductors in a circuit), the theories employed by engineers generally depend upon the work they do. For example, quantum mechanics and solid state physics might be relevant to an engineer working on VLSI (the design of integrated circuits), but are largely irrelevant to engineers working with macroscopic electrical systems. Even circuit theory may not be relevant to a person designing telecommunication systems that use off-the-shelf components. Perhaps the most important technical skills for electrical engineers are reflected in university programs, which emphasize strong numerical skills, computer literacy and the ability to understand the technical language and concepts that relate to electrical engineering.

For many engineers, technical work accounts for only a fraction of the work they do. A lot of time may also be spent on tasks such as discussing proposals with clients, preparing budgets and determining project schedules.[30] Many senior engineers manage a team of technicians or other engineers and for this reason project management skills are important. Most engineering projects involve some form of documentation and strong written communication skills are therefore very important.

The workplaces of electrical engineers are just as varied as the types of work they do. Electrical engineers may be found in the pristine lab environment of a fabrication plant, the offices of a consulting firm or on site at a mine. During their working life, electrical engineers may find themselves supervising a wide range of individuals including scientists, electricians, computer programmers and other engineers.
Sub-disciplines

Electrical engineering has many sub-disciplines, the most popular of which are listed below. Although there are electrical engineers who focus exclusively on one of these sub-disciplines, many deal with a combination of them. Sometimes certain fields, such as electronic engineering and computer engineering, are considered separate disciplines in their own right.
Power
Main article: Power engineering
Power pole

Power engineering deals with the generation, transmission and distribution of electricity as well as the design of a range of related devices. These include transformers, electric generators, electric motors, high voltage engineering and power electronics. In many regions of the world, governments maintain an electrical network called a power grid that connects a variety of generators together with users of their energy. Users purchase electrical energy from the grid, avoiding the costly exercise of having to generate their own. Power engineers may work on the design and maintenance of the power grid as well as the power systems that connect to it. Such systems are called on-grid power systems and may supply the grid with additional power, draw power from the grid or do both. Power engineers may also work on systems that do not connect to the grid, called off-grid power systems, which in some cases are preferable to on-grid systems. The future includes Satellite controlled power systems, with feedback in real time to prevent power surges and prevent blackouts.
Control
Main article: Control engineering
Control systems play a critical role in space flight

Control engineering focuses on the modeling of a diverse range of dynamic systems and the design of controllers that will cause these systems to behave in the desired manner. To implement such controllers electrical engineers may use electrical circuits, digital signal processors, microcontrollers and PLCs (Programmable Logic Controllers). Control engineering has a wide range of applications from the flight and propulsion systems of commercial airliners to the cruise control present in many modern automobiles. It also plays an important role in industrial automation.

Control engineers often utilize feedback when designing control systems. For example, in an automobile with cruise control the vehicle's speed is continuously monitored and fed back to the system which adjusts the motor's power output accordingly. Where there is regular feedback, control theory can be used to determine how the system responds to such feedback.
Electronics
Main article: Electronic engineering
Circuit board

Electronic engineering involves the design and testing of electronic circuits that use the properties of components such as resistors, capacitors, inductors, diodes and transistors to achieve a particular functionality. The tuned circuit, which allows the user of a radio to filter out all but a single station, is just one example of such a circuit. Another example (of a pneumatic signal conditioner) is shown in the adjacent photograph.

Prior to the second world war, the subject was commonly known as radio engineering and basically was restricted to aspects of communications and radar, commercial radio and early television. Later, in post war years, as consumer devices began to be developed, the field grew to include modern television, audio systems, computers and microprocessors. In the mid to late 1950s, the term radio engineering gradually gave way to the name electronic engineering.

Before the invention of the integrated circuit in 1959, electronic circuits were constructed from discrete components that could be manipulated by humans. These discrete circuits consumed much space and power and were limited in speed, although they are still common in some applications. By contrast, integrated circuits packed a large number—often millions—of tiny electrical components, mainly transistors, into a small chip around the size of a coin. This allowed for the powerful computers and other electronic devices we see today.
Microelectronics
Main article: Microelectronics
Microprocessor

Microelectronics engineering deals with the design and microfabrication of very small electronic circuit components for use in an integrated circuit or sometimes for use on their own as a general electronic component. The most common microelectronic components are semiconductor transistors, although all main electronic components (resistors, capacitors, inductors) can be created at a microscopic level. Nanoelectronics is the further scaling of devices down to nanometer levels.

Microelectronic components are created by chemically fabricating wafers of semiconductors such as silicon (at higher frequencies, compound semiconductors like gallium arsenide and indium phosphide) to obtain the desired transport of electronic charge and control of current. The field of microelectronics involves a significant amount of chemistry and material science and requires the electronic engineer working in the field to have a very good working knowledge of the effects of quantum mechanics.
Signal processing
Main article: Signal processing
A Bayer filter on a CCD requires signal processing to get a red, green, and blue value at each pixel

Signal processing deals with the analysis and manipulation of signals. Signals can be either analog, in which case the signal varies continuously according to the information, or digital, in which case the signal varies according to a series of discrete values representing the information. For analog signals, signal processing may involve the amplification and filtering of audio signals for audio equipment or the modulation and demodulation of signals for telecommunications. For digital signals, signal processing may involve the compression, error detection and error correction of digitally sampled signals.

Signal Processing is a very mathematically oriented and intensive area forming the core of digital signal processing and it is rapidly expanding with new applications in every field of electrical engineering such as communications, control, radar, TV/Audio/Video engineering, power electronics and bio-medical engineering as many already existing analog systems are replaced with their digital counterparts.

Although in the classical era, analog signal processing only provided a mathematical description of a system to be designed, which is actually implemented by the analog hardware engineers, Digital Signal Processing both provides a mathematical description of the systems to be designed and also actually implements them (either by software programming or by hardware embedding) without much dependency on hardware issues, which exponentiates the importance and success of DSP engineering.

The deep and strong relations between signals and the information they carry makes signal processing equivalent of information processing. Which is the reason why the field finds so many diversified applications. DSP processor ICs are found in every type of modern electronic systems and products including, SDTV | HDTV sets, radios and mobile communication devices, Hi-Fi audio equipments, Dolby noise reduction algorithms, GSM mobile phones, mp3 multimedia players, camcorders and digital cameras, automobile control systems, noise cancelling headphones, digital spectrum analyzers, intelligent missile guidance, radar, GPS based cruise control systems and all kinds of image processing, video processing, audio processing and speech processing systems.
Telecommunications
Main article: Telecommunications engineering
Milstar

Telecommunications engineering focuses on the transmission of information across a channel such as a coax cable, optical fiber or free space. Transmissions across free space require information to be encoded in a carrier wave in order to shift the information to a carrier frequency suitable for transmission, this is known as modulation. Popular analog modulation techniques include amplitude modulation and frequency modulation. The choice of modulation affects the cost and performance of a system and these two factors must be balanced carefully by the engineer.

Once the transmission characteristics of a system are determined, telecommunication engineers design the transmitters and receivers needed for such systems. These two are sometimes combined to form a two-way communication device known as a transceiver. A key consideration in the design of transmitters is their power consumption as this is closely related to their signal strength. If the signal strength of a transmitter is insufficient the signal's information will be corrupted by noise.
Instrumentation
Main article: Instrumentation engineering
Radar gun

Instrumentation engineering deals with the design of devices to measure physical quantities such as pressure, flow and temperature. The design of such instrumentation requires a good understanding of physics that often extends beyond electromagnetic theory. For example, radar guns use the Doppler effect to measure the speed of oncoming vehicles. Similarly, thermocouples use the Peltier-Seebeck effect to measure the temperature difference between two points.

Often instrumentation is not used by itself, but instead as the sensors of larger electrical systems. For example, a thermocouple might be used to help ensure a furnace's temperature remains constant. For this reason, instrumentation engineering is often viewed as the counterpart of control engineering.
Computers
Main article: Computer engineering
Personal digital assistant

Computer engineering deals with the design of computers and computer systems. This may involve the design of new hardware, the design of PDAs or the use of computers to control an industrial plant. Computer engineers may also work on a system's software. However, the design of complex software systems is often the domain of software engineering, which is usually considered a separate discipline. Desktop computers represent a tiny fraction of the devices a computer engineer might work on, as computer-like architectures are now found in a range of devices including video game consoles and DVD players.
Related disciplines

Mechatronics is an engineering discipline which deals with the convergence of electrical and mechanical systems. Such combined systems are known as electromechanical systems and have widespread adoption. Examples include automated manufacturing systems, heating, ventilation and air-conditioning systems and various subsystems of aircraft and automobiles.

The term mechatronics is typically used to refer to macroscopic systems but futurists have predicted the emergence of very small electromechanical devices. Already such small devices, known as Microelectromechanical systems (MEMS), are used in automobiles to tell airbags when to deploy, in digital projectors to create sharper images and in inkjet printers to create nozzles for high definition printing. In the future it is hoped the devices will help build tiny implantable medical devices and improve optical communication.[31]

Biomedical engineering is another related discipline, concerned with the design of medical equipment. This includes fixed equipment such as ventilators, MRI scanners and electrocardiograph monitors as well as mobile equipment such as cochlear implants, artificial pacemakers and artificial hearts.

Contactor


Contactor



In semiconductor testing, contactor can also refer to the specialised socket that connects the device under test.
In process industries a contactor is a vessel where two streams interact, for example, air and liquid.

A contactor is an electrically controlled switch (a relay) used for switching a power or control circuit.[1] A contactor is controlled by a circuit which has a much lower power level than the switched circuit. Contactors come in many forms with varying capacities and features. Unlike a circuit breaker, a contactor is not intended to interrupt a short circuit current.

Contactors range from those having a breaking current of several amps and 24 V DC to thousands of amps and many kilovolts. The physical size of contactors ranges from a device small enough to pick up with one hand, to large devices approximately a meter (yard) on a side.

Contactors are used to control electric motors, lighting, heating, capacitor banks, and other electrical loads.
Contents
[hide]

* 1 Construction
* 2 Operating principle
* 3 Ratings
* 4 Applications
o 4.1 Lighting control
o 4.2 Magnetic starter
* 5 References

[edit] Construction
Albright SPST DC contactor,
sometimes used in EV conversions

A contactor is composed of three different items. The contacts are the current carrying part of the contactor. This includes power contacts, auxiliary contacts, and contact springs. The electromagnet provides the driving force to close the contacts. The enclosure is a frame housing the contact and the electromagnet. Enclosures are made of insulating materials like Bakelite, Nylon 6, and thermosetting plastics to protect and insulate the contacts and to provide some measure of protection against personnel touching the contacts. Open-frame contactors may have a further enclosure to protect against dust, oil, explosion hazards and weather.

High voltage contactors (greater than 1000 volts) may use vacuum or an inert gas around the contacts.

Magnetic blowouts use blowout coils to lengthen and move the electric arc. These are especially useful in DC power circuits. AC arcs have periods of low current, during which the arc can be extinguished with relative ease, but DC arcs have continuous high current, so blowing them out requires the arc to be stretched further than an AC arc of the same current. The magnetic blowouts in the pictured Albright contactor (which is designed for DC currents) more than double the current it can break, increasing it from 600 A to 1,500 A.

Sometimes an economizer circuit is also installed to reduce the power required to keep a contactor closed; an auxiliary contact reduces coil current after the contactor closes. A somewhat greater amount of power is required to initially close a contactor than is required to keep it closed. Such a circuit can save a substantial amount of power and allow the energized coil to stay cooler. Economizer circuits are nearly always applied on direct-current contactor coils and on large alternating current contactor coils.

A basic contactor will have a coil input (which may be driven by either an AC or DC supply depending on the contactor design). The coil may be energized at the same voltage as the motor, or may be separately controlled with a lower coil voltage better suited to control by programmable controllers and lower-voltage pilot devices. Certain contactors have series coils connected in the motor circuit; these are used, for example, for automatic acceleration control, where the next stage of resistance is not cut out until the motor current has dropped.[2]
[edit] Operating principle

Unlike general-purpose relays, contactors are designed to be directly connected to high-current load devices. Relays tend to be of lower capacity and are usually designed for both normally closed and normally open applications. Devices switching more than 15 amperes or in circuits rated more than a few kilowatts are usually called contactors. Apart from optional auxiliary low current contacts, contactors are almost exclusively fitted with normally open contacts. Unlike relays, contactors are designed with features to control and suppress the arc produced when interrupting heavy motor currents.

When current passes through the electromagnet, a magnetic field is produced, which attracts the moving core of the contactor. The electromagnet coil draws more current initially, until its inductance increases when the metal core enters the coil. The moving contact is propelled by the moving core; the force developed by the electromagnet holds the moving and fixed contacts together. When the contactor coil is de-energized, gravity or a spring returns the electromagnet core to its initial position and opens the contacts.

For contactors energized with alternating current, a small part of the core is surrounded with a shading coil, which slightly delays the magnetic flux in the core. The effect is to average out the alternating pull of the magnetic field and so prevent the core from buzzing at twice line frequency.

Most motor control contactors at low voltages (600 volts and less) are air break contactors; i.e., ordinary air surrounds the contacts and extinguishes the arc when interrupting the circuit. Modern medium-voltage motor controllers use vacuum contactors.

Motor control contactors can be fitted with short-circuit protection (fuses or circuit breakers), disconnecting means, overload relays and an enclosure to make a combination starter.
[edit] Ratings

Contactors are rated by designed load current per contact (pole),[3] maximum fault withstand current, duty cycle, voltage, and coil voltage. A general purpose motor control contactor may be suitable for heavy starting duty on large motors; so-called "definite purpose" contactors are carefully adapted to such applications as air-conditioning compressor motor starting. North American and European ratings for contactors follow different philosophies, with North American general purpose machine tool contactors generally emphasizing simplicity of application while definite purpose and European rating philosophy emphasizes design for the intended life cycle of the application.

Current rating of the contactor depends on utilization category. For example IEC Categories are described as:

* AC1 - Non-inductive or slightly inductive rows
* AC2 - Starting of slip-ring motors
* AC3 - Starting of squirrel-cage motors and switching off only after the motor is up to speed. (Make Locked Rotor Amps (LRA), Break Full Load Amps (FLA))
* AC4 - Starting of squirrel-cage motors with inching and plugging duty. Rapid Start/Stop. (Make and Break LRA)
* AC11 - Auxiliary (control) circuits

[edit] Applications
[edit] Lighting control

Contactors are often used to provide central control of large lighting installations, such as an office building or retail building. To reduce power consumption in the contactor coils, latching contactors are used, which have two operating coils. One coil, momentarily energized, closes the power circuit contacts, which are then mechanically held closed; the second coil opens the contacts.
[edit] Magnetic starter

A magnetic starter is a contactor designed to provide power to electric motors. The magnetic starter has an overload relay, which will open the control voltage to the starter coil if it detects an overload on a motor.[4][5] Overload relays may rely on heat produced by the motor current to operate a bimetal contact or release a contact held closed by a low-melting-point alloy. The overload relay opens a set of contacts that are wired in series with the supply to the contactor feeding the motor. The characteristics of the heaters can be matched to the motor so that the motor is protected against overload. Recently, microprocessor-controlled motor protection relays offer more comprehensive protection of motors.

Sunday, May 30, 2010

Self-Contained Power Connector (SCPC) System


Self-Contained Power Connector (SCPC) System


Molex's Self-Contained Power Connector system is a simple two-piece system used to splice and tap solid and stranded non-metallic sheathed cable, quickly and easily. The SCPC system supports two and three conductors and ground circuits for AC power applications. The SCPC product line features insulation displacement contacts providing wire termination without the need to pre-strip the wires and is UL/CSA certified as a junction box. The Splice connectors splice two cable segments together and replace butt connectors, wire nuts, and junction boxes used in traditional splice applications. Tap connectors operate in similarly, used to support taps of existing cable segments, creating new branch circuits.

Wire Pin Terminals

Wire Pin Terminals


Wire Pin Terminals offer quick and easy connections in applications where set screws or clamps are used to make electrical contact with the wire. Wire Pins simplify the insertion of stranded wire into European style terminal blocks and other components, by preventing wire strand foldback, assuring a proper electrical contact and a stronger connection than just wire alone.

* Fits all popular pin-type (European) terminal blocks
* Available in wire sizes 10 to 22 AWG non-insulated, PVC insulated and nylon insulated
* Provides a reliable, vibration-proof connection
* Allows for quick wire connects and disconnects from components
* Can be used/clamped repeatedly without damaging the pin
* Made of pure electrolytic Copper
* Electro Tin plated per Mil-T-10727
* Conveniently allows for multiple wires to be inserted into 1 terminal block contact

Wire Range AWG Molex-ETC Order No. Insulation Color Max. Insul. Dia.
[mm (in.)] Overall Length
[mm (in.)] Pin Length
[mm (in.)] Pin Dia.
[mm (in.)]
Loose Piece Mylar Tape

Krimptite
18-22
(0.80 - 0.35) 19211-0003 19211-0004 17.02mm (.670") 9.40mm (.370") 2.03mm (.080")
14-16
(2.00 - 1.30) 19211-0005 19211-0006
10-12
(5.00 - 3.30) 19211-0003 19211-0002 20.83mm (.820") 11.68mm (.460") 3.05mm (.120")

Insulkrimp (PVC Insulation)
18-22
(0.80 - 0.35) 19212-0003 19212-0004 Red 3.68mm (.145") 22.61mm (.890") 9.40mm (.370") 2.03mm (.080")
14-16
(2.00 - 1.30) 19212-0005 19212-0006 Blue 4.45mm (.175")
10-12
(5.00 - 3.30) 19212-0001 19212-0002 Yellow 6.35mm (.250") 28.96mm (1.140") 11.68mm (.460") 3.05mm (.120")

Avikrimp (Nylon Insulation)
18-22
(0.80 - 0.35) 19213-0009 19213-0010 Red 3.56mm (.140") 21.84mm (.860") 9.40mm (.370") 2.03mm (.080")
14-16
(2.00 - 1.30) 19213-0011 19213-0012 Blue 4.32mm (.170") 23.62mm (.930")
10-12
(5.00 - 3.30) 19213-0007 19213-0008 Yellow 5.72mm (.225") 28.70mm (1.130") 11.68mm (.460") 3.05mm (.120")

Quick Disconnects


Quick Disconnects



Quick Disconnects (QDs) are female terminals that mate with male tab terminals, tab adapters, and terminal blocks fitted with male tabs. The terminal itself is constructed of tin-plated brass, per NEMA specifications. QDs can be fully insulated, non-insulated, or partially insulated. The insulators are either molded vinyl (PVC), extruded nylon, or molded nylon.

Molex has over 7000 cross referenced parts in our Competitor P/N Cross Reference System:

Several different products make up the Quick Disconnect family:

Fully Insulated Male Quick Disconnects
These fully insulated male Quick Disconnects are precision engineered, allowing the terminal to fit precisely into a female. This "splice" may be connected and disconnected without damage to the nylon insulation. The parts come in loose piece and on continuous carrier.

AviKrimp Fully Insulated Quick Disconnects
This is our top of the line Quick Disconnect. It is made of a Krimptite terminal with a brass sleeve on the barrel, and then completely insulated with a molded nylon housing. So you get all the benefits of an Avikrimp QD, plus it is fully insulated. Avikrimp Fully Insulated Quick Disconnects (FIQD) are fully licensed by TUV and tested to various VDE, IEC and DIN specifications.

Flags
This type of product is used when there is a space constraint, and a regular straight Quick Disconnect is too large. They are available in insulated and non-insulated versions.

Piggyback Quick Disconnects
Piggybacks can be used when multiple connections (also called piggyback) are required and there are a limited number of male tabs. The piggyback actually allows another QD to be connected to its tab and then the piggyback is connected to a tab.

Snap Plugs and Receptacles
These devices are available in both insulated and non-insulated versions. They are used in a variety of applications where a "quick disconnect" connection is needed, but there is not enough space for a normal QD coupler. The snap plug is a round bullet-like terminal that plugs or "snaps" into the female receptacle. Like a coupler set, the male and female pieces can be connected and disconnected many times.

PCB Tabs
Molex offers a large selection of standard PCB-mountable Quick Disconnect terminals. Some products offer a tab support mounting feature, which provides increased mounting reliability and terminal strength. Both strip applied and loose piece packaging are available. All products can be easily inserted into printed circuit boards using widely available, industry standard bench-type, and fully automated XY insertion tooling. Products are available in both vertical and right angle mounting configurations, are manufactured to NEMA specifications, and are UL and CSA recognized.

Magnet Wire Connectors


Magnet Wire Connectors



Molex offers a complete line of crimp terminals and connectors that provide solutions for the splicing and tapping of magnet wire and aluminum wire. Our product offering includes ring terminals with stud sizes from #6 through 1/2", male and female .250"x .032"quick disconnects, along with spade terminals. Our taps and splices have an open side which permits easy access to wire and makes internal coil tapping easy.

The terminals and connectors are made from copper alloy, tin plated and are designed to penetrate magnet wire insulation as they are applied, eliminating the need for stripping, brazing and welding.

Multi-Lock


Multi-Lock


Self-tapping (IDC) Tap-And-Run connectors The quick, convenient Multi-Lock connectors have many uses. Using only ordinary channel-lock pliers, these color-coded connectors make quick, reliable, pre-insulated splices without stripping, twisting, soldering or the need for special tools. They will tap-splice, pigtail-splice, parallel splice or in-line splice insulated Copper wire conductors for a wide range of applications. Automotive: automobile, bus, truck and trailer wiring for lights, horns, gauges and speakers, etc. Mobile: boat wiring systems, trailer wiring, mobile homes and recreational vehicles such as campers and ATV's. In the Home and Office: shop equipment, burglar and fire alarms.

Ultimate Wire Tap

The Wire Tap makes tapping into an existing wire quick, easy and reliable. This Tap-And- Run splice is actually a fully insulated female quick disconnect that can be spliced onto a wire and then mated with a fully insulated* male quick disconnect, all without stripping, twisting, soldering or the need for special tools.
Wire Range AWG Order No. Insulation Color
18-22 WT-2218 Red
14-18 WT-1814 Blue
12 WT-12 Yellow

* Also mates with partially or noninsulated quick disconnects

Perma-Seal™



Perma-Seal™


Perma-Seal terminals and splices provide a rugged, environmentally sealed connection for wire sizes 8 to 22 AWG that will insulate, seal and protect joints from physical abuse and abrasion, water, salt and other corrosive compounds. The NiAc insulation material shrinks up to 40% faster than comparable nylon or polyolefin products.



Waterproof adhesive seal
Perma-Seal terminals and splices give you long-lasting, moisture-proof connections that withstand water, salt, condensation, corrosion and heat, all of which cause serious problems for conventional, unsealed splices. The inner wall of the heat-shrinkable Perma-Seal sleeve is lined with a special hot-melt adhesive that is inert at room temperature, permitting wires to be inserted easily into the splices and terminals. As the sleeve is heated, the adhesive melts and flows under pressure from the tubing. This action fills any existing voids and creates a seal that repels moisture incursion even during pressure cycling, and stands up to some of the most rigorous tests that can be applied to high-performance splices, such as the salt fog test MIL-T-7928.

Tough and durable
The tough sleeve of Perma-Seal splices and terminals resists abrasion and cutting. This protection helps to maintain the insulation and sealing properties even in the most hostile environments, inside and out.

Terminal Blocks


Terminal Blocks



A Wide Selection of Terminal Blocks to Support a Broad Range of Applications

Molex offers a variety of terminal blocks in wire-to-board and wire-to-wire configurations to support applications ranging from HVAC equipment, power supplies and data acquisition to inverters, motion and process controls and factory and building automation.

In addition to the many industry standard terminal blocks, Molex also offers a variety of unique terminal blocks. These include the Beau™ EuroMate™ which is a pluggable barrier strip; the most complete line of 600V high power PCB terminal blocks; and the Positive Locking Terminal Blocks Connection System. Molex also sells an assortment of accessories for use with its barrier terminal strips such as jumpers, marker strips and quick disconnect tabs.

With the range of terminal blocks and accessories available from Molex, there is sure to be a terminal block to meet any design requirement.