What is power electronic ?
Power electronics is a field of engineering that deals with the control, conversion, and protection of electric power. It is used in a wide variety of applications, from consumer electronics to industrial motor drives and aerospace systems. The technology enables the development of efficient, cost-effective, and reliable power systems that can provide high performance and safety.
Application of Power electronics
Conception OF POWER ELECTRONICS
Power electronics belongs in completely to power masterminds and incompletely to electronics masterminds.
Power engineering is substantially concerned with generation, transmission, distribution and application of electric energy at high effectiveness.
Electronics engineering, on the other hand, is guided by distortionless product, transmission and event of data and signals of veritably low power position of the order of a many watts, or milliwatts without important consideration to the effectiveness.
In addition, outfit associated with power engineering is grounded substantially on electromagnetic principles whereas that in electronics engineering is grounded upon physical marvels in vacuum, feasts vapours and semiconductors.
Power electronics is a subject that enterprises the operation of electronic- principles into situations that are rated at power position rather than signal position.
It may also be defined as a subject that deals with the outfit and outfit working on the principle of electronics but rated at power position rather than signal position.
For example:-
semiconductor power switches similar as thyristors, GTOS etc. work on the principle of electronics( movement of holes and electrons), but have the name power attached to them only as a description of their power conditions. also, diodes, mercury- bow cures and thyratrons( gas- filled triode), high- power position bias, form a part of the subject power electronics; because their working is grounded on the physical marvels in feasts and vapours, an electronic process. As the addition of all similar power- rated electronic accoutrements would be a substantial task, the present book is devoted to the study of semi-conductor-based power- electronic factors and systems only. It should be understood that the ways used in the design of high- effectiveness and high- energy position power electronic circuits are relatively different from those employed in the design of low- effectiveness electronic circuits at signal situations. .
operations OF POWER ELECTRONICS
The period of ultramodern power electronics began with the invention of silicon- controlled- therapy( SCR) by Bell Laboratories in 1956.
Its protoytpe was introduced by GEC in 1957 and latterly, GEC introduced SCR- grounded systems commercially in 1958.
Since also, there have been emergence of numerous new power semiconductor bias. Power electronic systems moment incorporate power semiconductor bias as well as microelectronic intertwined circuits.
The term,' motor system', in general, is used to denote a static device that converts ac to de, de to ac, de to de or ac to ac. Conventional power regulators grounded on thyratrons, mercury- bow cures, glamorous amplifiers, rheostatic regulators etc. have been replaced by power electronic regulators using semiconductor bias in nearly all operations.
The development of new power- semiconductor bias, new circuit topologies with their bettered performance and their fall in prices have opened up wide field for the new operations of power electronic transformers.
A judicious use of power- semiconductor bias in confluence with microprocessors or microcomputers has further enhanced the control strategies and synthesizing capabilities of the power electronic transformers.
It's said that power semiconductor bias can be regarded as the muscle and the microelectronics as the intelligent brain in the ultramodern power electronic systems.
Table1.1 lists colorful operations of power electronics.
This list is still not total... No boundaries can be allocated for the operations of power electronics, especially with the present trend of integrated design of power- semiconductor bias.
microprocessors and the controlled outfit.. The power conditions of power- electronic systems range from a many watts in lights to several hundred megawatts in HVDC transmission systems.
It's believed that by the turn of the century, nearly 80 of the electric power consumed in mileage systems will pass through power- electronics and this figure will ultimately reach 100 in the future.
Aerospace Space shuttle power inventories, satellite power inventories, aircraft power systems.
marketable Advertising, heating, air conditioning, central refrigeration, computer and office outfit, uninterruptible power inventories, elevators, light dimmers and flashers.
Industrial Are and artificial furnaces, boasters and suckers, pumps and compressors, artificial spotlights, motor- valve changers, rolling manufactories, cloth manufactories, excavators, cement manufactories, welding.
Domestic Air conditioning, cuisine, lighting, space heating, refrigerators, electric- door openers, dryers, suckers, particular computers, other entertainment outfit, vacuum cleansers, washing and sewing machines, light dimmers, food mixers, electric robes, food- warmer servers.
Telecommunication Battery dishes, power inventories( dc and UPS)
Transportation Battery dishes, traction control of electric vehicles, electric locomotives, road buses , trolley motorcars, galleries, automotive electronica.
mileage systems High voltage de transmission( HVDC), excitation systems, VAR compensation, stationary circuit combers, suckers and boiler- feed pumps, supplementary energy systems( solar, wind). .
ADVANTAGES AND DISADVANTAGES OF POWER- ELECTRONIC
The advantages held by power- electronic systems are as under
i) High effectiveness due to low loss in power- semiconductor bias.
ii) High trustability of power- electronic motor system
iii) Long life and lower conservation due to the absence of any moving corridor.
iv) Fast dynamic response of the power- electronic systems as compared electromechanical motor systems.
( v) Small size and lower weight affect in lower bottom space and thus lower installation to cost.
(vi) Mass product of power- semiconductor bias has rebounded in lower cost of the motor outfit, Systems grounded on power electronics, still,
suffer from the following disadvantages
( a) Power- electronic motor circuits have a tendency to induce chimes in the force system as well as in the cargo circuit. In the cargo circuit, the performance of the cargo is told , for illustration, a high harmonious content in the cargo circuit causes dicker problems in de machines, increased motor heating and further accoustical noise in both dc and ac machines. So way must be taken to sludge these out from the affair side of a motor. In the force system, the harmonics distort the voltage waveform and seriously impact the performance of other outfit connected to the same force line. In addition, the harmonics in the force line can also beget hindrance with communication lines. It is, thus, necessary to fit pollutants on the input side of a motor.
(b) Ac to dc and ac to ac transformers operate at a low input power factor under certain operating conditions. In order to avoid a low pf, some special measures have to be espoused.
(C) Power- electronic regulators have low load capacity. These transformers must, thus, be rated for taking evanescent overloads. As similar, cost of power electronic regulator may increase.
( d) the rejuvenescence of power is delicate in power electronic motor systems. The advantages held by power electronic transformers far overweigh their disadvantages mentioned over.
As a consequence, semiconductor- grounded transformers are being considerably employed in systems where power inflow is to be regulated. As formerly stated, conventional power regulators used in numerous installations have formerly been replaced by semiconductor- grounded power electronic regulators.
POWER ELECTRONIC SYSTEMS
The major factors of a power electronic system are shown in the form of a block illustration
Main power source may be an ac force system or a dc force system. Main Power Source Command Control Unit Digital Circuit Power Electronic cargo Feedback Signal.
The output from the power electronic circuit may be variable dc, or ac voltage, or it may be a variable voltage and frequence.
In general, the output of a power electronic convertor circuit depends upon the conditions of the cargo.
For ex, if the cargo is a dc motor, the motor output must be malleable direct voltage. In case the cargo is a 3- phase induction motor, the motor may have malleable voltage and frequence at its output outstations. The feedback element in measures a parameter of the cargo, say speed in case of a rotating machine, and compares it with the command. The difference of the two, through the digital circuit factors, controls the moment of turn- on of semiconductor bias forming the solid- state power motor system. In this manner, geste Of the cargo circuit can be controlled, as asked , over a wide range with the adaptation of the command. .
POWER SEMICONDUCTOR DEVICES
Silicon controlled therapy( SCR) was introduced first in 1957. Since also, several other power semiconductor bias have been developed. All these semiconductor bias are enumerated below along with their conditions. Power diodes are available over to 3000 V, 3500 A, 1 kHz. Thyristors have conditions up to 6000 V, 3500 A, 1 kHz. SITHS( static induction thyristors) can operate up to 4000 V, 2200 A, 20 kHz. GTOs( gate- turn off thyristors) have conditions of 4000 V, 3000 A, 10 kHz. MCTs( MOS controlled thyristors) can work up to 600 V, 60 A, 20 kHz. Triacs have power conditions of 1200 V, 300 A, 400 Hz. BJTs are used up to power conditions of 1200 V, 400 A, 10 kHz. Power MOSFETs( essence oxide semiconductor field effect transistors) and SITs( static induction transistors) have fairly low range of 1000 V, 50 A and 1200 V, 300 A independently. Both these bias can, still, operate satisfactorily over to a frequence range of 100 kHz. IGETS( insulated gate bipolar transistors) are available over to 1200 V, 400 A and 20 kHz.
Grounded on( i) turn- on and turn- off characteristics and (ii) gate signal conditions,
the power semiconductor bias can be classified as under
(a) Diodes
These are unbridled amending bias. Their on and off countries are controlled by power force.
(b) Thyristors
These have controlled turned- on by a gate signal. After thyristors are turned- on, they remain latched- in on- state due to internal regenerative action.
(c) Controllable switches
These bias are turned- on and turned- off by the operation of control signals. The bias which bear as controllable switches are BJT, MOSFET, GTO, SITH, IGBT, SIT and MCT. SCR, GTO, SITH and MCT bearpulse-gate signal for turning them on; once these bias are on, gate palpitation is removed. But BJT, MOSFET, IGBT and SIT bear nonstop signal for keeping them in turn- on state. The bias which can repel unipolar voltage are BJT, MOSFET, IGBT and MCT. Thyristors and GTOs are able of supporting bipolar voltages. Triac and RCT( rear conducting thyristor) retain bidirectional current capability whereas all other remaining bias diode, SCR, GTO, BJT, MOSFET, IGBT, SIT, SITH, MCT) are unidirectional current bias. .
TYPES OF POWER ELECTRONIC
A power electronic system consists of one or further power electronic converter. A power electronic motor is made up of some power semiconductor devines controlled by integrated prefabricated. The switching characteristics of power semiconductor bias permit a power electronic motor to shape the input power of one form to affair power of some other form. stationary power converter perform these functions of power conversion veritably efficiently.
Astronomically speaking, power electronic converter ( or circuits) can be classified into six types as under
1. Diode Rectifier
A diode rectifier circuit converts ac input voltage into a fixed dc voltage. The input voltage may be single- phase or three phase. Diode rectifier find wide use in electric traction, battery charging, electroplating, electrochemical processing, power inventories, welding and uninterruptible power force( UPS) systems.
2. Ac to dc converter ( Phase- controlled rectifiers)
These convert constant ac voltage to variable dc output voltage. These rectifier use line voltage for their dicker, as such these are also called line- commutated or naturally- commutated ac to dc converter. Phase- controlled converter may be fed from 1- phase or 3- phase source. These are used in de drives, metallurgical and chemical diligence, excitation systems for coetaneous machinesetc.
3. DC to dc converter ( DC Choppers)
A dc chopper converts fixed dc input voltage to a controllable dc output voltage. The chopper circuits bear forced, or cargo, dicker to turn- off the thyristors. For lower power circuits, thyristors are replaced by power transistors. Bracket of eggbeater circuits is dependent upon the type of dicker and also on the direction of power inflow. Copters find wide operations in de drives, shelter buses , trolley exchanges, battery- driven vehicles etc.
4. DC to ac converter ( inverters)
An inverter converts fixed dc voltage to a variable ac voltage. The output may be a variable voltage and variable frequence. These converters use line, cargo or forced dicker for turning- off the thyristors. Inverters find wide use in induction- motor and synchronous- motor drives, induction heating, UPS, HVDC transmission etc. At present, conventional thyristors are also being replaced by GTOs in high- power operations and by power transistors in low- power operations.
5. AC to ac converter
These convert fixed ac input voltage into variable ac output voltage.
These are of two types as under
( a) AC voltage regulators ( AC voltage controllers)
These motor circuits convert fixed ac voltage directly to a variable ac voltage at the same frequence. AC voltage regulator employ two thyristors in antiparallel or a trinc. Turn- off of both the bias is attained by line dicker. Affair voltage is controlled by varying the blasting angle detention. AC voltage regulators are extensively used for lighting control, speed control of suckers, pumps etc.
(b) Cycloconverters
These circuits convert input power at one frequence to output power at a different frequence through one- stage conversion. Line dicker is more common in these transformers, however forced and cargo commutated cycloconverters are also employed. These are primarily used for slow- speed large ac drives like rotary kiln etc.
6. stationary switches
The power semiconductor bias can operate as stationary switches or contactors.
stationary switches retain numerous advantages over mechanical and electromechanical circuit combers. Depending upon the input force, the static switches are called ac static switches or dc static switches.
POWER ELECTRONIC MODULES
A power electronic motor may bear two, four or further semiconductor bias depending upon the circuit configuration. Power modules conforming of two, four or aix bias are, at present, available. therefore, a power electronic motor can be assembled from power modules rather of from individual semiconductor bias. A power module has bettery, Power Electronics performance characteristics as compared to conventional bias so far as their switching characteristics, operating speed and losses are concerned. Gate drive circuits for individual bias or power modules are also commercially available.
As a result of these developments, now intelligent modules have come in the request. Intellegent module, also called smart- power, is state- of- the- art power electronics and it consists of power module and a supplemental circuit. The supplemental circuit comprises of interfacing of power module with the input/ affair through proper insolation from low- voltage signal and from high- voltage power circuit, a drive circuit, protection and individual circuitry against maloperation like redundant current, over voltage etc, microcomputer control and controlled power force. The stoner has simply to connect the being force and the cargo outstations to the smart- power. At present, intelligent modules are being used considerably in power electronics. It's reported that there are further than twenty manufacturers of intelligent modules.
SUMMARY
Power semiconductor bias form the heart of ultramodern power electronics. A power electronics mastermind must understand the device completely for effective, dependable and cost-effective design of power converter.
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