Power Electronic Applications
1. Residential
Refrigeration and freezers, Space heating, Air conditioning, Cooking, Lighting, Electronics (personal computers, other entertainment equipment).
2. Commercial
Heating, Ventilating, and Air conditioning, Central refrigeration, Lighting, Computers and Office equipment, Uninterruptible Power Supplies (UPSs), Elevators.
3. Industrial
Pumps, Compressors, Blowers and Fans, Machine tools (Robots), Arc furnaces, Induction furnaces, Lighting, Industrial lasers, Induction heating, Welding.
4. Transportation
Traction control of electric vehicles, Battery chargers for electric vehicles, Electric locomotives, Street cars, Trolley buses, Subways, Automotive electronics including engine controls.
5. Utility Systems
High voltage dc transmission (HVDC), Static Var Compensation (SVC), Supplemental energy sources (wind, photovoltaic), Fuel cells, Energy storage systems, Induced draft fans and Boiler feedwater pumps.
6. Aerospace
Space shuttle power supply systems, Satellite power systems, Aircraft power systems.
7. Telecommunications
Battery chargers, Power supplies (DC and UPS).
Types of Power Electronic Circuits
1. Diode Rectifiers
A diode rectifier circuit converts ac input voltage into a fixed dc voltage. The input voltage may be single-phase or three-phase. Diode rectifiers find wide use in electric traction, battery charging, electroplating, electrochemical processing, power supplies, welding and uninterruptible power supply (UPS) systems.
2. AC to DC Converters (Phase-controlled rectifiers)
These convert constant ac voltage to variable dc output voltage. These rectifiers use line voltage for their commutation, as such these are also called line-commutated or naturally-commutated ac to dc converters. Phase controlled converters may be fed from single-phase or three-phase source. These are used in dc drives, metallurgical and chemical industries, excitation systems for synchronous machines etc.
DC to DC Converters (DC Choppers)
A dc chopper converts fixed dc input voltage to a controllable dc output voltage. The chopper circuits require forced, or load, commutation to turn-off the thyristors. For lower power circuits, thyristors are replaced by power transistors. Classification of chopper circuits is dependent upon the type of commutation and also on the direction of power flow. Choppers find wide applications in dc drives, subway cars, trolley trucks, battery-driven vehicles etc.
4. DC to AC Converters (Inverters)
An inverter converts fixed dc voltage to a variable ac voltage. The output may be a variable voltage and variable frequency. These converters use line, load or forced commutation 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 applications and by power transistors in low power applications.
AC to AC Converters
These convert fixed ac input voltage into variable ac output voltage. These are of two types as under:
AC voltage controllers (AC voltage regulators):
These converter circuits convert fixed ac voltage directly to a variable ac voltage at the same frequency. AC voltage controllers employ two thyristors in antiparallel or a triac. Turn-off of both the devices is obtained by line commutation. Output voltage is controlled by varying the firing angle delay. AC voltage controllers are widely used for lighting control, speed control of fans, pumps etc.
Cycloconverters:
These circuits convert input power at one frequency to output power at a different frequency through one-stage conversion. Line commutation is more common in these converters, though forced and load commutated cycloconverters are also employed. These are primarily used for slow speed large ac drives.
Static Switches
The power semiconductor devices can operate as static switches or contactors. Static switches possess many advantages over mechanical and electromechanical circuit breakers. Depending upon the input supply the static switches are called ac static switches or dc static switches.
1. Power electronics is based primarily on the switching of the power semiconductor devices.
2. Modern power electronics equipment uses,
- Power semiconductors that can be regarded as the muscle, and
- Microelectronics that have the power and intelligence of a brain.
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Must Read: What is Power Electronics?
