Note for Power Semiconductor Drives - PSD by praveen kumar
- Power Semiconductor Drives - PSD
- Note
- Electrical and Electronics Engineering
- B.Tech
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Control of DC Motors by Choppers Dr. D G Padhan PSD 1
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DC Chopper • a static power electronic device that converts fixed dc input voltage to a variable dc output voltage • considered as dc equivalent of an ac transformer since they behave in an identical manner • used all over the world for rapid transit systems • used in trolley cars, marine hoist, forklift trucks and mine haulers • offer smooth control, high efficiency, faster response and regeneration facility • The power semiconductor devices used for a chopper circuit can be force commutated thyristor, power BJT, MOSFET and IGBT Dr. D G Padhan PSD 2
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• • • • • GTO based chopper are also used These devices are generally represented by a switch. When the switch is off, no current can flow. Current flows through the load when switch is “on”. The power semiconductor devices have on-state voltage drop of 0.5V to 2.5V across them. • For the sake of simplicity, this voltage drop across these devices is generally neglected Dr. D G Padhan PSD 3
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PRINCIPLE OF CHOPPER OPERATION • A chopper is a high speed “on" or “off” semiconductor switch • It connects source to load and disconnect the load from source at a fast speed. • In this manner, a chopped load voltage is obtained from a dc supply of constant magnitude Dr. D G Padhan PSD 4
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