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Chopper

Multiquadrant operation of chopper

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Chopper

  1. 1. CHOPPER-FED DC DRIVES Presented by Jenitha.J
  2. 2. CHOPPER • Chopper is a static device. • It is a device which converts fixed dc input into variable dc output voltage. • It is also known as dc-to-dc converter. • Widely used for motor control. • And it is also used in switched mode power supply. • Converter offers greater efficiency, faster response, lower maintenance, smaller size and smooth control.
  3. 3. CHOPPER FED DC DRIVES • A dc chopper is connected between a fixed-voltage dc source and dc motor to vary the armature voltage. • A chopper is a high speed on/off semiconductor switch which connects source to load and disconnects the load from source at a fast speed. • Choppers are used to get variable dc voltage from a dc source of fixed voltage. • Chopper circuits are used to control both separately excited and Series circuits.
  4. 4. ADVANTAGES OF CHOPPER CIRCUITS • Ripple content in the output is small. • Current drawn by the chopper is smaller than the converters. • Peak/average and rms/average current ratios are small. • The chopper is supplied from a constant dc voltage using batteries. • Chopper circuit is simple and can be modified to provide regeneration and the control is also simple.
  5. 5. MULTIQUADRANT CHOPPER DRIVES o Forward motoring (I-Quadrant) o Forward Regeneration (II-Quadrant) o Reverse motoring ( III-Quadrant) o Reverse Regeneration (IV-Quadrant)
  6. 6. FORWARD MOTORING: Q1 T1 & T4 is ON Current Flow : VS + _ T1 _Motor_T4_VS - Current Ia & Va are positive Operates in First Quadrant
  7. 7. Q2 T2 is OFF. Diode D2 is FB Current flows through D3 & D2  Current Ia is negative & Va is positive. Operates in second quadrant. FORWARD REGENERATION
  8. 8. Q3 T3 & T2 is ON Current Flow : Vdc + _ T3 _Motor_T2_Vdc - Current Ia & Va are negative Operates in third Quadrant REVERSE MOTORING:
  9. 9. Q4 T4 is Turned Off, D4 is FB Current Flows through Va+ - D1 – D4 – Va- Va is negative. But current Ia is positive Operates in fourth quadrant REVERSE REGENERATION
  10. 10. 10 Single-Phase Half-Wave Converter Drive (1 cos ) 2 0 (1 cos ) 0 m a a a m f f f V V V V                
  11. 11. 11 Quadrant of Operation
  12. 12. 12 Waveform
  13. 13. 13 Single-Phase Semi-converter Drives (1 cos ) 0 (1 cos ) 0 m a a a m f f f V V V V                
  14. 14. 14 Quadrant of Operation Semiconverter – one quadrant converter One polarity of output voltage and current
  15. 15. 15 Waveform Summary
  16. 16. 16 Single-Phase Full-Converter Drives
  17. 17. 17 Quadrant of Operation Full converter – two quadrant converter Output voltage polarity can be positive or negative Output current has one polarity
  18. 18. 18 Waveform Summary
  19. 19. THANK YOU

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