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Principle of DC Chopper

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Working of DC Chopper

  • The function of the DC chopper is to convert fixed DC into variable DC.
  • A DC chopper is connected between supply source and load.
  • The variable output voltage is obtained by switching on and off SCR at regular interval. The on and off time of the SCR is in the micro second.

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  • When the SCR is switched ON during TON time, the output voltage across load is Vdc.
  • The output voltage across load becomes zero when the SCR is switched OFF during TOFF time.
  • The average output voltage across load depends upon switching time of the SCR.

VO = ( TON / TON + TOFF ) Vdc

= ( TON / T ) Vdc

= K Vdc

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Where VO = Output voltage

Vdc = Input voltage

TON = Chopper on time

TOFF = Chopper off time

T = Chopper time period

K = Duty cycle

If K > 1, Step up chopper

K < 1, Step down chopper

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  • The DC chopper works as DC transformer and variation of output voltage is obtained by duty cycle.

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Questions

Describe the Function of DC Chopper.

  • The function of the DC chopper is to convert fixed direct voltage into variable direct voltage.

Which are semiconductor switching devices used in chopper circuit?

  • MOSFET, IGBT, SCR, Power BJT

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Define : Duty Cycle

  • The duty cycle of DC Chopper is defined as the ratio of chopper ON time ( TON ) to the total Chopper switching time ( T ).

K = Duty cycle = ( TON / T )

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