Working Principle of DC Chopper

Function 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.
• When the SCR is switched ON during T_ON time, the output voltage across load is V_dc. 
• The output voltage across load becomes zero when the SCR is switched OFF during T_OFF time. 

• The average output voltage across load depends upon switching time  ( Turn on time + Turn off time ) of the SCR.

V_O = ( T_ON / T_ON + T_OFF ) V_dc

                                  = ( T_ON / T  ) V_dc

               = K V_dc

      Where V_O = Output voltage

                          V_dc = Input voltage

                         T_ON = Chopper on time

                        T_OFF = Chopper off time

                               T = Chopper time period

                              K = Duty cycle

                          If K > 1, Step up chopper

                              K < 1, Step down chopper

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

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