Current Commutated Chopper : Modes of Operation and Working

Current Commutation :

An external pulse of current greater than load current passed in reverse direction through conducting SCR. When current pulse attains a value equal to load current ,net pulse through the device becomes zero.

The current pulse is initially generated by initially charged capacitor.

In this commutation a diode is connected in antiparallel with main SCR, so that the voltage drop across the diode reverse biases the main SCR.

As this voltage drop is of the order of 1 volt , the commutation time is more than the voltage commutation.

To start the operation of this chopper the capacitor must be initially charged with supply voltage.

By closing the switch S ⇛ through charging through charging resistance RC

Assumptions :
Load current constant
SCRs and Diodes are ideal
RC is large & treated as open circuit during commutation interval

Modes of operation is explained in video

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[Devil-dnew]

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