What is the differencebetweenforced commutation and natural commutation?
Answers
Natural communication
1. It is also called as Phase commutation, line commutation or AC commutation.
2.The natural commutation is only possible in the AC circuit.
3.No extra circuit is necessary in order to turn off the SCR.
4.The SCR turns off automatically during negative half cycle of alternating supply when reverse voltage applied across SCR for sufficient time.
5.The time period of the negative half cycle should be more than the turn off time of the SCR.
6.There is no power loss in the circuit because no commutation circuit.
7.Class F is example of natural commutation.
Forced communication
1.It is possible only in the DC circuit.
2.As there is no natural zero current in the DC circuit, extra commutation circuit ( which include L and C ) requires in order to turn off the SCR.
3.The forced commutation may be voltage commutation or current commutation.
4.Class A, Class B, Class C, Class D and Class E are example of forced commutation.
5.Some power loss takes place in the commutation circuit.
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