Class F Commutation ( Line commutation or AC commutation )

• The class F commutation is also called as line or natural commutation because the SCR is turned off automatically during negative cycle of alternating supply. 
• There are no commutating components used in this method therefore it is not called as forced commutation method.
• The time duration for the negative half cycle must be greater than the SCR specific turned off time as per data sheet. 
• Figure A shows the circuit for the Class F commutation. 
• This method is applicable only for alternating supply. 
• This method is used in the line commutator rectifiers, inverters and cyclo – converters.

CLASS F COMMUTATION DRAWING AND WAVEFORMS.PDF

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