Compare Natural Commutation and Forced Commutation

Natural Commutation 

• It is also called as phase commutation, line commutation or AC commutation. 
• The natural commutation is only possible in the AC circuit. 

Commutation in the DC Machines

• The function of the commutator is to make alternating current into unidirectional. 
• The direction of armature conductors are in one direction when conductors pass through N – poles and in opposite direction when they are under S – poles and vice versa.  
• The reversal of current takes place when conductors pass out under influence of the N – poles and enter that of S – poles. 

Class C Commutation ( Voltage or Complementary or Type C Commutation )

Class C Commutation

The class C commutation is also called as voltage commutation because the SCR is turned off by applying reverse voltage across it. The SCR T1 is main SCR which is connected in series with load. The commutating capacitor C is connected between anode terminal of SCR T1 and SCR T2.