... ,10,13,14,20,21,27,28,31,42 51,53 937,38,51,57,64,70,75,85,87,1 004 320 ... ,052-056,058-064,066-079 082-087,088,096 121,001-003,006-011,016-0199 000 081 004,006 ... to change commutation , so that spark suppression in the permitted range, and the energy loss is small. (3) When carbon brush ...