For the Parallel Operation of Two or More D

For the parallel operation of two or more D.C. compound generators, we should ensure that

A) voltage of the incoming generator should be same as that of bus bar
B) polarity of incoming generator should be same as that of bus bar
C) all the series fields should be run in parallel by means of equilizer connection
D) series fields of all generators should be either on positive side or negative side of the armature