Direct-Current-Motor Control

Author: E.E. Kimberly

In Chapter 11 it was shown that the speed of a shunt or compound motor can be controlled within, a limited range by shunt-field current adjustment, but that for speeds below this range a reduced voltage across the armature becomes necessary. By using electron tubes both of these means become available, and the power is taken from single-phase or polyphase a-c power supply. Several circuits for accomplishing this control have been developed but, inasmuch as all have the same essential principles, the description of a typical one will suffice.