A.C. Series Motor Speed Control with Silicon-controlled Rectifiers

ABSTRACT

The article describes how a full wave phase-controlled power supply may be utilized to vary the speed of an a.c. series motor and how a closed loop system, driven from the output of a tachogenerator, may be incorporated to regulate the speed at every setting, against load and supply voltage variations. The problems associated with the design of trigger circuits for inductive loads and complete design of the control circuits are discussed and practical circuit design carried out. The circuit has actually been used to vary the speed of a 1½ h.p. motor in the range of 0–6000 r.p.m. and regulate the speed at every setting within the range of 100–6000 r.p.m.