A closed-loop speed control scheme with reversing and regenerating capability for a squirrel-cage induction motor is described. The scheme makes use of a fully-controlled bridge for a.c. to d.c. conversion, a currend-fed inverter for generation of variable frequency a.c. supply for motor and an analogue tachogenerator for speed feedback signal. The current-reference signal is generated by a novel slip calculator. This paper describes the slip calculator and the design of controllers based on an approximate model of motor. Experimental results validating the methods used for design of controllers are also presented. © 1980 Taylor & Francis Group, LLC.