Three-Phase Induction Motor Drives and Their Torque Characteristics

Notes on the induction motor, contrasted with the direct current machine where conductors on a rotating armature pass through a stationary magnetic field: here the magnetic field rotates, so no electrical connection has to be made to the rotor. Develops the slip, the equivalent circuit and the three-phase torque expression, showing that with a constant supply voltage torque is proportional to slip resistance over the impedance term and is therefore maximum when rotor resistance equals rotor reactance. Works through the torque-speed characteristics in the forward and reverse directions and the operating cases of motoring, plugging and generating at slip one and slip zero, and continues into the methods of controlling the machine.