Q6Electrical Machines and Drives

The torque-slip characteristic of an induction motor shows torque rising almost linearly with slip from s=0 (synchronous speed, zero torque) up to the slip at maximum (breakdown/pull-out) torque, sm, beyond which torque falls off as slip increases further toward s=1 (standstill). The curve therefore has a stable operating region (0 < s < sm) where torque increases with slip, and an unstable region (sm < s < 1) where torque decreases with increasing slip; the motor normally operates only in the stable, low-slip region near synchronous speed under steady load.