Magnitude, Amplitudes and Frequencies of Induction-Motor Air-Gap Transient Torque Through Simultaneous Reclosing with or Without Capacitors

Knowing the magnitude, the frequencies and the amplitudes of the air-gap transient torque will definitely help the engineer to steer the design away from any destructive transient situation shown at the early design stage. With this objective in mind, this paper analyzed the simultaneous reclosing (or starting) of an induction motor under constant speed with or without capacitors. The frequencies and amplitudes of reclosing transient torques are very different when the motor is reclosed at different slips. Sample case study showed that as far as simultaneous reclosing is concerned the ANSI C50.41 or NEMA MG-1 on reclosing does not have practical meaning in limiting the magnitude of the simultaneous reclosing transient torque. Reclosing and starting tests conducted on a 2500/1250-HP, 10/12-pole motor agreed with the calculations.