Damping circuit to suppress motor terminal overvoltage and ringing in PWM inverter-fed AC motor drive systems with long motor leads

This paper proposes an equivalent circuit analysis to suppress overvoltage and ringing in pulsewidth modulation inverter-fed ac motor drive systems where long motor leads are required. Conventional analysis of the phenomenon is based on voltage reflection theory for the terminal end of the long cable. The authors implemented another analytical method using equivalent lumped L and C of the cable, and a transfer function for the equivalent circuit with a simple damping circuit, C-R or L-R damping circuit constants are determined from the nonoscillatory condition of the transfer function. Digital simulations and experiments are used to verify that a simple damping circuit can satisfactorily suppress overvoltage and ringing in a drive system with a long cable, such as a 100-m cable.