Cost-Effective Control Scheme for Reduction of Torsional Torque Oscillations in Starting Large Induction Motors

Abstract

This article presents a cost-effective variable frequency drive for starting and operating large three-phase squirrel cage induction motors. The proposed drive employs the constant V/F control scheme, which regulates the rotor frequency such that it is always kept below a predetermined value. This has the effect of drastically reducing the motor shaft torque oscillations and significantly limiting the maximum value of the motor line current. In addition to its simplicity and hence cost-effectiveness, the proposed scheme is shown to be capable of (i) reducing the shaft torque oscillations to approximately 22% of that of the direct on-line start of the large motor, and (ii) limiting the motor line current to approximately 36% of that of the direct on-line start value.

Starting Pulse Vibration Torque Analysis of Aviation Variable Frequency Asynchronous Motor Based on Low-Frequency Step-Down Starting Methods

“…The ref [6,7] reduce the starting pulse vibration torque by changing the motor structure, such as groove shape or the mechanical bearing stiffness. The ref [8] proposes a method by reducing the starting voltage to decrease the starting pulse vibration pulse. However, this method further reduces the starting torque as the starting pulse vibration torque decreases and can only be applied to drive systems with no-load and light-load starting.…”