A Controller of Motor Discrete Variable Frequency Soft Starting and Harmonic Filtering

Abstract

The started motors with the discrete frequency converter are characterized by high starting torque and a large number of harmonics when the motors draw heavy-loads. It may pull down the voltage of the power supply net work and influence the other electrical devices. Furthermore, it increases the motor temperature, which may lead to motor damage. Therefore, an integrated device of motor discrete variable frequency starting and harmonic filtering was developed. In this paper, a controller is designed to control the motor during the soft starting/stopping and keep the harmonics in permitted ranges by harmonic filtering. The following works have been done in the study: the needs analysis of the controller, design the hardware based on the PLC and the software design of the controller. The motor starter developed with this controller has been successfully applied to the loads of the drive equipments. It can improve the starting performance when the motors draw the heavy-loads, save energy, stabilize the voltage of the power supply network.