Low-Cost Variable Speed Drive Based on a Brushless Doubly-Fed Motor and a Fractional Unidirectional Converter

Abstract

The paper presents a low-cost variable-speed drive system comprising a brushless doubly-fed motor (BDFM) and a fractionally rated unidirectional frequency converter. A simple control algorithm is proposed for regulating the drive's speed and torque. A method of starting the BDFM in the cascade mode is presented and the starting performance is analyzed. The efficiency of the BDFM is discussed and the dynamic performance of the drive is verified by experimental results obtained from a 180 frame-size BDFM.