Design of a Medium-Voltage High-Power Brushless Doubly Fed Motor With a Low-Voltage Fractional Convertor for the Circulation Pump Adjustable Speed Drive
Xi Chen, Xuefan Wang, Ming Kong, Zhenping Li
Abstract
The brushless doubly fed motor (BDFM) shows great potential for use in large medium-voltage adjustable-speed drive (ASD) systems due to its high reliability and cost benefits of a partially rated low-voltage power electronics converter. However, undesired performance caused by rich useless space-harmonics restricts the application of the BDFM in medium-voltage high-power ASD systems. In this article, a medium-voltage wound rotor BDFM consisting of specially designed stator and rotor windings is developed. First, the wound rotor with unequal turns and unequal pitches is designed and then compared with a nested loop counterpart. In addition, a 10 kV single-layer winding with shifted slot number in the stator is proposed to further reduce the space-harmonics by equivalent pitched effect. The finite element model of the BDFM is established to analyze electromagnetic performance and the influence of magnetic slot wedges. A lumped parameter thermal model is developed to quickly evaluate the average temperature rise of the proposed prototype. Field tests of driving a circulation water pump in a steel rolling mill were conducted to validate the feasibility of the proposed scheme.