Even if the control winding (CW) is short-connected, the brushless doubly fed machine (BDFM) still has problems such as small starting torque and large starting current during starting. At the same time, the large starting current can cause serious influence on the grid and the motor. In this paper, a method with multi-pole-pair harmonics combined (MHC) starting is proposed. First, this paper analyzes the basic working principle of BDFM with MHC starting mode. Then, the connection of the stator winding is designed and the rotor winding with composite coil is adopted. The principle and connection mode of stator winding and rotor winding are studied, and the design examples are given. Finally, the finite element model of BDFM is established on the basis of the winding design example, and the test prototype is designed and manufactured. The starting torque, starting current and air-gap flux density are analyzed by time-step finite element method under no-load and load conditions. The simulation and the experiments of test prototype have verified that the proposed BDFM can greatly reduce the starting current and increase the starting torque, and has better starting performance.

Brushless Doubly Fed Machine (BDFM), Composite coil, multi-pole-pair harmonics combined (MHC) starting, starting current, starting torque.