The Effects of Air-Gap Width on Performance of Brushless Doubly Fed Machine with Radial Laminated Reluctance Rotor

Abstract

Keywords: radial laminated reluctance rotor; brushless doubly fed machine; air-gap; finite element Abstract. A new type of AC variable speed brushless doubly fed machine with radial laminated reluctance rotor (RLR-rotor BDFM) is presented and analyzed in this paper. The rotor of the BDFM is structured by the radial reluctant lamination, and the electric brushes and slip ring are cast off. Therefore, this machine will be more reliable. The BDFM proposed in this paper can work under different modes--asynchronous operation, synchronous operation, super-synchronous operation and sub-synchronous operation, and its active and reactive power can easily be regulated. It has a g ood application prospect in converter-fed variable speed drive applications and variable-speed c onstant-frequency (VSCF) wind power generation systems. Firstly, this paper introduces RLR-rotor structure, the transient flied of the motor with three different air-gap widths is calculated by finite element method. Then the air-gap flux distribution and voltages of power winding with no-load operation are analyzed. The torque curves of these motors are plotted according to the calculation results, and the voltage of the power windings and harmonic contents at the maximum torque are solved. All the results indicate the effects of air-gap widths on machines, and provide insights into rotor structure optimization of RLR-rotor BDFM.