Unified torque modeling and optimum trade-off locus of the doubly salient motor with advanced angle control

Abstract

The doubly salient motor (DSM) is a novel motor with non-sinusoidal waveforms of the self-inductance, excitation inductance and back electro-magnetic force which bring convenience in drive. But at the same time, the non-sinusoidal waveforms cannot be linearized as dq components directly by Park Transformation as applied in the sinusoidal motors. The nonlinearity makes the precise analysis of the DSM very difficult. Besides, the torque characteristics, namely, torque ripple (TR) and the ratio of the torque to the current (T/i), are usually analyzed respectively. There still exists no theories which can consider both TR and T/i and find the best balance between them. This paper proposes a linearized model of the torque based on the multidomain analysis (time domain and complex-frequency domain) of the DSM. Then, a unified torque model (UTM) based on the above linearized model is further proposed. The T/i and TR are both calculated and the optimum trade-off locus is considered, defined, and simplified by directional derivative and L’Hospital’s rule. Based on the UTM, the resistive impedance tuning method of the advanced angle is proposed. The theory is verified by a 12/8 pole air-cooled prototype and related simulation and experimental results.