Extended HF Inductance Model of Multi-Salient Motors for HF and Pulse Voltage Signal Injection

Abstract

Spatial saliencies of AC motors can be acquired in the form of a saliency vector using high frequency signal injection or voltage pulse excitation. In both cases, the frequency spectrum of the saliency vector shows a large amount of harmonics caused by different effects, not only the spatial saliencies themselves. In addition to the well-known harmonics caused by inverter nonllnearities, it was recently shown that saliency-harmonic-products emerge in the saliency vector under pulse excitation of multi-salient motors. All these harmonics are detrimental for encoderless control as they take out signal strength of the saliency used to extract rotor or flux position. In this paper, the saliency harmonic products will be investigated for both high frequency signal injection and pulse excitation. The high-frequency induction motor model will be enhanced, accounting for these frequency components. Experimental results measured in a multi-salient motor confirm the existence of these saliency harmonic products and the need for their consideration for improved encoderless performance.