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In saliency-based sensorless methods, the amplitude of the injected voltage cannot be reduced to levels below its specified value because of the reasonable signal required for the noise ratio. Increasing the injection signal amplitude increases not only the acoustic noise and high-frequency (HF) losses, but also the total harmonic distortion (THD) of the output voltage and current ripples. A new pulsating semi-impulse signal injection method based on the current sensing technique is proposed for the sensorless control of interior permanent magnet synchronous motors (IPMSMs). The proposed method aims to control the motor speed and reduce some problems due to the HF signal injection involving acoustic noise, HF losses and THD of the output voltage. Taking into account the premium injection angle, these problems are reduced significantly as compared to those in conventional square-wave methods. Hence, the proposed method increases the sensorless driver efficiency and its application scope. The effectiveness of the proposed method is then confirmed with computer simulation and experimental tests. Experimental comparisons at the same injection frequency and injection effective voltage show that the performance of the proposed method is beneficial. All experiments were performed on a IPMSM with V-shaped PMs which is used in a refrigerator compressor.

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