Pulsating high-frequency signal injection has the problem of multiple zero-crossings when the phase current crosses zero-point, which deteriorates the distortion of highfrequency current caused by the zero-current-clamping effect. Thus, the accuracy of position observation is affected. To suppress multiple zero-crossings, improved sinusoidal and square-wave signal injection schemes are proposed. First, the relationship between the injection angle of the high-frequency signal and the phase of the high-frequency response current amplitude function is analysed. Based on the relationship, a special injection angle is calculated. By injecting the pulsating signal in the obtained special angle, the phase of the high-frequency current is shifted. The amplitude of the high-frequency response current is minimum when the fundamental frequency current crosses zero, thus reducing zero-crossing points of phase current. Furthermore, the error signal extraction scheme applicable to arbitrary angle injection is designed to observe rotor position. The proposed high-frequency signal injection method minimises the zero-crossings of the phase current at any value of the torque angle. Both of the novel sinusoidal pulsating injection sensorless control scheme and square-wave injection sensorless control scheme are confirmed by experiments on a 2.2-kW interior permanent magnet synchronous motor (IPMSM) drive platform.