Practical Issues in Sensorless Control of PM Brushless Machines Using Third-Harmonic Back-EMF

This paper presents some practical issues in the utility of third-harmonic back-EMF in sensorless control of PM brushless machines, including detection methods of the third-harmonic EMF, open-loop starting and normal operation of the machines in both BLDC and BLAC modes, as well as restrictions of the sensorless control