Speed control of a sensorless seven-phase Surface-mounted PM machines

This paper deals with the speed control of a position sensorless seven-phase Surface-mounted PM machine. A vectorial ccontrol is achieved using the first, the third and the fifth harmonic rotating dq-planes, the latter being used to sense the position in normal mode. In order to extend the low speed range, the control strategy and the plane used to estimate the position are modified at low speed. This approach is validated by time-step simulations. If the speed is large enough, experimental tests confirm the effectiveness of the speed control in normal mode when the position is sensed with the fifth harmonic. At lower speed, experiments show the possibility of using the third harmonic.