Rotor Position Sensorless Estimation of High Efficiency Synchronous Reluctance Motor at Low Speed for Realization of Low-Carbon Society

The global warming is serious problem, and the reduction of CO2 emissions, namely, the realization of low-carbon society is desired. Therefore, it is desired that the conventional servomotors widely used in the industrial community are replaced with the synchronous reluctance motors (SynRMs) whose efficiency is high even though they have no magnets. The rotor position information is necessary to use SynRMs as servomotors, and several rotor position sensorless estimation methods have been proposed. These methods, however, have difficulties at low speed when the voltage signal necessary to estimate rotor position is very small. The authors have proposed a new position estimation method using high-frequency extended e.m.f. (EEMF) in which high-frequency voltage and current are calculated using a disturbance observer. Simulations have shown the new method to be very useful. In this paper, the feedback control of the high-frequency currents is proposed for becoming able to estimate the rotor position even though the high-frequency currents are very small when the checking of the new proposed method by experiments. And the experimental results show that it is possible to drive the motor at low speeds with the coordinate transformation used the position   estimated by the new proposed method.