Direct axis current utilization for intelligent sensorless permanent magnet synchronous drives

Permanent magnet synchronous drives can be operated with a nonzero d-axis current component in order to obtain significant advantages. On the one hand, the sensorless position estimation in the low speed range including standstill can be improved by amplifying the saturation effects of the machine. Depending on the machine, this may cause an accuracy improvement of more than 30%. On the other hand, the direct axis current component can be utilized to realize a novel brake concept of the machine with minimum hardware effort. The hereby enabled saving of both the braking resistor and the position sensor yields an ultra low cost drive with very high power density.