A universal restart strategy for permanent magnet synchronous machines

In many industrial settings, momentary power disruptions commonly occur, resulting in tripping of large electric machines, which then have to be brought to zero speed before the machine can be restarted. This approach can result in frequent interruptions in an industrial process, which can have negative effects on productivity. A more practical control implementation would restart the machine back to the original speed as soon as power is restored, not having to wait for the machine to be at a standstill. This concept is known as flying restart. In this paper we propose an approach to implement the universal restart for PMSM through a simple identification algorithm which determines the speed and position of the machine back-emf so that the correct voltage vector can be applied and thus minimize the inrush current during the restart. Beyond the development of the basic algorithm, implementation issues will be considered to provide general guideline for the application of the developed algorithm.