Ultra high speed drive with permanent magnet synchronous motors and hardware based field oriented control

Ultra high speed drive applications like PCB drilling machines require mechanical speeds of 200,000 rpm and more. Usual solutions consist of a frequency inverter with induction motors or synchronous motors - the latter provide better efficiency resulting in less thermal losses. The practical problem, however, is not the efficiency during the drilling operation - it´s the time needed for acceleration or deceleration during a tool change. As a frequency inverter does not provide control features with respect to speed and/or position, drive acceleration needs around a minute. A sensorless field oriented control for ultra high speed machines can improve the acceleration and deceleration times significantly. Of course, an encoder on the motor shaft must be avoided. According to this contribution the field oriented control is performed by a hardware without processor or controller, as these are not fast enough to ensure the high frequencies necessary in that application. Experimental results prove the drive to accelerate and decelerate much faster than with a frequency inverter without speed/position control. The drive was operated properly until 250,000 rpm.