Realization of the I/f control method for a high-speed permanent magnet motor

The I/f control is an open-loop method of control of PM machines in which the reference current is set proportionally to the electrical frequency while the voltage is generated through a current regulator. A realization of the method for control of a very high-speed synchronous PM motor is presented in the paper. To add necessary damping to the system, the controller uses modulation of the electrical frequency in the way which is frequently utilized in the V/f method for high-speed PM machines. Adequate current reference is obtained based on measurements of the no-load voltage and speed decay. Stable speed control is achieved throughout the whole speed range.