Operation of the permanent magnet synchronous machine without a mechanical sensor

Permanent synchronous machines (PSM) score against asynchronous machines because of their simple control structure and a higher efficiency due to the small rotor losses. The necessity of sensors for angular speed and position represents a considerable restriction of robustness. Because of this, it is the aim of much research to substitute the mechanical sensors with more sophisticated models using only electrical quantities. If a certain angular velocity is exceeded, it is possible to determine the electrical rotor position from the EMF, which can simply be calculated from electrical terminal quantities (Schroedl and Stefan (1988)). At standstill and at low angular velocity, the EMF decreases and thus cannot be utilized to detect the rotor position. The author presents a new method for estimating angular position, velocity and load torque of PSMs. The method works properly at any speed and load condition. It combines the INFORM-principle (`indirect flux detection by online reactance measurement´) by Schroedl and Stefan and the Kalman filter technique