| Abstract |
The position sensors used in the synchronous PM motors (brushless DC and stepping motors) in order to switch the different phase transistors are generally of the Hall type. Our laboratory developed different solutions for the replacement of such sensors by an indirect position measurement, based on the back EMF detection. The present paper describes two different solutions. The back EMF being directly related to the mechanical and magnetical parameters, it is possible to deduce the necessary informations on the speed and the instantaneous rotor position. The proposed methods are of two types 1) the back EMF detection through the integrated voltage equations; 2) the third back EMF harmonic detection. At standstill, no position information can be detected. A starting and self-commutation method of the motor is proposed. Both solutions can be applied to a chopper power supply. Applications example, as a brushless DC motor for an artificial heart, are presented. |
