Method of controlling an electric motor, a system for controlling an electric motor and an electric motor

Abstract

A system of controlling an electric motor, a digital method of controlling an electric motor and an electric motor are described. The system of controlling an electric motor of N phases comprises a microcontroller (), an A/C converter () associated to the microcontroller (), a set of voltage meters (D) associated to the A/D converter (), a set of switches (SW) connected to an electric voltage (V) and associated to the microcontroller (), the microcontroller () selectively feeding, by means of at least two switches (SW) two phases (F) of the motor () with the voltage (V) during a period of time (T), the movement of the motor inducing the electric voltages (E), the set of meters (D) measuring the signals of electric voltages (f) and comparing these voltages with each other to determine the period of time (T). One describes also the calculation of a parameter, called H(r), used to adjust the instants of commutation according to the constructive type of the motor. The parameter depends upon the rotation of the motor. One also foresees the use of a digital filtering technique, to eliminate the effects of the modulation on the control method. The filtering is characterized by the arithmetic mean of the last k samples of each average electric voltage (f), these samples being synchronized with the period of modulation.