Equivalent Circuit of Linear Pulse Motor

Abstract

A linear pulse motor is used for open loop position control with no position detection. However, in order to realize the more stable and higher speed control without hunting or pull-out, it is desirable to control the motor in closed loop with the position of the magnetic poles fed back to the phase of input voltages or input currents. It is necessary to derive an equivalent circuit to explain the steady-state and transient characteristics in order to find an adequate control rule for high performance control of the linear pulse motor.
In this paper, magnetic equivalent circuit is obtained, based on the structure of the motor, and then the equivalent circuit of the motor is derived by solving equations for the magnetic equivalent circuit.
Next, parameters of the equivalent circuit are determined from the frequency characteristics of impedance when the motor is locked and the relationships between terminal voltage and motor speed when the motor is not excited. Then, characteristics of the maximum thrust force of the motor and the phase between the speed e. m. f. of the motor and input voltages or input currents versus the motor speed to obtain the maximum thrust force are calculated using the equivalent circuit. Validity of equivalent circuit is confirmed by experiments.