A Method of Sensing Line Voltages for Parameter Adaptation of Inverter-Fed Induction Motor Servo Drives

Moet high performance inverter—fed induction motor drive systems require signals corresponding to the input voltages of the motor for parameter adaptation. Low performance systems require the signals for stabilization. The voltage signals are used in the controller circuit and therefore requires isolation. Isolation of the voltage signals is not a cost-effective solution in low-power motor drive systems. The fact that the base drive signals to the transistor inverter are isolated makes them the ideal choice for the reconstruction of the motor line voltages. This paper describes a method of sensing line voltages from the base drive signals of the transistor inverter circuit. A step by step derivation of the voltage sensing algorithm is given which leads to a simple realization. The synthesized voltages are used in parameter adaptation for inverter-fed induction motor drives. The sensing scheme has been implemented on a laboratory prototype providing experimental results which are included in the paper.