Variable speed controller for an AC motor

摘要

To provide a trans-vector controller for an alternating current ("AC") motor that facilitates operating the secondary resistance of the AC motor without experimentally rotating the AC motor. In a preferred embodiment, the variable speed control circuit, including a secondary resistance value generating device, changes the direct current ("DC") exciting current and operates the secondary resistance of an induction motor by superimposing an AC signal with small amplitude outputted from a AC signal generator onto a reference current value immediately before the start of the induction motor in the state of DC excitation.