Patent ID: 8384338

Claim:
A system to estimate resistance of a stator winding of an AC motor, the system comprising: an AC motor drive having an input connectable to an AC source and an output connectable to an input terminal of an AC motor, the AC motor drive comprising: a pulse width modulation (PWM) converter having a plurality of switches therein to control current flow and terminal voltages in the AC motor; and a control system connected to the PWM converter and configured to: generate a command signal to cause the PWM converter to control an output of the AC motor drive corresponding to an input to the AC motor; selectively generate a modified command signal to cause the PWM converter to inject a DC signal into the output of the AC motor drive, with the control system being configured to control and set an amplitude of the injected DC signal being set such that torque pulsations in the AC motor caused by the injected DC signal are maintained within a preset tolerance range; decompose the torque pulsations in the AC motor into components at multiples of the fundamental frequency; and analyze the components of the torque pulsations and their correlation to the injected DC signal using sequence analysis theory in the d-q reference frame; and determine a stator winding resistance of the AC motor based on the DC signal of at least one of the voltage and current.