MOTOR CONTROLLER FOR DETERMINING A POSITION OF A ROTOR OF AN AC MOTOR, AC MOTOR SYSTEM, AND METHOD OF DETERMINING A POSITION OF A ROTOR OF AN AC MOTOR

摘要

A motor controller (4) for determining a position of a rotor (9) of an AC motor, the motor controller comprises a control input (12) for receiving a control signal, an output (13) for providing a power control signal for controlling power applied to a stator (7) of the AC motor, and an input (14) for receiving a feedback signal representative of the current in the stator. The control input (12) and output (13) are coupled by a reference path, and the input (14) is coupled to the control input (12) by a feedback path. A carrier signal injection element (42) injects a high frequency carrier signal in the reference path at an injection node. The motor controller (4) is arranged to generate the power control signal in dependence on the control signal, the feedback signal, and the high frequency carrier signal. A position determining element (18) generates a position signal representing the position of the rotor in dependence on the feedback signal which includes a carrier signal component comprising rotor position information. The motor controller (4) further comprises a filter block (39) coupled between the control input (12) and the injection node in the reference path for filtering signals in the reference path in a frequency range including the frequency of the high frequency carrier signal.