초록 ▼

Power is provided to the stator windings of an AC machine which includes a component at the fundamental drive frequency for the machine and a superimposed signal component which is at a substantially higher frequency than the drive power. The rotor has saliencies which result in a change in impedanc

Power is provided to the stator windings of an AC machine which includes a component at the fundamental drive frequency for the machine and a superimposed signal component which is at a substantially higher frequency than the drive power. The rotor has saliencies which result in a change in impedance as seen at the stator windings to the high frequency excitation signal as a periodic function of rotor rotational position. Such saliencies are inherent in some permanent magnet synchronous and all synchronous reluctance machines, and may be provided by appropriate modification of the rotor of induction machines. The stator response at the signal frequency is then detected to provide a correlation between the response at the signal frequency and the rotor position. The detection of the response at the signal frequency is preferably carried out by a heterodyne detection process, by mixing signals at the signal frequency with the measured stator currents, and filtering the mixed signals to isolate the signal indicative of the rotor position. Conventional squirrel cage induction motors can be provided with sufficient spatial variations in the stator winding impedance as a function of rotor position in various ways, including varying the depth and/or width of the slots over the rotor conductive bars, by varying the cross-section of the bars, or by filling or partially filling some of the slots.

대표청구항 ▼

A motor drive for providing drive power to polyphase AC motors such as motors of the type which have stator windings and a rotor which is constructed to provide impedance as seen by the stator windings which varies as a periodic function of the rotational position of the rotor, comprising: (a) drive

A motor drive for providing drive power to polyphase AC motors such as motors of the type which have stator windings and a rotor which is constructed to provide impedance as seen by the stator windings which varies as a periodic function of the rotational position of the rotor, comprising: (a) drive means, having output supply lines which can be connected to the stator windings, for providing polyphase AC drive power at a fundamental drive frequency to a motor connected to the output supply lines to receive the AC drive power and for also providing balanced polyphase power to the output supply lines at a signal frequency which is substantially higher than the drive frequency; (b) sensors connected to the output supply lines sensing the response of the motor to the power provided by the drive means and providing output signals indicative of the response; and (c) a heterodyne demodulator connected to receive the signals from the sensors and mix a signal which is a function of the high signal frequency with the response signals from the sensors to provide a signal indicative of the rotational position of the rotor.