Gm Global Technolgoy Operations, Inc.

Siwei Cheng

Yilu Zhang

Mutasim Abdurrahman Salman

Lei Hao

A system and method for determining the speed of an alternator, for example, a vehicle alternator. The method includes measuring the current or voltage of a vehicle battery for a predetermined period of time, and then notch filtering the measured current or voltage signal to remove known harmonics. A limited data point Fast Fourier Transform (FFT) spectrum analysis operation is performed to identify the frequency peaks in the filtered signal, where the highest peak represents a ripple current on the DC alternator signal. The highest peak in the FFT signal is identified, and an interpolation process is performed between that peak and an adjacent peak in the data to identify the actual frequency of the ripple current. The ripple current is then converted to the speed of the alternator.

Alternator speed estimation using spectrum analysis

A method for determining a temperature of an electric motor including stator windings includes injecting an AC current into a D-axis current of a stator winding at a frequency that is synchronized with a control frequency of the electric motor, determining a DC-phase current, determining a resistance of the stator winding corresponding to the DC-phase current and an applied voltage, and determining a temperature of the electric motor as a function of the resistance of the stator winding.

Method and apparatus for thermally monitoring a permanent magnet electric motor

A method for detecting whether the stator in a vehicle alternator has a turn-to-turn short circuit. The method includes determining an output current or voltage signal of the alternator, where the output current or voltage signal includes a ripple current frequency as a result of an AC-to-DC conversion. The method determines the speed of the alternator and a current output of the alternator. The method then determines the ripple current frequency of the alternator from the alternator speed, and determines a winding frequency from the ripple current frequency. The method performs an FFT analysis on the voltage and current signal, determines an amplitude of the winding frequency and compares the amplitude of the winding frequency to a predetermined amplitude, where if the difference exceeds a predetermined threshold, a turn-to-turn short circuit is likely occurring.

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Atlanta, GA, United States of America

Siwei Cheng