Method and apparatus for predicting winding failure using zero crossing times
First Claim
1. A method to be used with a motor controller, the motor controller providing stator winding currents at a frequency of X cycles per second and indicating zero crossing times when each current is zero, a set of ideal rotor signal data, an acceptable rotor error value, and a sampling period, the motor being of a design having p poles, the method predicting rotor winding failure, the method comprising the steps of:
- generating a sequence of error signals over the sampling period, each error signal indicating the period between consecutive current zero crossings, the plurality of error signals together forming an error signal spectrum;
analyzing the error signal spectrum to determine a signal amplitude of a rotor component within a region of interest, the region of interest being frequencies between K((2X/p)-n) and K(2X/p) Hz, where n is less than 2x/p and K is an integer;
determining a slip value indicating the difference in stator current frequency and the rotor frequency;
multiplying the signal amplitude by the slip value to produce a rotor signal; and
comparing the rotor signal to the ideal rotor signal data to produce a rotor error signal indicative of the degree of rotor failure.
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Accused Products
Abstract
A method and apparatus to be used with a motor controller for determining the degree of rotor winding failure and stator winding failure using current zero crossing times of the stator winding currents. An error signal sequence, consisting of phase angle errors between consecutive zero crossings over a sampling period, is generated and analyzed in different regions of interest in either the time or frequency domain, producing signals with varying amplitudes, the signal amplitudes together with other motor parameter measurements being used to determine the degree of rotor winding failure and stator winding failure.
45 Citations
23 Claims
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1. A method to be used with a motor controller, the motor controller providing stator winding currents at a frequency of X cycles per second and indicating zero crossing times when each current is zero, a set of ideal rotor signal data, an acceptable rotor error value, and a sampling period, the motor being of a design having p poles, the method predicting rotor winding failure, the method comprising the steps of:
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generating a sequence of error signals over the sampling period, each error signal indicating the period between consecutive current zero crossings, the plurality of error signals together forming an error signal spectrum;
analyzing the error signal spectrum to determine a signal amplitude of a rotor component within a region of interest, the region of interest being frequencies between K((2X/p)-n) and K(2X/p) Hz, where n is less than 2x/p and K is an integer;determining a slip value indicating the difference in stator current frequency and the rotor frequency; multiplying the signal amplitude by the slip value to produce a rotor signal; and comparing the rotor signal to the ideal rotor signal data to produce a rotor error signal indicative of the degree of rotor failure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An apparatus to be used with a motor controller, the motor controller providing stator winding currents at a frequency of X Hz and indicating zero crossing times when each current is zero, a set of ideal rotor signal data, an acceptable rotor error value, and a sampling period, the motor being of a design having p poles, the apparatus for predicting rotor winding failure, the apparatus comprising:
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a period calculator to receive consecutive zero crossing times from the controller over the sampling period, subtracts each zero crossing time from a preceding consecutive zero crossing time to produce a plurality of difference values, and subtracts 1/6th of the stator winding current cycle period from each difference value to produce a plurality of error signals, the plurality of error signals together forming an error signal sequence; a frequency analyzer to analyze the error signal sequence to determine a signal amplitude of a rotor component within a frequency region of interest between K((2X/p)-n) and K(2X/p) Hz, where n is less than 2X/p and K is an integer; a slip calculator to determines a slip value indicating the difference in stator winding current frequency and the rotor frequency; a rotor calculator to multiply the signal amplitude by the slip value to produce a rotor signal; and a comparator to compare the rotor condition signal to the rotor condition signal of the motor when it was healthy to produce a rotor error signal indicative of the degree of rotor failure. - View Dependent Claims (10, 11, 12, 13)
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14. A method to be used with a motor controller, the motor controller providing stator winding currents at a frequency of 60 Hz and indicating zero crossing times when each current is zero, a set of ideal rotor signal data, an acceptable rotor error value, and a sampling period, the motor being of a design having 4 poles, the method predicting rotor winding failure, the method comprising the steps of:
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receiving consecutive zero crossing times from the motor controller; subtracting each zero crossing time from a preceding consecutive zero crossing time to produce a plurality of difference values; subtracting 1/6th of the stator winding current cycle period from each difference value to produce a plurality of error signals, each error signal indicating the period between consecutive current zero crossings, the plurality of error signals together forming an error signal sequence; passing the error signal sequence through a bandpass filter having a bandpass between 27 and 30 Hz to produce a rotor component; determining a signal frequency and a signal amplitude of the rotor component; dividing the signal frequency by 30 to produce a frequency ratio; subtracting the frequency ratio from the integer one to produce a slip value; multiplying the signal amplitude by the slip value to produce a rotor condition signal; comparing the rotor condition signal to the healthy rotor condition signal data to produce a rotor error signal; and displaying the rotor error signal.
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15. A method to be used with a motor controller, the motor controller providing three phase supply line voltages and stator winding currents at a frequency of X Hz and indicating zero crossing times when each current is zero, the controller also providing a set of stator signal data and a sampling period, the motor being of a design having p poles, the method predicting stator winding failure, the method comprising the steps of:
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generating a plurality of error signals over the sampling period, each error signal indicating the time between consecutive current zero crossings, the plurality of error signals together forming an error signal sequence; analyzing the error signal sequence to determine a harmonic amplitude of a stator component of the error signal spectrum at 2X Hz, the harmonic amplitude being the first element in a coordinate pair; sampling supply voltages over the sampling period; splitting the supply voltages into a positive sequence voltage and a negative sequence voltage; dividing the negative sequence voltage by the positive sequence voltage to produce a voltage ratio, the voltage ratio being the second coordinate in the coordinate pair, the harmonic amplitude and the voltage ratio together forming a coordinate pair; and comparing the coordinate pair to the stator signal data to produce a stator error signal. - View Dependent Claims (16, 17, 18, 19)
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20. An apparatus to be used with a motor controller, the motor controller providing three phase supply line voltages and stator winding currents at a frequency of X Hz and indicating zero crossing times when each current is zero, the controller also providing a set of stator signal data and a sampling period, the motor being of a design having p poles, the apparatus for predicting stator winding failure, the apparatus comprising:
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a period calculator that receives consecutive zero crossing times from the controller over the sampling period, subtracts each zero crossing time from a preceding consecutive zero crossing time to produce a plurality of difference values, and subtracts 1/6th of the stator winding supply voltage cycle period from each difference value to produce a plurality of error signals the error signals together forming an error signal sequence; a frequency analyzer to analyzes the error signal sequence to determine a harmonic amplitude of a stator component at 2X Hz, the harmonic amplitude being the first element in a coordinate pair; a sensor for sampling supply voltages over the sampling period; a voltage splitter that splits the supply voltages into a positive sequence voltage and a negative sequence voltage; a voltage divider that divides the negative sequence voltage by the positive sequence voltage to produce a voltage ratio, the voltage ratio being the second coordinate in the coordinate pair, the harmonic amplitude and the voltage ratio together forming a coordinate pair; a comparator that compares the coordinate pair to the stator signal data to produce a stator error signal; and a display which receives and displays the stator error signal. - View Dependent Claims (21)
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22. A method to be used with a motor controller, the motor controller providing three phase supply line voltages and stator winding currents at a frequency of X Hz and indicating zero crossing times when each current is zero, the controller also providing a set of stator signal data and a sampling period, the motor being of a design having p poles, the method predicting stator winding failure, the method comprising the steps of:
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receiving consecutive zero crossing times from the motor controller; subtracting each zero crossing time from a preceding consecutive zero crossing time to produce a plurality of difference values; subtracting 1/6th of the stator period from each difference value to produce a plurality of error signals, the error signals together forming an error signal sequence; passing the error signal spectrum through a bandpass filter having a bandpass at 2X Hz to produce a stator signal; determining a harmonic amplitude of the stator signal, the harmonic amplitude being the first element in a coordinate pair; sampling supply voltages over the sampling period; splitting the supply voltages into a positive sequence voltage and a negative sequence voltage; dividing the negative sequence voltage by the positive sequence voltage to produce a voltage ratio, the voltage ratio being the second coordinate in the coordinate pair, the harmonic amplitude and the voltage ratio together forming a coordinate pair; and comparing the coordinate pair to the stator signal data to produce a stator error signal. - View Dependent Claims (23)
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Specification