Method and apparatus for evaluation of insulation in variable speed motors
First Claim
Patent Images
1. A method for evaluating insulation defects in a variable speed motor, comprising:
- determining a frequency spectrum of a drive signal applied to a variable speed motor;
selecting a sensor having a transfer function characterized by a cutoff at a frequency within an overlap of the frequency spectrum of the drive signal and a frequency spectrum of a discharge event, and having a rejection for reducing components of said drive signal to below a predetermined detection threshold for a discharge event;
applying to the sensor a signal S obtained from a drive input of said motor receiving said drive signal;
varying the voltage of the drive signal applied to said motor; and
determining a lowest voltage of the drive signal associated with inception of a discharge event represented in output of the sensor.
1 Assignment
0 Petitions
Accused Products
Abstract
A signal obtained from the drive input of a motor or an insulated winding is applied to a sensor that strongly rejects high frequency drive signal components yet passes discharge signal components. This allows discharge signal components to be detected in the presence of harmonics of the drive signal. The voltage of the drive signal may be varied so that the lowest drive signal voltage producing a discharge event may be determined. That voltage is the motor or winding'"'"'s corona inception voltage.
11 Citations
18 Claims
-
1. A method for evaluating insulation defects in a variable speed motor, comprising:
-
determining a frequency spectrum of a drive signal applied to a variable speed motor;
selecting a sensor having a transfer function characterized by a cutoff at a frequency within an overlap of the frequency spectrum of the drive signal and a frequency spectrum of a discharge event, and having a rejection for reducing components of said drive signal to below a predetermined detection threshold for a discharge event;
applying to the sensor a signal S obtained from a drive input of said motor receiving said drive signal;
varying the voltage of the drive signal applied to said motor; and
determining a lowest voltage of the drive signal associated with inception of a discharge event represented in output of the sensor. - View Dependent Claims (2, 3, 4, 5, 6, 7)
-
-
8. A system for on line analysis of a variable speed motor comprising:
-
a sensor receiving a signal obtained from a drive signal input of a variable speed motor driven by a pulse drive signal, the sensor having a transfer function for rejecting components in a frequency band of the drive signal that overlaps a frequency band of a signal produced by a discharge event, and for passing components of a signal produced by a discharge event;
a detector receiving output of the sensor for detecting components of a signal produced by a discharge event; and
an analyzer for determining a voltage of the drive signal at inception of a detected discharge event. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 17, 18)
-
-
16. An apparatus for determining the corona inception voltage of an insulated winding, comprising:
-
a transformer coupling a signal from an input of a winding driven by a high voltage drive signal comprised of a series of square pulses that approximate a sinusoidal waveform;
a filter, the transformer and the filter operating together to reject components of the signal passed by the means for coupling such that components of the signal that overlap components of signals produced by discharge events are suppressed to below a detection threshold of said components of signals produced by said discharge events; and
means for producing output indicative of a discharge event detected in an output signal of the filter.
-
Specification