Method of detecting lubricant degradation in an electrical machine

A computer program product comprising:

• a non-transitory computer readable medium;
• and
• a computer program stored in the computer readable medium, the computer program including computer code which when executed by processing circuitry of a control system causes the control system to perform the steps of:
• a) obtaining, via temperature sensor, a first outer bearing ring temperature,
• b) operating a power converter to change the speed of the electrical machine,
• c) obtaining, via the temperature sensor, a second outer bearing ring temperature when the speed has changed,
• d) determining a thermal response value of the outer bearing ring based on the first outer bearing ring temperature and the second outer bearing ring temperature,
• e) comparing the thermal response value with a reference thermal response value for the same speed change as in step b), and
• f) in case the thermal response value differs from the reference thermal response value, generating a control signal to trigger an alert indicative of lubricant degradation.

A control system for detecting degradation of a lubricant in a bearing of an electrical machine, comprising:

• processing circuitry, and
• a storage medium having a computer code, which when executed by the processing circuitry causes the control system to perform the steps of:
• a) obtaining, via a temperature sensor, a first outer bearing ring temperature,
• b) operating a power converter to change the speed of the electrical machine,
• c) obtaining, via the temperature sensor, a second outer bearing ring temperature when the speed has changed,
• d) determining a thermal response value of the outer bearing ring based on the first outer bearing ring temperature and the second outer bearing ring temperature,
• e) comparing the thermal response value with a reference thermal response value for the same speed change as in step b), and
• f) in case the thermal response value differs from the reference thermal response value, generating a control signal to trigger an alert indicative of lubricant degradation.

An electrical machine assembly comprising:

• an electrical machine provided with a bearing including an outer bearing ring,
• a temperature sensor configured to measure the temperature of the outer bearing ring, and
• a control system including:
• a processing circuitry,
• a storage medium having a computer code, which when executed by the processing circuitry causes the control system to perform the steps of:
• a) obtaining, via the temperature sensor, a first outer bearing ring temperature,
• b) operating a power converter to change the speed of the electrical machine,
• c) obtaining, via the temperature sensor, a second outer bearing ring temperature when the speed has changed,
• d) determining a thermal response value of the outer bearing ring based on the first outer bearing ring temperature and the second outer bearing ring temperature,
• e) comparing the thermal response value with a reference thermal response value for the same speed change as in step b),
• f) in case the thermal response value differs from the reference thermal response value, generating a control signal to trigger an alert indicative of lubricant degradation, and
• wherein the control system is configured to receive measurements of an outer bearing ring temperature from the temperature sensor and configured to control the electrical machine.