26th November 2018



On-Line Condition Monitoring for Diagnosis and Prognosis of Insulation Degradation of Inverter-fed Machines

A novel method is proposed to monitor ground-wall insulation of low voltage inverter-fed machines based on a multi-frequency measurement of equivalent insulation ground-wall capacitance and dissipation factor. Insulation degradation is continuously tracked via the capacitance and dissipation parameters. A link between ground-wall insulation capacitance and final lifetime is established. The relationship between capacitance progression and its value at final machine failure is used to develop a method for prognosis of the final failure time.

I. Tsyokhla, A. Griffo, J. Wang,
IEEE Transactions on Industrial Electronics, 2019

On-Line Motor Insulation Capacitance Monitoring Using Low-Cost Sensors

It has been demonstrated that the state of health of insulation can be evaluated on-line during machine operation with measurement of equivalent ground-wall capacitance, by measuring the commonmode leakage current generated by common mode voltage of standard two-level PWM converters. Low cost implementation of the monitoring system is key to wide adoption in industry. In this paper, inexpensive off-the shelf current sensors are evaluated for use in leakage current monitoring. A full low cost system is designed, built and tested. The testing emphasis the both the short term precision and long term accuracy of the measurement. It is shown that it is possible to use low-cost sensors for long term monitoring, with acceptable compromises

I. Tsyokhla, A. Griffo, J. Wang
IEEE Energy Conversion Congress and Expo ECCE 2019

Lifetime of Machines Undergoing Thermal Cycling Stress

In modern applications, electrical machines are facing increasing thermal cycling and resulting mechanical stress due to harsh variable loading, however there is little information in literature that shows the impact of severe cycling conditions on insulation health. An accelerated aging test is performed in this paper on seven motor stator samples that are operated under various thermal cycling conditions at high temperature. It is shown that there is a severe but predictable lifetime decrease with increased thermal cycling stress. The impact of this must be considered at the design stage for applications requiring high temperature cycling to ensure fulfillment of the required lifetime.

A. Griffo, I. Tsyokhla, J. Wang
IEEE Energy Conversion Congress and Expo ECCE 2019