Electrostatic Shielding for Bearing Current Mitigation - An Analysis of its Thermal Impact on the Motor

Abstract

This work presents a study on the use of electrostatic shields to reduce bearing currents (both Electrostatic discharge machining and circulating currents), focusing on its thermal impact on the motor operation. 2-D finite element models are utilized to analyze the temperature distribution inside the coil winding slot of motors both with and without shielding. The results show that the shielding device can be used with a negligible influence on the temperature rise inside the slot. In addition, it is demonstrated that for some shield configurations, the stator winding eddy current loss can be attenuated. In such cases, the shield presence can also lead to a temperature reduction in the stator conductors. Furthermore, the developed models can be expanded to be used in the analysis of any other motor equipped with this type of solution, aiding the design and implementation of the shielding device. Keeping in mind that the majority of the motor failures are due to bearing problems, this paper contributes to the industry by addressing issues closely related to the reliability topic, such as solutions to increase the motor availability, which is the very case of the shielding device.