Improvement of Spatial Resolution of Space Charge Measurement at High Temperature using PEA Method

Spatial resolution of space charge distribution measurement using PEA (Pulsed electro-acoustic) method at high temperature was improved by applying a thin piezo-electric sensor film with a glass substrate. Partial discharge generation is one of problems to be solved in motor winding when the driving voltage of motor is elevated to downsize it. In the high-voltage drive of motors, the space charge accumulation in the thin insulating layer of the winding is said to affect the partial discharge generation. Therefore, it is necessary to evaluate the space charge accumulation in thin insulating materials of the winding. Especially, since high temperature characteristics of the partial discharge is said to be important, the measurement of the space charge distribution for the thin insulating layer is required at high temperature. However, the spatial resolution of the ordinary PEA measurement system was not enough to measure the space charge distribution in such thin insulating materials for windings, especially at high temperature. Therefore, the PEA measurement system was improved using a thin sensor film, which is available at a relatively high temperature, as a sensor of the PEA measurement system with a high heat-resistant glass substrate. In this report, a typical measurement result of the space charge distribution observed in 25 µm-thick polyimide sample at 80°C is introduced.