A novel modified archimedes spiral antenna for partial discharge detection in inverter-fed electrical machines

This paper proposes a modified Archimedes Spiral antenna (MASA) for detecting partial discharge (PD) in pulse-width modulation- (PWM) controlled inverter-fed electrical machines. The occurrence of PD is both a source and indication of insulation degradation in electrical machines. With the widespread electrification of transportation and many reliability critical applications, PD phenomenon remains a big challenge as it deteriorates the insulation system and can lead to premature failure of an electrical machine. Online condition monitoring using embedded sensors to detect PD in the insulation system has been suggested in the literature but has been difficult to implement due to geometrical constraints and bandwidth limitation of existing sensors. The proposed MASA overcomes these challenges. The design is based on the modification of polar coordinates equation of Archimedes spiral and its operation demonstrates how the geometrical constraint which inhibits other sensors can be overcome by physically integrating it within the end-winding of a machine. With its ultra-wide bandwidth (0.3 – 2 GHz), it is capable of effectively capturing the expected spectrum of PD in inverter-fed electrical machines, which is verified experimentally. Another novelty of the proposed sensor is its inherent ability to discriminate between commutation disturbance and PD pulses without the need for an external high-pass filter, making the solution suitable for condition monitoring and PD detection in inverter-fed electrical machine in service.