Using Smart Converter to Obtain Traction-Machine Insulation Health State Information

Abstract:
In traction applications, inverter-fed machines are widely used, where they operate near and even above their rated values leading to high strains on the machine. Especially the winding insulation of the machine suffers from increased stress caused by high inverter switching frequencies and fast voltage rise times (high dv/dt rates) through the continuous development of new semiconductor technologies (silicon carbide SiC or gallium nitride GaN). A smart converter, which is a power inverter with integrated control, monitoring and protection functions, enables a safe and reliable operation of a drive. With an integrated smart online monitoring method by evaluating the current response after voltage step excitation, the detection of incipient insulation degradation is possible and enables that further maintenance tasks can be defined if necessary. With the usage of the integrated current sensors of the inverter and a low ADC sampling rate due to economic reasons, a special signal acquisition strategy is implemented to improve the performance of the method despite the limited hardware and software resources imposed by product constraints.