Isolation design considerations for power supply of medium voltage silicon carbide gate drivers

Single switch capable of blocking 10 kV and higher voltages are presently being developed and demand improved gate drivers for their functioning. Induction based gate drivers have been the foremost solutions in this regard. Design challenges that have been outlined for these drivers are low coupling capacitance, strong magnetic coupling and smaller dimensions with isolation not considered in depth. In this paper, first isolation requirements and its physical realization guidelines are provided from IEC 61800-5-1 for electric drives application. Based on study, two system insulation designs: single and double PCB are derived for lower MV and higher MV system respectively. Current loop gate driver with double PCB design is found to be practical and economical solution for higher MV power electronics systems. Afterwards, shortcomings of three state of art induction solutions at both system and magnetic link level is discussed. Improved transformers with primary MV cable providing mandatory solid insulation are fabricated. It is shown through impedance measurements that the cable has negative effect on the magnetizing inductance and coupling capacitance compared to state of art transformer solution. At the end, both set of transformers are tested with 64 kV impulse and 32 kV overvoltage with only improved transformers showing positive results.