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Power Module STGIPS30C60-H - Boosttrap capacitor with a three phase output in low fundamental frequency.

Question asked by daniel45675 on Dec 22, 2014
have a switching frequency of 16 kHz, bootstrap  capacitor of 5 uF in each half bridge. After 10 Hz of fundmental frequency all is ok about output wave voltage, but when I decrease fundamental freq, bootstrap capacitors have to discharge more time than when working in more fundamental freq, causing wrong pulses in the three phase output that finally I want to connect to a 1Hp induction motor. In the image attachment I show you, upside, one of the three phase output voltage, and below, the voltage of bootstrap capacitor corresponding to one of two half bridge IGBT of the output voltage show upside.

I wonder if you can recommend a solution to get a better output voltage.