Return to Answer

With a peak voltage > 325V to a boost cap into a UF4004 less than 1 Ohm might be excessive capacitance. 100 nF is around 13 ohms at 100kHz and lower at the harmonics resulting in a peak current of 32A at 100Khz.

Consider that this cap only needs to be much greater than the gate load to create a boost voltage. Consider a much smaller cap like < 10nF.

But on second thought, you are probably using PWM much lower and so the rate of Vrms frequency and thus acceleration current of the motor df/dt can be as much as 10 x the rated full load current (depending on Vpk/DCR) might have been the cause of failure.

Normally VFD's will modulate PWM with a constant V/f ratio as it speeds up.

Finally, always verify your parasitic crosstalk from mutual capacitance and ESL inductance do not skew the dead-time of your commutation. Test with a resistive load such as a tungsten lamp before validating your design assumptions on a motor.

With a peak voltage > 325V to a boost cap into a UF4004 less than 1 Ohm might be excessive capacitance. 100 nF is around 13 ohms at 100kHz and lower at the harmonics resulting in a peak current of 32A at 100Khz. But for the 1st pulse from a square wave, the current will depend on the ESR of the cap and series R for RC risetime. Ic=CdV/dt-V/ESR

Consider that this cap only needs to be much greater than the gate load to create a boost voltage. Consider a much smaller cap like < 10nF.

But on second thought, you are probably using PWM much lower and so the rate of Vrms frequency and thus acceleration current of the motor df/dt can be as much as 10 x the rated full load current (depending on Vpk/DCR) might have been the cause of failure.

Normally VFD's will modulate PWM with a constant V/f ratio as it speeds up.

Finally, always verify your parasitic crosstalk from mutual capacitance and ESL inductance do not skew the dead-time of your commutation. Test with a resistive load such as a tungsten lamp before validating your design assumptions on a motor.

With a peak voltage > 325V to a boost cap into a UF4004 less than 1 Ohm might be excessive capacitance. 100 nF is around 13 ohms at 100kHz and lower at the harmonics resulting in a peak current of 32A at 100Khz.

Consider that this cap only needs to be much greater than the gate load to create a boost voltage. Consider a much smaller cap like < 10nF.

But on second thought, you are probably using PWM much lower and so the rate of frequency and thus acceleration current of the motor df/dt can be as much as 10 x the rated full load current (depending on Vpk/DCR) might have been the cause of failure.

With a peak voltage > 325V to a boost cap into a UF4004 less than 1 Ohm might be excessive capacitance. 100 nF is around 13 ohms at 100kHz and lower at the harmonics resulting in a peak current of 32A at 100Khz.

Consider that this cap only needs to be much greater than the gate load to create a boost voltage. Consider a much smaller cap like < 10nF.

But on second thought, you are probably using PWM much lower and so the rate of Vrms frequency and thus acceleration current of the motor df/dt can be as much as 10 x the rated full load current (depending on Vpk/DCR) might have been the cause of failure.

Normally VFD's will modulate PWM with a constant V/f ratio as it speeds up.

Finally, always verify your parasitic crosstalk from mutual capacitance and ESL inductance do not skew the dead-time of your commutation. Test with a resistive load such as a tungsten lamp before validating your design assumptions on a motor.

With a peak voltage > 325V to a boost cap into a UF4004 less than 1 Ohm might be excessive capacitance. 100 nF is around 13 ohms at 100kHz and lower at the harmonics resulting in a peak current of 32A at 100Khz.

Consider that this cap only needs to be much greater than the gate load to create a boost voltage. Consider a much smaller cap like < 10nF.

With a peak voltage > 325V to a boost cap into a UF4004 less than 1 Ohm might be excessive capacitance. 100 nF is around 13 ohms at 100kHz and lower at the harmonics resulting in a peak current of 32A at 100Khz.

Consider that this cap only needs to be much greater than the gate load to create a boost voltage. Consider a much smaller cap like < 10nF.

But on second thought, you are probably using PWM much lower and so the rate of frequency and thus acceleration current of the motor df/dt can be as much as 10 x the rated full load current (depending on Vpk/DCR) might have been the cause of failure.