Why does Fuji recommend to connect a resistor between G-E terminals of IGBT terminal?

If voltage is applied between C-E while the gate is open, the divided voltage by Cres and Cies is applied to the gate, as well. This may lead to a gate breakdown from overvoltage, or a breakdown by heating from elevated device temperature due to a unstable ON state of the gate. As such, for the inverter circuit, the sequence where voltage between C-E is applied after gate circuit is established is recommended. Even if this sequence is not set up, a resistor inserted between G-E to stabilize the gate potential will help to avoid this breakdown phenomenon. In that case, a resistance of about 10kΩ against open (infinite resistance) is recommended. If the resistance is too small, you will see problems such as lower gate voltage than the designed value and an increased current consumption in the drive circuit (because the gate voltage will be the one divided with gate resistance RG.) Therefore, a resistance sufficiently low against the open value is enough and you don’t need to change it according to the current rating of the device.

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