We are designing high power traction inverter to drive three phase PMSM. When operating at 330Vdc bus voltage we see the gate signal toggling but IGBT is not responding. Please see the photo attached. We are using NPT type IGBT which can handle 1200V/150A. When we see this issue, IGBTs are drawing 30A. Gate driver is going from +15V to -8V. Can someone help us to debug this problem?
Take a look at the gate current. Although we think IGBT is a component only drove by voltage, it request some current to change the state. The series resistance of the gate drive circuit limits this current. So, try to regulate this resistance to increase the gate current.
take a look at these references,maybe they can be useful:
http://www.ppi-uk.com/wp-content/uploads/AN-7003_Gate_Resistor-Principles_and_Applications_rev00.pdf
http://www.ppi-uk.com/wp-content/uploads/AN-7004_IGBT_Driver_Calculation_rev00.pdf
Cleiton, Riccardo,
Thanks for pointing out that the instantaneous gate current could be low in our gate diver power supply. We checked that manually and the maximum instantaneous current was around 2.5A.
We tested this with several different gate resistors and several different PWM frequencies. And we tested the same igbt with a pure resistive load but we did not find latch ups. We only see this latch ups when the motor is running. Even with the motor this only happens for currents higher than a certain (Ic) current value . That certain current value is different for different (Rg) gate resistor values and different PWM frequencies.
When the same set up is tested on a resistive load no latch up is noticed.
This is the doubt I am having now. If this is happening due to a inability to provide sufficient gate current, why does not it occur in both under motor and ressistive load.
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