In an AC motor drive, the output stage is the power-switching block that converts the DC-link voltage into the variable-frequency three-phase voltage applied to the motor. This switching is typically done with IGBT (Insulated Gate Bipolar Transistor) modules.
Core function
The IGBTs are driven by a gate driver circuit using a PWM signal. If switching speed and dead-time are not set correctly, a phase short (shoot-through) occurs and the module is instantly damaged.
Common mistakeReplacing a failed IGBT without checking the gate-driver circuit is the most common cause of repeat failure.
Fault symptoms
- Sudden trip with an overcurrent fault
- Fault persists even when run without a motor
- Measured phase-to-phase or phase-to-DC short on the module
Typical measurement values
- Collector-Emitter (off)
- High impedance (MΩ)
- Body-diode drop
- ~0.3–0.5 V (healthy)
At the ELKAR lab, IGBT and gate-driver repair is done in an ESD-protected environment with a 1-year warranty after load testing.
Related Faults
Related Topics
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