IGBT Saturation / Short Circuit

What does 7 mean?

This fault indicates a serious hardware failure such as a defective IGBT, a de-saturation short circuit within an IGBT, or a short circuit/overload in the brake resistor. This fault suggests significant damage to the power stage and continuing operation can cause further severe damage or injury.

• Catastrophic short circuit (phase-to-phase or phase-to-ground) on the motor output terminals (T1, T2, T3) due to damaged motor cables.
• Internal failure of an Insulated Gate Bipolar Transistor (IGBT) module in the inverter bridge, leading to a short circuit condition.
• Brake resistor short-circuited or overloaded, drawing excessive current from the DC bus and exceeding IGBT ratings.
• Driver circuit fault within the IGBT gate drive unit, causing improper switching or saturation detection failure.
• Excessive current demand from the motor beyond the drive's output capabilities, stressing the IGBTs.

Click steps to track your progress.

1. 1

   Disconnect the motor cables (U, V, W) from the drive output terminals (T1, T2, T3).

2. 2

   Measure the resistance between each output phase terminal (T1-T2, T2-T3, T3-T1) and from each phase to the PE terminal (ground). Look for near-zero resistance.

3. 3

   If a brake resistor is installed, disconnect it and measure its resistance (e.g., terminals BR+ and BR-) for a short circuit or open circuit.

4. 4

   With input power off and DC link discharged, perform a diode test across the IGBTs (from DC+ to T1, T2, T3 and from T1, T2, T3 to DC-) using a multimeter diode function.

5. 5

   Inspect the cooling fan operation and heatsink for any obstructions or excessive dust buildup that could lead to overheating of the IGBT modules.