Allen-Bradley · PowerFlex 750
The power supply on the U-phase gate driver board has failed. This affects the control of the U-phase output and can lead to motor malfunction or drive damage.
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1. With drive power off, measure the output voltage of the U-phase gate driver board's internal power supply (e.g., 18VDC) for Port 3 at its designated test pads.
2. Conduct a detailed visual examination of the U-phase gate driver board (Port 3) for any evidence of overheating, component damage, or lifted traces.
3. Use an ohmmeter to measure the resistance between the gate and emitter terminals of the U-phase IGBTs on Port 3 (drive powered off, DC bus discharged) to check for internal shorts or degradation.
4. Ensure all electrical connections to and from the U-phase gate driver board (Port 3), including ribbon cables and power leads, are securely attached and undamaged.
5. Verify the integrity of the DC bus voltage that supplies the gate driver boards, measuring it at the input terminals of the power stage with a multimeter.