oH3 Control Board/Ambient Overheat fault in delta drive

oH3 Control Board/Ambient Overheat fault in delta drive troubleshooting

Description

oH3 is distinct from heatsink overheating. It signifies that the ambient temperature inside the VFD casing, specifically around the control board (PCB), has exceeded safe limits. This protects the delicate microprocessors and capacitors from thermal degradation.

Causes

1. Cabinet Temperature: The electrical panel has no ventilation, and the internal air temperature has risen above 50°C.
2. Broken Internal Fan: Large Delta drives have small auxiliary fans specifically for the circuit boards, separate from the main heatsink fans. If these fail, pockets of heat form.
3. Sunlight: The drive or panel is exposed to direct sunlight.
4. Sensor Failure: The on-board NTC thermistor near the CPU is damaged.

Solution

Environmental control:
1. Panel Cooling: Install exhaust fans or AC units in the electrical cabinet.
2. Check Circulating Fans: Look inside the drive (through vents) to see if small internal fans are spinning.
3. Spacing: Ensure other hot devices (braking resistors, reactors) are not mounted directly below the VFD control board.
4. Dust Cleaning: A thick layer of dust on the circuit board acts as a thermal blanket. Power down, discharge, and gently blow off the PCB with dry compressed air.