oH2 External Motor Overheat (PTC) fault in delta drive

oH2 External Motor Overheat (PTC) fault in delta drive troubleshooting

Description

While oH1 refers to the drive's own heatsink, oH2 relates to the external motor temperature. This fault triggers when the drive's specialized input (often AVI or a dedicated PTC terminal) detects that the resistance of the motor's embedded Thermistor/PTC has spiked, indicating the motor winding is too hot.

Causes

1. Motor Overheating: The motor is genuinely hot due to overload, blocked cooling fins, or a broken cooling fan.
2. Wiring Open Circuit: The wire connecting the motor PTC to the drive is broken. Since PTCs increase resistance with heat, an open wire (infinite resistance) looks like infinite heat to the drive.
3. Wrong Parameter: The analog input (AVI) is set to "PTC Mode" in parameters, but nothing is connected to it.
4. Threshold Set Too Low: The trigger level (Voltage or Ohms) in the protection parameters is set too sensitively.

Solution

Thermal verification:
1. Feel the Motor: Is the motor physically hot? If yes, check for fan blockage or overload. Allow it to cool.
2. Measure Resistance: Disconnect the PTC wires at the drive end. Measure the resistance with a multimeter. A cold motor should read low (e.g., 100-500 ohms). If it reads open (OL), the sensor inside the motor is blown or the wire is cut.
3. Bypass for Test: If you suspect a false alarm, place a resistor (e.g., 1k Ohm) across the PTC terminals. If the fault clears, the wiring or motor sensor is the issue.
4. Disable Function: If your motor does not have a thermistor, ensure the associated AVI/MI input parameter is NOT set to Function 20/21 (PTC input).