Motor Overtemperature (PTC TRIP)

What does OH3 mean?

The motor's PTC thermistor has detected an overtemperature condition, triggering a TRIP fault. This is usually caused by the motor operating under impermissible high currents or frequent/long acceleration processes, or simply if the PTC sensor is not connected while monitoring is active (C0119 = 1 or 4). Continued motor operation in an overtemperature state will lead to severe winding damage and premature motor failure.

• Motor operating under impermissibly high currents or frequent/long acceleration cycles.
• Motor cooling fan failure or blocked motor cooling fins.
• Damaged motor bearings causing increased friction and heat generation.
• PTC thermistor wiring to the drive is open circuit or has high resistance.
• Motor thermal protection parameters (e.g., P1-60) not correctly configured for PTC input.

Click steps to track your progress.

1. 1

   1. Measure the motor winding temperature or motor case temperature (if accessible) to confirm an actual overtemperature condition.

2. 2

   2. Verify motor current (C0004) against its nameplate data during operation to identify overload.

3. 3

   3. Disconnect PTC thermistor leads at the drive and measure its resistance directly at the motor terminals; compare to PTC data sheet (typically <250 Ohm cold, >3k Ohm hot).

4. 4

   4. Check the wiring continuity and secure connection of the PTC thermistor to the drive's dedicated input terminals (e.g., XA-XB).

5. 5

   5. Inspect the motor's cooling fan and fins for proper operation and cleanliness.