Motor Overtemperature (PTC Warning)

What does OH51 mean?

The motor's PTC thermistor has detected an overtemperature condition, triggering a WARNING (not a TRIP). This typically occurs when the motor operates under impermissible high currents or frequent/long acceleration processes, or if the PTC sensor is not connected while monitoring is active (C0119 = 2 or 5). While a warning, continued operation can still lead to motor damage if the condition escalates.

• Prolonged motor operation at currents exceeding its nominal rating (P5-01, P5-02).
• Insufficient cooling of the motor due to blocked fan, dirty cooling fins, or high ambient temperature.
• Inadequate motor sizing for the application, leading to continuous overloading.
• Incorrect motor thermal model parameters (e.g., P6-10 to P6-13) configured in the drive, leading to underestimation of heating.
• Faulty PTC thermistor or wiring to the drive's PTC input (e.g., terminals X1/X2), causing erroneous temperature readings.

Click steps to track your progress.

1. 1

   Monitor the actual motor current (U0-01) and compare it against the motor's nominal current (P5-01) and drive's nominal current (P2-01).

2. 2

   Inspect the motor's cooling fan for proper operation and clean any dust or debris from the motor's cooling fins.

3. 3

   Measure the ambient temperature around the motor and ensure it is within the motor's specified operating limits.

4. 4

   Review and adjust motor thermal model parameters (P6-10 to P6-13) in the drive controller to match the motor's thermal characteristics more accurately.

5. 5

   Disconnect the PTC thermistor wires from the drive (terminals X1/X2), measure the resistance across the thermistor; it should be below ~1.6 kOhm at ambient and increase significantly with temperature.