Motor Overheat Alarm (Level 3)

What does OH3 mean?

This alarm signals that the motor's temperature has reached an elevated state, specifically when the motor temperature analog input (H3-09=E) exceeds the 1.17V threshold (OH3 level). It serves as an early warning for potential overheating, but does not stop the drive unless configured to do so. Ignoring this alarm could lead to a more severe OH4 fault or motor damage if temperatures continue to rise.

• Inadequate cooling airflow around the motor due to blocked vents, dust accumulation, or a damaged external cooling shroud.
• Ambient temperature in the motor vicinity exceeds the motor's specified operating limit (e.g., >40°C or as per datasheet).
• Motor temperature sensor (e.g., PT100, PTC) type or wiring incorrectly configured in Parameter H3-09 or miswired to the drive's analog input.
• Bearing failure or lubrication breakdown within the motor or driven equipment, causing excessive friction and heat generation.
• Drive parameter H3-01 (Motor Thermal Time Constant) set too low for the actual motor, leading to premature thermal modeling warnings.

Click steps to track your progress.

1. 1

   Visually inspect the motor cooling fins, fan shroud, and air intake/exhaust vents for obstructions, dust, or debris. Clear as needed.

2. 2

   Measure the ambient temperature directly at the motor using a calibrated thermometer (e.g., Testo 110) and ensure it's within the motor's design limits.

3. 3

   Verify the motor's internal or external cooling fan operation by observing its rotation and airflow when the motor is running. Replace fan if failed.

4. 4

   Using a multimeter, measure the voltage across the analog input terminals (e.g., H3-09) on the drive during operation and compare to the 1.17V alarm threshold.

5. 5

   If a PT100 sensor is used, measure its resistance at ambient temperature (should be approx. 100 Ohms at 0°C) and compare to expected values in its datasheet.

6. 6

   Check Parameter H3-01 (Motor Thermal Time Constant) and ensure it is correctly configured for the specific motor's thermal characteristics (refer to motor datasheet).