Overcurrent trip during acceleration

What does E.OC1 mean?

This overcurrent trip occurs during acceleration when the inverter output current reaches or exceeds approximately 230% of its rated current. It indicates that the motor is experiencing excessive load, sudden acceleration demands, or a potential electrical fault. The inverter trips to protect itself and the motor.

• Motor accelerating into an excessive mechanical load, such as a jammed conveyor or a high-inertia load with too short an acceleration time (Pr. 7).
• Incorrect motor parameters (Pr. 3, Pr. 4, Pr. 5, Pr. 9, Pr. 19, Pr. 82) entered into the inverter, leading to inaccurate motor model and control during acceleration.
• Mechanical binding or friction in the driven equipment (e.g., worn bearings, misaligned shafts, seized gearbox), significantly increasing the torque required for acceleration.
• Sudden voltage sag on the input AC supply during acceleration, causing the inverter to draw more current to maintain output power.
• Motor winding insulation breakdown (inter-turn short) or a ground fault in the motor cable, leading to excessive current draw.

Click steps to track your progress.

1. 1

   1. Increase the acceleration time (Pr. 7) in increments of 10-20% to reduce the current demand during startup and smooth the acceleration profile.

2. 2

   2. Verify and correct all motor-related parameters (Pr. 3 (Rated motor current), Pr. 4 (Motor rated slip frequency), Pr. 5 (Motor capacity), Pr. 9 (Rated motor voltage), Pr. 19 (Motor rated frequency), Pr. 82 (Motor no-load current)) against the motor's nameplate data.

3. 3

   3. Disconnect the motor from the driven load and test run the motor in no-load condition to determine if the fault is motor-related or load-related, monitoring output current (U, V, W).

4. 4

   4. Measure the resistance of the motor windings (U-V, V-W, W-U terminals) with a multimeter and compare them to each other (should be balanced) and to the motor's specified values. Check for resistance to ground.

5. 5

   5. Check the mechanical system for any binding, excessive friction, or misalignment. Use a torque wrench or an appropriate diagnostic tool to assess mechanical integrity of the load.

6. 6

   6. Monitor the incoming AC supply voltage (R, S, T) with a recording voltmeter during acceleration to detect any significant voltage sags.