How to Solve Servo Alarm 4
  • 28 Dec 2020
  • 1 Minute to read
  • Contributors
  • Dark
  • PDF

How to Solve Servo Alarm 4

  • Dark
  • PDF

Article Summary

Zhafir Service Department Training Files
Servo alarm NO.4


As the voltage of DC bus is more than 500 volts, and the inverter capacitor discharge also take some time. So please be very careful while doing inverter-related operation.

Alarm principle:

When the output current is over a certain value, the servo alarm NO.4 (E.OC) occurred.


  1. Inverter failure.
  2. External circuit short circuit.
  3. Motor power wire short circuit between three phases or to the ground.


  1. Uninstall the output three phases (U, V, W and ground), then shut on the motor to see if the alarm is still on.
  2. If the alarm gone, normally it may the external circuit short circuit or motor failure. Based on the customer feedback information, in this case, the most possibilities are:

First, the shield place of power wire is damaged, result in poor insulation to the ground or between phases, in this case, you can coat the wires with insulation tape. See the following picture.

Second, the output power wires damaged by the movement of tank chain. Most likely on the ejector axis. See the following picture is the ejector unit.

Third, poor insulation of the power wire plug, this is occasionally occurring, need to replace the plug and re-welding the wires.

Fourth, motor three phases short circuit, need to replace the motor.

3. If the alarm is still on, it is the inverter failure, need to replace the inverter.

If need to replace the motor or inverter, please go to the instructions “How to replace a motor” or “How to replace an inverter.”

Was this article helpful?