How to Solve Servo Alarm 1
  • 28 Dec 2020
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How to Solve Servo Alarm 1

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Article Summary

Zhafir Service Department Training Files
Servo alarm NO.1


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:

We have four inverters to control the motion of injection, mold, charge and ejector respectively, in which the injection inverter is supplied by external three phases through filter and reactor, the other three are supplied by DC voltage rectified by injection inverter through DC bus. 

This DC bus structure can “store” the regenerate energy by servo motor break to the inverter capacitor, cause the voltage increase on the DC bus, while the voltage goes too high, the excess energy should be released by breaking resistor. When the breaking resistor circuit fail, voltage goes too high and occur servo alarm NO.1 (E.OP).


  1. Control parameter not appropriate, acceleration too large or something like that. (The possibility is very small if the internal parameter is not changed.)
  2. Input voltage too high. (This possibility is small.)
  3. Breaking resistor damaged. (This possibility relatively big.)


  1. Check the input voltage.Measure the resistance of breaking resistor.

  2. Normally the resistance is 20-30Ω, if these is short circuit or open circuit, then the breaking resistor is failed.

3. Ask the customer whether they have change the internal parameters, if they do, please change it back and test again.

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