Indramat Fault Code F878

New Indramat MDD Servo Motor

Indramat fault code F878 is not one of the more common problems with Indramat servo motors, but it can also be one of the most frustrating. When you see an F878 message, you’re looking at a velocity loop error — it’s all about the speed.

Understanding Indramat fault code F878

A velocity loop senses the speed at which the load is moving in a motion control system. You might use a velocity loop for machine cutting tools, for example. Sensors measure the difference between the command velocity — the speed at which the load should be moving — and the actual velocity.

A couple of things can cause this:

  • variance between command and actual velocity is over 10% of maximum motor velocity
  • current demand is at or above peak current limit

This error doesn’t typically occur with established servo motors. It tends to happen when you move or reconfigure your system.

What causes F878 errors?

First, you might have an issue with a cable. Let me tell you, when you stop everything at the plant for a couple of days in order to replace a motor and then discover that you could just have replaced the cable, it’s enough to ruin your day. Check this first. Sometimes it’s just not connected properly, and you don’t even have to replace the cable, just fix the connection.

Second, you might have the velocity loop parameters wrong. Double check this before you start saying, “I’m SURE…” because it’s a lot cheaper than replacing your motor.

If both these things are good, then you may need a new motor. This is obviously the least preferable option. However, a factory-repaired Indramat servo motor is just about the same as a brand new Indramat servo motor.

Give us a call at 479-422-0390; we can expedite a factory repair, provide emergency replacement units, or offer troubleshooting support directly over the phone.