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info@servotechusa.com • 1-866-80SERVO

Resolver Overspeed

Your servo has run away and your drive pops an error code. You write down the error code and look it up in the manual. The code corresponds to a "resolver overspeed" alarm. Next to that is written "check the feedback cables" as a probable solution. You replace the cable and get the same alarm.

The Basics

Check Cable Shielding

  1. Check grounding of cables.
  2. Shields may be grounded to inside of cabinet.

If Previously Disassembled...

  1. Check resolver position relative to motor.
  2. Check alignment of resolver.

Check Wiring for Changes

  1. Swapped resolver wires can:
    • Cause reversed resolver direction
    • Change zero position location
    • Cease functioning
  2. Check wiring connections.

My Servo Motor Needs Repair.

  1. Call 1-866-80SERVO.

Now What?

Resolver overspeed is a very common alarm, and it is one that can have many causes. Many of these causes are easy to fix, and eliminating the different causes can help you determine what part of your system needs repair.

Are Your Cables Properly Shielded?

Your cables should have an internal shield that is properly grounded. Shields are usually grounded directly to the inside of a cabinet. Resolver based systems are very sensitive to noise and can be prone to alarms if not properly shielded.

Has Your Servo Been Disassembled?

Have you had your motor rebuilt or tried to do it yourself? If so was the resolver properly aligned to the motor? If for any reason your resolver has changed its position in relation to your motor your system will not run. A misaligned resolver can cause many alarms including resolver overspeed.

Has Your Wiring Been Changed?

If you have swapped drives or changed cables then your wires could have been connected incorrectly. Swapping resolver wires can cause the resolver to swap direction, change to location of the zero position, or not function at all. Miswired resolvers can cause overspeed alarms.

In Summary

Torque Loss is a common problem. The root cause needs to be determined so you can be sure that you are fixing the right problem. If you find you have to send your servo out for repair, it is best to make sure they have the equipment to do the job.

These are some causes for resolver overspeed. In many cases resolver overspeed is caused by something other than a bad servo. If you are having trouble with this alarm you should try to eliminate these possible causes before you send anything out for repair.