Posted by Michael Norman on Fri, Oct 16, 2009 @ 08:43 AM
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, 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.
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.
Posted by Michael Norman on Fri, Oct 02, 2009 @ 02:57 PM
The Coupling on your motors shaft needs to be removed or put back on. You grab a hammer and some prybars....
First off, put the hammer and the prybars back. Your servo has very sensitive feedback sensors installed in the motor. These devices are attached directly to the shaft and are easily damaged. Any hammering could break the glass of an encoder. Prying on the coupling could also break glass or drive the rotor of a resolver into the servomotors endbell destroying it. In order to remove your coupling easily, there are a few things to evaluate about it.
Are there any setscrews or bolts on the end of the shaft. Take the time to clean the coupling and look. If you find one setscrew there are probably more. Pulling the coupling off of the shaft without removing setscrews will damage the shaft.
Does your coupling have threaded holes that can be used as backdrives? Many couplings have compression rings that can be pushed apart using the backdrive holes. This will allow you to pull the coupling off by hand.
Use a puller, not prybars. Using a puller will move the coupling in relation to the shaft. Prybars will pull the shaft and the coupling away from the motor possibly damaging the bearings and/or feedback. If you put alot of force on the puller and the coupling still will not budge then try adding some quick heat to the coupling. If you can heat the coupling before the shaft the expansion will help free the coupling.
These are some tips to remove a coupling from the shaft while minimizing possible damage to your servomotor.