shop "incoming" motor run for refurbishment / rewind 1

[electricpete]

How common is it to do an incoming run upon receipt of a motor in repair shop for rewind or refurbishment ?

Do any customers request this? Do any shops do it as a matter of course even if not requested? What benefit does it buy you?

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

 

[edison123]

pete

The motors coming in for rewind have damaged windings and it is impossible to have an incoming run. In my shop, we normally note down the original winding sequence (UVW) and repeat the same sequence during rewind. In some cases, the winding damages are so severe that you cannot note down the original sequence. In such cases, we provide longer leads for two of the terminals and ask the client to swap them in case of wrong rotation direction during an initial bump test.

Again, any shop-run direction is meaningless since the supply sequence in my shop could be different from that in the motor site.

 

[electricpete]

Part of our objective in doing an incoming run would be to note the direction of rotation for a specific connection on the shop's supply so that it can be recreated when it goes out. Then at least we know that when we get the motor back it will be the same setup as it went out.

It can cost us several hours of time during critical outage windows to change the rotation if the motor is rotating wrong during initial check. That is because we have to tag the motor back out to swap leads, then release the clearance again for running.

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

 

[electricpete]

By the way, you are right in deducing that the reason this question originally came up was in the context of phase rotation.

But I was told it is a somewhat common practice and there might perhaps be other benefits. Maybe shop will find a problem during the run before they go into the motor. (although I have a hard time imagining they'd find anything we hadn't seen when the motor was running ).

I take it you and your customers have never seen any need to do an incoming test?

Another by-the-way - many of the motors we send to the shop are working fine when we send them. But after soemtimes 20+ years of service, we send our large critical motors for refurbishment and sometimes even rewind.

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

 

[edison123]

If it is only a refurbishment job with no winding damage, then there is no chance of original DOR being changed since we don't touch the original winding - so to say.

In refurbishment/trouble-shooting cases (like vibration, bearing issues), we run the motor on receipt to note down the preexisting conditions. After refurbishment works (not involving rewind), we rerun the motor and record the pre-despatch conditions.

If it is a preventive rewind, we do an incoming run to note the original DOR but such preventive rewinds are far and few, especially with today's copper prices.

Generally, our clients trust us to do the relevant checks and tests.