On Wed, 26 Jan 2011 13:47:09 -0600, "Pete C."
wrote:


Pete Keillor wrote:

On Wed, 26 Jan 2011 13:06:20 -0600, "Pete C."
wrote:


Winston wrote:

Pete C. wrote:

Winston wrote:

I Googled but didn't find anything that would
work quickly.

Who makes an inexpensive tester that I can plug
into 208 V 3 phase L14-30 outlets to determine
phase rotation?

I'm aware of this circuit but I want something
I can buy at the Borg and leave at a worksite:
http://www.opamp-electronics.com/tut...on_2_10_03.htm

--Winston

You won't find one at the Borg, since they don't carry anything three
phase. You will find them at most any real electrical supply house for
~$100 or so. The good thing is that those phase rotation meters usually
also include motor test functionality so you can identify the leads from
an unpowered three phase motor as long as you can manually turn it more
than half a turn.

It helps to know the proper nomenclature.
Good info. Thanks!

--Winston

One additional note is that there aren't too many three phase loads
you'll run across that will be harmed by running reverse rotation for a
couple seconds, so most of the time you can just blip the load on and
see if it's running the correct direction, and if it isn't swap two
phases before trying again.

Don't try that if there's an impeller threaded on a shaft. If
possible, I had motors decoupled from loads before doing that. Wasn't
always possible.

Pete Keillor

I've not seen anything threaded on like that without some additional
locking provision, like a slipped in key and locknut. Certainly it is a
requirement to look over the device in question to determine what effect
a couple seconds of reverse rotation will actually have.

Threaded was standard for a lot of centrifugal pump impellers, no key
or nut. We were warned about that when being trained in r&d in the
chemical industry. If you checked rotation with the coupling
connected you had an even chance of having the impeller rattling
around loose in the pump housing. Of course, now they wouldn't let a
kid fresh out of college anywhere near that type of equipment. Back
then (35 yrs ago), we were expected to keep pilot plants running
around the clock, even if it meant swapping 3 phase 460v motors,
checking fuses, replacing packing, etc. It was more fun back then.

Pete Keillor