Junk yard 3 phase motor ??

At the risk of continuing to show my electrical ignorance.... I've read a lot of posts (all that I have time for anyway) about you fine gentlemen building your own RPC's. I'm not gonna try that.

I have found a complete panel "kit" from American Rotary. It states all you need is to add your own 3 phase motor. In my case I'm doing a 20 hp. ...For a EZ PATH (7.5 hp) cnc lathe and a cnc Compu Mill with a Fagor Controller. (5 hp)

You guys mention getting them from a salvage yard, etc. And now the question...

If they're in a salvage yard, aren't they junk? How do I know I get one that usable?

Thank you Rick

Rick,

Other than a mechanical issue, the most common ailment would be a shorted winding. A simple test with an Ohmmeter for a open winding and a insulation check with a megger would give you a good diagnosis on the internals. The bad news is the poor old motor should be real dry to get a valid reading with the megger.

If the thing has been setting in the junk pile out in the weather for any lenth of time, you won't get a true reading. There are lots of old motors out there, some are free, others are cheap and some are free and functional. A spin to check the mechanical s and two meters to check the electrical integrity...but it has to be dry.

The junction box should have at least 9 motor leads. If it only has three, it means it has been rewound and only the leads the customer needed were pulled out. This will mean it's dedicated to a single voltage, 240 or 480 volts. It's a crap shoot.

Stuart

I would guess that probably 90% of the motors you see in a junk yard (barring any obvious physical damage) are servicable. As far as 3 phase goes, there is very little market for smaller ( say under 25hp) used motors. Most companies simply are not going to search for a used motor to fit a machine, they just call and get a new one. Time is money.
Actually most motors find their way into a yard as part of a junked machine, and often the machine is perfectly fine, just oboslete or no longer needed.
That being said, a quick inspection for burnt windings, frozen bearings, or other damage will usually yield a good motor. Take along a meter and check for continuity between the motor frame and each of the wires there shouldn't be any. At this point your odds are pretty good. Then, if practical check the continuity of each winding segment. This requires disconnecting all the connections at the connection box and knowledge of the winding configuration (not always practical in a junkyard). Each segment should show continuity.

Good hunting,
-Tom

Motor needs home

I have a 20 HP Lesson 240/480 volt 3 phase that needs a home. As far as I know it is virtually unused and has never sat outside. Bought it to build a phase converter (which I never got around to and it is taking up shop space that I really could use). 1.5 inch diameter shaft with keyway and key (.5"). Unfortunatly I can't give it away but if you are interested PM me and we can talk.

Doug