3 phase contactors...a discovery

[flutedchamber]

I recently rewired my lathe and installed new contactors because the old ones chattered.

When I started the lathe with the new contactors installed...THEY chattered like the old ones.

After a bit of head scratching I noticed that the contactors were being fed thru the load (T) side of the unit and the load was connected to the line (L) side of the unit. I reversed the wires and all worked fine (even the old contactors worked fine..but don't tell my wife).

So..I email a friend that is an electrical engineer and ask him why this happened. He said they should work no matter which way they are wired. He has helped me with other questions that I had, like with my phase converter and was always spot on with his info.

So..I don't know WHY..but the 'L' side is the line (feed) side, and the 'T' side is the load (motor) side.

PS Out of curiosity I took my old contactors apart and can find no reason why they chatter when they have the feed and load wires reversed, which has no effect on the coil feed wiring. And...the contacts were very worn, so I don't feel too bad for replacing them.

Just thought I'd let you know what I found out. I'm sure it would be the same for single phase contactors.

 

[flutedchamber]

[quote author=turbinedoctor link=topic=3640.msg26624#msg26624 date=1316555083]
Have you tried putting them back to see if the chatter comes back. I see no reason why it would make a difference.

Turbo
[/quote]

Yes I have. If I wire the old contactors correctly..that is the supply to the L side and the motor to the T side all is well..no chatter. :headscratch::headscratch::headscratch::headscratch::headscratch: