Motor ground wiring problem (dumb question?)

PIndelicato

PIndelicato

Joined
Sep 16, 2002
Messages
1,577
Hello,

I'm trying to wire up a new/used motor that I picked up a while back, and I'm stumped with something (potentially dumb) about wiring the ground. The green screw in this photo, which I assume is the ground terminal, does not go all the way in and therefore does not allow secure connection to the green ground wire. I've run the screw in and out a bunch of times, wire brushed the threads, etc. and it doesn't go any further in (any more fiddling or force and I'm worried it will strip the threads.)

Is there something wrong with this particular motor's ground terminal? Is it missing a part that would fill the extra space? Is there a special connector I need to use on my wire for this type of ground terminal?

IMG_0091_zpsbbb50cf8.jpg


Thanks for any advice!
 
How is the motor marked...110..? 220...?
Looks like more than three wires going into the motor.
Did your motor come with a schematic..?

Most likely, the green screw is not grounded itself, but is a connection for the
wiring ground to the motor ground.
 
Hi Russ,

It's a 230/460 three phase motor, this model: http://www.electricmotorwholesale.com/LEESON-112627/

there are 9 yellow wires coming out of the motor labeled T2, T3, etc. 3 of them get twisted together, and then each pair of the remaining wires get connected to one of the three wires coming from my VFD (red, white, black plus green for ground), like shown here:

http://beaumontmetalworks.com/motors/VFD-WIRING.gif

Basically, it seems to be just like this motor except for the apparenty different location of the ground screw. http://www.beaumontmetalworks.com/kmg1pics/VS-KMG-4.jpg
 
There is a 'cutout' in a section of the screw shaft...is this a style of ground screw that is not supposed to bottom out in the hole, but the wire is instead meant to go inside this void and then screwed in?

IMG_0097_zps9b6b8608.jpg
 
That looks more like a self taping screw. The ground wire from the motor, and the one from
your power source would wrap around the screw and be held in place together when the
screw is tightened.

Is yor breaker box set up for 220/440 3 phase...? If it's residential power, it's probably
single phase.
 
Lol! It doesn't matter what voltage or type of motor it is. None of those things make difference on the EGC ( Equipment Grounding Conductor) besides maybe the size, which is proportional to the amperage of the motor being supplied. Sometimes there is a little metal ring/cup underneath the green grounding screw that the wire is wrapped around on top of. Just take your incoming EGC, the green wire, strip it back and wrap it around clockwise. Strip it back long enough to make the difference up in the gap under the screw. All you are doing is grounding the metal parts of the motor in case of a ground fault. :)
 
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