Mill wiring question

[682bear]

I was about to wire my K&T horizontal mill to my RPC when I found something that I'm not sure I understand.

First, this is the data plate off the motor on the mill...



The line coming into the switchbox on back of the machine has 3 conductors and a ground. It is wired to the 'line' side of the switch/fuses...



There is an identical cable hooked to the 'load' side... this exits the switchbox and enters a second box with a transformer in it...



It is wired to the 'L1-L2-L3' terminals on the transformer. The 'T1-T2-T3' terminals are then wired to the motor.

What is the purpose of the transformer? If the motor operates on 208v 3 phase, it should run off my RPC, correct? Why would it need a transformer? Is it possibly a step down transformer to provide 220 volts from a 440 volt input?

-Bear

 

[markba633csi]

It's too small to be a transformer; it looks like a line filter or perhaps a self-resetting overload protector? Arrow-Hart makes breakers so I'm tending toward the latter
-Mark

 

[Mini Cooper S]

According to the internet, that's a contactor. A magnetic switch that disconnects if the power goes out, that way the machine won't start up unexpectedly when the power comes back on.

Richard

 

[682bear]

Oh, ok... it looks like a transformer from the side...



I guess that is the electromagnet for the contactor that I'm looking at instead of a transformer winding... that makes sense...

Thanks! -Bear

 

[NC Rick]

Oh, ok... it looks like a transformer from the side...

View attachment 336274

I guess that is the electromagnet for the contactor that I'm looking at instead of a transformer winding... that makes sense...

Thanks! -Bear

Motor protection heater? Normally Cutler hammer when I saw them three phase fuses.

 

[markba633csi]

So then, how does it work? I don't see a reset button- is it self-resetting somehow?
Never seen one of these before
-M

 

[682bear]

So then, how does it work? I don't see a reset button- is it self-resetting somehow?
Never seen one of these before
-M

I don't know... I googled the part number and verified that it is a contactor, but never found any info about how it works...

At least now I know I should be ok wiring it into my RPC system...

-Bear

 

[682bear]

Ok, I wired the K&T into my RPC system, turned it on and.... absolutely nothing happened.

So, I grabbed my voltmeter and started checking for voltage. I had power coming into the contactor, but no power coming out of the contactor.

I bypassed the contactor and connected the motor directly to the 'load' side of the switch.

It runs, now... or the spindle does, anyway. None of the feeds are working, but the spindle runs smoothly, anyway.

The contactor was put on for a reason, so I will replace it. They don't seem to be very expensive.

Thanks for the help.
-Bear

 

[markba633csi]

I think the reason for it's being there is mostly not there anymore. Personally, I would just run without it
-Mark

 

[John O]

Before replacing the contactor, find where the wires from the feed motors go, might be a separate power supply