Need Wiring Help - Enco Mill 100-1525

GT Mills

Mohawk Aero
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I just bought an Enco 100-1525 knee mill (c1991) for $1800 plus $250 delivery. It is in great shape. It came with Phoenix Rotary phase converter. I smoked the motor this evening. Please help if you can.

First off, the switch was no good and I rebuilt it without too much trouble. I got the mill running. I drilled some hold down holes in a 1-1/2" aluminum plate to start milling it today, running it on low speed. No problems.

I set it up to start milling, and turned it on to high speed. It ran for a few minutes, then the motor started speeding up. I looked up and a puff of smoke came out of the motor - I snapped off the switch immediately, of course.

On this mill, the wires are labeled (apparently by the manufacturer) such that 5 of the 6 are labeled differently at each end. They go like this, switch end/motor end: 1U/1U; 1V/1W; 1W/1V; 2U/2W; 2V/2U; 2W/2V

When I checked the wiring at the switch against what I had written down before I took things apart to repair the switch, I found that I had swapped two wires at the switch: 2U and 2V. But I don't think that is the problem.

The wire map shows that for Low Speed, power goes to 1U, 1V, 1W and 2U, 2V, 2W are open. For High Speed, it shows 1U-1V-1W tied together, and power to 2U, 2V, 2W. (At the motor, there is a double-side terminal strip, 1 UVW and 2 UVW. All the wires and their markers match at the motor terminal strip.)

But that ain't how things were switching! I disco'd all the wires at the motor and did a continuity check at the switch connectors. This showed another oddity: On Low Speed, power went to 1U, 2V, 1V with the rest open; and on High Speed 1U-2V-1V tied together and 2U 1W 2W had power.

BTW, the motor was turning in the right direction.

It is a simple matter to straighten out the wiring at the switch terminals w/o tearing apart the switch again.

But now I am wondering if it matters which way the wires from the converter to the switch are run to which terminal? Two wires from the single phase go to the converter and also the switch, and a third wire from the converter goes to the switch. Should this third wire be the one that does not switch for directional control? I thought it didn't matter, but now I am wondering.

I checked the motor with a digital ohm meter. On the scale for 200k ohms, it reads within 5-10% of a readout of 0.35 between all motor leads on the #1 side, and again on all leads on the #2 side. I'm hoping the motor isn't destroyed...is there any hope?

Any thoughts or suggestions before I try to power it up again?
 
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Does anyone know the HP rating on the ENCO 100-1525 variable speed head? (waiting for my photos to be approved.)
 
I have the same mill, though mine's not originally variable speed. It's been a long time since i was deep in the motor wiring of my mill. I put on a VFD. I remember it had to be an odd hookup because to motor was not a normal 2-speed. The ratio between high/low was something like 4 or 5 to 1. If you post pics, get a clear one of the motor nameplate.
 
Smoke is bad, one of the windings may be burned and there could be an inter-winding short, or one may develop soon. It sounds from your description that the correct connection would be the first one: 1u 1v 1w powered for low and 2u 2v 2w powered for high.
Here's the proper way to approach it, first you need the correct wiring diagram for the machine, second you need to positively identify the motor and switch wires with the help of a ohmmeter or continuity checker. Third you should try to check for shorts in the motor between windings or from windings to ground (the frame) again using a meter.
Then reconnect and cross your fingers. If you shut it off quickly enough when you saw smoke you might be OK. You should check the phase converter too for equal voltages. Be careful, don't get shocked. Been there, done that. Still here. Smarter.
Mark S.
 
I re-wired things and fired it up, it runs in their both directions and at the right speeds. I milled at low speed for 20 minutes and the motor got pretty hot to the touch. Is that normal?

Where can I find a replacement motor? I doubt this one is going to last long now that I smoked it.
 
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If we do have the same oddball motor, I can try to retrace my wiring to confirm. I'm sure mine is correct since I've had no problems on my VFD in several years of use. This points to a benefit of VFDs over rotary converters in that you will usually get a VFD shutdown and error code before you doing anything bad to the motor.


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Have you tried the high speed at all? And does it get evenly hot all around or just one particular spot on the case?
Mark S.
 
I ran the mill at low speed for about 1/2 hour...then tried high. After a couple of minutes it fried itself completely.

My local electric motor shop said their price to rewind it is $1200-$1500, he suggested I just get a new motor.

I found www.use-Enco.com, called and they have a replacement in stock $821.33

Then I found www.MSCDirect.com, called and they have one in stock for $726.67 so I ordered, it should be here in a day or two.

Sadly, the 8/2 pole motor I had is lost. The replacement part is only the 4/2 pole motor. The 8/2 is far more desireable, it has slower spindle speeds on low switch settings, down to 100 RPM. It also makes changing from milling to drilling much easier, since you don't have to change the belt steps.

Oh well.

On a happier note, I got my photos posted to my album on here, so I can include pix here for anyone interested.

I'll have to come up with something more elegant for the vac hose hanger, until then my rope is good for a giggle. Also, I haven't yet bothered to get some flex conduit for the wiring protection. One thing that is nice, I was able to put the noisy vac and RPC in a storage room behind the door, and run the wiring and hose through the wall. So I shut the door and the only thing I hear is the mill. I like that, a LOT. When I was training using my friend's mill his LOUD vac was right next to the mill. Not thinking, we didn't have ear protection and I got tinitus in my left ear. It has faded with time, but there for about 8 months it was terrible, especially first thing in the morning. It comes back now and then but doesn't seem to last as long and isn't such a bother.

 
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Sorry to hear about the motor's demise. What I would do is get a standard 56C frame 3 phase motor off eBay and make an adapter plate to fit it to the machine. Then get a VFD and toss the RPC. I know the urge might be to get a single phase motor but resist. Knob controlled speed is too nice. On eBay, a good name-brand (sometimes even new) 3-phase motor can be under $100. Don't worry about getting one that's "inverter rated". Any modern 3-phase motor will be fine on a VFD in a home shop environment. For the VFD, I probably wouldn't bother with eBay because new ones are not that expensive. A nice Hitachi is around $200.


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You might be able to find an exact replacement motor on ebay. This motor might just drop in: http://www.ebay.com/itm/REPLACEMENT...ING-MACHINE-VSM3-SP-STEP-PULLEY-/401200615543

Mill motors are normally ''special'' in that they have a non-standard end bell for mounting and an odd shaft length (extra length) and diameter. Many are a roughly equivalent to a NEMA 145TC frame motor or the metric equivalent.

I suspect your motor is a 2HP. First measure the shaft then compare to a NEMA 145TC frame motor. It also may be a metric motor.

You absolutely need a reversing motor, when you shift into back gear, the spindle rotation reverses relative to the motor.

I would go with a 3 phase motor and a sensorless vector VFD, that way you get a very wide speed range.
 
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