3Ph Drill Press Electrical Issue

[mike93lx]

Hi all, I have a 40's Charles Allen Drill press that is running a 3 phase Westinghouse 1/2 hp motor (nameplate indicates 1938). It is running off a home-built rotary phase converter (built by the gentleman that restored the press). It is using a very old, possibly original, Allen Bradley starter/switch.

I recently found that the frame of the drill press is energized but I can't figure out where the issue is. There are no frayed wires in sight (I have not taken apart the motor) and the press is functioning fine otherwise.

When the phase converter is running but the switch is off, I get no power to the frame. As soon as I turn on the switch and motor, the frame energizes. I disconnected the motor from the switch and again, no power to the frame, which leads me to believe it is the motor.

Any advice on what to do? I am not comfortable with tearing into the motor, especially considering its age, not to mention that I know little about 3-phase.

Thanks!

A few pics for those curious. Please forgive the clutter around it, I'm reorganizing the garage right now.

Switch


Press Overall


Motor Wiring Diagram (look really close at the bottom left for a date stamp)


Allen Name Plate


Drive System

 

[Milton Shaw]

Hook up a ground and you should see real quick if its a short or not. Could be phantom voltage because of not grounding the drill itself. Put a small fuse on it before you hook up the ground to make sure you don't damage anything. Phantom voltage is voltage picked up from metal and wires being close together, it shows up on digital VOM meters but is such low amps that it doesn't hurt you. Phantom voltages from un-grounded high voltage lines can kill you, lots difference on phantom voltages in home shops.

 

[Rookie2]

I would guess that the wires to the motor or something inside the motor is grounding out. Your ground wire must not be hooked up at the panel or you would be tripping a breaker. I wouldn't rule out that starter switch and or overloads.

Disconnect from the panel all power and ground then run a continuity test on all wires to metal , with switch on vs off .

 

[mike93lx]

Thanks for the replies.

I did some further troubleshooting and identified the issue. The leads in the motor's junction box are frayed and must have been shorting to the case. I've pulled the motor and and am looking into having them replaced.

A couple things to note base don the replies, the ground is definitely connected in my panel. The press is isolated from ground by a couple layers of 3 mil plastic, which must be enough to not cause a tripping issue. The ground is definitively connected in the panel.

This also isn't a phantom issue. I found out it was live my using it while grounded and received a solid shock. The frame was metering out at the full voltage of one of the legs and would drop off to zero instantly at shutoff.

One thing I found that was interesting is that there is no ground passing through the phase converter. The gentleman that built the converter used a 120/208 plug (L18-20P) instead of a 4 wire 240 plug (L15-20 ?) that is grounded. I think I am going to switch it over and hookup a ground while I have things opened up.

 

[454ragtop]

If it were me, I'd replace the motor with a single phase. A 1/2 HP motor isn't that hard to come by, in fact I left a nice Leeson at a yard sale the other day just because they are so easy to find. That switch will work with a single phase motor as well.
HTH, Jim

 

[mike93lx]

If it were me, I'd replace the motor with a single phase. A 1/2 HP motor isn't that hard to come by, in fact I left a nice Leeson at a yard sale the other day just because they are so easy to find. That switch will work with a single phase motor as well.
HTH, Jim

If the motor was toast, yes, i would likely change to single phase, but as long as i can keep this old westinghouse running, it will stay on the press.

 

[larry_g]

Have you ohmed out all the leads? I would check each leg of the motor to the frame for resistance with the switch open. If a good short you should find it with the ohm test. If you do find a short to the press frame then disconnect the power leads at the motor and check the motor leads again. If no short is found in the motor then check the resistance of the feed leads from the switch to the frame. If your lighting up the frame then something is shorted. I would find the short before hooking up a ground to the frame if at all possible. Hooking a good ground to the frame may let some smoke out before opening the circuit breaker. If you can find the short, fix it, then hook up the ground for normal operation.

lg
no neat sig line

 

[mike93lx]

The motor is off the press, but I have not ohmed the leads. After I moved the leads around, the frame was no longer energized, with no other changes, so I am assuming that the leads are the cause since the insulation has significantly degraded and is missing in several places.

I talked to a guy that owns a nearby motor repair shop about it. He is interesting in saving the old motor and is going to do some free bench testing and give me a quote on the repair. Hopefully he can repair it without rewinding, but we'll see.

Once the motor is sorted out, I'll get swap out the existing plug/receptacle and get a ground hooked up.