What's new
What's new

Bridgeport Motor Overheats!

JoeSchwartz

Plastic
Joined
Feb 24, 2007
Location
New England
We have a 1 hp 1965 Bridgeport Mill at the old shop where I work. It has not been used for about 10 years. I turned it on for the first time a couple weeks ago and after 3 minutes, smoke was pouring out of the motor. The last guy to use it, 10 years ago, states that he never had any problems. I sent the motor out to be tested and they say it is perfect.

It is attached to a 3-5 HP Phase-a-matic static converter. When I turn on the mill, the converter clicks and the light comes on. The motor seems to run fine, until it overheats and smokes. Thought it might be the switch, but all the connections are tight. The converter is also attached to a 5 HP Clausing Lathe, which runs without problems.

I hate to buy a replacement static phase converter if that will not solve the problem. But I would rather do that than invest in a rotary converter. The mill isn't going to get the kind of use that would justify a rotary converter. Does this sound like the issue?
 
The static converters are sized to the HP and a 3-5 HP unit will have wrong-sized start and run caps for a 1HP motor.

probably your problem is a run cap which is wrong-sized and permitting too much current, possibly due to a resonance type condition.

Possibly it is simply never disconnecting the start caps. There is, IIRC, a light on the converter which should go out when the motor has started. Does it?
 
Put your clausing lathe in "neutral" so the spindle isn't turning, and turn the lathe "On". Now you have a rotary converter - the lathe motor will be the rotary after being started by the static phase converter. Now try operating your mill and see what happens. If all works out OK, then get your self a 5hp 3-phase motor and wire up your static to it - now you have a rotary 3-phase converter for both your machines.
 
I talked to the phase-a-matic folks and they made both of your suggestions, so I am betting you are correct. The frustrating part is that I found out there used to be another static phase converter in the shop but it was removed about 3 years ago when a new circuit breaker was installed. I suspect it was properly sized to the mill and the electrical contractor didn't realize that we needed both of them.

I was thinking of buying a 2 HP rotary converter, strictly for the mill. Is just running a 5 HP idler moter as good? It looks like a rotary converter is about $200-$300 more than just using an idler motor.
 








 
Back
Top