More Bridgeport mill help needed

by all appearances, a 3 phase motor, probably wired for 440 if memory serves

It looks like your maintance man is right. You can run that motor on either 220 or 440 but 3 Ø only.

John

The three wires 1,2, 3 are your power wires to the motor connected for

480. For 220vac you would tie 1&7. 2&8 3&9 together and these would be your power into the motor. Wires 4,5, and 6 would be tied together.

I am not sure how the contactor is wired into the circuit but there should be either a control transformer on the machine that would have to be switched to 220 from 480 or the coil on the contactor has to be replaced. IF you have a 110 volt outlet they might be using that for the power for the contactor coil. The transformer may have jumpers or taps to change the input voltage to 220. The taps on a control transformer are usually labeled H1, H2, H3 and H4. Each transformer is different as to how they change the taps on the input voltage so you should look closely at the transformer and see if there are any instructions or diagrams on it.

John

That wiring is just right for 440, 3-phase. To convert to 240 3-phase, connect 4, 5 and 6 together and tape up. Connect the mains to 1&7, 2&8 and 3&9.

It would be EXTREMELY rare to find an original Bridgeport spindle motor that was single phase.

Jon

Common way to do this (though numbering schemes may vary, and what I will ASCII draw here is based on your numbers as connected.

Be sure to use a fixed-pitch font like Courier in your newsreader to avoid distortion of the image (a common problem with proportional pitch fonts):

7 4 1 +-----WWWWWWWWWW-----+-----WWWWWWWWWW-----+ (L1) | | 8 5 2 +-----WWWWWWWWWW-----+-----WWWWWWWWWW-----+ (L2) | | 9 6 3 +-----WWWWWWWWWW-----+-----WWWWWWWWWW-----+ (L3)

The "WWWWWWWWWW" represents a specific winding in the motor.

This is wired for the higher-voltage possibility. Now to re-wire as the lower voltage possibility: 7

+-----WWWWWWWWWW-----+--+--- (L1) | | | +-----WWWWWWWWWW-----+ | | 4 1 | | 8 +-----WWWWWWWWWW-----+--+--- (L2) | | | | +-----WWWWWWWWWW-----+ | | 5 2 | | 9 +-----WWWWWWWWWW-----+--+--- (L3) | | +-----WWWWWWWWWW-----+ 6 3

Or -- in text, 4, 5, and 6 are tied together and insulated with tape. 1 and 7 are tied together and make one phase (L1) 2 and 8 are tied together and make another phase (L2) 3 and 9 are tied together and make the last phase (L3)

Whichever way it is wired (high voltage or low voltage), you reverse it by interchanging any two of the three AC line feeds. (E.G (L1) and (L2) -- or either of those and (L3) -- not not all three moved at once, which will leave it running the same direction that it was. :-)

Note that the other end of windings 7, 8, and 9 are tied together inside the motor, just as you are tying together the 4, 5, and

6 wires when you are adding the second windings in series with the first. You could call the joined ends of the 7, 8, and 9 windings "10" if you wanted to -- but since you can't get at it, don't bother to name it. :-)

Typically, for a reasonable sized milling machine, the high voltage wiring pattern will be for 480 V and the low voltage pattern will be for 240 V.

Good Luck, DoN.

I thought so too, but the motor plate tells the tale.

That plate certainly *said* 3 PH and may still say 3 PH. That also is not an original data plate.

[ ... ]

Except that the nameplates on Bridgeport motors are normally anodized plates with clear places for stamping the data which may change, such as voltage.

What I suspect is that someone had the motor rewound to single phase at one time, and pulled the drive screws and flipped the plate over and stamped new information (including the Bridgeport name) into it. If you pull the drive screws (use dikes to get under the heads), and look at the other side, I suspect that you will find the original nameplate. Later, someone re-wound it as three phase again. I think that I can see some reversed letters from the original stamping on the other side.

Or -- it *could* have been a third-party motor (or third-party modification to the existing motor), which would again explain why the "Bridgeport" name had to be stamped into the nameplate, instead of etched into it as is normal.

Anyway -- what you *currently* have is a three phase motor wired for 460 or 480 VAC, no matter its history.

Re-wire as I showed for the lower voltage 230/240 VAC and double the current of the thermal fuses in the starter (assuming that you are not going to be driving it from a VFD. If you are -- the starter is not really needed.

Good Luck, DoN.

Could you tell me the reason for the 115/230 designation (where the 115 is stamped over). I was unaware 115 volts came in 3 phase. Also, how can I tell it's not an original data plate? Obviously it has been restamped, and do you have a link to a picture of an unmolested data plate, so I can see what has been wiped off over the years.

My thoughts on the 115/230 designation is that the data plate was reused from some other motor and restamped.

A couple original motor data plates on Bridgeports: