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Bridgeport Mill Wiring

Jacksquat

Aluminum
Joined
Oct 11, 2016
I know similar questions have been addressed many times on these forums, however, I’ve included a couple photos that may add interest.

I have a Bridgeport 2J made in 1976. I made a simple phase converter (generator) for it using a couple motors, and I’ve rewired the motor at the head for 220v. Given all I’ve read on this site and others, I think this machine was tailored for use at high voltage. The mill came from a machine shop where it was powered at 440v.

You can see the front of the cabinet in one of the photos. The other photo contains a picture of the inside of the cabinet. Given my research, the motor starter will likely require a coil so I can operate at 220v. In addition, perhaps the overload protection (heaters) will need replacing. Do I have this right? Can you point me to the components within the cabinet that need replacing or adjusting? I want to be sure I have things right before shelling out the bucks. I’ll likely have the machine professionally inspected at the end of the project. Thanks a million!


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If the transformer input was 440V and the control voltage is 220V then all you would have to do is remove the shorting bar on the input side of the transformer. The transformer (lower left) has four terminals on the left side. If you number them from 1,2,3,4 going from bottom to top, you see that 2 & 3 have a shorting bar.Then short 1 & 2 and short 3 & 4. Transformers have wiring directions printed on them. A closer inspection will verify.

The Bridgeport contactor (lower one) has three heaters (on the right side) which will have to be changed. A close inspection on the contactors will probably verify what voltage the coils are.

Again, assuming that the transformer is a 440/220 input, 220 output and all the coils are 220V. So inspect closely or take some close-up pics that are in focus.
 
I hope I’ve taken images of the necessary components. I was trying to do all this on the fly before work this morning, and I may not have been as careful as I needed to be. Please let me know, if that’s the case. I didn't see a wiring diagram on the transformer, but I'll look again.

Beside shorting the terminals of the transformer as you’ve suggested, you mentioned changing the heaters on the contactor. Can you explain how that would be done? I’ve included close-up images that may help with coil voltage. The wiring obscures what’s written. The following was indicated:

TB-159-1
110-120 60 Hz
110v 50 Hz

To recap, it seems I’ll need to short the proper terminals at the transformer and change the heaters, and the machine should be ready for operation. Your help is invaluable, rons, and I greatly appreciate it!

20170628_053357.jpg20170628_054132.jpg20170628_054957.jpg
 
Rather then buy three heaters and a coil it may be cheaper to buy a newer contactor with adjustable overloads from Ebay. Or maybe you can find one with the correct heaters already installed.
Bill D
 
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I didn't see a wiring diagram on the transformer, but I'll look again.

Beside shorting the terminals of the transformer as you’ve suggested, you mentioned changing the heaters on the contactor. Can you explain how that would be done? I’ve included close-up images that may help with coil voltage. The wiring obscures what’s written. The following was indicated:

TB-159-1
110-120 60 Hz
110v 50 Hz

To recap, it seems I’ll need to short the proper terminals at the transformer and change the heaters, and the machine should be ready for operation. Your help is invaluable, rons, and I greatly appreciate it!

View attachment 202197View attachment 202198View attachment 202199

Disconnect X1 and X2 wires and read what voltage you get between X1 and X2 when you alter the jumpers on the H terminals. Disconnect the shorting jumper from H2 to H3. Then short H1 to H3 and Short H2 to H4. It looks like all your devices use a control voltage equal to 120V.

The three heaters are located underneath the left contactor, last picture. Each heater is attached with two pan head screws.
 
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Disconnect X1 and X2 wires and read what voltage you get between X1 and X2 when you alter the jumpers on the H terminals. Disconnect the shorting jumper from H2 to H3. Then short H1 to H2 and Short H3 to H4. It looks like all your devices use a control voltage equal to 120V.

The three heaters are located underneath the left contactor, last picture. Each heater is attached with two pan head screws.

Are you suggesting I rearrange the order of the jumpers on the H terminals (H1, H2, H3, and H4) to take a multimeter reading at X1 and X2? If so, should I be looking for a reading of 220v prior to shorting the H terminals as you indicated?

Given the control voltage of 120, are the coils good as they are? In other words, would I only need to change the heaters? This has been a great education. I hope I'm not trying your patience.
 
Rather then. buy three heaters and a coil it may be cheaper to buy a newer contactor with adjustable overloads from Ebay. Or maybe you can find one with the correct heaters already installed.
Bill D

Those are mechanically interlocked reversing contactors. New heaters will be much cheaper than new contactors.

Rons is correct about rewiring the transformer. If you are hesitant, after rearranging the input side disconnect a wire on the output side and verify you have 120V before energizing the rest of the circuit. Your coils is 120V, so they will still be proper after reconfiguring the transformer.

Your machine will still function properly with the wrong heaters. You may trip out an overload with a heavy cut, but it will be usable with spindle loads less than 1/2 rated power.

How about a couple pictures of the whole mill? I've never seen a Series 1 manual Bridgeport with an electrical cabinet.
 
Are you suggesting I rearrange the order of the jumpers on the H terminals (H1, H2, H3, and H4) to take a multimeter reading at X1 and X2? If so, should I be looking for a reading of 220v prior to shorting the H terminals as you indicated?

Given the control voltage of 120, are the coils good as they are? In other words, would I only need to change the heaters? This has been a great education. I hope I'm not trying your patience.

Remove wires from X1 and X2 for safety.
Remove jumper from H2 to H3.
Jumper H1 to H3 and H2 to H4.
Apply 220V to H1/H3 and H2/H4.
Read voltage on X1 to X2. If the reading is 120V then go pop a beer. :cheers:

If you have trouble getting heaters then it's possible to install a different overload heater block with a adjustment control, would just involve a moving a couple of wires. But to keep things stock get the heaters for the new voltage range.
 
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Those are mechanically interlocked reversing contactors. New heaters will be much cheaper than new contactors.

Rons is correct about rewiring the transformer. If you are hesitant, after rearranging the input side disconnect a wire on the output side and verify you have 120V before energizing the rest of the circuit. Your coils is 120V, so they will still be proper after reconfiguring the transformer.

Your machine will still function properly with the wrong heaters. You may trip out an overload with a heavy cut, but it will be usable with spindle loads less than 1/2 rated power.

How about a couple pictures of the whole mill? I've never seen a Series 1 manual Bridgeport with an electrical cabinet.

Thanks, gbent. I appreciate the information. At least I'll be able to operate until I find the proper heaters.

Thanks for your interest in the mill. All I have here is a couple pictures, and one is not so good. If you want to see anything else on it in particular, let me know, and I can post this evening.

s-l1600(1).jpgs-l1600.jpg
 
Remove wires from X1 and X2 for safety.
Remove jumper from H2 to H3.
Jumper H1 to H2 and H3 to H4.
Apply 220V to H1/H2 and H3/H4.
Read voltage on X1 to X2. If the reading is 120V then go pop a beer. :cheers:

If you have trouble getting heaters then it's possible to install a different overload heater block with a adjustment control, would just involve a moving a couple of wires. But to keep things stock get the heaters for the new voltage range.

Wonderful, rons! Do you think small pieces of wire with the proper connectors will serve well enough as jumpers between the H terminals?

I'm definitely looking to keep things stock, so I'll be watching for the proper heaters.
 
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Do you think small pieces of wire with the proper connectors will serve well enough as jumpers between the H terminals?

If it was done properly at the factory, the links connecting H2 and H3 are double stacked and are to be used to make the connections.

Thanks for the picture. Evidently it was purchased by a company who was a stickler for the regulation that nothing should restart automatically after a power failure. I hadn't seen an electrical cabinet like it, but the "manufactured for Bridgeport" label on the starters suggests it was a factory option.
 
Wonderful, rons! Do you think small pieces of wire with the proper connectors will serve well enough as jumpers between the H terminals?

That strap looks like a shorting bar for a bench power supply, which shorts a negative supply terminal to earth ground. I made some myself out of some .025 stainless. For you I would use about .050 thick stock.
Not sure if your transformer terminal screws will fully extract.

Cut out two rectangles, mill slots on same end and just slide into position. That's for a nice looking job.

(Otherwise almost anything will work. If you use a couple of paper clips then it would look :ack2:)
 
If it was done properly at the factory, the links connecting H2 and H3 are double stacked and are to be used to make the connections.

Thanks for the picture. Evidently it was purchased by a company who was a stickler for the regulation that nothing should restart automatically after a power failure. I hadn't seen an electrical cabinet like it, but the "manufactured for Bridgeport" label on the starters suggests it was a factory option.

Thanks, gbent. I'm glad I asked about the connections. I suppose jumpers for connecting adjacent terminals are easy to come by. I'll make my connections using jumpers like the one now connecting H2 and H3. I'll swap H1 for H4 and jumping H1 to H2 and H3 to H4 should then be doable.
 
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Ok, rons. machining the pieces occurred to me, too. Thanks for the stock size recommendation. Using a commercial jumper also seems like a reasonable approach. In the meantime, I'll use a little solid-core wire to jump the terminals, just to see if I can get the machine running. I'll let you know how it turns out.
 
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Thanks, gbent. I'm glad I asked about the connections. I suppose jumpers for connecting adjacent terminals are easy to come by. I'll make my connections using jumpers like the one now connecting H2 and H3. I'll swap H1 for H4 and jumping H1 to H2 and H3 to H4 should then be doable.

I'm not sure you are following well. Typically, H1 goes to H3, H2 goes to H4, and the links connecting H2 and H3 are removed and used to make the prior mentioned connections.

You can google images for "wiring diagrams for 120-240/480 transformers" to see a proper wiring diagram. It is up to you to decide if it fits your transformer.
 
Thanks, gbent. I thought rons said the following:

Remove wires from X1 and X2 for safety.
Remove jumper from H2 to H3.
Jumper H1 to H2 and H3 to H4.
Apply 220V to H1/H2 and H3/H4.
Read voltage on X1 to X2. If the reading is 120V then go pop a beer.


Do you agree with the rons's jumping arrangement above? Sounds to me like you are saying remove the double stack and jump H1 to H3 and H2 to H4. Thanks for your patience.
 
Thanks, gbent. I thought rons said the following:

Remove wires from X1 and X2 for safety.
Remove jumper from H2 to H3.
Jumper H1 to H2 and H3 to H4.
Apply 220V to H1/H2 and H3/H4.
Read voltage on X1 to X2. If the reading is 120V then go pop a beer.


Do you agree with the rons's jumping arrangement above? Sounds to me like you are saying remove the double stack and jump H1 to H3 and H2 to H4. Thanks for your patience.

Yes, thats what I am saying. I believe rons actually said the same thing, but notice he renumbered the terminals in his post. See below:

If you number them from 1,2,3,4 going from bottom to top,
 
Yes, thats what I am saying. I believe rons actually said the same thing, but notice he renumbered the terminals in his post. See below:

Right about that. I had to use some numbering order because the first picture was out of focus. I made corrections to my posts to match your transformer.

If you want to understand about the jumper(s):

index.png

For a high voltage input the terminals H2 & H3 are connected together, the winding from H1 to H3 and the winding from H2 to H4 are in series.
For a low voltage input the terminals H1 & H3 are connected together and the terminals H2 & H4 are connected together. The winding from H1 to H2 is in parallel with the winding from H3 to H4.
 








 
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