Help Choosing a Transformer

c91x

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Bridgeport 2J 1.5 hp that is wired for 480v. I only have single phase 240 in the shop.

It appears rewinding my motor is not as cheap as it used to be so i'm looking for other options and no the motor does not have 6 or 9 wires. It has 3 heading into the housing and the other voltage numbers on the name plate have been stamped over.

I would like to find a transformer to backfeed that will be enough to power this one machine. I'll either run it after a rotary phase converter or run it single phase 480v feeding a 480V VFD. With the VFD i will have to go to a 3-5hp rated one because of having to derate it for single phase input.

Can anyone suggest a tranformer that will work? I've been reading and researching and it appears a 3kva will do the trick but i don't want to waist money on a smoke show if i choose wrong.
 
I have taken motors to a electric motor shop and had the extra leads brought out so they could be connected for low volts. Otherwise, a 3 phase buck/boost transformer would work, I had a radial drill in my shop that we did this with, but we had "real" 3 phase power.
 
Probably best to speak to someone in technical at Automation Direct or Wolf Automation. Not an electrician but the 2 approaches I have seen is similar to what you have outlined which would be an 240 single phase to RPC with a 240 to 480 3 phase step up transformer in the 3-6kVa, the latter has listing at Automation Direct, the 6KVA can be fed as step-up or step-down (they run around $600). Otherwise a single phase step-up transformer feeding a 3-5 Hp 400-480 VFD. Technically although the VFD is derated, the input would need to be at the VFD rated 3 phase input x ~1.7 for single phase. There are also issues with THD with single phase input on a 3 phase input VFD, often a DC choke is required when running a 3 phase VFD off of single phase. So something like a 3kVa for 3 Hp, 5kVa for a 5 Hp VFD. The VFD's run in the $200-300+ range for a 3-5 Hp 400-480VAC 3 phase input. So price wise not much difference in either path. A replacement 240VAC 3 phase input 2 speed 3 Hp VFD rated motor is not much more.
 

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As much as I dislike VFDs, this sounds like the most appropriate solution. The transformer(s) will be very costly, even used. In essence, three transformers will be required, A-B, B-C, C-A. You can wire "open delta" with two transformers, but. . . The final output will only be 56%, if I remember correctly. The inverse of square root of three rides in my mind as well. I'm not sure which one fits. The last stroke did have some effects. . .

In any case, the transformers must be sized to the application. The "full load amps" or FLA will be listed on the motor nameplate. Multiply that by 480 then divide by 1000 to get kilo volt amps or KVA, the normal measurement for transformer sizing. With the transformers, you will still need a phase converter,

There is a control transformer of fairly common design with a metal can (squared corners) that should be reasonable cost. They are available from 250 VA up to dozens of KVA. In my day, they were available for about $50 bux and up, depending on size, to several thousand bux. Todays prices will be higher. . . They are classed as "Dry" and "Sand Cast" types. Each transformer will have eight(8) leads, H1, H2, H3, H4 and X1, X2, X3, X4. H1-H4 will be 240/480 and X1-X4 will be 120/240 volts. I highly recommend local acquisition, they are heavy.

Acme is a common brand, though not the only brand, and can be seen at:

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With the big money of VFDs and transformers and such, would it be cheaper and easier to just get a 240 1 PH motor.

If you were really interested in the VFD for speed control then just buy a 220 3ph motor instead of the messing with transformers and filters.

There are a lot of 220 1 ph Bridgeports out there so it means someone makes a motor that will bolt on.
 
Thank you for all the comments. Your responses scared me enough to call a few more motor repair shops.

With the big money of VFDs and transformers and such, would it be cheaper and easier to just get a 240 1 PH motor.

If you were really interested in the VFD for speed control then just buy a 220 3ph motor instead of the messing with transformers and filters.

There are a lot of 220 1 ph Bridgeports out there so it means someone makes a motor that will bolt on.

The 2J has a long shaft for the vari-disc setup. I can't find anything besides new 2hp units for 1200.
I have taken motors to a electric motor shop and had the extra leads brought out so they could be connected for low volts. Otherwise, a 3 phase buck/boost transformer would work, I had a radial drill in my shop that we did this with, but we had "real" 3 phase power.

I found a shop that will do this for $200. The other shop i had called didn't even mention this so thank you.
 
Worth checking both of these vendors out for Bridgeport parts. Mataco has an extended shaft that is suppose to work with many standard 2 Hp motors per their description, they also sell replacement motors but expensive.
https://www.machinerypartsdepot.com/

 
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