Advice powering 3-phase 440v 7.5hp lathe

[jbruning]

Hi All!
Looking for some advice.
I may have the opportunity for a lathe that is 440/480v three phase only with a two speed 7.5 hp motor. Full load current around 10.5 amps.
I don’t have three phase or 440/480 power and am wondering what my options are and if they are affordable enough to purchase the lathe when the lathe comes available (shop is ‘planning’ an upgrade).

I have searched on the forum and found some helpful and interesting information but I’m not sure if I have everything straight piecing it together from the different threads.
I have 240V single phase available. Closest/easiest source is a 100 amp subpanel within about 30ft (probably about 50ft wire run). My initial thoughts were to either build or buy a 10hp rotary phase converter but when using a 7.5 hp lathe as a load in a couple of the commercial RPC manufacturer’s calculators, it specs out a 15 hp RPC. Only the lathe would be run off the RPC. So in your experience would the 10hp be undersized?

Since a transformer would also be needed, I don’t know how the demands or losses of that might affect the size of the RPC required or the specific size and specs. of a transformer. A simple calculation of 480vx10.5A= 5040va x 1.732 = 8,729 but I don’t know how much ‘extra’ capacity might be needed for startup loads. My initial thought was 15kva.

Looking at the used market for transformers most of what I see are step down and may be able to be reversed but many I see are 480delta/208wye.
I have seen a couple of new ones that are 240v step up to 480wye…close to $2k. Does it sound like something along those lines is my best bet?

Thanks,
John

 

[Overland]

Most US made industrial 3 phase motors can be wired either 220 or 440 volts. If you check the nameplate you can see if this is the case.
If I'm right, quite easy to convert to 220 volts.
At 220 volts, the amps will double, so 21 amps.
An idea may be a VFD ( variable frequency drive). This will take 220 volts single phase and supply 220 volts 3 phase.
I have a lot of experience, and good luck with Fuji.
This one would work well for you:

Fuji Electric - FRN0047C2S-2U

FRN0047C2S-2U | Fuji Electric | $571 in stock.

This model will supply 26 amps, 3 phase, 220 volts.

You will need an isolation switch of some sort, and you must wire the motor directly to the VFD.
If you have a clutch on your spindle, no problem.
If no clutch and direct link from motor to spindle, you will need to switch the VFD on/off directly (low voltage control circuit) quite easy to do.

This is a very simple convenient way create 3 ph from single phase.

good luck,
Bob

 

[BT Fabrication]

yes, big loaded motors need about double on a rotary converter to deal with inrush amps. if not it can burn things up inside the motors and keep tripping breakers.
better bet is spend the $1300-2000 and but a single phase motor to replace it.

 

[jbruning]

Most US made industrial 3 phase motors can be wired either 220 or 440 volts. If you check the nameplate you can see if this is the case.
If I'm right, quite easy to convert to 220 volts.
At 220 volts, the amps will double, so 21 amps.
An idea may be a VFD ( variable frequency drive). This will take 220 volts single phase and supply 220 volts 3 phase.
I have a lot of experience, and good luck with Fuji.
This one would work well for you:

Fuji Electric - FRN0047C2S-2U

FRN0047C2S-2U | Fuji Electric | $571 in stock.

This model will supply 26 amps, 3 phase, 220 volts.

You will need an isolation switch of some sort, and you must wire the motor directly to the VFD.
If you have a clutch on your spindle, no problem.
If no clutch and direct link from motor to spindle, you will need to switch the VFD on/off directly (low voltage control circuit) quite easy to do.

This is a very simple convenient way create 3 ph from single phase.

good luck,
Bob

Thanks. I will give that a look. I know there are some safety switches and things in the control panel, but that could be figured out with the control circuit. IF the motor can't be wired 220, the VFD could maybe be run a single speed motor at 30hz to get the other half of the speeds, if there would be enough torque and no overheat problems.

 

[jbruning]

yes, big loaded motors need about double on a rotary converter to deal with inrush amps. if not it can burn things up inside the motors and keep tripping breakers.
better bet is spend the $1300-2000 and but a single phase motor to replace it.

Thank you! I wasn't sure how to figure the inrush demands so that makes sense. Single phase conversion could be an option I suppose, but I don't know about the two-speed issue. With a single speed motor I would lose half of my speed options.

 

[Phil in Montana]

With the 2 speed, without a vfd you will need 480 volt 3 phase. With a vfd you can use the high speed winding only but you will still need 480 volt and the tork will drop off at the lower speed. You might be able to have a motor shop rehook the motor for 240 volt maybe. I would use a step up transformer and a vfd...so 240 single phase in 480 single phase out... to vfd 480 in single phase and then 480 out 3 phase from vfd to motor...Phil

 

[scsmith42]

I'm running a 15hp 480V sawmill edger off of a 240 30hp RPC on a 200A single phase service, via a step up transformer. Works fine.

The RPC and the transformer were both purchased used. I don't think that I have 1K invested in the pair.

The transformer can be fairly small as far as dry-pack's go, since the current load is so small.

Look around your area for a dealer in used industrial electrical supplies. They should be able to assist with the transformer.

 

[jbruning]

With the 2 speed, without a vfd you will need 480 volt 3 phase. With a vfd you can use the high speed winding only but you will still need 480 volt and the tork will drop off at the lower speed. You might be able to have a motor shop rehook the motor for 240 volt maybe. I would use a step up transformer and a vfd...so 240 single phase in 480 single phase out... to vfd 480 in single phase and then 480 out 3 phase from vfd to motor...Phil

Thanks, Phil. That is another idea that could work well. It seems like there may be a few options for me to think about.
John

 

[jbruning]

I'm running a 15hp 480V sawmill edger off of a 240 30hp RPC on a 200A single phase service, via a step up transformer. Works fine.

The RPC and the transformer were both purchased used. I don't think that I have 1K invested in the pair.

The transformer can be fairly small as far as dry-pack's go, since the current load is so small.

Look around your area for a dealer in used industrial electrical supplies. They should be able to assist with the transformer.

Lots of good ideas......This would be a nice way to go since it wouldn't require any additional messing around with the wiring on the lathe itself. Additionally, it would be easy to add any additional 240v 3 phase machines too. I am in a rural area so it may take a bit of looking around, but the used industrial electric supply is a good suggestion. Thank you.

 

[rons]

Looking at the used market for transformers most of what I see are step down and may be able to be reversed but many I see are 480delta/208wye.
I have seen a couple of new ones that are 240v step up to 480wye…close to $2k. Does it sound like something along those lines is my best bet?

You would spend a lot and have a heavy hunk of iron along with a RPC that may not be so quiet. How can you stand that?

Better to replace the motor and some coils. Probably spend less than half. My benchmark is a 5hp Baldor motor is $1000.
The other side is getting a used one for $10/hp so say $100 - $200. Replacing the bearings for no more than $100.

 

[Jraef]

...
I have 240V single phase available. Closest/easiest source is a 100 amp subpanel within about 30ft (probably about 50ft wire run). ...

Start here. ^^^
10HP @240V single phase is going to need 50A, then you will have to add for losses in whatever you do to convert. You only have a 100A panel. What other loads are on that panel? The point being that you may not have enough extra power to run this unless you increase the service size regardless of how you get power to the lathe.

 

[jbruning]

You would spend a lot and have a heavy hunk of iron along with a RPC that may not be so quiet. How can you stand that?

Better to replace the motor and some coils. Probably spend less than half. My benchmark is a 5hp Baldor motor is $1000.
The other side is getting a used one for $10/hp so say $100 - $200. Replacing the bearings for no more than $100.

The noise is a consideration. I had thought about mounting placing the idler and transformer in an attic accessible via a stair way directly above the machine, or putting at least the transformer outside. Replacing the motor and coils wouldn't be that big of a job but I haven't found an acceptable two speed available, so that may leave me a bit compromised and/or using a vfd. A few things to think about. Thank you!

 

[jbruning]

Start here. ^^^
10HP @240V single phase is going to need 50A, then you will have to add for losses in whatever you do to convert. You only have a 100A panel. What other loads are on that panel? The point being that you may not have enough extra power to run this unless you increase the service size regardless of how you get power to the lathe.

Thank you. Good points.....extrapolating the 50A to a 15hp RPC would indicate 75A then which would be a lot. The 100A panel is about 20ft from the 200A service entrance but it is in a different part of the building with much more difficult access. When the lathe is being used the only other thing operating off of that panel is a lighting circuit with 80W worth of LEDs.

 

[rons]

so that may leave me a bit compromised and/or using a vfd.

A VFD will have to be connected directly to your drive motor. Connection to your input control cabinet is not acceptable.

 

[jbruning]

A VFD will have to be connected directly to your drive motor. Connection to your input control cabinet is not acceptable.

Yes, I understand that. Thank you!

 

[scsmith42]

As per our PM - the system here will not let me send a pic via PM, but I can post one here in your thread. This is a photo of the data plate from the step up transformer that I'm using for my 15 hp edger.

 

[Overland]

You should probably start with a good understanding of the existing motor. Get a photo of the motor information plate, and post it here; then you'll get some good advice.
Bob

 

[mksj]

If the stock motor cannot be rewired for 240VAC, not sure the practicality on upsizing the RPC, buying a step-up transformer and all the ancillary costs of the install. A new 5-7.5Hp 3 phase 230/260VAC 1750 RPM replacement motor can be had for $500-600, a lot less than the cost of a step-up transformer. If the lathe is not going to be used for heavy turning, use a 5 Hp motor and this will reduce the cost of the RPC or VFD used. A VFD would be less than a new RPC, but you could make a 10Hp RPC at about the same price point if you can find a local motor and add an RPC control box. With a 5Hp motor you can either go with a native single phase input VFD like the (Yaskawa GA50UB018ABA) or use a 3 phase input VFD in a derated mode (Hitachi WJ200-075LF, FUji, etc.) which run around $700.

 

[jbruning]

As per our PM - the system here will not let me send a pic via PM, but I can post one here in your thread. This is a photo of the data plate from the step up transformer that I'm using for my 15 hp edger.

View attachment 344362

Thank you!

 

[jbruning]

You should probably start with a good understanding of the existing motor. Get a photo of the motor information plate, and post it here; then you'll get some good advice.
Bob

I don't have an image and it is located some distance from where I am, unfortunately. However, I was able to get the information that is on the plate....below.

Type AEEF
Frame 132S
Poles 4/8
Output 7.5/3.75 HP 5.5/2.8 KW
Volts 440 (note there is no indication of dual voltage)
HZ 60
Insulation 2
Rating Continuous
Amps 10/7
RPM 1720/860