New to me VN #24! Few questions to start

I picked up a #28, excited about getting it making chips! Came with 3 heads, supports, bars with a ton of spacers, and about 3 pallets of tooling!

I find that the motors are 550 volt. I have 240V 3 phase coming in. I really do not want to get an odd ball transformer that will never be used for anything else. My thoughts are replace the spindle motor (284 frame, still available) with a 230V and have the motor on the gear box re-wound for same, reason being looks like that frame (204) is now obsolete. Anyone who has been down this road, I am all ears! How are you running a 550 volt system? If it were 480V I would get a bigger transformer than needed and set up a panel with room to grow, but this is a bastard size to me.

I am sure I will have more questions as I get this thing going.

and just noticed that I had a typo in the title, and cannot seem to change it.......Indeed it is a 28 universal mill.....

Transformer is the easy way to do this. For one thing, those motors are a lot better than anything you will be able to buy now. My experience with rewinds is that they are just not the same quality as factory new. I picked up a 15KVA transformer to step up a mill that was 440-only from my rotary converter. I think I gave $100 for it.

The rewind alone is going to be $500 or more. Electric motor rewinding is something that doesn't scale. A 5hp motor rewind doesn't cost 1/10th the price of a 50hp. They cost pretty much the same, except for material cost, which is probably just a few hundred bucks. The wire is not the expensive part, the cost is cutting, burning, cleaning and the actual winding and installation of the coils.

spock said:

I picked up a #28, ...

I find that the motors are 550 volt. I have 240V 3 phase coming in. I really do not want to get an odd ball transformer that will never be used for anything else. ... If it were 480V I would get a bigger transformer than needed and set up a panel with room to grow, but this is a bastard size to me. ...

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What's the HP rating of the motors?

Assuming 5HP spindle and 2HP feed motors, you probably need about 5kVA total (actually a bit more, but it's doubtful you'd ever need to run both spindle and feed at full power). 5kVA at 550VAC draws about 9A per phase, let's call it 10 to make things easy. One option is to get a large, 3-phase isolation transformer to convert 240VAC to 480VAC, then use two or three small, single-phase boost transformers to bump the 480 up to 550. A boost transformer doesn't need to handle the full power of the load, just the product of the voltage difference and the load current. You need a 15% (70V) boost at 10A, so 750W (minimum) boost transformers will do the trick (1kVA would be better). Common step-up/down isolation transformers can be used as boost transformers, but you have to pay attention to the insulation ratings and current limits of the various windings. This is a job for an industrial electrician. IIRC, 550VAC is used in Canada and 550V machines show up mostly in the northeaster US, so look for a guy who's worked up there.

Here are discussions about powering a 550VAC machines:
https://www.practicalmachinist.com/vb/bridgeport-and-hardinge-mills-and-lathes/hardinge-hlv-h-220v-550v-320559/index2.html
https://www.practicalmachinist.com/vb/general-archive/have-220-volts-need-550-volts-90939/

Cal

Here's how I powered my 575-V Aciera F5 mill: link. I bought two single-phase 600:240 isolation transformers on eBay for less than $200 each, and wired them open delta, corner grounded. The F5 has a 3 hp spindle motor and a 1 hp feed motor.

spock said:

I picked up a #28, excited about getting it making chips! Came with 3 heads, supports, bars with a ton of spacers, and about 3 pallets of tooling!

I find that the motors are 550 volt. I have 240V 3 phase coming in. I really do not want to get an odd ball transformer that will never be used for anything else. My thoughts are replace the spindle motor (284 frame, still available) with a 230V and have the motor on the gear box re-wound for same, reason being looks like that frame (204) is now obsolete. Anyone who has been down this road, I am all ears! How are you running a 550 volt system? If it were 480V I would get a bigger transformer than needed and set up a panel with room to grow, but this is a bastard size to me.

I am sure I will have more questions as I get this thing going.

Click to expand...

Cal emailed me to chime in here. I seem to be a resource for problems like this.

I need more info to help out here:

1. A list of all motors on the machine (you list 2 and there may be more), good photos of each nameplate is most helpful.
2. What kind of 240 Volt 3 phase do you have? Delta corner ground, Delta floating ground, 120/240 High leg delta?
Or do you have a 120/208 Volt system.
If you are not absolutely sure of your power, post some photos of the transformers feeding your service.
3. Pictures of the inside of the electrical cabinet.

Bill

spindle motor is 7.5 hp (8 amp), feed motor is 1.5 hp.(1.8 amp)

My incoming in 123/123/213 (245 line to line)

I am still leaning toward a rewind on the feed motor. It is about 70 years old. Yes, I know they don't make them like they used to, but my thinking is why buy a weird transformer to run a motor that cannot be replaced? Rewind now or maybe later and buy transformer? Does not seem to balance out. A good local motor shop is comfortable with the project and replacing the spindle motor and rewinding the feed is still cheaper than one transformer (not including the option mentioned above by rklopp).

You have a 120/240 Volt High leg (wild leg) system, an excellent choice for a small shop.

Are both motors single speed?

Pictures of what is inside the electrical cabinet are needed to determine if what you are proposing to do, is a viable solution. Unless one of the following questions really is the killer, I would go the this way if it was mine.

Are the motor starters US NEMA or European standards?
Are the motor starters large enough to operate the motors at 240 Volts? NEMA 00 and a 1 or larger? Is there room to change them if needed?

Depending on what it has for thermal relays for motor protection, either heater replacement or thermal relay replacement will be required.
Are the heaters available? Is there space to replace the relays with more modern replacements?

Are the wires to the spindle motor 12 AWG. or larger?
Is the main disconnect and wiring rated for at least 30 amps (10 AWG wires or larger)?
Are there any line voltage fuses? They will need to be changed to higher amperage too.

Then on to the control transformer, does it have 240 Volt taps? If no control transformer, what is the coil voltage of all motor starters and relays?

All of the above questions need to have answers before changing/rewinding motors.


Since you have a 120/240 high leg system, there are several transformer systems to increase the voltage and will keep the existing motors and controls intact. This may be the least effort solution. Make sure that you have a way to turn off the transformers when not in use, (saves electricity and heat) a wall mounted fused disconnect by the machine works well for this. Circuit breakers seem to get forgotten if they are the only way.

If you go ahead with the motor change/rewind route, I would make sure everything that is done will leave the machine as a 240/480 volt.
When rewinding the motor, have it done as a 240/480 Volt. This will keep it's value when a new owner is needed. If it is in nice shape, it probably will outlast you.

1) yes, single speed
2) see picture
3) Nema
4) Nema 1, I think plenty of room if needed
5) heaters: yes C8.67A and C2.2A
6) 12 AWG
7) yes, 30 easy
8) yes, replaceable fuses
9) transformer/coil voltage: has an option for 220 volt primary (I have the book with schematics)

My brother is an excellent electrician, but is out with a bum knee, so I really appreciate the help!

I think everything looks OK for the rewind, only thing is the contactor for coolant pump robs voltage from the drum switch to get the 550 it needs. I will pull that pump and replace with something else and cut off voltage to that contactor.

spock said:

9) transformer/coil voltage: has an option for 220 volt primary (I have the book with schematics)


I think everything looks OK for the rewind, only thing is the contactor for coolant pump robs voltage from the drum switch to get the 550 it needs. I will pull that pump and replace with something else and cut off voltage to that contactor.

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Not sure why the last 2 lines in the quote above don't show in your post.

The book and schematics will be for a standard US machine, 220/440 for that vintage.
The transformer in the pix appears to have only 4 wires from it to the terminal strip, so it may be only single voltage primary. EZ to change out.
Is the coolant pump contactor the one in the top of the box? If yes, just rewire the wires to the top of it to after the disconnect and use it to power whatever you use for a pump.

Those are GE starters and ebay is full of heaters.

Bill

Is the coolant pump contactor the one in the top of the box? If yes, just rewire the wires to the top of it to after the disconnect and use it to power whatever you use for a pump.

Yes, and it took some head scratching to figure out why that one was 550 volt to such a small motor. By getting some voltage from the drum switch, they set up a safety so you cannot power feed table unless spindle is running. Pretty slick.