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Which transformer to get to step up 240v to 480v?

Jaxian

Stainless
Joined
Feb 24, 2013
Location
Santa Cruz
Hey guys, could use some help on a transformer question. I just picked up a Monarch series 62 Dyna-shift tracer lathe. While I was attaching the wiring to the disconnect I noticed there was no way the #4 wire I had run would fit in the connectors. I knew that was the correct size for the 20hp motor on the machine so was stumped for a second then realized the machine was set up for 480v.

Everything in the cabinet and the main motor are 240v/480v so I figured no big deal. Then I started looking at all the I believe they are called heaters and other stuff in the cabinet that had amp ratings and it was all ok for 480v but not rated high enough to switch to 240v. It was like 25hp at 480v but only 15hp at 240v.

So I have read on here that trying to over current those is obviously bad and all the wiring and everything is too small for 240v current.

So I am guessing the easiest thing to do is get a step up transformer from 240v to 480v. The rating on the motor is 24.7 amp at 480v and there is a little 1hp hydraulic pump for the tracer but that is about it for load. Not a lot of electrical stuff on this machine.

TLDR:
Any recommendations on what transformer to get to step 3 phase 240v to 480v with a 25 amp load (20hp motor).

Thanks guys.
 
If you were not across the continent...

I've got just the piece for your needs, I no longer need to use it Square D! but it is HEAVY and far away........

This post is just a tease. Seek and you will find!
 
When I bought my NEW three phase transformer from ACME nearly 20 years ago they wanted 1.5 times on the KVA (as compared to HP) - that would put you at 30 KVA. That's like 72 amps on the 240v
 
I can't imagine a lathe motor being asked to put out full HP for extended periods. The 1.5 over is likely VERY CONSERVATIVE. Heat being what it is.
 
Reading the NEMA table it said for that motor at 240v it wanted a 70amp circuit even though the motor max amp draw at 240v was only 49.7 amps. The wires and circuit breaker I set up were for a 70amp circuit. So big enough to feed the appropriate transformer.

I just looked on a transformer website and got overwhelmed by the number of selections to pick the correct one.

So you guys are thinking a 30KvA 3 phase unit is right? What would the nomenclature for that look like if I wanted to look for one?
 
This is the electrical enclosure. I am pretty sure most of it is original. I don't know very much about electrical but if I have to hack out and rewire all those big starters that don't have a high enough rating at 240v that would be a huge mess. Also I assume finding the correct replacements and ones that will fit back in the same place would be tough. I don't know how much of the other stuff in there needs to be changed either.

If this box looks like I can just switch over to 240v then I will, but that big double starter thing with the visible plate says it's only good for 15hp at 240v. Is that plate for both of them? Seems dumb that they would make it 240v/480v and make all the wiring and starters only good for 480v.

Or is there something else that needs changing also? Heaters?

Series 62 electrical 001.jpg
Series 62 electrical 002.jpg

If you guys need better pictures let me know and I will take them close of whatever you need.

No idea why it has a sideways duplicate picture.
 

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Tried to zoom in on the data plate of the main starter relay thing that has the rating that seems too low if it is both. If that doubles with the other one with no data plate that seems to be connected to it then I guess I can just swap it to 240v. Would that work or is there more?

Series 62 electrical 003.jpg

EDIT: Other than swapping all the transformers and motor wires and other stuff that is 240v/480v changeable.
 
First off you are never ever ever going to run an engine lathe at 25 hp. Maybe if it had 30" swing and you were turning rolls but certainly not anything in the 14" - 18" swing size.

Second is, it's really unusual for a dual-voltage machine to have undersized wiring. It wasn't worth the $3 savings on copper to do that. I wouldn't say impossible but def unusual.

Very first thing I would do is check the motors to see that they are dual-voltage. If you can reconnect them, then it's a simple job of heaters and maybe switching the leads on a control transformer. The cost of shipping alone on a 240-480 v 3 phase tranny is going to be many times what a few heaters cost.

If the motors are not reconnectable then you're stuck, but if they are, you're never going to even pull 10 hp on that thing, so don't worry about it.

Check the control voltages while you're in there, should have a separate transformer with taps you can connect for different voltages. Otherwise the coils in the contactors might have to be changed too.
 
Reading the NEMA table it said for that motor at 240v it wanted a 70amp circuit even though the motor max amp draw at 240v was only 49.7 amps. The wires and circuit breaker I set up were for a 70amp circuit. So big enough to feed the appropriate transformer.

I just looked on a transformer website and got overwhelmed by the number of selections to pick the correct one.

So you guys are thinking a 30KvA 3 phase unit is right? What would the nomenclature for that look like if I wanted to look for one?

Three Phase Dry Type General Purpose 480 / 240. Acme did not mind my smaller one being run "backwards" as a step up but being MADE as a step down. May be a differing story on 30 KVA - ASK THEM. Step ups are generally far and few between. All these NEW will come at a hefty price

Zero issues on mine over the last 18 years
 
Ok, based on what everyone is saying here and my own opinion there is no way Monarch makes a machine like this dual voltage and doesn't put in big enough wiring. Makes no sense.

So the thing that started me worrying is this box on top of the factory electrical panel. It is a non factory disconnect as required in California. Notice it is a 480v box with lugs way too small for 240v wires. The wires out from main panel do look to be #4 size and capable of 240v service. Can't read the writing on them. My wires are #2 as it was all I had and the cost of wires is too much now to not use them.

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Here are all the motor plates. Main, tracer and coolant. All dual voltage.
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There are a number of other transformers and starters and they are all dual voltage. So if that main starter is a double of the visible rating plate then I should be good to go.
 
Here is the main starter. It appears to be wired together. It only has one plate on it. On that one plate the numbers are too low at 240v, but if you can double that number then it is just fine. Crossing my fingers. What do you guys think? I have not seen enough of these to have enough experience to form an opinion, more of a guess.

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I appreciate what your are saying Thermite, these systems are basic and can be rewired by someone with a bit of knowledge.

What I am trying to determine, and it seems like the case, is that I don't need to replace anything other than that non factory 480v disconnect. I just have to switch all the 240v/480v stuff to the 240v settings.

If there are other parts I need to switch please let me know. I will hit the electrical supply place tomorrow and get a disconnect and a 70amp circuit breaker for it.
 
There are copper adapter terminals that you can get at your local home center that will take large bare wire on the one end and have lug or a smaller screw terminal on the other.

Without dissecting it completely, that set of starters looks like your basic reversing starter setup. If for whatever reason you thought you needed to change that out, do as has been mentioned and remove the whole panel and install the new stuff on it. There are certainly Youtube videos that will show you step by step how to wire a reversing starter setup. That or you'll be walked through a full diagram of it.

It does look like all your motors are multi voltage, so no problems there.

On the other side, as mentioned earlier, I also ran a transformer backwards for years without trouble.Even in a rotary phase convertor situation. See if there's a surplus electrical supplier in your area. That's where I got mine and all that I wanted with it. Mine was aluminum wound, so bigger then it would have been otherwise, but also less expensive. Granted this was 20 years ago. I did have both a 220 and 440 breaker panels feeding the system. Not sure how much of all that you'd need for a single device.
 
If there are other parts I need to switch please let me know. I will hit the electrical supply place tomorrow ...
Before you get carried away buying stuff (have you ever made a single trip to the hardware store ? :D) ...

Most of the time it's not a problem but I collect the anomolies so nowadays I look first ... pull the covers off the motors and make sure they have all the wires to reconnect at 240v. There ARE single-voltage motors out there, or people switch stuff around, or whatever. The thing is 50 years old, after all. If the main motor is 480 only then you have to do a little thinking ... name plates are not the complete story.

And check that the coils for the contactors are 110 and you have a control transformer that can be rejumpered. It's rare, but I have seen higher-voltage contactor coils.

The one contactor you mention as "the main starter. It appears to be wired together" is most likely a forward-reverse set of contactors. It's set up so that when you are connected in forward, you cannot connect in reverse. There should be a lockout bar in there somewhere.

Yeah, you can probably get by not changing the heaters but they only cost a couple bucks. When you are working hard one Friday night and kick one out and there's no place to get one until Monday, you'll probably wish you'd changed them. As a cheapskate I have experience in this field :)
 
I've purchased several dry pack transformers at auctions over the past ten years at a fraction of the new price. If I were you, I'd check with local dealers that deal in used commercial /industrial electrical supply and see what you can locate.

You might even find something local on e-bay or Craigslist.

They are extremely simple to wire.
 
If you change the voltage and find sourcing heater elements for the old Westinghouse difficult just buy another starter.

My Series 62 was supplied with the a similar but single direction starter, I replaced it with a NOS but more contemporary CH reversing starter

No pics of the old, here is the new one fitted an easy swap.

If possible go with the low voltage change, much more practical in your situation.

Steve
 

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