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Wiring a a transformer to step up voltage question

BigIron101

Plastic
Joined
May 20, 2018
I need to step my 240 3ph up to 460. Wiring a transformer backwards so my input is going in on the "x" side, out on "h" side. My output is going to a step down transformer back to 240 3ph but so I can get 24v 3 phase. My question is what do I do with my ground wire going into the first transformer? The second one also has green ground wires that need to go somewhere, do I just put them together so I have circuit protection. Right now with no ground hooked up my machine does run, it just doesn't seem right to me. Thanks
 
Why can't you go straight into the 240 input of the machine and save the step up-step down? Is your 240 service wye or corner grounded delta? You should have an earth ground on the machine frame for safety reasons. If you connect your green wires to the frame you could get in a situation where you have a hot frame because of leakage in the transformer. In other words, more information is required.

Bill
 
I am using a rotory phase converter to get my 240v 3ph. I was told the only way to get the 24v 3ph was by stepping down through a transformer. It's for a Clausing Colchester Combi 4000 lathe.
 
How does stepping 240V 3Ph up to 460V 3ph, and then back down to 240V 3ph, get you 24V 3ph?

You need to provide more info....
 
I was told that the only way to get the 24v 3 phase was by going through a transformer. Everything works I am confused about the ground issue.
 
I am using a rotory phase converter to get my 240v 3ph. I was told the only way to get the 24v 3ph was by stepping down through a transformer. It's for a Clausing Colchester Combi 4000 lathe.

That is what you must do if the required voltage is 24V 3 phase (twenty four volts three phase). You wrote 24V 3 phase twice so is that right, or do you mean 240V 3 phase?

Why you would step up to 460 VAC?
 
That is what you must do if the required voltage is 24V 3 phase (twenty four volts three phase). You wrote 24V 3 phase twice so is that right, or do you mean 240V 3 phase?

Why you would step up to 460 VAC?

Yes the machine is 240 volt 3 phase main power but also needs 24 volt 3 phase. The 24 volt 3 phase is why I need to go through the transformer. Sorry for the confusion.
 
The point is, you do need a transformer to get 24V 3ph from 240V 3ph, but you need a transformer that converts 240V 3ph to 24V 3ph.

There is no need to convert the 240V 3ph to 460V 3ph, unless you happen to have a 460V 3ph-to-24V 3ph transformer that you have to use.
 
I believe the transformer that came with the machine goes from 460v 3 phase and steps it down to create the 240 volt 3 phase and also the 24 volt 3 phase. It also sends 110v single phase to the machine I believe. I have a total of 9 wires from second transformer to the machine. I bought it used through a machine jockey and this is how they had it wired when I looked at it because the only had 240v three phase in their building.
 
Well, now that you have told the whole story, it does sound like using the 240v to 460V transformer is what you need to do.
 
So what do I do with the green ground wire coming to the first transformer from my rotory converter? How do I ground my lathe so it is protected? Again sorry about the confusion.
 
Why can't you go straight into the 240 input of the machine and save the step up-step down? Is your 240 service wye or corner grounded delta? You should have an earth ground on the machine frame for safety reasons. If you connect your green wires to the frame you could get in a situation where you have a hot frame because of leakage in the transformer. In other words, more information is required.

Bill

Make a drawing on paper to identify how the transformers are configured. Read '9100's words again. Take pictures.
 
If you are feeding the rotary converter conventional single phase 240 V, the ground in the common of the incoming line which is 120-0-120. If the 240/480 transformer is wye connected in the 240 V winding and fed from your converter, you cannot ground the winding unless it is actually two 120 V windings in series. You need to draw up exactly what you have or get someone who really understands the system. Otherwise, if you are lucky you will only blow a fuse, but it can be a lot worse. This is not a place for an amateur experiment.

Bill
 
I'm seriously questioning your interpretation of something needing 24VAC 3 phase. It would have to be for something totally oddball and custom; that is not a standard voltage for anything. If true, the first thing I would try to do it replace it with something off the shelf. It's more likely that you are reading something incorrectly. Can you post something that says that?
 
I'm seriously questioning your interpretation of something needing 24VAC 3 phase. It would have to be for something totally oddball and custom; that is not a standard voltage for anything. If true, the first thing I would try to do it replace it with something off the shelf. It's more likely that you are reading something incorrectly. Can you post something that says that?

I'm thinking this is 24V taps off a control transformer that feed an "H bridge" style 3 ph. input bridge rectifier for 24VDC control voltage. I have a Battenfeld molding machine with a power supply like that, which has input taps for every standard voltage from 208 to 460. Rather than screwing around stepping the entire input up to 460, it would be worth finding someone who can design a new method of providing 24VDC, since it likely doesn't require much current capacity, but the OP doesn't sound quite up to the task.

Dennis
 








 
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