240 to 120/240v transformer

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lowvoltman

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I've got a request for a single phase trans. 120/240 v to 120/240 v wired like the attachment.
Why would anyone even need a trans. in this case? What would the be the safety issues if the neutral was not grounded
on the secondary side? I don't get it.?
 

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lowvoltman said:
I've got a request for a single phase trans. 120/240 v to 120/240 v wired like the attachment.
Why would anyone even need a trans. in this case? What would the be the safety issues if the neutral was not grounded
on the secondary side? I don't get it.?
Click to expand...

IMHO... It could have been added as extra impedance in a system, or to act as a filter.
 
If the input is at the top, then the transformer is taking a possibly floating 120V input and producing center tapped 120/240.
There could be a variety of reasons to do that.
One would be to get a balanced 120/240 from a single ended 120 input without using an autotransformer (for some unknown reason).
The X to Y input is NOT 240.
 
That diagram doesn't indicate what connections you are going to use, so why would anyone assume anything? Could be that they just want a reliable source of 120V from a 240V supply. If for example it's in a control panel for a machine that might be connected to a 120/240 3 phase 4 wire delta system, which terminal you tap off of to try to get 120V without a CPT can result in you getting 208V and frying your controls. So by specifying a CPT wired as 240V primary, 120V secondary, the phases used to tap to the primary become irrelevant. That's the most common reason by the way.
 
Jraef said:
That diagram doesn't indicate what connections you are going to use, so why would anyone assume anything?
Click to expand...
I see the diagram as showing a parallel connection of the input windings on the H side and a series connection (with center tap) of the secondary windings on the X side. Given that the transformer is rated as 120/240 to 120/240, what more were you expecting to see?
 
I see something in this that makes no sense to me.

The transformer is suppose to be 120/240 to 120/240.

Ok' we can't drive the two 120 volt windings in parallel with 240
volts Right?

What voltage are X and Y

Where is this neutral coming from, shouldn't the neutral be H1 and H3 or H2 and H4?



Or is this Transformer suppose to be a 240/480 to 120/240?

Forget about that I thought of two more reasons it could be used this way

1.-They just have one circuit free in there panel or they want to use a 1 pole breaker.
2.-Or as Jon said if they wanted to use this to drive a 120/240 Log cabin service with a 120 volt Generator.

But you need to do some work on the H side.
 
I used one to power the active filter for my European Bose-901 speakers when I brought them back to the states. The filter needed 240VAC which was hard to find in a receptacle in rental property. Ditto for EU sewing machine, apartment sized refrig., waffle iron, steam iron, ....

It's just a transformer.
 
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