reverse fed 240-460 load

[Fossil]

I have a reverse fed 240 to 460 transformer 30kva.
what is the maximum amps load at 460v that i can expect
from this transformer. The transformer is fed with 2/0awg
and of course is ungrounded ue to the removal of the grounding
strap. At present the only load is a 20amp 460v shipping container
freezer unit.

 

[infinity]

What's the "grounding strap"?

 

[templdl]

You have provided very little information about the transformer.
Can you advise what is on the name plate not just 240 and 460, delta or wye, etc.

 

[benaround]

30000/460/1.732=37.65a

 

[Pierre C Belarge]

fossil
Metallic parts are still required to be grounded/bonded. If the strap you mention that has been removed is the strap usually supplied by the manufacturer, that strap needs to be reconnected. That is not the X/O termination point. It bonds the metallic frame to the enclosure.

 

[LarryFine]

I have a reverse fed 240 to 460 transformer 30kva.
what is the maximum amps load at 460v that i can expect
from this transformer.

1. Asking the manufacturer is the best course of action.

2. Probably a bit less than 30kva for several reasons.

3. The output voltage may be a bit low, because many transformers are wound with losses in kind, and reversing the unit reverses the compensation.

 

[Jraef]

My handy little transformer slide chart says a 30kVA 3 phase transformer is good for 36A full load at 480V, requiring a max. 50A breaker. The 240V side will require a 100A breaker

 

[templdl]

Personally I would not reply to this question unless I knew more about the transformer name plate information about which has been ignored so far.
Providing an answer with so little information about the application could be a bit dangerous. How can one reply without knowing more about the transformer. Is it being assumed that it has a HV delta to a LV wye?

 

[LarryFine]

Personally I would not reply to this question unless I knew more about the transformer name plate information about which has been ignored so far.

Too late!

Is it being assumed that it has a HV delta to a LV wye?

How would that affect the OP's question?

 

[templdl]

Since this is assuming, should it be assumed that the secondary (LV) side by a delta and the primary (HV) side be a wye then it's a no brainer. Should it be assumed that the transformer is a common D-Y step down transformer and you wanted to use it as a step up then you have to address the XO issue which some manufacturers may have bonded to the enclosure.
And how does one size the pri OCPD? Is there consideration give that the, even though it could be assumed that the inrush of the HV and LV sides are proprtional, that should the LV side be energize that the inrush is much higher and can trip an undersize OCPD.
I have been an application and sales engineer for about 25 years and I have become very apprehensive about providing advice or information in response to a question that doesn't provide complete information. If one small detail is left out the answer could lead to catastrophic results. All too often people ask me questions in order to get an answer that they want to hear and I don?t want the responsibility of providing them an answer that may very well get them hurt.
As you may be able to tell you can get a bit gun shy when the questions are ambiguous.

 

[benaround]

Templdl,

FWIW, In 42 years of doing this stuff I have never seen the XO bonded to the case or

anywhere else for that matter, from the manufacturer.