230 volt 3ph transformer grounded?

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mrblue1482

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Ive been asked to do a build out for a machine shop. The building has a 3ph 480v wye system. Since most of the equipment is 3ph 230v, so the electrical engineer designed the job with a 480v to 230v transformer (delta to delta). Does this system need to be grounded? If so, how can I do that without an xo terminal? As of right now I have everything bonded throughout. Thanks
 
mrblue1482 said:
Ive been asked to do a build out for a machine shop. The building has a 3ph 480v wye system. Since most of the equipment is 3ph 230v, so the electrical engineer designed the job with a 480v to 230v transformer (delta to delta). Does this system need to be grounded? If so, how can I do that without an xo terminal? As of right now I have everything bonded throughout. Thanks
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It likely needs to be and probably should be grounded, to do so you would ground one of the phases. This will give you corner grounded Delta.
 
Bob,
Why would it need to be grounded? The grounding of this system is a design issue and not a code issue.

It is important to note that the ungrounded system will require a ground detection system.

The grounding and bonding rules for an ungrounded system at the same as those for a grounded system except that there is no system bonding jumper for the ungrounded system.
A new rule in the 2011 code requires that the panel supplied by an ungrounded system be marked to identify it as an ungrounded system.
 
As explained, grounding is not necessary, but is usually desirable. You can corner ground, often referred to as Grounded B phase but these require 'special breakers and panels, or you can get a transformer with a 240/120V 4 wire delta secondary.

Please, do not get in a habit of thinking that all electrical systems need an X0 or neutral connection.
 
don_resqcapt19 said:
Bob,
Why would it need to be grounded? The grounding of this system is a design issue and not a code issue.
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That would be why I said likely ........ :)

I did not have time to look it up, after taking the time to look it up I agree that it is a design issue.

My personal preference is grounded systems for most locations but that is because that is what I am used to. In industrial locations I can certainly see the benefit of using ungrounded systems I do not see that benefit in a machine shop.
 
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