Delta-Wye transformer neutral wire

[Williams_Diesel]

Hello all,

Looking for some advice/clarification on a transformer installation. Our facility currently has 240V (delta)/3ph/60hz utility power. We are installing a piece of test equipment that requires 380-480V/3ph/50-60hz @ 32amp service. Based on these requirements we are going to purchase a 3 phase 30kVA isolation transformer 240D - 480Y. According to the equipment manufacture, the equipment has three "hots" and a ground, no neutral wire connection. In this case, can we use the selected transformer (delta-wye) and just ground/bond the neutral on the secondary (480V) side? Or should we go with a delta-delta transformer?

 

[jim dungar]

Use the more common delta-wye transformer.

 

[LarryFine]

In this case, can we use the selected transformer (delta-wye) and just ground/bond the neutral on the secondary (480V) side? Or should we go with a delta-delta transformer?

Welcome to the forum.

Definitely the grounded-neutral wye secondary.

 

[electrofelon]

I concur with the above. Y'all dont seem to have much need for me, carry on.....

 

[Julius Right]

In my opinion, if you don't expect to supply 480/sqrt(3)=277 V for some other equipment you don't need a neutral wire. However, according to NEC art.250.4.A.5, you have to install a grounding wire, since the earth is not an effective ground fault current path.