WYE source to a DELTA transformer primary? 2

[blcpro]

A quick question on power transforming:
It appears that our building is supplied with 480 3-phase power in WYE form. That is, a four-wire system. We just moved into this building and are in the process of hooking up our power transformers to step down the power for 220 3-phase. But on close inspection we discovered that our transformer is a DELTA-WYE tranformer (DELTA Primary). If our power source is WYE, will there be a problem connecting to the DELTA primary of the transformer? What is done with the WYE-neutral? Is it a normal practice to leave this neutral unconnected?

 

[DanDel]

If your transformer is 480V Delta primary, and 220V Wye secondary, yes it is common practice to not use the neutral provided at the 480V Wye service. Simply bring the three phase conductors (and ground), and follow the code requirements for your location.

 

[jbartos]

Suggestion: A chain connections of transformers from upstream to downstream:
1. primary delta, secondary wye (grounded) - upstream transformer, e.g. 4.16kV-D/480V-Y
2. primary delta, secondary wye (grounded) - the first downstream transformer, e.g. 480V-D/220V-Y
3. primary delta, secondary wye (grounded) - the second downstream transformer, e.g. 220V-D/110V-Y
4. etc.
is considered the industry standard since it:
1. Breaks the zero sequence path
2. Solidly grounded wye establishes good system grounding
3. It is good for the secondary multivoltage system, e.g. 380Vphase-to-phase/220Vphase-to-neutral
4. Etc.

 

[blcpro]

Thanks for the help, DanDel and jbartos!

 

[rbulsara]

This is very normal configuration. No neutral is connected to the primary side of a delta-wye transformer. But a equipment ground condcutor is required.