I need some engineering feedback on a workaround. I need to power a 480Y/277V secondary system from a 3-phase, 3-wire source where no neutral is available.
I know a Delta-Wye transformer is normally used for this, but all I have available right now is a 500kVA Wye-Wye transformer (440V Primary / 480Y/277V Secondary). There will be various loads so it may not be balanced at all times.
Proposed Configuration:

• Primary Side: Connect the 3-phase lines to H1, H2, and H3. Leave the primary neutral (H0) completely disconnected and floating, since there is no source neutral.
• Secondary Side: Connect the loads normally to X1, X2, and X3. Bond the secondary neutral (X0) to ground to get the 277V single-phase reference.

My Questions:

1. what is the impact
2. will it cause issues

 

Don't understand your reference to no source neutral, ?
What voltage are you interested in ending up with?
If you ground the star point to a valid earth ground rod/system it will produce a neutral sourced termination ?
Or without connected to earth ground, an isolated neutral.!

 

Obtaining your output voltage will be a challenge with that configuration. You haven’t told us your source voltage

 

What is the nature of your load??

 

source voltage is 440. but this is more of a general question. if i have a wye to wye transformer. i on the primary side i only hook the phase lines a,b,c and do not connect a neutral. what is the impact. wll the transformer operate correctly? i believe it will as long as the load is balanced but if the load is unbalanced will it create problems?

 

source voltage is 440. but this is more of a general question. if i have a wye to wye transformer. i on the primary side i only hook the phase lines a,b,c and do not connect a neutral. what is the impact. wll the transformer operate correctly? i believe it will as long as the load is balanced but if the load is unbalanced will it create problems?

Depends on the imbalance, and the resulting voltage swings have on your application. If your loads are largely 3 phase, or balanced single, you should be ok. Current on the secondary neutral will manifest as voltage fluctuations.

 

is this a correct statement on how it will affect the primary side?
if the secondary side has a bonded neutral it has a path for the current imbalance but the draw from the secondary side causes the primary side to draw more current to feed the secondary side but no path for the imbalance if there is no neutral