Primary Change Not Transformer Winding Change?
Primary Change Not Transformer Winding Change?
On a three phase pad mount transformer when reconnected from a delta to a wye on the primary how do I calculate the wye voltage?
Assumptions:
1) You are not changing the transformer configuration, i.e., the primary winding of the transformer is Delta connected. In this case the applied voltage phase to phase was, let's say, 12470 volts as a three wire Delta connected supply. If you now choose to supply the transformer via a three or four wire Wye system, then the only requirement is that the phase to phase voltage is 12470 volts. The transformer will operate as before with the a possible phase shift.
2) If you are reconnecting the primary windings of the transformer such that they will be connected in a Wye configuration instead of a Delta configuration, then you have to consider that the voltage across each winding on the primary side of the transformer must remain the same. Let's say that the original supply was 12470 volts phase to phase. Therefore each primary winding was energized at a voltage of 12470 volts. If you now configure the primary windings in a Wye configuration, then the primary supply voltage must be 12470 volts phase to neutral (4 wire grounded Wye) or reference common point (ungrounded neutral point). To achieve this the primary voltage phase to phase for the supply must equal 12470*square root (3) = 21,599 volts.
Hope this helps,
Newton Law