transformer delta 4-wire
- Thread starter eliezer
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Re: transformer delta 4-wire
My reference states that when two units of the same kva rating are used to supply only a balanced three-phase load, the combined rating of the two units must be 115% of the three phase load if the load on each transformer is not to exceed nameplate rating.
The two transformer open-delta configuration is frequently installed with one large and one small transformer to supply a combination of single phase and three phase load where the single phase load is much larger than the three phase load. Since one of the transformers would be center tapped for a 120/240v load, that transformer would need to be sized large enough to serve that load also.
My reference states that when two units of the same kva rating are used to supply only a balanced three-phase load, the combined rating of the two units must be 115% of the three phase load if the load on each transformer is not to exceed nameplate rating.
The two transformer open-delta configuration is frequently installed with one large and one small transformer to supply a combination of single phase and three phase load where the single phase load is much larger than the three phase load. Since one of the transformers would be center tapped for a 120/240v load, that transformer would need to be sized large enough to serve that load also.
charlie
Senior Member
- Location
- Indianapolis
Re: transformer delta 4-wire
For an open delta bank.
Place all of the single phase load on the lighting (larger) transformer and split the three phase load by multiplying it by the inverse of the square root of three (.577) to add to the lighter and the kicker (smaller).
For a closed delta bank.
Split the single phase load by placing two thirds on the lighting (larger) transformer and one third on the kicker (smaller) transformer. Split the three phase load by placing one third on the lighter and each of the kick-ers.
For an open delta bank.
Place all of the single phase load on the lighting (larger) transformer and split the three phase load by multiplying it by the inverse of the square root of three (.577) to add to the lighter and the kicker (smaller).
For a closed delta bank.
Split the single phase load by placing two thirds on the lighting (larger) transformer and one third on the kicker (smaller) transformer. Split the three phase load by placing one third on the lighter and each of the kick-ers.
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