Open delta grounded primary to Wye grounded secondary

[Jpflex]

Maybe i misunderstood one of the questions.

The transformer would have to be a standard three winding transformer arrangement in order to create a true wye output. It is only the source that can be open delta.
You cannot get (3) line-line voltages from an open wye, so it can not be used for 3-phase motors.

I wasn’t aware that y could not be used leg to leg for 3 phase motors or systems?

Are you sure about this? L1,2. L1,3 L2,3?

 

[jim dungar]

I wasn’t aware that y could not be used leg to leg for 3 phase motors or systems?

Are you sure about this? L1,2. L1,3 L2,3?

An open Wye does not provide (3) lines/hot. You only get L1, L2, and Neutral (using your designations).

 

[jim dungar]

I have heard of open delta but only in engineering books I have read. In fact all deltas are to be opened and checked for voltage Or current between Legs to be closed and prior to closing them together.

If there is a voltage between points then legs are likely reversed and delta should not be closed until addressed. There was something also beneficial about them such as output but I forgot what it was

Across the US, open delta configurations are very common as the utility can create one by using just (2) single phase transformers. One good thing about this is the transformers do not need to be the same size which makes it easy to feed services which are predominately single phase with only relatively little three phase loading.

 

[tortuga]

Yeah outside up on a pole utility open hi-leg delta is common.
What I have never seen is what the OP alluded to inside the building 'open delta primary' to wye configuration.

 

[Jpflex]

An open Wye does not provide (3) lines/hot. You only get L1, L2, and Neutral (using your designations).

Here is documents in an electrical engineering book which suggest it can be done. All three legs are being utilized on loads. Neutral is made if loads are unbalanced

 

[jim dungar]

Here is documents in an electrical engineering book which suggest it can be done. All three legs are being utilized on loads. Neutral is made if loads are unbalanced

That exhibit shows (3) windings therefore it does not represent an open wye.

 

[MTW]

To obtain a wye from an open delta system, you use a standard closed delta primary and a wye secondary. Nothing exotic required.

 

[Jpflex]

That exhibit shows (3) windings therefore it does not represent an open wye.

Isn’t an opened y closed once a load is placed across legs? Or what is meant by open y?

 

[synchro]

That exhibit shows (3) windings therefore it does not represent an open wye.

Isn’t an opened y closed once a load is placed across legs? Or what is meant by open y?

It's called an open wye because it's made with only 2 of the 3 windings (with L-N voltages 120° apart from each other) that would be connected together at the neutral point of a wye configuration. And so one of the three L-N voltages in a wye will not be present in an open wye.

In an open delta one of the windings of a closed delta is missing, but all the line voltages of a closed delta are still present. In a closed delta, with a balanced 3-phase unity PF load, the current drawn from each winding will be in phase with the voltage across it. But in an open delta, the current will be 30° offset from the voltage. Therefore, if three 1-ϕ transformers are configured in a closed delta configuration and one is removed to form an open delta, the kVA capacity will drop to cos(30°) x 2/3 = 0.577 of what a closed delta would provide, and not just by 2/3 from having one of three transformers missing.
Also, the L-L impedances at the output of an open delta will not be symmetrical, but will be higher across the open portion because it doesn't have its own winding to contribute current.

 

[gene6]

To obtain a wye from an open delta system, you use a standard closed delta primary and a wye secondary.

No offence but I think we all know that. The OP Question.meo was discussing a open delta to wye. I have never seen such a configuration.

 

[retirede]

No offence but I think we all know that. The OP Question.meo was discussing a open delta to wye. I have never seen such a configuration.

The way I read the OP, the open delta is the utility source. It is not describing the transformer primary.

 

[MTW]

It would have been clearer if the OP had posted a tag from his transformer and precluded any doubts of a reverse fed transformer or an enigma unit that contained an open delta primary input winding, with a wye output winding. It just don’t exist.

In this situation you just use a standard delta to wye isolation unit, that is likely what he is using in this case, but calling it an open delta winding. Only the input source is open delta, not the input winding.

I have an open delta service at my shop and use two single phase four winding transformers to both step up and down 3 phase voltages for testing equipment. But you cannot obtain a balanced wye output from a open delta input winding, without a standard 3 leg isolation ,delta to wye core and winding. That is what the OP has, even though that is not what he is labeling it.

If he would post up the tag, then we could all see and better understand, that it’s a terminology difference, not a winding type difference.