High leg delta and corner grounded delta

[The electron man]

When it comes to high leg delta and corner grounded Delta is there a special transformer that's wired internally for these types of connections ??

 

[LarryFine]

When it comes to high leg delta and corner grounded Delta is there a special transformer that's wired internally for these types of connections ??

The high-leg, yes, in the sense that the opposite (main) winding needs a center tap to be the neutral.

 

[The electron man]

The high-leg, yes, in the sense that the opposite (main) winding needs a center tap to be the neutral.

Can you please explain that better still new to this subject regarding high leg delta and corner grounded systems thanks

 

[LarryFine]

Can you please explain that better still new to this subject regarding high leg delta and corner grounded systems thanks

Simply, what fixes the voltage to ground from any given terminal is which terminal one chooses to intentionally ground.

A high-leg delta has as a high leg because of the voltage between that terminal and the grounded neutral.

A corner-grounded delta has two terminals with line-to-ground voltages same as the line-to-line voltage.

 

[ActionDave]

When it comes to high leg delta and corner grounded Delta is there a special transformer that's wired internally for these types of connections ??

The secondary of a transformer is only magnetically coupled to the primary. There is no wiring connection from the primary to the secondary coils ever.

This is an old post from Larry Fine that I have used in the past that I have used to explain the grounded/neutral conductor. His example does not use three phase but it might be helpful for your question. https://forums.mikeholt.com/threads/understanding-the-neutral-conductor.140537/

 

[LarryFine]

This is an old post from Larry Fine that I have used in the past that I have used to explain the grounded/neutral conductor.

That's so funny! I actually thought about posting a link to that here. Thank you.

 

[electrofelon]

Just to emphasize: how many terminals an electrical system has is unrelated to if or which terminal is grounded.

There are probably a few exceptions (well actually quite a few if you get into medium voltage transformers built for an MGN wye system) but usually a terminal is not "internally grounded" where its buried in the guts of a transformer. Typically it's brought out just like the other terminals , but where a given terminal is very commonly grounded, the manufacturer often provides a removable strap.

 

[The electron man]

The secondary of a transformer is only magnetically coupled to the primary. There is no wiring connection from the primary to the secondary coils ever.

This is an old post from Larry Fine that I have used in the past that I have used to explain the grounded/neutral conductor. His example does not use three phase but it might be helpful for your question. https://forums.mikeholt.com/threads/understanding-the-neutral-conductor.140537/

This make it a bit easier to understand


So for a corner grounded you would have a double lug one for power and one to ground let's say the b phase

But for a high leg how would you center tap the between phases

This is new to me and confusing also I'm a visual learner so picture and diagrams help a lot thanks for the help

 

[LarryFine]

But for a high leg how would you center tap the between phases

Simple. The neutral of a high-leg delta is identical to the neutral of a 120/240v 1ph secondary.

Before I go on, let me know if you understand that concept, as explained in the link posted above.

 

[The electron man]

Simple. The neutral of a high-leg delta is identical to the neutral of a 120/240v 1ph secondary.

Before I go on, let me know if you understand that concept, as explained in the link posted above.

Yes I understand how a 120v/240v transformer works

Since you said the high leg delta works the same my question is dose the manufacturer tap the coils for you and you just terminate at the neutral lug

And how would you wire the corner grounded method in the field

Thanks again its greatly appreciated

 

[ActionDave]

That's so funny! I actually thought about posting a link to that here. Thank you.

What's even funnier is the last time I posted a link to it was during your hiatus and I described you as a member who had stopped posting and you replied "I'm back" that day.

 

[LarryFine]

Since you said the high leg delta works the same my question is dose the manufacturer tap the coils for you and you just terminate at the neutral lug

Yes. Either only one secondary has a center tap, or they only provide a neutral terminal for one of them.

And how would you wire the corner grounded method in the field

Simply, you select one line, ground it, color it white or gray, and don't put a fuse in it. (3p breaker okay)

 

[The electron man]

Yes. Either only one secondary has a center tap, or they only provide a neutral terminal for one of them.


Simply, you select one line, ground it, color it white or gray, and don't put a fuse in it. (3p breaker okay)

What's do you mean by one secondary every transformer only has one secondary

 

[The electron man]

Yes. Either only one secondary has a center tap, or they only provide a neutral terminal for one of them.


Simply, you select one line, ground it, color it white or gray, and don't put a fuse in it. (3p breaker okay)

So in a corner grounded system there is no neutral only 3phase like in a 3 phase motor

 

[ActionDave]

So in a corner grounded system there is no neutral only 3phase like in a 3 phase motor

Yes. In a corner ground there is no neutral, but there is a grounded conductor. We toss around the word neutral on the job when it is more properly called the grounded conductor.

 

[ActionDave]

What's do you mean by one secondary every transformer only has one secondary

Pretty sure he means only one secondary coil.

 

[The electron man]

Yes. In a corner ground there is no neutral, but there is a grounded conductor. We toss around the word neutral on the job when it is more properly called the grounded conductor.

So in a corner grounded system you can't pull 120v but since one of the phases is grounded it provides us with ground fault protection

 

[ActionDave]

So in a corner grounded system you can't pull 120v but since one of the phases is grounded it provides us with ground fault protection

Correct.

 

[LarryFine]

What's do you mean by one secondary every transformer only has one secondary

I meant each of the three secondaries of a 3ph transformer.

I get the impression that I think of 3ph transformers as three 1ph units more than most members do.

 

[LarryFine]

So in a corner grounded system there is no neutral only 3phase like in a 3 phase motor

Basically. You choose one line to become the grounded phase, unless it's supplied with one.

As with a 1ph neutral, you treat it as a line conductor, other than OCP, such as not re-bonding it.