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Introduction to the Delta Wye transformer connection Part 7c

In this part, we're going to look at how the transformer connection is actually defined by the Dyn11 and the DAC which basically mean the same thing.

This type of Delta connection is often defined by DAC. This designation is mainly used in the United States and how it works is very simple. What it's telling is that polarity side of winding A is connected to the non-polarity side of winding C. Let's draw that over here. We're saying that the polarity side of winding A is connected to the non-polarity side of winding C. And once you've defined the pattern, the next pattern is that the polarity side of winding B is connected to the non-polarity side of winding C. And the polarity side of winding C is connected to the non-polarity side of winding B.

Now if you're having a hard time understanding this pattern, all you have to do is write AC here and add the missing phasor which is a B. And then repeat the same thing over here. ACB.

The first pattern is this – the polarity side of winding A is connected to the non-polarity side of winding C. This is the second pattern. We're saying that the polarity side of winding B is connected to the non-polarity side of winding A. This is the third pattern, we're saying that the polarity side of winding C is connected to the non-polarity side of winding B.

Okay so another type of a connection is a DAB delta connection – and although it tells us how it's connected, it doesn't tell us the phase relationship between the HV winding and the LV winding. All this tells us is the connection.

And then this designation of the Delta Wye transformer connection is very popular outside of the United States. This gives us a lot of information but it's also very confusing at first. Let's break it down step by step.

The capital D tell us that the HV winding is connected in Delta. The lowercase wye tells us that the LV winding is connected in wye or star – same thing. Because the n comes directly after the wye – the n tell us that the LV winding's neutral bushing is available. Now the LV neutral bushing is available but that doesn't mean the neutral bushing is actually grounded. Here is the neutral that I'm referring to. So it's telling us that the neutral bushing is available but it's not telling us that the neutral is actually grounded or not.

So the las thing is – is this 11. And this right here is the source of all our problems. The way that this is defined – well first of all, there is not a lot of resources out there that explains step by step how this 11 designation actually works. And if it was described in these resources it would be described as 11 increments of 30 degrees phase shift between the HV winding and LV winding.  But my friends, this type of a description is extremely confusing – at least to me, it was very confusing.

The first question that popped up in to my head – which two quantities were they referring to when they say HV winding and the LV winding.  We have V phase A on the HV winding, we have VAB on the HV side. We have VAG on the HV side. So which quantities are they referring to when they say the HV winding.

The other question that pops into my head is that these increments of 30 degrees – so they say 11 increments of 30 degrees and that equals 330 degrees. So which direction is this 330 degrees phase shift?

For example – let's say this ambiguous HV quantity was defined as A. Now we could go CCW 330 degrees like that and that would be defined as the LV winding a. So we can go CCW 330 degrees. Or we can go CW 330 degrees like that and call that winding "a" and then we have 330 degrees in that direction.

So which direction are they actually talking about? Because based on the direction, we're going to have two completely different phasors. So this 11 here introduces a lot of confusion.

I think this is a pretty good place to stop. If you haven't subscribed already, please click on the bottom right corner of this screen, there should be a subscribe button. Please subscribe to this channel and share these videos with your friends and colleagues. And the other request that I have – is that like me, I know there are lot of people out there who question a lot of things about power systems in general. So if you have any questions, please comment away in the section below.

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