Explained! The Delta High Leg (Center Tapped) 4 Wire Transformer (Electrical Power PE Exam)

In this video, we review a four-wire, three-phase, 240 volt delta connected transformer secondary with a 208V "high leg" created by center tapping the B phase winding.

Do you know what the most common mistake is when calculating the high leg voltage magnitude from a four-wire delta transformer with a center-tapped phase winding?

It is making the mistake of NOT using complex numbers (only using magnitudes), or, forgetting to include the angles in your calculations.

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[electricalpereview]

0:05 - Problem statement
0:17 - Setting up the transformer circuit values
2:21 - Setting up the center tapped winding voltages (VBN and VNC)
5:44 - KVL equation to solve for the high leg voltage (VAN = VAB + VBN)
7:29 - Determining the voltage rating of the high leg delta transformer
7:50 - Reviewing the "trick" to this problem
8:08 - Delta high leg applications and purpose (theory)

[germanaleyva]

Thank you for the tutorial high leg 4 wire delta transformers

[cdiology]

I'm actually from Jamaica and I must say that, I really apprecilove this video... because many times, even here, a lot of electricians don't know why, or how we have these varied voltages with a delta or a star secondary connected winding transformer. So, i must say again, keep on doing this field a great service by dispersing knowledge like this! Really fulljoyed your video. Blessings and respect!

[offgridsystems]

Electrician here, this was excellent, thank you

[ChoompMedia]

This is by far the best explained tutorial of a high leg 4 wire delta transformer I've ever come across. Thanks for spelling it out for us and walking us through how to obtain the three voltages. Thanks Zach - your PE Review course is by far the best I've come across.

[boxedtheatre]

This is literally one of Zach's best videos, I even shared it with my coworkers. It's easy to get confused on the high leg transformer, and what that means for ratings and wiring.

[aaroncurry]

OMG. I work in the electrical utility industry and not until after watching this video it really made sense. I mean I knew the basics of high leg delta transformers, but this video really breaks down the HOWs and WHYs behind it.

[danbeesmer]

Zach has made the center tapped transformer finally make sense. In general, most books are very confusing. This video makes it very easy to understand.

[MoisesFeliz]

It was not until I found this video by Zach that I really learned about the topic - he explains it very clear and simple!

[josueayalallanas]

Oh god! The explanation i eas looking for months on youtube, i finally found it. This gold for me thabk you. Keep on doing what you do this is great! Ive been learnng a lot thru youtube for the last months, thabk you thank you thank you

[AIArchiveLabs]

Very helpful to see it broken down in each part to show the different voltage and magnitudes. Sometimes the terminology can be a little tricky.

[nasheetarman]

Excellent explanation of High leg delta. See this in older substations a lot and your explanation helped.

[Sparky-wwre]

Great video! You see this sometimes in commercial installations, usually older facilities. A very rare high leg delta also exists, most experienced electricians will never have worked with it but only know they exist, and it is a 480/415/240 volt high leg delta, the voltage between A - C phase and neutral is 240 volts, the high leg to neutral is 415 volts. Basically identical to the 240 volt high leg delta, but the voltages doubled. Interestingly enough, you are allowed by the NEC to install a high leg delta system even today, but are kind of pointless.

[kaels]

This is a great explanation on a high leg delta system, and I've used it to help explain the center tap to some of my trainees! Thanks!

[MotorsportsX]

can you explain neutral and ground connections when using these down stream in a plant? Im curious how a step down transformer (480 to 240) is connected in regards to the neutral connections, and how to prevent ground loops.

[sethtaylor]

The winding with the neutral is used for general convenience outlets. The 240 delta is for large machines and equipment on the premises. Often the "lighting pot is at least 50 KVA and the wing points are minimum of 25 KVA. ST, ex First Energy JCP&L

[jolyonwelsh]

You can also use basic trigonometry or Pythagoras theorum to calculate the voltages. Although it would only give you the magnitudes.

[sunilpsoni]

zach, this is a very simple explanation useful for a quick lesson

[ytooob]

Awesome video thanks! It definitely makes it look simple compared to other sources out there.

[MINHAJUDDINKhan]

Is there any further explanation how AN is 208...where AC is 240 and CN is 120 or AB is 240 and BN is 120.