How to Solve Any Auto-Transformer Problem using KCL and KVL (Electrical Power PE Exam)

Calculate the power rating to the nearest MVA of a 4,160 volt auto-transformer configured from a 1,000 kVA rated 4,160V-480V single-phase transformer (answer choices below):
(A) 0.9
(B) 5
(C) 10
(D) The power rating does not change.
The answer is (C) 10 MVA. Full solution is given in the video.
__________________________________
**** PE EXAM ***
🔥 SUBSCRIBE for more videos on how to pass the NCEES® Electrical Power PE Exam!
/ @electricalpereview
.
🚀 Ready to PASS the NCEES® Electrical Power PE Exam? Sign up for our FREE online study program for the PE Exam:
courses.electricalpereview.co...
.
👀 Electrical Engineering PE Practice Exam and Technical Study Guide by Zach Stone, P.E.:
amzn.to/2zKz17u
.
*** FE EXAM ***
⚡ Looking for help with the NCEES® Electrical and Computer FE Exam? Visit our FE Exam RUclips Channel:
/ @electricalfereview7050
.
👇 Ready to pass the NCEES® Electrical and Computer FE Exam? Sign up for our FREE online study program for the FE Exam:
www.electricalfereview.com

[@bertalev2010]

This is my new favorite explanation video. How simple you make things is beyond me!

[@electricalpereview]

Thanks for your comment, glad it helped!

[@paulmattern8011]

Zach, another great video and help understanding the subject.

[@jtthomas1]

This video helped me understand this concept. When in doubt, use circuit analysis! Always better than memorizing formulas.

[@kingd3223]

Thank you for this amazing explanation

[@issybella7]

This helped me understand this topic.

[@arashmoazami6658]

Great Video Zach

[@shahryarfarhang200]

I like the way you described it. Awesome

[@electricalpereview]

Thanks Shahryar, glad you enjoyed it

[@subrinanoureen]

Great Video

[@juliabrodovsky3096]

Great video, thank you so much. I kept wondering what the "c" subscript in the NCEES manual was!

[@electricalpereview]

Hi Julia, thanks for your comment. Glad to hear you enjoyed the video.

[@shozu3]

Beyond necessary. Was one of my harder topics

[@OddRobb]

Couldn't you also use the common:series turn ratio to find the input/output power rating? Using Nseries = 480 and Ncommon = 4160

[@electricalpereview]

You sure can

[@user-do8fq9jg7o]

Hi my name is Nish I am doing electrical engineering N1 and need help could you please assist me with tutoring me?

[@shabirafzal100]

Why do we use I common the same as I primary.
I primary = I common + I secondary
In the problem you hv considered I primary equal to I common which means secondary current is zero as per KCL. Pls clear my confusion.

[@shabirafzal100]

I believe we cannot use Ip and Is from orignal single phase transformer. We dont we derive primary and secondary current again when we hv kVA and new Voltages for auto transformer.

[@electricalpereview]

This is an auto-transformer that is being made from a single-phase transformer. Picture opening up a single-phase transformer and shorting the windings together on one end and changing where your tap termainls are in order to use both windings as an auto-transformer.
Each winding on the single-phase transformer cannot exceed it's rating, so the full load current of each winding will be the same with respect to the voltage direclty across it when we reconfigure the single-phase transformer into an auto-transformer.
The common current (Ic) of the new auto-transformer will equal the primary current of the previous single-phase transformer that it was made from (Ip).
The primary current of the auto-transformer is designed as Ipri to avoid confusion.
Take a look at a new video we published earlier this year that goes through all of the circuit analysis relationships of auto-transformers, I think it will help clear up any confusion:
ruclips.net/video/XB9yTOtIzDc/видео.html