# Autotransformers



## aggieman_09 (Mar 9, 2015)

Does anyone have a reference with any good autotransformer examples? I did an internet search but I didnt come up with much. Thanks


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## MyBeardAndMe (Mar 14, 2015)

I struggled too with finding good publications on autotransformers. I just wrote down the formulas in my binder whenever I came across an autotransformer problem in the practice exams I have.


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## zm83 (Mar 14, 2015)

Chapmans book on electric machinery and power system findamentals covers this well


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## MTO (Mar 31, 2015)

Georgia Tech binder has a good reference on autotransformers


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## iwire (Mar 31, 2015)

MTO said:


> Georgia Tech binder has a good reference on autotransformers


yup, it's only a few pages as well. I am sure someone here will give it to you for free or something small for an exchange. I sold my binder


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## MyBeardAndMe (Mar 31, 2015)

I would appreciate the reference in the GaTech binder if anybody has it.


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## JB66money (Apr 1, 2015)

Hadi Sadaat's textbook has a really good explanation and example problems on auto-transformers as well. However Stephen Chapman is good for learning this topic.


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## Kovz (Apr 1, 2015)

Here's the section from the Chapman book on Autotransformers.

https://www.dropbox.com/s/5xldchvs38j64fv/Chapman%20Autotransformers.pdf?dl=0

I have the GA Tech section on them as well, but I will PM those who asked for it.


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## aggieman_09 (Apr 1, 2015)

Thanks!


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## phatman492 (Jan 9, 2016)

Will you please send me the GA Tech section on autotransformers Kovz? It has been tough finding much on this topic.  Thanks in advance. [email protected]


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## brianbui (Jan 18, 2016)

Will you please send me the GA Tech section on autotransformers Kovz? Thanks in advance. [email protected]


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## dianevp (Dec 16, 2016)

Would you be so kind to send me the GA Tech section on autotransformers Kovz? Thanks in advance [email protected]


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## Zach Stone P.E. (Dec 19, 2016)

This is something I would be glad to help with.

Auto transformers may seem tricky at first, but are actually quite simple once you really understand the basics of how they operate. 

In my opinion, and the way we teach it in our online course, the best way to really understand how they operate is to practice solving problems that ask you to reconfigure an a single phase transformer into an auto transformer by stacking the coils on top of each other like this:

Secondary coil N2 stacked on top of Primary Coil N1:




(Continued in next post)


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## Zach Stone P.E. (Dec 19, 2016)

Looks like I already exceeded the file size limit for uploads and I cannot upload the following image for stacking the primary coil N1 on top of the secondary coil N2. 

Can anyone suggest a way to upload more images, and is there a third party host anyone has success with using for posting on engineer boards?

Here is a video demonstration of deriving the different formulas when you stack coils.  

It is from our YouTube channel but it is taken directly from our online course









Remember that power in always equals power out for an ideal transformer and you can derive just about every expression that you need to. 

Don't forget to brush up on the benefits and drawbacks of autotransformers vs standard transformers in case you encounter a conceptual theory question on the exam

Autotransformers are mostly used to improve voltage regulation and as a motor starting application. 

There is more information on autotransformers and practice problems available on our online course.

If you'd like to sign up and access it the link is in my member profile.  

If you have any other questions let me know and I will do my best to answer them. 

Good luck!


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