# DOE, BOOST, BUCK, CONVENTIONAL AUTOTRASNFORMERS



## elminses (Apr 7, 2012)

Spin - UP PE sample exams have a few questions on autotransformer types. Doe, Boost, Buck, Step-up, conventional.

I'm an electrical consulting engineer, i don't get much into circuit diagrams of internal workings of equipment. If someone could either supply or point me to a reference that has each type of autotransformer diagram drawn out so I can learn and be able to tell the difference between them it would be most appreciated.

Thanks ahead of time!


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## CntrSnr2001 (Apr 7, 2012)

i'd like to know too, please


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## DetroitEE (Apr 7, 2012)

There's no such thing as a Doe autotransformer...I believe it is almost meant to be a joke, since there is such a thing as "buck" autotransformer.


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## Ivory (Apr 7, 2012)

There is also a boost and stepup.


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## Power12 (Apr 7, 2012)

For autotransformers, you should know step-up, step-down and the buck &amp; boost.


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## elminses (Apr 7, 2012)

Here will be my assumptions based on your comments. Please correct if they are wrong.

step - up : will be where an auto transformer diagram has a small transformer stepping a larger transformer up to larger voltage. ex. 1200V + 120V = 1320V because the load requires 1320v

step - down : will be where an auto transformer diagram has a small transformer stepping a larger transformer down. ex. 1200V - 120V = 1080V because the load requires 1080V

buck boost : will be when an auto transformer diagram is + / - a voltage on a transformer. 1200V +/- 120v = 1080V-1320V because the load can take a span based on AC voltage.

I'm just wonder how these would look diagram wise, if someone could just doodle in paint so I can just see the diagram it would be most appreciated.

thanks again.


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## vskneifl (Apr 7, 2012)

I ran into this question last night and I found this website that really helped.

/&gt;http://www.allaboutcircuits.com/vol_2/chpt_9/5.html

Basically the step up / step down depends on if the load or source is connected to the center tap between the two coils. The buck / boost is dependent on the polarity of the coils and how they are connected.

See the attached table for more details note the dot polarity of the coils for the buck and boost.

Hope this helps.


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## vskneifl (Apr 7, 2012)

Well for some reason the table did not upload correctly so I have attached it here as a jpg.


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## elminses (Apr 8, 2012)

Thanks again everyone for your help!


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## stinkycheese (Apr 8, 2012)

thanks vskneifl for the upload!


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## majorever (Aug 16, 2016)

Thank you this helps


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