# DOE, BOOST, BUCK, CONVENTIONAL AUTOTRASNFORMERS

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### #1 elminses

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Posted 07 April 2012 - 10:42 PM

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.

### #2 CntrSnr2001

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Posted 07 April 2012 - 11:21 PM

i'd like to know too, please

### #3 DetroitEE

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Posted 07 April 2012 - 11:44 PM

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.

### #4 Ivory

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Posted 08 April 2012 - 12:19 AM

There is also a boost and stepup.

### #5 Power12

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Posted 08 April 2012 - 12:22 AM

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

### #6 elminses

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Posted 08 April 2012 - 01:14 AM

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.

### #7 vskneifl

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Posted 08 April 2012 - 03:00 AM

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

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.

### #8 vskneifl

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Posted 08 April 2012 - 03:15 AM

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

### #9 elminses

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Posted 08 April 2012 - 06:08 PM

Thanks again everyone for your help!

### #10 stinkycheese

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Posted 08 April 2012 - 11:04 PM