# Spin-up problem 3-76 Auto Transformer terminology



## 170B (Aug 30, 2012)

Spin-up has several problems on AutoTransformers about terminology. Boost/Buck, Step up/down.

I thought I knew, but apparently I don't. Can someone explain how to tell from a connection diagram if an auto transformer is boost/buck? and step up/down?

Thanks


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## Wildsoldier PE (Aug 30, 2012)

GA Tech course have all the combinations posible...too bad that GA Tech binder alone is hard to understand it needs to go with the videos

(null)


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## 170B (Aug 30, 2012)

Been there done that.

Spin-up 2-4 says that one is a step-up/buck, that seems impossible, isn't step up a boost? confused.


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## Power12 (Aug 30, 2012)

Step up and Step down are independent of boost or buck. I know step up is if the windings increase, and step down if the windings decrease. The buck or boost is a function of the dots on the windings, I always get confused on what determines when they are boost or buck.


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## Power12 (Aug 30, 2012)

I figured it out. If the dots are opposite each other on the windings it is buck. If they are in alignment it is boost.

For a step-up and buck, the windings should increase from source to load. The dots on the windings should not be aligned but be opposite each other.


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## 170B (Sep 19, 2012)

I thought if it was bucking it was stepping down, boosting = stepping up...?


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## ruffryder (Oct 11, 2012)

I think the convention of boost vs buck is not common anymore. I have search my text books and there is no terminology that refers to this nomenclature. I find it odd that it would be in these sample tests. It doesn't seem like it means anything either.


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## jayache80 (Oct 11, 2012)

I too was equally confused by this. I've always referred to bucking as step-down, and boosting as step-up- but as it was said here, they don't seem to have anything to do with each other. My guess was that when the windings were aligned (same dots, Boost) the current capacity is "boosted" and that when the windings are not aligned (opposite dots, Buck) the current capacity is "bucked," all of this having nothing to do with whether the voltage is stepped-up or stepped-down. If anyone can correct me or shed some light on this, please do!


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## ruffryder (Oct 11, 2012)

It can be easy to guess a definition, but if I can't find it in a book, or rather a number of books I am highly suspect of its ability to be used.


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## jayache80 (Oct 24, 2012)

Yes I think this problem is bunk. If the author of the Spin-ups exams could chime in? All sources I find use the dot alignment to either buck or boost the VOLTAGE. And, frankly, this is my experience with messing around with coils on the test bench :]


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## ruffryder (Oct 25, 2012)

Yep, problem is bunk, terminology is bunk.


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## pbo064 (Feb 7, 2013)

The chart is helpful for this problem.


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