Cram for Exam Vol 3. Q 63 - Transformer B: Vout > Vin?

[akyip]

Hey guys,

For those of you who have Cram for PE Power Exam Vol 3, I'm having some trouble on question 63. This question is about discerning whether two transformers are boosting or bucking based on their connection diagrams.

I have no issues with Transformer A being a step-up/boosting autotransformer with Vin > Vout.

But I have trouble visualizing how Vout > Vin for Transformer B, as the solution states. Attached is my understanding of how the transformers are drawn out. For each transformer, the top diagram is given in the problem, and the bottom diagram is my interpretation... To me, it looks like Vin is across the common winding only, which is part of how I cannot understand Vin to be greater than Vout in the top diagram for Transformer B...

Thanks for any help on this!

 

[Orchid PE]

@akyip You may have already figured this out, but keep track of the polarity markings on the windings.

 

[akyip]

@akyip You may have already figured this out, but keep track of the polarity markings on the windings.

View attachment 18701

I just revisited this problem with what you said in mind, plus a bit of KVL. This makes sense now. Thanks, Chattaneer!