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Step-up, Step-down, and Isolation Transformers
34 questions By Tony R. Kuphaldt
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Question 25 of 34
Explain how the construction of an isolation transformer differs from that of a step-up or step-down transformer.
Reveal answerStep-down transformers have fewer secondary turns than primary turns, while step-up transformers have more secondary turns than primary turns. Isolation transformers have equal turns in both windings.
Notes:Ask your students to explain the relationship between primary and secondary turns, and how this affects the voltage transformation ratio, based on mutual inductance.
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Question 26 of 34
When calculating power in transformer circuits, how do the primary and secondary circuit powers (Pprimary = VprimaryIprimary and Psecondary = VsecondaryIsecondary) compare with each other? Is one greater than the other? If so, which one, and why?
Reveal answerIdeally, Psecondary = Pprimary, although this equivalence is never quite exact. In practice, Psecondary will always be a little bit less than Pprimary.
Notes:The simplest answer to this question is that Psecondary = Pprimary, and this is a useful principle when doing transformer circuit calculations. Even when it is not precisely true, it is still a useful tool for checking the veracity of our calculations. Ask your students why this is.
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Question 27 of 34
Explain why transformers are used extensively in long-distance power distribution systems. What advantage do they lend to a power system?
Reveal answerTransformers are used to step voltage up for efficient transportation over long distances, and used to step the high voltage down again for point-of-use circuits.
Notes:Ask your students to explain the answer in detail, rather than just repeating what the given answer states. Why is high-voltage power distribution more efficient than low-voltage distribution? Why would high voltage have to be stepped down for point-of-use applications?
Creative and interesting excercises.