Homework problem:(adsbygoogle = window.adsbygoogle || []).push({});

A transformer on a pole near a factory steps the voltage down from 3900V to 220V. The transformer is to deliver 1180kW to the factory at 91% efficiency. Find the power delivered to the primary in kW.

What I've done:

Well, I thought that power in equals power out. So I worked all the math to prove that and used P=IsVs, solved for Is then used that to find Ip (Ip=VsIs/Vp). Then found P=IpVp. I got 1180kW! I then calculated in the efficiency--not correct. And then in the follow up question, I found out that my Ip isn't even correct. What's wrong here?

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# Transformer engineering problem

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