# Single phase Transformer Problem



## sbsklewis (Mar 4, 2013)

Here is one that is simple, but I am stuck, any advice would be appreciated.

A single phase. 1200:120 volt transformer has an equivalent impedance of 10j ohms referred to the low voltage side. Determine the applied voltage to the high voltage primary necessary to deliver rated voltage to a resistive load of 10 ohms.


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## Flyer_PE (Mar 4, 2013)

I may be reading too much into this problem but here's my solution:1697V


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## DK PE (Mar 5, 2013)

I agree with Flyer's solution but have another method. Draw the ckt out similar to Flyer's. Now move the impedances (both given on low or seconday side) to primary using turns2. Now you have a primary voltage of something in series with 1000 + j1000 ohms. You know the seconday current must be 12A to develop rated 120 volts across 10 ohms resistive load. This corresponds to a primary current of 1.2 A. So what primary voltage needs to be applied across our 1000 + j1000 to cause a 1.2A current to flow?

I would recommend borrowing/buying a copy of Wildi text if you don't have. Doesn't need to be latest version so you can get is reasonably $$.


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## sbsklewis (Mar 6, 2013)

Thanks for the help, for some reason I was reading the 10 ohm resistance load as just being a resistance not the load, which as was pointed out allows the problem to be worked easily. Another lesson in reading the question/problems carefully.


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