Single phase transformer and net KVA output

[anand raj]

Homework Statement

a 4 kva, 230/115 volt, 400 HZ, single phase transformer originally designed for use in air crafts, is available in a laboratory for obtaining 115 volt supply from standard 230 volt,50 HZ mains if overloading of the device is not permitted then net kva output is...

Homework Equations

The Attempt at a Solution

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here frequency is varying voltage remaining the same
kva being proportional to frequency
x = kva output for 50 HZ
4/x = 400/50
x = 0.5 kva
i don't know whether it is right or wrong, but the answer is this.

 

[NascentOxygen]

The wording of the question seems to imply (but stops short of stating unequivocally) that the transformer is to deliver 115V at 50Hz. I can't offer a technical opinion, but according to this reference http://www.edn.com/design/component...sformer-at-a-frequency-it-wasn-t-designed-for

For a power transformer designed for 115VRMS at 400 Hz but used at 60 Hz, the input voltage must not exceed 115×60/400 = 17.25 VRMS

Perhaps others can offer a critique of the suggested scheme.