Calculating No-Load Voltage for DC Generator

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Homework Statement

The ratings of a dc generator are given (16 kW, 250 V, and 64 A) when it rotates at 1000 rpm. Then the question asks to find the no-load voltage at 1000 rpm when there isn't a circuit hooked up to the generator.

Homework Equations

P = IV
V = IR
Kirchhoff's circuit rules
\omega = 2(\pi)(f)

The Attempt at a Solution

I know the answer is suppose to be 2400 V, but I have no idea why the no-load voltage is greater than 250 V.

 

[member 553083]

I thought that the no-load voltage would be equal to the rated voltage because there isn't a circuit attached, but clearly that isn't the case. Can someone explain why this is so? Is it because the generator has an internal resistance that's not being accounted for in the rated voltage? If so, how would I go about solving this problem? Thanks.