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In an answer to this question, for a motor used as a generator, the following was said:

The maximum current that can be drawn from a generator is generally a fixed value that is not determined by speed.

What equation(s) show this?

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    $\begingroup$ The trick is that a maximum is by definition a fixed value. It doesn't imply that that value will be reached at any given speed for any given load. $\endgroup$ – Random832 May 13 '16 at 17:30
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The current that a generator can produce is limited by the wire used in its construction. At some current level, the I2R losses in the wire will cause excessive heating inside the generator, as well as a voltage drop at the output.

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That statement about the current being independent of speed is just plain wrong. This should be obvious by thinking about the limiting case. When the generator isn't spinning at all, it won't produce any current, but it will produce current at some finite speed.

You can easily prove to yourself that the statement is wrong. Take a simple brushed DC motor. These also work backwards as generators. Connect it to a ammeter. That's essentially shorting its output while measuring the current. Now spin the motor (generator). The current will be proportional to the spinning speed.

I didn't follow the link to where this quote came from. Perhaps there are various qualifying statements around it. However, taken by itself without some specific context, that statement is wrong.

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