Max Power vs Current Ratings at Low Voltages - RC Groups
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Sep 21, 2011, 05:22 PM
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Max Power vs Current Ratings at Low Voltages

Hi. I have a question about the maximum power ratings listed on the Neu website.

I need a ~200RPM output at a voltage of ~20V and ~25A (~500W)continuously. Since the maximum gearbox ratio is 6.7, I need a motor with a kV of around 1400-1450kV.

Two possible choices seem to be the 1110G-1400kV or the 1509G-1450kV. However, my required power rating is close to the maximum continuous power listed but my input voltage is much less than the maximum allowable voltage listed.

The maximum current is calculated by [Max Power]/[Max Voltage], correct so I don't think this will work, right?

My understanding is that the true cause of the motor's limitations is not power, but current or voltage (whichever is exceeded first). The motor's max voltage is limited by it's kV and mechanical rotation limits while the current is limited by the motor's heating. It is these two together that limit the maximum power which means that the max power is only valid if the max voltage is being used.
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