Quote:
Originally Posted by Ether
Everything Adam and Thad said, plus this minor item, which may be key to understanding:
If you're commanding the motor controller via PWM, you're not commanding power, you're commanding output PWM duty cycle.
If the motor controller is linear, then 10% command will create 10% output duty cycle which will effectively cause 10% of the battery's voltage1 to appear at the motor's input, which -- if the motor is stalled -- will create 10% of the motor's stall current to flow through the motor which will create 10% of the motor's spec stall torque.
The electrical power being put into the motor is Pin = current*voltage, which will equal (10% of spec stall current)*(10% of battery voltage) which will equal 1/100th of the input power at motor stall at spec voltage.
That's why the motor doesn't overheat.
1Let's assume, for sake of simplicity, that the battery is a constant 12 volt source (same as motor spec voltage).
2The output mechanical power at the motor's output shaft is Pout=shaftSpeed*loadTorque. When the motor is stalled, shaftSpeed is zero so Pout=0. Therefore all the input power Pin is dissipated inside the motor as heat.
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Good catch, I overlooked that his question was more related to the motor controller's "10%" output than to the motor itself.