I have a big misunderstanding.. when we say the pwm is 10% the motor should be off for a longer time.. But the motor driver draws most current at 10% pwm .. I am not able to understand this concept..
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\$\begingroup\$ Because the motors stalls more easily. \$\endgroup\$– DKNguyenCommented Jan 3, 2020 at 16:54
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\$\begingroup\$ PWM ratio affects the effective voltage applied to the motor - which changes the no-load speed and the speed/load curve. The current drawn will be dependent on the way that the mechanical load responds to the changed speed - you haven't said what the load is. With fans the load drops off rapidly with reducing speed, but at very low speeds, bearing friction and cogging will consume most of the available torque and can bring the motor to near-stall. \$\endgroup\$– Phil GCommented Jan 3, 2020 at 17:53
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\$\begingroup\$ At 10% PWM (if properly implemented) the motor draws 10 times more current than is drawn from the power supply. "But the motor driver draws most current at 10% pwm" - Do you have a particular case where the motor is drawing more current than you expect? If so, please provide details (motor specs, volts, amps, rpm, load being driven etc.) \$\endgroup\$– Bruce AbbottCommented Jan 3, 2020 at 20:14
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When PWM is correctly implemented (i.e. high enough frequency...) it is electrically equivalent, from the perspective of the motor, to changing the voltage across the motor terminals. The justification for why this is true is explained very well in this answer: Is there an ideal PWM frequency for DC brush motors?. As mentioned in some of the comments, you are likely observing this effect because at a lower speed your motor is encountering a greater load than when it is spinning quickly.
