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A DC motor specified max 15V or 18V, 2A, given input by SMPS 24V


How is it harmful to a motor if a DC motor specified max 15V or 18V, 2A, given input by SMPS 24V max 2A?

A DC motor specified to 15V nominal will rotate faster at 24V, and excessive speed wears the brushes out faster. Is it a problem? Maybe, maybe not.

Another issue is, if the motor is rated at 2A nominal, if you just plug the motor in to 24V when it's standstill, it will take significantly higher current (stall current), maybe 10A, maybe 20A. The SMPS would probably just enter short-circuit protection mode (hickup protection for example), so the motor would not turn.

Solution to this is active current limiting (usually done as a PWM controller driven by a current sense signal), but then it becomes a motor controller design job. But if you do that, then you can also limit the maximum duty cycle, so 24V will not be problem either as you can limit the motor speed.

It might be possible to modify the switched mode power supply to give 15V or 18V.

If the motor is powered off a PWM speed controller, just limit the duty cycle so the maximum speed isn't exceeded.

Brushed or brushless?

A brushless motor will probably easily blow up the controller IC past its maximum rating while a brushed motor is a lot more resilient to short-term or gradual overvoltage.

I've abused small brushed DC motors before, usually they will take 2-4 times their rated voltage or more for a while, but it's hard on the brushes, commutator and bearings.


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