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I have a blower motor which runs on 12v with 25min running 5min rest rating. I want to run it at 5v-1amp (significantly lower speed) for at-least 14hour continuously. Will that hurt burn the motor? The reason I think it may work is because I am running almost at the third of the rated voltage.

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  • $\begingroup$ Will it start or even run properly at 5V? $\endgroup$ – Solar Mike Jul 20 '20 at 15:07
  • $\begingroup$ It will certainly stall more easily at 5V. 14 hours is ~28 times longer than 25 minutes. And 5V is nowhere near 28 times less. So even not knowing anything about motors, intuition should tell you something will go wrong. $\endgroup$ – DKNguyen Jul 20 '20 at 18:44
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Assuming the limitation is power/heat buildup...

The power dissipated in the motor winding is a square function... if you decrease the voltage by 50% (and therefore the current) you have decreased the power by a factor of 4... down to 25% of its original value. Any motor rated to run for 25min "ON" time, and at 80% duty cycle, will surely have no problem running continuously at 5 volts... if indeed it will run at all.

Just understand that you don't have a say over how much current the motor will try to draw. If it required 25 Amps at 12V, that's the equivalent of 2.083 Ohms in the windings. At 5 Volts and 2.08 Ohms, it's still going to require around 2.4 Amps. (although the load of the fan/blower will be quite a less at the lower voltage & speed, offsetting some of the Current)

As long as the motor will run at 5 Volts, and it doesn't try to overload your 5V power source, it should be fine.

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  • $\begingroup$ A hand on the motor will also give a good idea of how its coping. $\endgroup$ – Transistor Jul 20 '20 at 21:14
  • $\begingroup$ Yes, it runs approximately at 5/7GPM at 4cm water at 4.6V which is what I need. Coming from physics background power/heat buildup is what I assumed is the limitation - but was not sure if that is it. BTW the rating of the blower is 12V 8A peak, I do not have a power supply to check the running amps at 12v. $\endgroup$ – Tweeker Jul 22 '20 at 14:08

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