Hi,
I have a small motor. IIRC it is from a device powered by 2 AAs. I want much more power and speed from it for a brief period of time (1 or 2 seconds a few times a day at most). Is it OK to power such motor from 5, 9 or even 12V?
A motor is a looong wire encased in huge amount of metal acting as a heat sink. I would think it is nearly impossible to overheat the motor by such short pulse. Is it true? Is there something else that may be damaged in the motor with such abuse? The gears and other mechanical parts will probably also suffer but since it will be used not so often it should be also not so important.
People overpower things all the time.
Are you willing to risk failure by trying?
If the motor fails can you get another?
If the motor fails spectacularly and catches fire, will it present any safety issues?
If you can manage the safety issues, I say Try it!
If it works, then you know.
If it does not work, you needed a more powerful motor any way.
Overheating is not your problem, you probably will have commutation problems if the wires do not melt. Your current will probably go in the several amp range, not sure as I do not know what motor you are using. This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil
The main problem is not the higher voltage which initially causes overspeeding which would eventually mess up the bearings/bushing. The real question is how much load is there on the motor? A high load plus serious overspeeding will dramatically increase the current drawn and it's the current that what may well damage the commutator/brushes or burn out the windings.
But as vinceherman says, the only way you'll know without a detailed motor spec is to try it.
Steve
I have tried to measure the motor. The DDM says inductance is 500 uH. Resistance seems to be about 3 Ohm but I am not sure with this. It has no markings indicating voltage/current rating. But it has nearly exactly the gearing I need - it would save me a lot of work to use this particular motor.
I am aware higher voltage in stalled motor increases power dissipation by square of the voltage. I thought the most fragile part are the tiny long copper (?) wires. However I have no idea how to make a guesstimate if it harms the motor. Is the power dissipation the only problem or is there also another hard limit for the current? If it is only power dissipation how long it takes for copper to heat when it is conducting excessive current? Which temperature is too high?
No it's not just in a stalled motor that the current increases like that it's in any motor with any sort of load at all on it.
And if it's a brushed motor the commutator and brushes are usually damaged first. Many small "toy" motors have fragile metal brushes and they can be destroyed in seconds by excessive speed and current. It's the bouncing and sparking that does it (a bit like an arc welder!).
It seems odd logic to say the motor has the gearing you want but then plan to run it 4 times faster than its original speed.
Steve
If this is a motor removed from some commercial piece of equipment, it may have a thermal fuse imbedded in the windings that will open up when the heat is too great. It cannot be repaired and it cannot heal itself.
Paul
Paul_KD7HB:
If this is a motor removed from some commercial piece of equipment, it may have a thermal fuse imbedded in the windings that will open up when the heat is too great. It cannot be repaired and it cannot heal itself.Paul
Not for a brushed DC motor, there are multiple windings and they all spin round!
"Is it OK to power such motor from 5, 9 or even 12V?"
I'm not sure of your situation, but why not reduce the voltage of the power supply using a 7805 or similar voltage regular chip? Power diodes will drop voltage .7v per diode in series.