over voltage of a 12vdc motor

I have a 12vdc motor from a power car window and I need to run it at a higher speed. The load on the motor is pretty low. What can I expect if I run this motor at 18 or 24 v?

Reply to
CCE
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The motor brushes get stressed by high currents; if you start the motor on higher than normal voltages they'll get stressed more, leading to faster (sometimes immediate) wear.

The motor bearings get stressed by high speeds; running the motor on a higher voltage will make it go faster. Whether this causes problems depends on your bearings.

Iron losses will be higher because the armature windings will be running at higher than normal frequencies, but if you're loading it lightly this may not be an issue.

The brushes may bounce if you're going at 2x the normal speed, leading to quicker (but not immediate) wear and intermittent lower torque.

If you're driving it from something that can limit the current as it starts up you may be fine, or you may run into brush or bearing problems. If it's a car window motor chances are that it's running pretty close to the limits of its design, but you can only tell by giving it a whirl.

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Reply to
Tim Wescott

I recall reading in a car manual that those's motors may have a overcurrent device (polyswitch?) type device somewhere. The device might trip with the added current from the added voltage.

Those motors are probably designed for a short run time... Given enough time, continuous use and higher voltages will probably cook the motor. D from BC

Reply to
D from BC

Eventual overheating and failure seems a safe assumption.

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Reply to
Meat Plow

The duration is pretty short, say 5 to 10 seconds every 3-4 minutes. This is for a hobby project and will only get used once a month or so.

Reply to
CCE

Smoke. I expect the window winder motors are not continuosly rated.

However I run those 9.5vdc cordless drill type motors at 12v, the normal bearings dont last long so I replace them with ball types, the brushes seem to last ok though.

It all depends how long you run the motor for and how long you want the bearings brushes to last and how hot you let it get.

Colin =^.^=

Reply to
colin

"CCE"

** Count the contacts on the commutator and find how many poles it has.

Allow 2.5 volts DC for each pole as a safe max working voltage.

3 pole = 7.5 volts

5 pole = 12.5 volts

etc.

Go much above that and expect very short life from the commutator.

Automotive heater fan motors typically have 11 poles, even though rated for nominally 12 volts, so can take 24 volts DC long as the current draw is not too high.

Watch out for switch on surge currents that can damage the commutator at high voltages.

....... Phil

Reply to
Phil Allison

Thanks for everyone's input. Your posts have answered my question!

Reply to
CCE

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