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If it's a DC motor (running off a battery or rectified supply) put a pair of strong magnets, one each side of the existing magnets in the motor. You'll be able to feel when they're in the right place. This will increase the magnetic field and make the motor run faster without risking burning it out.
Tried it ? My guess is that the external applied field will be "shorted" by the low reluctance metal case of the motor.
Yep, I tried it a while ago as I thought the same as you, but it does work. I got around 20% speed increase on a cheap and nasty 3V motor and less on better quality ones, as you'd expect. That was using three 6mm x 6mm dia. cylindrical magnets on each side
I was only measuring off-load speed (disc + white band + reflective opto-sensor + 'scope for measuring) but according to Maxwell's(?) equations, the force is proportional to the field, so torque should increase on a loaded motor.
If the field is REDUCED, the back emf falls and the speed increases, if the load is light.
Ah . . . It's a long, long, long time since uni and motor / dynamo theory is something I haven't touched since so I'll happily defer to you on that.
I did find that with a CDROM drive tray motor I could stall it but not make it any faster. Maybe the effect I was seeing was the opposite of what I thought I was doing ;¬)
I did find that with a CDROM drive tray motor I could stall it but not make it any faster. Maybe the effect I was seeing was the opposite of what I thought I was doing ;¬)
It has to be admitted, that, looking at your profile, I ain't that far back from your temporally speaking ;-) I did do a lot of motor theory then, and I keep a hand in still because they are such funny little buggers - so deceptively simple to understand.
My theory here is that you are field weakening - remember the shunt wound DC motor ? No field, motor spins off to infinity, given a chance. Scary in the EE lab. That's why I wondered about the things ability to provide torque/power rather than RPM.
Steve
My theory here is that you are field weakening - remember the shunt wound DC motor ? No field, motor spins off to infinity, given a chance. Scary in the EE lab. That's why I wondered about the things ability to provide torque/power rather than RPM.
Steve
Jan 2, 2010. 12:38 AMstephenniall
says:
Fit a gearing system To gear it up or down
Increase Voltage
If you increase voltage i reccomend a heatsink or some sort of cooling it as it will get rather warm quickly
Increase Voltage
If you increase voltage i reccomend a heatsink or some sort of cooling it as it will get rather warm quickly
Jan 1, 2010. 8:44 PMWillard2.0
says:
If it is a DC motor, just up the voltage. Don't run a motor at more than 50% of the rating (12V motor running at 18V, or 6V motor running at 9V) otherwise you risk fire and that mysterious blue smoke that makes motors not work.
If it is a AC motor, then I have no clue.
Willard
If it is a AC motor, then I have no clue.
Willard
But remember, if you run them at above their working specification, they won't live for as long. You may just want to buy a motor with a higher RPM, or buy a gearing system for your current one if you have plenty of torque.
Jan 1, 2010. 10:00 PMalex-sharetskiy
says:
If it's an AC motor, you can still increase speed by increasing voltage
If it's small it probably isn't, but AC motors tend to run in proportion to the frequency, not voltage.
L
L
SOME kinds of AC motor, for a small change in speed, CAN be affected by voltage. As Lemonie says, most are only affected by FREQUENCY.
Ta, I was careful to use the word "tend", as I knew it wouldn't be a universal rule...
L
L
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