If you are driving down the road and you have a 24" fan in the back of your truck that is unplugged with the switch on and the wind is turning the fan, will it shock someone if they grab the prongs of the plug?
Just curious!
James
I'm not absolutely certain, but a semi-educated guess is, no.
I expect it has an induction motor, so there would be no permanent magnetism except a little stray left over and no mechanism to generate more field. Therefore it would not make significant voltage.
Induction motors can generate electrical output if they are driven at a sufficient speed AND they have something to develop reactive load current (out of phase with the voltage). Your fan would not have that.
An induction motor connected to the power grid and driven over speed will send power back into the grid. There are also youtube videos where someone demonstrates independent generation using a load capacitor to develop the reactive current.?ÿ
If your truck is un-plugged it won't turn over, thus not contributing to the air velocity hitting the fan blades.
Mr cow, something may be hitting that fan....
Experimental data: I put analog and digital voltmeters across the plug of a box fan and ran it on high.?ÿ When I switched the power strip (not the fan switch) off the meters dropped about as fast as if I had just disconnected them, while the fan was still turning.?ÿ There might have been a small voltage , but there wasn't enough to distinguish from just the natural fall of the meter needle, or digital meter's averaging time. Certainly not enough to shock.
My mother had her carpet cleaned yesterday and called to see if I had any fans to help dry the carpet. I loaded two of our bigger fans in the truck and headed that way. Along the way, I got to wondering about the fans generating electricity.
I started to get my 14 yr old nephew that was at my mother's house to ride with me down the 4 lane highway and hold onto the plug but then I thought about having to move the rest of the furniture by myself and decided not to.
I didn't know there were different types of motors. I will google Induction Motor and learn something. I have been told that I could connect a single phase motor to a three phase motor and use single phase electricity to generate three phase. This question came up at the fire station because we had converted the station to single phase after Hurricane Ike to be able to use a new generator that was installed with a grant from FEMA. In doing so, we can no longer use the 3 phase Fire Siren from 1947 that's on a 45' pole outside the station.
Thanks,
James
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@flga-2-2?ÿ
Happy to be of service.?ÿ Your wife sends us little presents to thank us for annoying you.?ÿ She says you now only have her to do that job instead of all the people you were trying to stay ahead of at work.?ÿ She appreciates the break.
The three of us share an initial.?ÿ Los Tres Amigos.
I'm fairly certain you have had experience with a milk cow's material-laden tail slapping you in the head.?ÿ So, I'm guessing you are referring to such material.
@jaro?ÿ
I always thought; if you have an electric motor, with a big cog, that drove a small cog, that ran a generator, that ran the electric motor; you'd have a perpetual motion machine. I had someone smarter than me, explain it to me, once, but I don't remember what it was. Probably flew right over my head....
The problem with that is pretty simple. You would be converting back and forth between electrical and mechanical (kinetic) energy. Nothing is 100% efficient, so you get less energy out than you put in with each device and it grinds to a stop.?ÿ The missing energy (from the inefficiency) is the heat that is generated in the devices.
@bill93?ÿ
That's vaguely, the answer I remember...
The problem I have; if the big gear (attached to the electric motor) makes 1 revolution, the small gear (attached to the generator) makes 100 revolutions. Why doesn't that generate (at the generator) more energy (electricity) than the motor needs?
@bill93?ÿ
That's vaguely, the answer I remember...
The problem I have; if the big gear (attached to the electric motor) makes 1 revolution, the small gear (attached to the generator) makes 100 revolutions. Why doesn't that generate (at the generator) more energy (electricity) than the motor needs?
Because it takes 100 times the torque on the big gear's shaft as what you get on the little gear's shaft. Power is proportional to torque times rotation speed, minus friction.
?ÿ
Nufff Said
I'm fairly certain you have had experience with a milk cow's material-laden tail slapping you in the head.?ÿ So, I'm guessing you are referring to such material.
Did you know that your eyes can be hurt, by a cows tail, scratching your eye ball? Our cow thinks she is blessing you with her tail. We tie it out of the way. Feces do fly, when we forget.
N
@dougie I thought we already established that the fan would not generate electricity, therefore you can't be shocked, not even mildly.
@bill93?ÿ
I remember that, now, too. It takes just as much energy to turn the small gear 100 times as it does to turn the big gear once, because of torque; and there's the friction....?ÿ
