Home Repair forum - how does an electrical motor work?

Author

how does an electrical motor work?

philip5malin@hotmail.com

2005-07-28, 4:21 am

My pestal fan is not working. So I decided to junk it and meanwhile
also take it apart to investigate. I am puzzled by the electrical
wirings so I am asking this question. The elecetrical motor has
bushings on 2 sides with 2 wires black and white. This part I
understand that the wires brings in electricity and rotate the middle
magnet to spin around the outside megnetic coil which is energized by
2 wires +/- AC. The Power cord comes with a white wire that go into
the housing, another lead go into a samll box. This box is outside of
the cyclindrical housing, it is a small 3cmx3cmx1cm box with 3 small
wires black, red, purple ,(box which I can adjust speed). Then another
box 1cmx1cmx1cm with 2 wires blue and grey that look like a resistor.
So there are total 5 wires that go into the motor housing: black,red,
purple, white, gray, blue. I think it only need 2 wires to make a
motor spin. What do the other wires do? If I use a voltmeter to test
each wire, what should I get if it is normal?

Lou@GoForIt.net

2005-07-28, 9:21 am

CL (dnoyeB) Gilbert

2005-07-28, 10:21 am

meirman

2005-07-28, 11:21 am

In alt.home.repair on 27 Jul 2005 23:43:34 -0700
philip5malin@hotmail.com posted:

>My pestal fan is not working. So I decided to junk it and meanwhile
>also take it apart to investigate. I am puzzled by the electrical
>wirings so I am asking this question. The elecetrical motor has
>bushings on 2 sides with 2 wires black and white. This part I

You must mean brushes.

>understand that the wires brings in electricity and rotate the middle
>magnet to spin around the outside megnetic coil which is energized by
>2 wires +/- AC. The Power cord comes with a white wire that go into
>the housing, another lead go into a samll box. This box is outside of
>the cyclindrical housing, it is a small 3cmx3cmx1cm box with 3 small
>wires black, red, purple ,(box which I can adjust speed). Then another
>box 1cmx1cmx1cm with 2 wires blue and grey that look like a resistor.
>So there are total 5 wires that go into the motor housing: black,red,
>purple, white, gray, blue. I think it only need 2 wires to make a
>motor spin. What do the other wires do? If I use a voltmeter to test
>each wire, what should I get if it is normal?

You might be using voltmeter the way that I do, to include everything,
but if you mean an actual voltmeter, it does nothing unless the motor
is plugged in. Don't plug it in. Use an ohmmeter. Open the boxes.
Get a book at the library.

Meirman
--
If emailing, please let me know whether
or not you are posting the same letter.
Change domain to erols.com, if necessary.

Jeff Wisnia

2005-07-28, 1:21 pm

philip5malin@hotmail.com wrote:
> My pestal fan is not working. So I decided to junk it and meanwhile
> also take it apart to investigate. I am puzzled by the electrical
> wirings so I am asking this question. The elecetrical motor has
> bushings on 2 sides with 2 wires black and white. This part I
> understand that the wires brings in electricity and rotate the middle
> magnet to spin around the outside megnetic coil which is energized by
> 2 wires +/- AC. The Power cord comes with a white wire that go into
> the housing, another lead go into a samll box. This box is outside of
> the cyclindrical housing, it is a small 3cmx3cmx1cm box with 3 small
> wires black, red, purple ,(box which I can adjust speed). Then another
> box 1cmx1cmx1cm with 2 wires blue and grey that look like a resistor.
> So there are total 5 wires that go into the motor housing: black,red,
> purple, white, gray, blue. I think it only need 2 wires to make a
> motor spin. What do the other wires do? If I use a voltmeter to test
> each wire, what should I get if it is normal?
>

Sorry I can't give you a complete and accurate answer Phillip, but you
might as well have asked, "How does a wristwatch work". There are too
many variations in motor and system designs for anyone to be able to
accurately determine what you've got there.

Unfortunately your command of english isn't sufficient for you to fully
and clearly describe what you've got there. I'm guessing english isn't
your first language because you state dimensions in metric units. But,
my command of languages other than my own makes it impossible for me to
describe anything at all other than english, so I'm not putting you
down, Philip, you're doing better than I could.

That said, lets see what can be done to satisfy your curiousity.

I don't know what a "pestal fan" is, but a guess would be "pedestal
fan", a term usually used to describe a fan with a "tall" floor stand.

You say it has "bushings" on 2 sides". If they really are on the sides,
then I think you probably mean "brushes" which would likely make the
motor be the type which is called a "universal motor".

Look at Paragraph 1.2 on this page:

http://en.wikipedia.org/wiki/Electr...niversal_motors

You didn't say how many fan speeds the "adjust speed box" gives you. If
it's just three (zero-slow-fast) the "resistor" you mention is probably
a diode rectifier which, when placed in series with the motor "throws
away" half of the electric current, so the motor runs slower.

If there's more than three speeds, then the motor's field winding may
have some "taps" in it, which would permit the switch to change the
number of field coil turns the current flows through, thus changing the
strength of its magnetic field and affecting how "hard it will pull" the
motor's rotor and fan blades against air resistance.

Here's another simple page describing how various types of motors work:

http://my.execpc.com/~rhoadley/magacmot.htm

Without a complete wiring diagram of what's in your fan, I wouldn't dare
hazard a guess as to where to put a voltmeter's leads or what you'd
measure on them.

Keep up the curiousity, Philip. Many of us here probably took apart a
family alarm clock when they were young to "see how it worked". (And a
lot fewer of us put it back together again so it worked.) That's one way
of learning how mechanical and electromechanical systems work. Too bad
the same can't be said of electronic technology, you won't get much of a
clue about how a microprocessor does its thing by cracking it open.

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."

PipeDown

2005-07-28, 8:21 pm

The AC motor in the fan has a field winding (the outer coils) and a rotating
coil. In a single speed motor, only two wires need to go to each but in a
multiple speed motor there may be more than one field winding that can be
switched in and out of the circuit by the speed switch. These additional
wires would be these additional field windings. One wire may be common to
two or more windings and thus the odd number.

Not sure if they switch in parallel or series but it probably dosen't much
matter. The things you call bushings are probably actually bearings. A
bushing simply lines the edges of a hole and dosent necessarily move.

<philip5malin@hotmail.com> wrote in message
news:1122533014.551421.28110@g49g2000cwa.googlegroups.com...
> My pestal fan is not working. So I decided to junk it and meanwhile
> also take it apart to investigate. I am puzzled by the electrical
> wirings so I am asking this question. The elecetrical motor has
> bushings on 2 sides with 2 wires black and white. This part I
> understand that the wires brings in electricity and rotate the middle
> magnet to spin around the outside megnetic coil which is energized by
> 2 wires +/- AC. The Power cord comes with a white wire that go into
> the housing, another lead go into a samll box. This box is outside of
> the cyclindrical housing, it is a small 3cmx3cmx1cm box with 3 small
> wires black, red, purple ,(box which I can adjust speed). Then another
> box 1cmx1cmx1cm with 2 wires blue and grey that look like a resistor.
> So there are total 5 wires that go into the motor housing: black,red,
> purple, white, gray, blue. I think it only need 2 wires to make a
> motor spin. What do the other wires do? If I use a voltmeter to test
> each wire, what should I get if it is normal?
>

holycow@MOO.com

2005-07-29, 12:21 am

On Thu, 28 Jul 2005 11:27:14 -0400, Jeff Wisnia
<jwisnia@conversent.net> wrote:

>You say it has "bushings" on 2 sides". If they really are on the sides,
>then I think you probably mean "brushes" which would likely make the
>motor be the type which is called a "universal motor".

Is that the kind of motor that will work anywhere in the universe?
I bet they were developed by NASA for space. Since they are
universal, will they work on both AC and DC, and on any voltage from a
common D cell battery all the way up to the 500,000 volt output from
the generator at a nuclear power plant? Add to that, will they run
off of static electricity when I rub a wool stocking against my coat
(after all, that's electricity). And what about lightning? That's
electricity too. Universal motors are the best, because they will run
anywhere, any time, off of any power source.

Matt

2005-07-29, 2:21 pm

philip5malin@hotmail.com wrote:
> My pestal fan is not working. So I decided to junk it and meanwhile
> also take it apart to investigate. I am puzzled by the electrical
> wirings so I am asking this question.

The following site will lead you to all the information needed to
understand and fix your fan:

http://courses.uiuc.edu/cis/program...elec_engin.html

LinkBot