Non-diy_efi, dyno help

[Pat Ford]

Previously, you (Todd....!!) wrote:
> >From what I remember, and I believe I'm close to accurate...
> 
> There are only two known things that reduce inductance, none of which
> are materials themselves, one is distance(i.e. space), the other is
> another EMF(electro magnetic field)(This electromagnetic field
> cancelation effect is used in the donut shaped electronics a lot)
> 
> In other words coating a metal with plastic will not hender the
> inductance(Creation) of electricity... only space and/or another EMF...
> 
> Right?
 Yes but eddy currents are not magnetic, they are electric.
 Have you ever wondered why transformer cores are made of little plates
rather then a solid chunk of iron?? Read on Mc Duff

> 
> So I must ask, from which principle are you deriving that a coated
> stator reduces eddy currents(or feedback currents)?

 the eddy currents are at a right angle to the change in flux, so the
plastic coating between the plates stop the little whirl pool type currents

 picture the lines of flux going straight down ( hold your left hand in a fist 
thumb down), the induced current in a plate of steel will form a little swirl
centered around the line of flux ( the current will circulate in the direction 
of your fingers). picture the plate being turned on its edge, now the whirlpool 
currents cant get as big. that is what is done in a transformer BUT one plate 
doesn't carry enough 'magnet current' so many plates are stacked.  

 if the plates are not insulated they still carry eddy currents just not as well

 I've taken some liberties with what actualy happens to make visualization easier.
( and because I can't actually remember all of the fancy assed names from physics
I took 15 yrs ago :)

> 
> Or am I just WAY off, and if so WHY am I way off....

eddy currents are not magnetic beasties.

> 
> Just wonderin.........
>

I hope this helps and doesn't muddy the water for you
 
> Later....
> 
> Todd....
> 
> Don.F.Broadus at ucm.com wrote:
> > 
> > The eddy current dyno uses a iron drum that rotates around an electro
> > magnet. Since the drum is not laminated like motor stators
> > eddy currents are induced into the iron very easy. A chopped DC or straight
> > DC voltage powers the electromagnet. The eddy currents slow the drum
> > producing a load and also great amounts of heat. An eddy current dyno would
> > make a poor motor since the magnetic losses would be very high. Great dyno
> > find, I wish junk yards around here were that good.
> > 
> > Don
> > 
> > 
> > > -----Original Message-----
> > > From: David Piper [SMTP:dapiper at mail.one.net]
> > > Sent: Saturday, June 05, 1999 8:28 PM
> > > To:   diy_efi at efi332.eng.ohio-state.edu
> > > Cc:   brucep at ptd.net
> > > Subject:      Re: Non-diy_efi, dyno help
> > >
> > > Check w/ Mustang Dyno in Twinsburg, OH
> > >
> > > TurboDave
> > >
> > > >My question is this can the eddy current unit from this dyno be used to
> > > make
> > > >a motor dyno?
> 

--
Pat Ford                           email: pford at qnx.com
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