Re: alfa-digest V9 #401

["Bob Gauthier" <gauth@xxxxxxxx>]

Excuse me all, and no offense meant to anyone,

Is this the Alfa Digest or my undergrad EE class?  I appreciate everyone's
knowledge on the myriad of subjects here but do we really need to
continuously clarify, correct, modify, etc the minutia that us academics
live for-- does anyone besides us really give a hoot? What about the rest
of the world for whom a sundial gives the right time as opposed to an
atomic clock?

I have a friend that absolutely must be correct, all the time, every time,
and he argues about it as if being correct is some measure of his
intrinsic worth. I've told him that I love him regardless of whether he is
technically correct or not.


Not sorry for the rant. And truly no offense meant as I do the same thing
far too often in my quest for precision and perfection.

PS I love you guys too

bob

George Graves said:
> While all you say is true, the back EMF is CAUSED by the inductive
> nature of the motor (I.E. when each section of the coil is
> de-energized, the magnetic field it creates, collapses causing a back
> EMF to be generated). This makes it work much like a swinging choke in
> a switching power supply .
>
> George Graves
> '86 GTV-6
> now with 3.0 liter 'S' engine
> and Power Steering
>
>
> On Thursday, April 10, 2003, at 07:02 AM, alfa-digest wrote:
>
>> From: Richard Bies <bies@domain.elided>
>> Subject: Re: Ohm's law
>>
>> I've read with interest, and will try a slightly different
>> approach....
>>
>> That the motor is largely "inductive" makes little difference in DC
>> analysis -- but the mechanical "load" on the motor is reflected as a
>> seemingly <lowered> resistance.
>>
>> The running motor has the applied voltage on its input.  That voltage
>> both
>> meets the electrical resistance -- and the mechanical load.  When
>> running
>> no-load, the motor is <generating> a "back" voltage (essentially)
>> equal --
>> it is, in effect, a motor and a generator at the same time -- acting
>> as if
>> the electrical resistance were extremely high (little current flows).
>> Then as the mechanical load is increased, current flows to supply that
>> load -- the electrical resistance seeems to have dropped (when the
>> motor
>> is completely stopped, to the resistance which would be measured by a
>> meter on the terminals of the stationary motor) the "back" voltage has
>> dropped to zero, and only the bare electrical resistance is present.
>>
>> As the torque of an electric motor is coupled to this current flow,
>> this
>> is why it is ideal in many applications -- self-regulating:  as the
>> demand (mechanical load) increases, the torque also increases, tending
>>  to
>> hold the speed steady (unlike an internal combustion motor, in which
>> torque dropps-off sharply below a given speed, and it quits) the
>> electric
>> motor will burn itself up as the limit is approached (not always a
>> good thing -- why there are fuses -- but it dies trying).
>>
>> r.m.bies
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