alt.energy.renewable

As for back emf or induced voltage- note that in any motor we are looking at
d(phi)dt =d(Li)/dt
which in a transformer becomes Ldi/dt but in a motor becomes Ldi/dt +i
(dL/da)(da/dt)
where a is the angular position and da/dt =w is the angular velocity and is
called the "speed voltage" as opposed to the transformer voltage. Typically,
the "speed voltage" is much greater than the "transformer voltage" (Ldi/dt)
in a motor. Mechanical power transfer is related to this speed voltage-not
the transformer voltage. The source must still supply the mechanical power
needed plus the transformer power output plus losses resulting in less than
100% efficiency. An estimate is that you should be happy to get 75%
efficiency for a 1HP 24V device.

With regard to the core material- the Metglas has lovely magnetic properties
but needs to be cast and you do want to have a core structure which is
closed except for the necessary air gaps. note that any motor, because of
these gaps will have a considerably higher magnetizing current and copper
losses in the primary than a transformer so even as a transformer, the
efficiency will be lower than the 98% that you mention (which is about the
maximum efficiency of a 2-5 KVA well designed transformer-consdering
mechanical action, it drops lower). The mmf to produce a given flux in the
core is negligable compared to that of the gap so the metglas implies a more
expensive material with less manufacturing flexibility to gain something
that can be gained with a larger core cross section using standard
transformer steel laminations at lower cost. --


--

Don Kelly dhky@shawcross.ca
remove the X to answer
----------------------------
"Don Kelly" wrote in message
news:wqJCj.88072$w94.84197@pd7urf2no...
> ----------------------------
> "The Flavored Coffee Guy" wrote in message
> news:b5ff84a9-5c74-4b96-9514-4327823ada88@e6g2000prf.googlegroups.com...
>> Just remember this, a transformer is designed for a purpose and it can
>> be either a step up transformer or a step down transformer.
>> Everything else you need to know is here.
>>
>>
>> Go to this web site to pick up the basic theory:
>> http://elgersmad.homestead.com/files/resonance/transformer_motor_theory.pdf
>>
>> Go to this link to understand that it will work:
>> http://www.gutenberg.org/files/11498/11498-h/11498-h.htm#4
>>
>> Go to this link for the formula an equations required to design and
>> build your own:
>>
>> Notes for an Introductory Course On Electrical Machines and Drives
>> http://www.egr.msu.edu/~fzpeng/ECE320/ECE320-Notes-Part1.pdf
>>
> -------------------------
> So you have a crude switched reluctance/induction motor with the secondary
> on the stator rather than the rotor. So???
> Note that in an efficient induction motor, core eddy currents are as small
> as they can be made and the rotor currents are in well designed short
> circuited rotor windings. They are, in fact, transformer secondary
> windings. In fact, a conventional induction motor is simply a transformer
> with a rotating secondary. In this respect, you have simply switched rotor
> and stator-basically as you have stated.
> Note also that if the rotor windings of a conventional motor are brought
> out to to an external load, power can be taken from these windings - as in
> a wound rotor motor. In that way it is a transformer as well as a motor.
> Note that the input power must supply the losses, transformer output and
> mechanical output and all are interrelated. Definitely an efficiency, at
> best, considerably lower than that of a stationary transformer. No
> overunity involved.
>
> As for the emf kick, it is really questionable as to what you are trying
> to imply. Are you talking about back emf 0-if so, why? It exists in any
> motor and is related to power transfer in all motors.
>
> Why the capacitor?- resonance isn't going to give any energy boost and
> secondary frequency will vary in any case.
>
> Anyhow, your msu reference is not bad at an introductory level. I can't
> say the same for the theory in the main article.
>
> However, have fun.
> --
>
> Don Kelly dhky@shawcross.ca
> remove the X to answer
>
>