Terry Blanton wrote:
On 12/20/06, Stephen A. Lawrence <[EMAIL PROTECTED]> wrote:
Do you mean reduce resistance?
For a given voltage the time for the current to rise to 67% of its
steady state value is given by L/R. Since I must achieve a certain
current to achieve a certain magnetic field strength of the
electromagnet, the rise time is essentially wasted duty cycle. If I
am duty cycle limited, I want to minimize the rise time.
You're also throwing away a lot of energy by "charging" the coil fresh
and then shutting it off again each time the motor goes around. Most of
the energy you pump into the coil is presumably just wasted when you
open the circuit a few milliseconds later.
Is there any way you could "save" the energy? Maybe put a big cap in
parallel with the coil, sized so the resonance frequency of the LC pair
matches the motor's expected rotation rate. Then the external power to
it which drove its oscillation would just have to make up for resistive
losses and provide the energy to pull the rotor over the hump -- you
wouldn't be paying for the energy to pump up the B field every time around.
I don't know if that would actually be practical, though.
The obvious way is to raise the voltage; but, I don't want to exceed
0.5 times the break down voltage of the insulation. As Jones points
out, I could use a different core; but, the super permalloy (aka
spermalloy :-) being used is probably the best choice.
I think we've decided that the least expensive approach for now is to
use solid CO2 to increase the duty cycle of the EM by pulling out any
heat generated by the coil. (BTW, Jones, virtually every local
supermarket sells dry ice these days.) Besides, the condensing water
vapor will give the whole test rig that mad scientist look. :-)
Ironic that one of the goals of a magnetic motor is to reduce
greenhouse gas emissions, however.
Terry
