----- Original Message ----- From: "Stephen A. Lawrence" <[EMAIL PROTECTED]> To: <vortex-l@eskimo.com> Sent: Friday, December 22, 2006 4:21 PM Subject: Re: [Vo]:
> > > 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. It's about 63% actually (1-exp(-1)), not that it makes much difference :) Michel > 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 >> >
