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Re: [TCML] HV wire ?
Why not just use flexible welding cable? For example, McMaster-Carr part
number 7818A14 (http://www.mcmaster.com/#welding-cable/) is the proper gauge
and has a insulation thickness of 0.124". While not rated for high voltage,
124 mils of insulation is good enough to hold off 15 kV for most
dielectrics. Just don't rely on the insulation alone, use a reasonable
standoff in addition where the conductor approaches anything that it would
want to arc to. Air is more or less excluded from the wire during the
process of vacuum drawing the insulation onto the stranded core, limiting
the corona issues that you would run into....besides, the corona degradation
of polymers takes time so unless your coil has an unusually high duty cycle
the cable will likely last for a very long time in Tesla duty (whereas the
stuff that's rated for HV is expected to last under continuous service for
years)
Just some thoughts.
Jason
On Tue, Jun 15, 2010 at 12:54 PM, Michael Twieg <mdt24@xxxxxxxx> wrote:
> We might peak at 2000amps, and if we burst at a high repitition rate the
> rms
> primary current could feasibly get that up to 500A. We definitely couldn't
> run that high for extended periods of time, though. And no, we're not
> looking at 10MW or something ridiculous. The load is mainly reactive, not
> resistive, so we're only looking at real power delivery of maybe 30KW
> average.
>
> And the wire has to be somewhat flexible, so tubing isn't an option. It
> will probably need to be between 1 and 2 meters long. IMO this isn't
> incredibly critical, but we wanted a pro solution if possible.
>
> -Mike
>
> On Tue, Jun 15, 2010 at 9:24 AM, jimlux <jimlux@xxxxxxxxxxxxx> wrote:
>
> > Michael Twieg wrote:
> >
> >> This is for out DRSSTC, the cable going between the primary coil and
> >> primary
> >> capacitor. The primary will see maybe up to 500 amps RMS, and the
> voltage
> >> at that note may be up to 15KV peak. We were advised by a professional
> >> power electronics engineer to not simply throw rubber insulator on a
> >> cable.
> >> Apparently air between the conductor and insulator will ionize, which
> will
> >> chemically degrade the insulation over time. We were just looking for a
> >> more robust solution.
> >>
> >>
> > They're right about the insulation degradation.
> >
> > But, as others have posted, why insulate at all?
> >
> > 500A RMS? at 15kV that's almost 10 Megawatts.
> >
> > Perhaps you mean you've got pulses, during the pulse you've got 500A RMS?
> >
> > Anyway, you're looking for tubing here, both for the low inductance, and
> > because at the frequency, skin effect means that you're only using the
> > outside layer of the wire, so why spend the money on copper you aren't
> > using. Use 1/2" copper tubing or something similar. You could also
> > probably use the shield of coax cable. you can connect the center
> conductor
> > in parallel.
> >
> > In any case, trying to find insulated wire rated for the insulation is
> > going to be a chore.
> >
> > Also, just how long a run is this? And does it really make much
> > difference? If you went from AWG0 to AWG 20, it's going to be roughly a
> > factor of 10 in AC resistance. If the run is, say, 2 feet long, that's a
> > few milliohms difference. At 500Arms that's about 250W/milliohm, but I
> > suspect that's pulsed(e.g. you don't have a handy 10 MW wall socket to
> plug
> > into), and in any case, the average power dissipation will be quite low.
> >
> >
> > Or, more practically, if you want insulated wire, get some AWG14 HV wire
> > and try it. If it melts, THEN go get your insulated copper bar stock...
> >
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> >
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