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Re: [TCML] HV wire ?
Thanks everyone for the tips and questions. It was difficult to find
what we needed in small quantities, most companies want to sell 100'
or 500' spools for kilobucks. We ended up getting a donation of 20'
of 25kv 1/0 from a local electric supply company, however our backup
plan was this wire here:
http://www.tpcwire.com/tpc2.aspx?Id=MediumVoltage_MobileSubStation_TypeSHCables
We found a lot of wire meant for burial that was suitable, but not
flexible enough for our application. The cable meant for a "mobile
substation" has thinner strands and non-pvc casings so they're less
stiff than the stuff meant for burial.
We're trying to make a professional go at this coil, we've got CNC'd
bus sheets, high-flow water-cooled custom heatsinks for the h-bridge,
shock-mount 19" travel racks for all our power electronics, and so
forth. For a less demanding coil we would have gone with the sleeved
option, or just no HV shielding and try to position things so it's not
a problem. For this coil we want to arrive at a venue and be set up
to do a musical tesla coil show within 1 hour, so we need a guaranteed
no-problem solution, hence the HV wire.
In terms of gauge, we wanted 1/0 because we are handling lots of
current and want low resistance.
many thanks again for the comments, hope this thread will be helpful
to future googler's.
Ian
On Tue, Jun 15, 2010 at 4:49 PM, David Sharpe <sparktron01@xxxxxxxxx> wrote:
> Allied Wire and Cable stocks 7.5kV EDPM non-shielded cable from #8 up
>
> http://www.awcwire.com/ProductSpec.aspx?id=EPDM-7500V
>
> It is also available in 15kV from Industrial Electric Wire and Cable.
>
> http://www.iewc.com/CatalogProduct.aspx?product_id=53
>
> Note 5/15kV EPR 210 Jumper Cable
>
> Our company is rebuilding on old GE Magnablast 5kV (2.3kV actual)
> contactor with Joslyn Vacuum contactor and these conductors as used
> as "whips" to terminate to isolation switches and 2.3kV horizontal
> busbars in MCC lineup. Tape ends with Scotch 160 for stress cones
> and job is done. FWIW using 4/0 conductors on contactor where motor
> has a connected load (measured) of 20A (100-125HP induction motor).
> Massive overkill, but you don't mess around with 2.3kV MCC fed by a
> 2500kVA transformer either...
>
> Regards
>
> 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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>>
>
>
>
> --
> Dave Sharpe, TCBOR/HEAS
> Chesterfield, VA USA
>
> Sharpe's Axiom of Murphy's Law
> "Physics trumps opinion!"
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> http://www.pupman.com/mailman/listinfo/tesla
>
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