Re: [TCML] Looking for pulse cap

[Steve Ward <steve.ward@xxxxxxxxx>]

The RMS current is "simply" calculated from the peak current and the
waveform shape.  I use my pspice model of the DRSSTC to calculate ballpark
Irms figures for the primary.  At 120BPS and 1500A peak, assuming a linearly
ramping primary current with a quick decay after the 200uS burst, i get
figures around 120A RMS.  The primary RMS current will be proportional to
the square root of the BPS, so doubling the BPS yields sqrt(2) times the RMS
current in the primary.

In any case, my 80A rated snubber caps do get a bit warm (and they are quite
massive in size) in a matter of 10's of minutes when used for tank cap
duty.  Depending on the thermal mass of the capacitor and the anticipated
run times, i think you can get by with an Irms rating of maybe half what you
would need to meet "spec", simply because it will take a significant time to
reach thermal equilibrium and overheat the dielectric.

Steve

On Tue, Sep 15, 2009 at 8:42 PM, Quarkster <quarkster@xxxxxxx> wrote:

> Phillip -
>
> RMS primary currents of hundreds of amps are much higher that I would have
> expected, although I have only seen data for peak current.
>
> Do you happen to have any measurement data on DRSSTC tank current values?
>
> Regards,
> Herr Zapp
> ----- Original Message ----- From: "Phillip Slawinski" <
> pslawinski@xxxxxxxxx>
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Sent: Tuesday, September 15, 2009 5:50 PM
>
> Subject: Re: [TCML] Looking for pulse cap
>
>
>  DC,
>>
>> Can you clarify?  What stray inductance?  If you mean in the cap bank,
>> then
>> no, it will not kill the IGBTs.  Stray inductance in the primary circuit
>> will only reduce coupling to the secondary.  It will NOT kill the IGBTs.
>>
>> Zapp,
>>
>
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