Re: Bmax calculation for driver transformmer

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

But, the frequency you should be using is NOT the 250 kHz (unless you
really want to drive the gate with a sine wave)... the real issue is the
dV/dt, and the equation you used (popular for power transformers and CW
sine applications) essentially calculates that from Vrms and frequency.
If you want decent square edges, you probably need to figure your frequency
at several tens of MHz, or possibly higher.



Tesla list wrote:
> 
> Original poster: "rob by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<rob-at-pythonemproject-dot-com>
> 
> I found this, so I thought I'd post it.  It shows that even with very
> few turns Bmax in negligible on gate driver transformers:
> 
> I am using material similar to Amidon #75 in
> FT-82 size.  Thus Ae, the cross sectional area is about 0.25 cm
> squared.  Gate drive is 9V rms, or 1/2 the square wave swing that I AC
> couple to the transformers.  Using a derivative of the Biot-Savart law,
> Bmax=
> Vrms * 1e2 / (4.44 * N * Ae * F), where F is in Mhz.
> 
> Thus for my 5 turn transformers at 250khz, Bmax= approx 650 gauss.  Bsat
> is up in the thousands, so even with my small # turns, I am way below
> the saturation point.
> 
> Rob.
> 
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