Re: Calculating the drain I - SSTC

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

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi Sue,

Theoretically, the switching current would be a square wave, but it is 
probably more of a flat top sine wave.  No matter, we'll assume it is a 
300Vp-p sine wave.  The primary should be a pretty good filter anyway so 
the 3rd, 5th... harmonics go away.

Reactance can be calculated with just like resistance.

R == ZL == L x 2 x pi x Fo = 18.9e-6 x 2 x 3.14159 x 221300 == 26.28 ohms

The voltage is like 300 / 2 / SQRT(2) = 106Vrms sine wave...

So....  106Vrms / 26.28 ohms reactive gives about 4 amps.  Not too bad at 
all, but it is RF so the skin depth in copper is only:

SD = 2.602 / SQRT(F) = 0.00553 inches.

I would just use 10 gauge house wire like everyone else does for what I 
guess must be some kind of tube or CW coil  ;-))

Cheers,

         Terry


At 01:10 PM 12/26/2003, you wrote:
>On a more serious note, I measured the inductance of my primary today, and
>found it to be 18.9 mico henrys. How do I calculate the current that will be
>flowing through it when I have 300 VDC on the rails, and I am switching at
>221.3 KHz?.
>
>I remember reading somewhere that sine wave formulas don't work with square
>waves, and that somehow harmonics enter into the formula, but I dont
>remember how it went :-(
>
>I'm almost done with this thing! I just gotta build the driver and low
>voltage power supply!
>
>Sue