Re: OLTC primary loss measurement

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Paul,

I was not able to find any time to work on this yeasterday.  But today...

The 20,40,60...  Volts I gave is a "metered" voltage.  The actual firing
voltage is twice that number.

If  Rpri =  2 x pi x F x L / Q 

Vfire	Qpri	Rpri

40	4.7	0.0197
80	7.3	0.0127
120	10.0	0.00927
160	12.1	0.00766
200	14.0	0.00662

So the graph looks like:

	http://hot-streamer-dot-com/temp/OLTC09-02-01.gif

If one uses your equations below which seem to fit very well:

	http://hot-streamer-dot-com/temp/OLTC09-02-02.gif

Looks like I can expect a Q of 21.4 at 4.3mOhms for Rpri.  

Vds Seems high here at 8 volts.  Probably not too surprising given that so
many terms are at work in the "real" system.  However, if we pump 2000 amps
peak into the system, the loss for Vds is:

8*2081 = 16648 watts peak

While the loss for Rpri is:

2081^2 x 0.00662 = 28668 watts

The system peak power is about 200*2081 = 416kW  

Of course, 416000 /(16648 + 28668) = Q = 9.18 here in my guess work.  Off
by the square root of two...

I will have to think about if Rpri or Vds has any reason to be so high.
Have to think about cap and Lpri second order resonances and other horrific
things...   Probably still have enough drive there in any case, but I just
like to know exactly "why"...

Cheers,

	Terry

BTW - I'll copy the list in case others are interested in just nitty gritty
details...

At 03:36 PM 9/1/2002 +0100, you wrote:

>I ran the primary alone as shown:
>>
>> http://hot-streamer-dot-com/temp/OLTC08-31-06.jpg
>>
>>I ran at 5 input voltages of 20,40,60,80, and 100 volts as read on the 
>>meter.  On 120 VAC that can go up to 150 volts and at 240 vac in it goes up 
>>to 300 volts.  So I still have 3x the voltage to go.  I didn't go higher 
>>here since I am not sure where the "power" is going?
>>
>> The files are at:
>> http://hot-streamer-dot-com/temp/OLTC/8-31PriD-1/


>
>> I ran at 5 input voltages of 20,40,60,80, and 100 volts
>
>TEK00000: 20 volts
>PK  FREQ kHz (Error +/-)    Q FACTOR (Error +/-)   LEVEL
> 1   37.198 (0.01%,2Hz)        4.66 (22.33%, 1.0) -6.3dB
> 2  105.675 (0.01%,5Hz)       19.57 (37.56%, 7.3) -29.4dB
>
>TEK00001: 40 volts
>PK  FREQ kHz (Error +/-)    Q FACTOR (Error +/-)   LEVEL
> 1   36.534 (0.01%,2Hz)        7.27 (15.79%, 1.1) -5.2dB
> 2  108.118 (0.01%,6Hz)       30.73 (53.12%,16.3) -30.0dB
>
>TEK00002: 60 volts
>PK  FREQ kHz (Error +/-)    Q FACTOR (Error +/-)   LEVEL
> 1   36.471 (0.01%,2Hz)        9.95 (13.28%, 1.3) -4.9dB
> 2  108.834 (0.01%,5Hz)       44.21 (63.17%,27.9) -29.2dB
>
>TEK00003: 80 volts
>PK  FREQ kHz (Error +/-)    Q FACTOR (Error +/-)   LEVEL
> 1   36.534 (0.01%,2Hz)       12.12 (13.28%, 1.6) -4.5dB
> 2  108.976 (0.01%,5Hz)       50.65 (63.17%,32.0) -30.4dB
>
>TEK00004: 100 volts
>PK  FREQ kHz (Error +/-)    Q FACTOR (Error +/-)   LEVEL
> 1   36.590 (0.01%,2Hz)       14.04 (11.17%, 1.6) -4.4dB
> 2  108.971 (0.01%,5Hz)       48.13 (63.17%,30.4) -30.7dB
>
>
>Note the low level of harmonic content at all voltages, which
>suggests that non-linearity within the RF cycle isn't a problem,
>ie your diodes are turning on/off ok, etc.
>
>Summarising
>
> V    Qpri
>
> 20   4.7
> 40   7.3
> 60  10.0
> 80  12.1
>100  14.0
>
>If power dissipated is given by Ip^2Rp + Vds * Ip
>where Rp is effective R of coil+caps and Vds is volts drop
>across IGBTs, then
>
> Energy dissipated per cycle = Ip * (Ip*Rp + Vds)/F
>
>and
>
> Energy stored = Lp*Ip^2
>
>then [fixed font]
>
>   Q = 2 * pi * F * Lp * Ip^2
>       ----------------------
>         Ip * (Ip*Rp + Vds)
>
>
>     = 2 * pi * F * Lp * Ip     = 2 * pi * F * Lp
>       --------------------       ---------------
>          Ip*Rp + Vds               Rp + Vds/Ip
>
>If Ip = Vp/(2*pi*F*Lp)
>then
>   Q = 2 * pi * F * Lp
>       ---------------------
>       Rp + Vds*2*pi*F*Lp/Vp
>
>and
>
>  1/Q =     Rp      +    Vds * 1
>        ---------              --
>        2*pi*F*Lp              Vp
>
>
>If we plot your data as 1/Q against 1/Vp, and extrapolate,
>we estimate a Q tending towards 30 at high voltage, which
>means that Rp will be around 0.003 ohms.  The slope gives
>a Vds of around 3.5 volts.
>
>I guess you're coming up with the difficulty of getting a
>high Q in a very low impedance resonator.
>--
>Paul Nicholson,
>--