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200BPS rotary gaps and cap selection
On 8th April Gary Lau wrote:
> It will be interesting to run a similar simulation with the gap firing
> multiple times per half-cycle, to see which cap size draws highest power
Do you mean like this.....
"PSpice simulation to determine most effective tank capacitor size for
maximum power transfer using ballasted radar transformer and 200 BPS
synchronous rotary,"
The ballasted transformer was measured and then PSpice simulation was
carried out after modelling the transformer winding res. and ind. etc.
Open circuit voltage: 10Kv rms
Short circuit current: 224mA rms
Effective leakage ind: 142H (referred to HV sec.)
50Hz resonant cap: 71.3nF
For each capacitor value that was tried the firing delay of the simulated
rotary was "Manually" adjusted to give TWO EQUAL BANGS per half cycle
of the supply voltage. This involved many, many hours of simulation
to get the optimum firing delays to the nearest 10us ! This is necessary
to avoid getting one insignificant bang and one MASSIVE bang per half
cycle. I'm sure the massive bang would overvolt something in the real
world.
Once the best firing angle was found for each capacitor, the firing
delay, firing voltage, and RMS supply current were examined.
>From these the following parameters were calculated,
Simulation results:
C = Capacitor value in nF
t = RSG firing delay (in ms after mains zero cross)
V = Capacitor firing voltage
P = Power throughput (= 200 * 0.5 * C * V * V)
VA= Mains supply VA
pf= Power factor (kind of like a measure of efficiency)
C [nF] t [ms] V [v] P [W] VA pf
15 0.01 17717 471 825 0.571
20 0.04 19655 773 953 0.811
22 0.10 20049 884 1074 0.823
24 0.17 20314 990 1150 0.861
26 0.24 20570 1100 1233 0.892
28 0.35 20699 1200 1319 0.910
30 0.46 20790 1297 1405 0.923
32 0.57 20792 1383 1494 0.926 <---- Max firing volts
33 0.63 20757 1422 1534 0.927
34 0.69 20739 1462 1575 0.928 <---- Best power factor
36 0.81 20639 1533 1654 0.927
38 0.93 20484 1594 1727 0.923
40 1.05 20296 1648 1801 0.915
42 1.17 20068 1691 1864 0.907
44 1.28 19843 1732 1927 0.899
46 1.38 19524 1753 1988 0.882
48 1.49 19237 1776 2041 0.870
50 1.60 18946 1795 2090 0.859
52 1.70 18608 1801 2136 0.843
54 1.80 18271 1803 2178 0.828 <---- Maximum power thru'
56 1.89 17914 1797 2213 0.812
58 1.98 17585 1794 2248 0.798
60 2.07 17216 1778 2282 0.779
65 2.27 16354 1738 2345 0.741
70 2.45 15500 1682 2396 0.702
80 2.76 13914 1549 2467 0.628
100 3.22 11327 1283 2526 0.508
50Hz resonant cap: 71.3nF
Cap for max voltage: 32.0nF (45% of 50Hz res cap)
Cap for best power fac: 34.0nF (48% of 50Hz res cap)
Cap for max power: 54.0nF (76% of 50Hz res cap)
So which cap do you choose ?
Well I did this work to try to decide what cap to use for my new coil.
I finally chose to build a total of 44nF of tank capacitors, this
is in between the maximum efficiency and maximum power values.
However I realise that using 44nF only draws 1927 VA through my
transformer, so I have made provision to lower the ballast inductance
if desired in order to get more power and to get closer to the maximum
power match.
Since there has been a lot of "eye-strained hours" looking at a PC
I hope this bit of research leads to big sparks for myself and others,
PS. If anyone is interested in my 200BPS sync rotary simulations I have
graphs of the above data along with PSpice schematics for other
simulations including the chaotic behaviour of static gaps. I could
post these to a "Tesla Friendly" site.
***** US Readers BEWARE, this all refers to 50Hz UK power *****
Richie Burnett,
- Spendin' far to long at the PC
in sunny Newcastle