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PG13
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14
Once saturation occurs, the flux stops increasing in the core, and the current
that was induced in the feedback winding abruptly halts and reverses direction
due to a “ringing” effect. This reversal in current direction then turns off Q3
and begins to turn on Q4, which quickly ramps up the flux in the core now
heading in the other direction. (Fig 2).
This cycle goes back and forth continuously until power is removed.
To control the output voltage we can simply adjust our driving voltage.
Here’s why I chose a 12.6VAC transformer instead of a 16VAC transformer to
be used with your PG13.
One quirk we have come across is that our high voltage design cannot
produce a high current arc directly to ground. For this to actually occur we
would need a lot more parts in the circuit, and also it would reduce the safety
considerably. We decided to go for safety and stick with a lower power design.
Besides, you can pull some pretty hot arcs onto a screwdriver and other
objects, no ground needed!
To find out what we have for output voltage is a simple matter of turns ratios.
See the chart below to see the transformer secondary windings that were in
the different models of transformers that I sampled.
Winding Turns Wire Diam.
CHT-0126A: 2000 0.1mm
CHT-0126B: 2500 0.1mm
CHT-0126C: 4000 0.1mm
CHT-0126D: 6500 0.06mm
Since we chose the C version of the transformer, we see that we have 4000
windings in the secondary. Now we need to know what is in the primary. Since
we were trying to achieve highest possible voltage output along with a decent
current output, I compromised at 9 turns center tapped on the primary. Since
we are in a push-pull configuration, this essentially doubles our supply voltage
across the primary. So let’s say we have a 12.6 VAC transformer supplying
our kit, and we need to know what our output voltage will be. First we have to
find what the supply voltage will become after converting the 12.6VAC which
is an RMS value to the DC value after rectification. First we convert to peak to
peak:
12.6VAC * SQRT(2) = 17.81 Vpk/pk
Then we subtract 1.4 volts for the diode drops in the bridge rectifier.
17.81—1.4 = 16.41 VDC
Now realize that the 12.6VAC rating is at the current rating of the
Содержание PG13
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