# [TCML] Test of Saturable Reactor in my 200bps SRSG Medium Teslacoil

```Hello List,

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I want to start a discussion about the possibility of using a saturable reactor for current limiting - especially in a system based on a synchronous rotary spark gap. The idea of using a saturable reactor for current limiting is not new I know, but I think very less information about this is available.
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My particular goal is, to do the current-limiting of my big coil (runs up to 30kW input power) with 2 heavy saturable reactors. After getting suitable reactors and also the help of a very friendly listmember getting the beasts running, I now start some tests with one of my reactors in combination with my medium sized teslacoil, I have postet about this TC several times in the last weeks. In combination with a dummy load, this TC is an optimal device for performing some nice tests.
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First of all, I made a video which shows the test-setup:

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In the test, I have replaced the original air - gapped ballast inductor (which I have well built) by the saturable reactor. The original inductor is set to the inductance value of 31mH, which I got out of Richie's Resonant charging design procedure. Now we all know, that the inductance of 31mH of such an air gap-inductor REMAINS NEARLY CONSTANT when different voltages are applied. It doesn't matter, if 20Volts, 100Volts or 240Volts are applied - every time this thing has 31mH. Now let's have a look at the saturable reactor, which shows a completely different behaviour, I did the following test to check its properties:
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I applied a DC-controlcurrent of 20 Ampere to the reactor's controlwindings and made a measurement of different voltages and the current flowing and calculated the inductances. As you can see in the following table, the inductance is not constant as it would be in an air gapped inductor. The inductance changes with the applied voltage:
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Voltage in Volt  Current in Ampere Inductance in mH

20                       3,65                           17,44
40                       6,50                           19,59
60                       9,18                           20,80
80                       11,63                         21,90
100                     13,87                         22,95
120                       15,92                       23,99
140                       17,62                       25,29
160                       19,20                       26,53
180                       20,47                       27,99
200                       21,50                       29,61
220                       22,48                       31,15
240                       23,33                       32,75

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This change in inductance is because there is no air gap in the core I think (correct me if I am wrong). Okay now have a look at the second video showing the test I performed at the reduced voltage of 150V:
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