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Registered Member #2750
Joined: Sun Mar 21 2010, 08:47PM
Location: Poland
Posts: 46
So my first light was delayed by bad weather and rain I ran my coil first time today and I'm not especially satisfied with the results. I dont know how exact tune that coil. I set the ocd to 1kA but current wont ringup as high. Now I can only put ~250VAC from the variac maybe this is my problem - too low bus voltage. Can someone show me proper primary current waveform with the secondary ? I see something strange - ringdown after last cucle looks like it has changed the phase after some cycles. I dont have picture but I get when i run next time - maybe tomorow if not it will rain. I add vide from today:
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Dzejwor wrote ...
So my first light was delayed by bad weather and rain I ran my coil first time today and I'm not especially satisfied with the results. I dont know how exact tune that coil. I set the ocd to 1kA but current wont ringup as high. Now I can only put ~250VAC from the variac maybe this is my problem - too low bus voltage. Can someone show me proper primary current waveform with the secondary ? I see something strange - ringdown after last cucle looks like it has changed the phase after some cycles. I dont have picture but I get when i run next time - maybe tomorow if not it will rain. I add vide from today:
That looks ok, I bet you just need more bus voltage! I run 650VDC on my big DRSSTC to get 12 feet.
Here is a proper DRSSTC ring up and ring down with no secondary in place
The changing phase you see at the end is the point at which the IGBTs stop driving and the diodes start back rectifying the energy left in the tank circuit back into the bus capacitor.
Keep in mind though that the ring up and ring down with charge depending on how you have it tuned and the coupling factor.
Registered Member #2750
Joined: Sun Mar 21 2010, 08:47PM
Location: Poland
Posts: 46
Yes I know this but I see something diferent than in my other coils in current ringdown. I show this later now I go outside to make some tests with doubler and higher bus voltage. Ofcourde my waveforms without primary are good.
Registered Member #2750
Joined: Sun Mar 21 2010, 08:47PM
Location: Poland
Posts: 46
If I put secondary in place I have something like this it is strange to me in other coils I always had diferent ringdown - like without primary but with notches. I twas get at around 100V bus voltage. My scope fails again but it's not important now this is time base generator.
So I test rail voltage up to the 660V with no problems using voltage doubler but I stil need more tunning. I cant break 2.5m (8.2 feet). Video from today tests:
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
I agree with Gregory, tuning is most likely your issue. If tuned and coupled in particulate ways you can see "notches" form in the primary current similar to what you are seeing now. These notches would only occur with the secondary in place because it's a function of coupling and tuning and not just one.
You can see a notch starting to form in primary current in this simulation of a DR:
Registered Member #2750
Joined: Sun Mar 21 2010, 08:47PM
Location: Poland
Posts: 46
So after some tests I came to the conclusion that my waveforms are not as good as I thought before. I have some bad oscilations at output voltage and slev rate on the gates are to low - 500ns falltime and around 2uS rise time. So I must redesign GDT or whole gate driver but I dont know how. What is the best way to make goodworking GDT ? I think my core is not so good for this job. I use TX58/41/18 made of 3E25 material - They work wery good in my smalest coils. Here is core datasheet and material What material will be better ? I can get 3C90 or 3F3 other will be dificult to buy in my country Is there a better method of winding 4:1:1:1:1 GDT ? I make four twisted pairs of wires and twist them together. one wire of each pair is my secondary second is part of four times longer primary. I see Finn's GDTs and they look similar.
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Huge DRSSTC Project
Is there a better method of winding 4:1:1:1:1 GDT ? I make four twisted pairs of wires and twist them together. one wire of each pair is my secondary second is part of four times longer primary. I see Finn's GDTs and they look similar.
