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Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111
your core seems to be a bit small if you had 4 you will be better off or 1 2" core wraped with cat-5. With thease big bricks I prefer direct drive with seperate power supply that way the gates will get a signal for shure. but each prefers there own and I hate dicking around with transformer saturation
Registered Member #2405
Joined: Fri Oct 02 2009, 12:59AM
Location: Wisconsin
Posts: 140
Goodchild wrote ...
I agree, this is why I suggested core saturation. In my setup I have a massive 2" OD 5000u GDT core.
I actually have a different core that I built up for the GDT it is about 2" diameter, however I did find the problem, and well in all actuality there is not a problem.
Talk about looking for a ghost problem...Here is why I think things got hot, I am using the interrupter signal as normal, but I am using a signal generator for the feedback, now when I decrease PRF using the interruptor well of course the feedback signal is not going to change and stays consistant. So the gate resistors get hot because the unit *Thinks* it needs to stay on and fire again. Now when I increase the PRF the gate resistors run nice and cool like they should and everything looks fine.
The gate signal looks good I thought for sure it might be core saturation as well in the beginning. Especially not knowing the actual AL or material of the cores. But I managed to find the AL of the cores based on the amount of turns and the measured inductance, and its about 4000, but that dont really help in finding the material, but they work.
So I think I have found the problem and well really I dont think there was one...how humbling is that???
So in conclusion I would like to thank everyone that put some input into this problem it was greatly appreciated Looking at Erics assembly photos helped a lot too so I want to say thank you for those and the Spreadsheet you sent.
No matter how long a person has been doing this kind of stuff there is always something new to learn and building these up can be a humbling experience to say the least.
So thanks to everyone!!!
I will post photos of it once I get it all back together and a few things changed in there.
Registered Member #2405
Joined: Fri Oct 02 2009, 12:59AM
Location: Wisconsin
Posts: 140
The new CM300 Hbridge. All the GDT signals look very good and no noticeable ringing. The drive circuitry is not phase lead adjustable yet, although I am having some boards spun up so it will be. I am also going to make a larger cabinet for it so I can add more bus capacitance and a larger tank capacitor. this cabinet is just too small. It was actually meant for a much smaller coil.
120 vac in with a doubler so bus voltage is 340 volts. Once I get it all back together I will post some images of the primary current and such.
The initial test produced 5.5 foot streamers and I believe it will be better than this once I get it outside and test it at full power.
One thing I did notice was my F0 was 112kHz which IMO is too fast for these bricks. So I am going to change the secondary from a 6" to 9.5" which I have on another coil which will bring the F0 down to around 75kHZ which should then be fine. As of now I have the OCD set at 350 amps.
Two different top loads will be tried one is 6" x 24" and the other 15" x 45" one is spun aluminum and the other is made from foam and wire mesh. I do I have a tube bender and may make a tube type toroid for it.
So I will post pics as the experimentation progresses.
Picture taken with my cell phone not a decent camera this time.
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CM300DU-12NFH Full Bridge
