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Registered Member #1790
Joined: Fri Oct 31 2008, 10:10AM
Location: Sydney, Australia
Posts: 40
Hi everyone,
Well I am a building pll sstc, but I have ran into a problem. The GDC are overheating, I have tried various series capacitors but it does not help, and if I place a 5 ohm resistor in series it doesnt even turn the FET's on. I am really stuck with this.
Btw the coil details,,
Half bridge of irfp460's
3 uf dc block cap's
secondary is around 4.5 by 11 cm.
ucc gdc's
GDT is 4cm diameter and has 15 turns.
I am currently feeding 65 volts into the bridge and i am getting approx.. 1.5 inch breackout that is very bushy and spherical if you know what I mean =)
And there is another problem, i dont know why but the coil performs greatly and then i turn it off, comeback half an hour later and it isn't locking anymore , and i have to fiddle with it to get it back to good performance and not get harsh sound out of the breakout point.
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
Feeding 4x irfp460s at .5-1MHz (guessed by the size of your secondary) is just too much for them in a CW coil. I would suggest something in a to-220 case, like a tc4421/tc4422 pair, or a (much preferable) ixdi414
Or you could try paralleling a few sets of the ucc's you have
Registered Member #1790
Joined: Fri Oct 31 2008, 10:10AM
Location: Sydney, Australia
Posts: 40
... wrote ...
Feeding 4x irfp460s at .5-1MHz (guessed by the size of your secondary) is just too much for them in a CW coil. I would suggest something in a to-220 case, like a tc4421/tc4422 pair, or a (much preferable) ixdi414
Or you could try paralleling a few sets of the ucc's you have
Hi,
Its actually 2 irfp460, but yes they will be substituted with the to-220 21/22's, I dont really want to parralel the ucc's as someone here did that but didnt get good performace , cant remember who it was really.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
What is the cap going from Mr. 37322 to the gdt? I used .39uf and 5 ohms for running at about 350khz with one primary one secondary gdt using irfp460. Idk how good it was really working, i have no scope(dangit!) and it must not have been locking(using Uzzors' schematic, the halfbridge one, just using class-e) because i took the antenna OFF and performance didn't change. What is the freq you are running? Higher freq means higher heat :P. And yea, i have also seen that ucc's didn't like to be paralleled. Check the ucc's waveforms if you have a scope, and maybe take a pic or even a vid. If there is too much inductance on the driver, or there is not enough decoupling caps, OR it is not smoothed/regulated good, it could be the driver. Also, the gdt core may not be good, or it could be saturating. Sooo, just put good decoupling caps on the driver ic, and the ucc's for sure, mess with the cap connecting gdt and ucc, and check to make sure gdt core is good. Also, make sure the supply to the driver and ucc's is good and smoothed and regulated even.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Tekken_LordS wrote ...
And there is another problem, i dont know why but the coil performs greatly and then i turn it off, comeback half an hour later and it isn't locking anymore , and i have to fiddle with it to get it back to good performance and not get harsh sound out of the breakout point.
Maybe tuning cap is drifting it's value? Is it a ceramic one? Try using a different cap (foil).
Registered Member #599
Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624
putting several uccs in parallel works perfectly.
I have seen one monster sstc with 2 identical primaries, 2 identical IRFP460 H bridges, 2 identical GDTs driven by one stack of UCCs (3 inverting and 3 non inverting)
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Problem with UCC's overheating
, and i have to fiddle with it to get it back to good performance and not get harsh sound out of the breakout point.
