Kapanadze Cousin - DALLY FREE ENERGY

[TinselKoala]

   It does look like the same or similar type of TL494 circuit as what I am working on. Adrian's push pull driver, (first blurry image below). 
 
   I've got my TL 494 push pull circuit connected up and running.  But, it's overheating the mosfets,  big time. Any ideas as to what to do about it.
   Here's a couple of pics of my set up as it looks right now, (2nd and 3rd images) below.

Nick, can you please refresh my memory as to the following:

1. Are you using pulldown resistors on the pins 9 and 10 outputs of the 494, as in the Stalker schematic up above?
2. What is the value of the Gate resistors between the driver chips and the mosfet Gates?
3. What is the value of the resistors between the 494 outputs and the driver chips?
4. What is the voltage you are supplying to the gate driver chips, and where does it come from?
5. What is the part number of the mosfets you are using?

Can you post a scopeshot of the mosfet Drains, one on CH1 and the other on CH2, probe grounds to the common Source connection? (I'm assuming here that the Source connection is a true ground and you won't be creating a dangerous groundloop by connecting your probe grounds here.)

Mosfet overheating can be caused by a number of things but the most common is that the mosfet is staying in the "linear conduction region" too long and not switching fully ON and OFF hard enough. This can be caused by not enough Gate drive current, too short duty cycles, wrong mosfet for the job (too high Rdsson, too high gate capacitance, etc).

[TinselKoala]

Yess, but this 60hz source would have effect on TC output coil?, this is possible right?

I'm afraid I can't answer that, because this is the first time I've seen that connection used. I can tell you that in normal Tesla coils, you definitely do NOT want the mains power supply connected to the secondary as this can be very dangerous to people and equipment.

[NickZ]

   TK:
   I did find one thing that I did which may cause the mosfet overheating. I connected my 1k snubber resistor as well as the the 18v zeners before the 10 ohm resistor, and they should be connected after that 10 ohm resistor.
So, I'll correct that, first. And see if that helps with the overheating, or not.
  My push pull driver and snubbers are like the Stalker diagram that I posted just a few posts ago. His latest version,  same as the diagram below.   I am leaning on Stalker approach, as it's simpler, using only a barebone component count.
   I am using the IRFP260N MOSFETs. And I added MUR1560 diodes between drain and source, although it's hard to see them in the picture.
  Thanks for your help.
  I'll post another video when I get things working better, and show some scope shots also.

[TinselKoala]

@Nick:
OK, that will make some difference I'm sure.
But...
1. Are you using pulldown resistors on the 494 output pins as indicated in Stalker's schematic? This may make a difference by assuring that the pins of the 494 turn off hard and fast.
2. Note that Stalker's schematic specifies IRF3205 mosfets. The ON state resistance of the P260n is 0.04 ohms and it is rated at 50 amps maximum. The 3205 has ON state resistance of 0.008 ohms and it is rated at 110 amps maximum. In your application with snubbers I am not sure whether the difference in maximum drain-source voltage is going to be significant (200V for the P260n and 55V for the 3205.) But the difference in the On-state resistance is significant: at the same current, the P260n will be dissipating a lot more power (getting hotter) than the 3205 would.
3. All that notwithstanding, how hot is too hot? The p260n may be getting hot to the touch but I've tested these mosfets and they have no problem running at over 100 degrees C (boiling water) as long as the heat is properly removed. You could try bigger heatsinks and/or fan cooling.
4. I still don't know the value of your Gate resistors between the drivers and the gates. (I'm not talking about the snubber network). I can't read what it says on the photo of Stalker's schematics. These resistors should probably be 10 ohms, certainly not greater than 100 ohms.
5. The MUR1560 is a good fast high-current diode, I use them a lot myself. I'm not clear, however, how this works when used in addition to the snubber network. Maybe someone with more experience can help out here.

[AlienGrey]

@Nick:
OK, that will make some difference I'm sure.
But...
1. Are you using pulldown resistors on the 494 output pins as indicated in Stalker's schematic? This may make a difference by assuring that the pins of the 494 turn off hard and fast.
2. Note that Stalker's schematic specifies IRF3205 mosfets. The ON state resistance of the P260n is 0.04 ohms and it is rated at 50 amps maximum. The 3205 has ON state resistance of 0.008 ohms and it is rated at 110 amps maximum. In your application with snubbers I am not sure whether the difference in maximum drain-source voltage is going to be significant (200V for the P260n and 55V for the 3205.) But the difference in the On-state resistance is significant: at the same current, the P260n will be dissipating a lot more power (getting hotter) than the 3205 would.
3. All that notwithstanding, how hot is too hot? The p260n may be getting hot to the touch but I've tested these mosfets and they have no problem running at over 100 degrees C (boiling water) as long as the heat is properly removed. You could try bigger heatsinks and/or fan cooling.
4. I still don't know the value of your Gate resistors between the drivers and the gates. (I'm not talking about the snubber network). I can't read what it says on the photo of Stalker's schematics. These resistors should probably be 10 ohms, certainly not greater than 100 ohms.
5. The MUR1560 is a good fast high-current diode, I use them a lot myself. I'm not clear, however, how this works when used in addition to the snubber network. Maybe someone with more experience can help out here.

Are you talking about this ? You also need large electrolytic and 100nf caps close to Fet drivers as they need to pulse large amounts of current driving capacitance loads 4.7uf is just not enough and keep wiring down to a minimum. As previously mentioned, you also need to drag the high voltage 'pulses' away from those HexFet devices. ( push to shove) personly Fast IGBT's would work far better in that placement and changing the 12v drive reg to 15 volt.