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Registered Member #3076
Joined: Fri Aug 06 2010, 07:45PM
Location: San Francisco CA
Posts: 18
hi again,
I ordered parts for my ZVS driver now that I have played with my 555 driver..I kept blowing out IRF510 's or I would stick with it longer...
I notice that the Mazilli driver calls for a hand wound inductor on a toroid of 47-200 uH. I have some ferrite toroids laying around and some wire. I don't know what the spec on the toroids are and have only a little experience and one HAM book for a particular CW radio, with some info on these kinds of inductors.
I'd like to be able to make an educated guess at a good value of what this inductance should be and what it will be. Can someone direct me to a site or offer practical wisdom? My power supply is 25 V and 6 A max, so I run it with a safety margin of 20 V 5A max. Plus I am weary of the power of this new driver. My secondary is 5" by 6.5" with about 650 turns of 30 AWG. My caps are not ideal, but working, 0.01 uF ceramic at 2KV each, using 10 in series I get 1nF per string, 5nF max. Single static gap of two brass bolts with ground ends to a moderate point.
As well, I have read there is a mistake in the schematic for the driver. Since I am new to MOSFETs it is not staring me in the face yet. Would someone mind re-iterating this problem so a novice like can see it.
The whole tuning thing of the DC TC is really confusing me too....I am thinking that to really be in tune (cancelled reactance leaving only real resistance) I will need a series spark gap. Right ? I want full caps, but at the right time, as set my break down voltage---> SG distance...
Registered Member #540
Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
The MOSFETs should have a Vds rating of at least 3-3.5 times the input voltage so that might be why the IRF510s are dieing. The series inductor value isn't critical at all but something around 200uH is preferable. If you have a broken ATX power supply, you can take the yellow and white core and wind about 50 turns on it and that should be sufficient.
Are you powering a flyback transformer that is the supply of a SGTC or something else?
As far as I know, there isn't any problem with the schematics because I built one directly from them and it ran with no problems...
Registered Member #3093
Joined: Mon Aug 09 2010, 11:40PM
Location:
Posts: 68
Posted: Sun Aug 15 2010, 12:13PM hi again,
I ordered parts for my ZVS driver now that I have played with my 555 driver..I kept blowing out IRF510 's or I would stick with it longer...
I notice that the Mazilli driver calls for a hand wound inductor on a toroid of 47-200 uH. I have some ferrite toroids laying around and some wire. I don't know what the spec on the toroids are and have only a little experience and one HAM book for a particular CW radio, with some info on these kinds of inductors.
I'd like to be able to make an educated guess at a good value of what this inductance should be and what it will be. Can someone direct me to a site or offer practical wisdom? My power supply is 25 V and 6 A max, so I run it with a safety margin of 20 V 5A max. Plus I am weary of the power of this new driver. My secondary is 5" by 6.5" with about 650 turns of 30 AWG. My caps are not ideal, but working, 0.01 uF ceramic at 2KV each, using 10 in series I get 1nF per string, 5nF max. Single static gap of two brass bolts with ground ends to a moderate point.
As well, I have read there is a mistake in the schematic for the driver. Since I am new to MOSFETs it is not staring me in the face yet. Would someone mind re-iterating this problem so a novice like can see it.
The whole tuning thing of the DC TC is really confusing me too....I am thinking that to really be in tune (cancelled reactance leaving only real resistance) I will need a series spark gap. Right ? I want full caps, but at the right time, as set my break down voltage---> SG distance...
thanks again... wbgTC
When I built the ZVS driver, I followed the schematic exactly, and had no problems with it. I think the problem could be A) You don't have enough inductance on your limiter, or B)Your mosfet cannot stand up to the challenge. The IRF510, although it is rated for 100 volts and 6.4 amps, It can only DISSIPATE 34 watts of power. not a possible 150 from 6X25.
I would say to wrap a large inductor (~100 turns 16 awg on a non-powder toroid), or get some better mosfets than the ones Radioshack supplies.
Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608
i built a ZVS driver using 2 irfp250 mosfets, it works great! my power supply is 13.8v 7amps. I hand wound my inductor with 20 turns of 16 gage, it was perfect for my flyback, I had guessed with the size an made several ones with different wire gage and toroid size. Basically the higher inductance the more voltage you get the lower the inductance the more current you get play around and find the one that works the best. -zak
Registered Member #3076
Joined: Fri Aug 06 2010, 07:45PM
Location: San Francisco CA
Posts: 18
OK...thanks I'll post some pics of my setup soon...
I did have my IRF510 on a nice heat sink and a 12volt computer fan attached...so over heating seems unlikely...I had one from Radio Shack, and two others from a drawer in my professor's research lab...little dusty
My ZVS and flyback will be powering a tesla coil...secondary is 3 " by 6.5 " about 700 turns....
Registered Member #540
Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
When the MOSFETs died, were they hot or cold? If they were hot, it's probably from over heating but like you said, it's unlikely. A lot of people have commented that they could get high powers out and the MOSFETs would stay cold. If they were cold when they died, it could either be from over voltage or parasitic oscillations (which start taking over at higher input voltages). Just to make sure, you mounted the MOSFETs on their own separate heat sink or had some form of insulation between the MOSFET body and the sink right?
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
It is not recomended that you use a ferrite core for the series inductor, it usually works but a powdered iron core like those found in an ATX power supply is a safer bet. Wind 50-100 turns of wire on it, and you will be fine.
Also, the IRF510 mosfets you are using are borderline too low of a voltage, they should work but something like the irfp250 would be a safer bet (and can be found for ~$1 if you look around).
Also, what schematic are you using and where did you hear that there was an error? The only comment I can think of that should have been made is that for high input voltages (<~20v) it is best to run the gate supply from a seperate 12v supply, which has also been detailed in a schematic.
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
The series inductor shall have significantly more inductance than the inductances of the two primary coils wound on the flyback core, and shall not saturate. With too small series inductance or a saturated core, and a power supply that can supply enough current, the driver self-destructs.
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Mazilli ZVS driver---first time build ? about 47-200uH inductor and other general
