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Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714
mohiuddinHimel wrote ... i electroplated the PCB board to increase copper thickness and current carrying capability. ...I really wonder will this pcb copper layer be able to carry 200/300 amps to the work coil :/ :/ any suggestion
I like your electroplating work. Any idea how much copper you added? (for example, using before-and-after measurements of weight, thickness, or electrical resistance)
It would not be hard to measure the sheet resistance (Google that) of your PCB square, with or without capacitors, using a four-terminal method. Run a known, constant current of a few amperes from one corner to the opposite corner. Then with a voltmeter on a millivolt range, measure the voltage difference between two places on the board. It's educational to find and mark lines of constant potential using one voltmeter probe, while the other probe is connected to a reference place such as a third corner. The constant potential lines will approximate circular arcs in the neighborhood of your current source and sink points.
Registered Member #4497
Joined: Thu Apr 19 2012, 12:53PM
Location: Behind you
Posts: 62
How much can those two inductors vary? I made identical coils but one has 144uH an another one has 131uH... It's kinda hard to rewind it because the wire is 2.5mm in dia and i have only few meters
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Slenderman wrote ...
How much can those two inductors vary? I made identical coils but one has 144uH an another one has 131uH... It's kinda hard to rewind it because the wire is 2.5mm in dia and i have only few meters
I measure my inductors to be within the same tolerances as yours.
I will try to upgrade my circuit with some 300V MOSFETs, have to source a new power supply and much better tank capacitor too.
Registered Member #2310
Joined: Wed Aug 19 2009, 08:04PM
Location: Santa Catarina - Brazil
Posts: 169
Mads Barnkob wrote ...
Slenderman wrote ...
How much can those two inductors vary? I made identical coils but one has 144uH an another one has 131uH... It's kinda hard to rewind it because the wire is 2.5mm in dia and i have only few meters
I measure my inductors to be within the same tolerances as yours.
I will try to upgrade my circuit with some 300V MOSFETs, have to source a new power supply and much better tank capacitor too.
That's a good idea! Lets keep working to see the limits of the godd mazzili driver!
Registered Member #2578
Joined: Sun Dec 27 2009, 09:21PM
Location: USA Utah
Posts: 31
I believe the problems that most people have with a ZVS driver is that they do not have a powerful enough power supply, If the voltage drops below 10 volts they can latch up and burn out a mosfet. if you power it with a little wall wart and then load it too much, it will stop oscillating, but the mosfets will "survive". if you do the same thing with a better power supply, like a good supply from a computer (some are not good at all) you will fry mosfets. assuming all components you have in the schematic are good, this strategy should work.
I noticed in earlier posts marko mentioned over current detection, I think under voltage would be better, the real dangerous problem is if it stops oscillating. Feed the beast every thing or it will stop oscillating. just don't over load it.
Markos schematic operates around 50 khz which is too slow for small parts like nails and screws, but would work better for larger items like a solid 3/4" bolt and up. that is why some people here can't melt anything with it, it gets hot but will never absorb enough power to melt it effectively. I think markos inductor coil is too small to work as effectively as it could, more turns maybe try slightly smaller cap value also.
Registered Member #2310
Joined: Wed Aug 19 2009, 08:04PM
Location: Santa Catarina - Brazil
Posts: 169
D Rosey wrote ...
I believe the problems that most people have with a ZVS driver is that they do not have a powerful enough power supply, If the voltage drops below 10 volts they can latch up and burn out a mosfet. if you power it with a little wall wart and then load it too much, it will stop oscillating, but the mosfets will "survive". if you do the same thing with a better power supply, like a good supply from a computer (some are not good at all) you will fry mosfets. assuming all components you have in the schematic are good, this strategy should work.
I noticed in earlier posts marko mentioned over current detection, I think under voltage would be better, the real dangerous problem is if it stops oscillating. Feed the beast every thing or it will stop oscillating. just don't over load it.
Markos schematic operates around 50 khz which is too slow for small parts like nails and screws, but would work better for larger items like a solid 3/4" bolt and up. that is why some people here can't melt anything with it, it gets hot but will never absorb enough power to melt it effectively. I think markos inductor coil is too small to work as effectively as it could, more turns maybe try slightly smaller cap value also.
Registered Member #485
Joined: Sun Jul 09 2006, 01:14AM
Location: San Francisco
Posts: 36
First, thanks for making this circuit available!
I have been collecting components to make an induction heater based on Markos circuit but I just realized I got mks capacitors instead of mkp capacitors (these) Is that going to be a problem? I looked at the specs and it looks like the mkp ones are better for this type of application but Im not sure.
I am planning on first making a demo unit but then I intend on one that a little more robust as I would like to use it for some forging. Would the MKS caps work this its application?
The circuit seems to work fine when I'm providing it with a stable 12V, but as soon as I hook up 24V the MOSFET's pop. Taking a meter to it shows a dead short between ground and power. I replace the MOSFETs and it works fine again. So I'm not sure why it would pop almost instantly under 24V, but run just fine at 12V. Does anyone have any ideas? 12V doesn't really get me any melting power, only glowing power...
The circuit seems to work fine when I'm providing it with a stable 12V, but as soon as I hook up 24V the MOSFET's pop. Taking a meter to it shows a dead short between ground and power. I replace the MOSFETs and it works fine again. So I'm not sure why it would pop almost instantly under 24V, but run just fine at 12V. Does anyone have any ideas? 12V doesn't really get me any melting power, only glowing power...
Thanks!
how big is your work coil ?; how many turns?
i looked up the part # on your capacitors and they are 1 microfarad each, are they connected in parallel; if so that s 27 microfarads, way more than the 4 microarads in Marko's design, that seems like a lot
if you plan on running it on only 24 v (30v max), then 100 Vds MOSFETS are probably a better choice than irfp250's due to their lower Rds ON; Marko recomended that the MOSFETs used have an Rds ON of less than 50 milliohms
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Royer induction heater
