Author Topic: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"  (Read 17476 times)

Offline petespaco

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Badpeter-
  Maybe try casting the dagger vertically?  That way it would be certain to fill.  I think they do cannons that way.

Offline hightemp1

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links did not work, for me?  Any ideas for a "simple" -more power" controller board add-on for these heaters?

Hmmm--- I just tried both links and they did work for me.  Just a simple "click" on each one and there I was.

I don't have any idea for a "more power" controller board to add on.  However, maybe you want to bit the bullet and buy the $1000 unit that is 7 KW.
https://www.ebay.com/i/221663967797?chn=ps
(This is just one of the many sellers)
  That ought to do it.  You will, however, need a TIG  water cooler for it and they run at least $400 more.

I still feel that it's a "heat in vs heat out" equation.  You only get 3412 btu's of heat for each 1 KW of electricity.  So, if you are losing more than you are putting in, the temperature quits rising, right?   There is still the opportunity for any or all of us to conserve more heat.

The error I get is "Oops, something went wrong" on a blank white page - maybe just my server?

On conserving more heat:  I will likely be using kaowool with the narrow 1.5 kilo crucible and may try thin layer of koawool with the smaller crucible/liner combo.  Problem with porous insulation is the contribution to faster burning of graphite.  Unless there are some trade secrets we are not privy to, short graphite crucible life  may be a necessary evil in trying to adapt these heaters to melters.  Also, of course, the extra space the insulation uses will further decrease BTUs to crucible because insulation pushes proximity of crucial farther away from coil so I may be slicing my kaowool to maybe 1/2" (use gloves and mask when handling wool).

On $1500 furnace -->  I can only dream :(

Bert,  excellent stuff!  My take is because metal is better conductor maybe heat will not be great enough to melt copper even with insulation?  If it could melt, then maybe a descent  alternative considering we are currently only getting 6-10 melts with graphite anyhow?  And, if copper alloys without aluminum were used maybe iron crucible life would significantly exceed a graphite one?   A simple temperature test I suppose would be to find metal tube (preferably stainless) surround it with insulation and see if white hot temps can be attained.
Other unknowns exist, including previously mentioned metal contamination effect (good or bad).



« Last Edit: June 12, 2019, 07:25:40 PM by hightemp1 »

Offline hightemp1

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Badpeter-
  Maybe try casting the dagger vertically?  That way it would be certain to fill.  I think they do cannons that way.

Vertical may cause too much turbulence.  I was thinking at an angle, not to steep, maybe 25 degrees with the blade edge pointing down.  Just a wild guess though.
« Last Edit: June 12, 2019, 05:38:42 PM by hightemp1 »

Offline Bert911

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One approach could be a cheap steel pipe, weld a cover on the end and maybe use some of this coating.
The material costs are so small, if you have the welding stuff.

Keep in mind that using normal tools on really high quality stainless can ruin them.

I tested different pipe diameters and most of them easily reached the 2 kW power limit of my heater. The heater has a current and voltage sensor, so I can't go that high above the rating.
I can trick the unit by changing the components, but it's also nice to have a real power display without adding 50% or so on top.
I have a beefy 5kw adjustable unregulated power supply for 0-200V that comes handy, so it was no problem to get the highest possible power output with different shapes.

For example, I start with 30V with 1.5 kW then it rises up to the 2 kW and then it reaches curie temperature it goes down to 800W, and I turn the Voltage up to 60V and have my 2kw again.

These exact numbers depend on many things like the material, the coil, the geometry of the workpiece. Just some figures out of my mind, to get the point.
At the end of next week I can do some more tests.

If you use steel, you should really look the temperatures of the mosfets. I was able to get 50 A even at 30 V with good fitting steel tubes.

I think my coil has an inner diameter of 40 mm/ 1 5/8" something like that and 6 turns, runs with 157 kHz and uses an overall capacitance of 0,86 µF, which are rated for 100 A.

Robert
« Last Edit: June 16, 2019, 10:12:15 PM by Bert911 »

Offline hightemp1

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One approach could be a cheap steel pipe, weld a cover on the end and maybe use some of this coating.
The material costs are so small, if you have the welding stuff.

Keep in mind that using normal tools on really high quality stainless can ruin them.

I tested different pipe diameters and most of them easily reached the 2 kW power limit of my heater. The heater has a current and voltage sensor, so I can't go that high above the rating.
I can trick the unit by changing the components, but it's also nice to have a real power display without adding 50% or so on top.
I have a beefy 5kw adjustable unregulated power supply for 0-200V that comes handy, so it was no problem to get the highest possible power output with different shapes.

For example, I start with 30V with 1.5 kW then it rises up to the 2 kW and then it reaches curie temperature it goes down to 800W, and I turn the Voltage up to 60V and have my 2kw again.

These exact numbers depend on many things like the material, the coil, the geometry of the workpiece. Just some figures out of my mind, to get the point.
At the end of next week I can do some more tests.

If you use steel, you should really look the temperatures of the mosfets. I was able to get 50 A even at 30 V with good fitting steel tubes.

I think my coil has an inner diameter of 40 mm/ 1 5/8" something like that and 6 turns, runs with 157 kHz and uses an overall capacitance of 0,63 µF, which are rated for 100 A.

Robert

Wow, fascinating stuff, all way over my head.  My take on your variable PS, is since we don't have a sweet ass PS like that I'm thinking we could sort of simulate one??  Using graphite as an example: Peter's crucible uses 38 amps when new, but if it had more graphite (wider/taller) maybe it could use 60 amps?  But since we are limited to 50 amps on the 2500w unit we would have to gradually lower the crucible (instant variable amp/power regulator),  lowering it completely when metal is all melted, or when fully inserted and safely stays below 50 amps??  Granted this is a crude variable PS - problems include accelerated burning of lower part of crucible, rigging up a lowering device.

On stainless steel,  yea I tried to file it once and it practically filed my file. ???

I am not a welder but always wanted to try.  Also, thought about welding a SS tube but did not think welding would hold at 2300f, but then again I know nothing about welding either, but ignorance has never  stopped me from blabbing out ideas.  Not sure if same "dipping crucible" concept holds with steel because of curie stuff happening :-\ ?
« Last Edit: June 12, 2019, 09:00:10 PM by hightemp1 »

Offline petespaco

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hightemp1:
Quote
But since we are limited to 50 amps on the 2500w unit we would have to gradually lower the crucible (instant variable amp/power regulator),  lowering it completely when metal is all melted, or when fully inserted and safely stays below 50 amps??
I think this is an excellent idea.


Offline T3sl4co1l

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Yes, exactly.  There is a best-load matching condition.

Too low resistivity, and there's no voltage drop in the work, the magnetic field reflects nearly perfectly, and frequency simply rises, instead of DC current being drawn.

Too high resistivity, and there's no current flow, the magnetic field penetrates nearly perfectly, and little DC current is drawn.

We know that, somewhere inbetween, current consumption is higher.  We don't necessarily know if we're on the rising or falling slope of that curve, or optimally on the peak, but we know definitely that there must be a peak, somewhere between these extremes!

This has been today's shop application of calculus.  Cheers. ;)

Likely, it just so happens that a full heel of molten copper is below the peak, while a chunk of steel above curie temperature, is above the peak.  Graphite of this thickness is certainly above.

Different people have different setups, landing above or below as well.

The positioning of that peak, is driven by the number of turns of the work coil, how close it is to the work, the characteristics of the power supply, etc.  Frequency affects skin depth, which affects the equivalent load that a given chunk of material reflects.

If you're below the peak, I would suppose, try adding another turn or two; if below, remove a turn or two.

This type of supply also delivers the most power into the lowest Q factor, and the lowest impedances.  Q can be lowered by reducing the distance from coil to work.  (You need some space for insulation, and loads like copper won't give a terribly low Q anyway, even at point blank distance; there's only so much room to push in this direction.)  Impedance can be lowered by reducing inductance and increasing capacitance.

Tim
« Last Edit: June 13, 2019, 03:12:05 PM by T3sl4co1l »

Offline petespaco

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Here's my final test of watching the surface of the molten copper with better camera filters:
/>
Pete Stanaitis
----------------

Offline badpeter

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^^^Yesterday I found a steel valve cap just the right size, that probably can be used as a crucible. Can't wait to test it out! needs a bit of cutting which ill have to go around somehow. I wonder whats the draw is going to be. Due to its shape it cannot be taken out of the coil though.
Wish I had any welding tools or such, maybe Ill find someone who has that.
Dagger hopefully on Friday=) New patented "sunken" mould style will prevent metal from escaping on the sides. 8)

I wonder if it is a good idea to find optimal power consumption by shorting turns of the coil to quickly change its characterictics (easier than fiddling with caps) and watch how output changes.

peterspaco - satisfying to watch the molten surface! I may try something like this, my dslr has some manual settings for video, maybe I can get away without filters even. or use an old floppy to cover the lens!
« Last Edit: June 13, 2019, 06:55:32 PM by badpeter »

Offline hightemp1

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Here's my final test of watching the surface of the molten copper with better camera filters:
/>
Pete Stanaitis
----------------

-Melting action is indeed very clear now - nice!  Definitely more of a shimmering than bubbling. Maybe even more of a medium stirring rather than heavy stirring.
-I'm betting that is dross on the sides covering most, effecting some of the mixing while also highlighting it?  Wondering what the best way to skim it off would be? 
-2200 degrees Fahrenheit with very little preheat time is sweet! 
-Insulation was smoking starting off.  Extraction of fumes especially inside, sure would not hurt (again, I just use a hepa filter sized to my box fan cranked up on high).  Some sort of high temp spreadable ceramic on lid/insulation, hot face I think it's called, may reflect heat back into crucible better?
-Just weighed my new crucible similar to yours = 138.5 grams, 6.33cm.  Hoping for 10 melts?

Bads, nice score on the cap buddy!  Trying with some sort of brushed on high-temp ceramic, or as-is? 
-sunken mold sound interesting.  To cut a couple keys in plaster, I just used a small spoon to hog out a little plaster on first layer.
-no clue on shorting stuff - the word itself scares me.
-yeah,watching molten metal, kinda like sitting in front of bonfire - sweet!
-tomorrow I will post some before/after, cut-up pieces of a sprue and a gate that I purchased from a local foundry some 30 years ago. 
« Last Edit: June 13, 2019, 10:50:44 PM by hightemp1 »

Offline petespaco

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I thought I'd wait until someone else mentions the "shorting turns" thing.
When I did that, (unintentionally, early on)  I always liked to have a bunch of extra Mosfets and gate components around.  And even some heavy copper wire to use for replacing evaporated pcb traces.  For me, half a second is tooooooo  looonnnggg!  But maybe your heater's circuit is different.
See:
https://spaco.org/Blacksmithing/ZVSInductionHeater/1000Watt12to48VoltZVSInductionHeaterTroubleshootingGuide.htm
for how and WHY I used to have to repair them!
I have seen people do that "shorting" thing with other units, but you'd better be sure that your driver  board itself has a current limiting function.  Just because your power supply may have current limiting is NOT good enough.  It's the degradation of gate signals that kills the board.

Offline hightemp1

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Two identical sprues on top left.  Top right is a gate, I think.  No idea what end products were.  Notice the diameter 3/4" of sprues - they must have been large castings.  Pieces on bottom were cut to fit in our small crucible (the larger ones still might not be small enough - :()  First melt may be making ingots to fit my crucibles.  Alloy is silicon bronze and total weight is five pounds.  Took me 30 minutes to cut several pieces - much, much slower than cutting up wood, though my bandsaw is in dire need of a good tune-up.  Used a regular 6 tooth/in wood cutting blade at lowest speed (maybe 600 rpm?) and it worked just fine.  Still have not received my induction heater from China.
« Last Edit: June 14, 2019, 09:06:49 PM by hightemp1 »

Offline Bert911

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I finished the circuit for the unit.

Printing on the Board:

2000W Rated Power
input voltage DC24V- DC70V
maximum input current <48A
ZVS2000S High frequency induction heating
8300515

As far as I can tell, the controller checks for a mosfet fault before switching the relay on.
Voltage, current a temperature are always checked.
You can add an extra external switch for short heating applications.
There's a potentiometer to limit the max current.

The controller does NOT know if the circuit is oscillating or not, but you can check your setup with a low current setting. In case something went wrong, the unit should open the relay faster, that's handy before start working with different coils/voltages or after a repair for obvious reasons.

If the coil inductance is way too high/low, it can detect a mosfet fault.
The components with an "X" are unknown.

Due to the applied voltage of 100V, the mosfets, transistors, optocoupler and the resistor "R15" blew up. This resistor is crucial for the proper working. I have to wait for the new one board to get the value to repair it properly.
If I had removed the heat sink, the mosfets were most likely also got damaged and since there was no information available.
I wanted to know, how high I can get with the input voltage.

The measured current from the unit was way too high, I shortened the shunt and adjusted the value with some extra tin.
With that method you can also increase the maximum power output relative simple.

The optocoupler for the fan/pumpe is always on.
« Last Edit: June 16, 2019, 04:18:44 PM by Bert911 »

Offline petespaco

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Thanks so much for putting up the schematic.
  I'm not too sure yet, exactly how the system "checks the Mosfets" before turning power on, though.

Re: your comment about max input voltage:
The datasheet for the IRFP260N says 200 volts max.  Somebody on this forum has said the you can expect to see pi X the input voltage across the Mosfet.
If that is true:
48                     55                       65  Volts In
3.14159            3.14159             3.14159
150.79632   172.78745   204.20335 Volts across Mosfet



This seems to imply that you might get away with 55 volts, but 65 volts would be over the top.


Offline Bert911

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I updated the schematic a bit (removed the 1k resistor after the relay) and there are two versions now.
One with the real component names and one for ltspice simulation with other components.

If the relay is open, the voltage over c3 and c4 goes up to 22V, after that the unit can activate the mosfets and recognize a voltage drop.
If the mosfets are shortened or the transistors are damaged the voltage won't rise/fall.

Since the 200V are the minimum rating, it should be OK to 70V.


Changelog:
-added diode name/diode model to the simulation
-added correct transistor model to the simulation
« Last Edit: June 17, 2019, 08:17:59 AM by Bert911 »

Offline petespaco

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Quote
Since the 200V are the minimum rating, it should be OK to 70V.
I respectfully disagree.  On the datsheet that I saw, "200" was the ONLY number.  There was no entry at all in the "max" column.

Where do all the "uC" points go?
It appears to me that they would all originate at the output of the opamp, but I guess I just don't understand that kind of a schematic diagram.


Offline Bert911

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The µC stands for microcontroller.
I didn't bother to track the all the way back to it.
Of course this isn't the whole schematic since there is also an lcd display.

https://www.banggood.com/2000W-ZVS-Induction-Heating-Module-Board-Flyback-Driver-Heater-Good-Heat-Dissipation-With-Coil-Pump-Power-Adapter-Kit-p-1464491.html?cur_warehouse=CN

5V worth arguing? Rule of thumb is 4 times.

Offline petespaco

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Thanks for clearing that up and thanks for the link.  Now I understand that there's a lot more going on than I thought.
That's quite a package!
When I multiply 65V X 45A, I get 2925 watts.  I wonder why they only rated it as a 2000 watt unit. 

Offline hightemp1

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Thanks for clearing that up and thanks for the link.  Now I understand that there's a lot more going on than I thought.
That's quite a package!
When I multiply 65V X 45A, I get 2925 watts.  I wonder why they only rated it as a 2000 watt unit.

Robert, 2.2kw was stable?  maybe making this a superior design & deal?  Input, 120 or 240, make any difference on output?  2 to 2.5kw area makes a 20 amp circuit on 120 volt doable.

Update:  Per Product Description - (Short Circuit/Overload: Input current is greater than 40A, voltage greater than 55V, enter protection).   If so designed, then should not go over 2.2kW, I presume.
« Last Edit: June 17, 2019, 05:35:37 AM by hightemp1 »

Offline Bert911

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Thanks for clearing that up and thanks for the link.  Now I understand that there's a lot more going on than I thought.
That's quite a package!
When I multiply 65V X 45A, I get 2925 watts.  I wonder why they only rated it as a 2000 watt unit.

Robert, 2.2kw was stable?  maybe making this a superior design & deal?  Input, 120 or 240, make any difference on output?  2 to 2.5kw area makes a 20 amp circuit on 120 volt doable.

Update:  Per Product Description - (Short Circuit/Overload: Input current is greater than 40A, voltage greater than 55V, enter protection).   If so designed, then should not go over 2.2kW, I presume.


The heater goes in protection mode, if the voltage is below 20V, greater than 70V, current greater than 48A or the heat sink temperature over 65°C.
Even fast peaks are detected and trigger the protection.

The mains voltage doesn't matter at all, the input voltage of the unit is relevant. Btw my supply uses 3x380V.

Note that the idle loses increases with a higher input voltage, but also the heating capacity of the coil, it also increases the oscillating current through the coil. So the capacitors need to handle these extra current.
These caps are rated for 50A effective current, this is already reached at 54V input voltage and the standard coil.

ICap, peak=2*Pi*f*UCap,peak
UCap, peak≈Pi*Uinput             // measured Peak Voltages from multimeter could be off by 50% due to high frequency
ICap, effektive≈ICap, peak/1.414

This oscillation current through the caps shouldn't depend on the load.
With 3kw input wattage there could easily be a loss of 500W or more.

Pworkpiece=Pinput-Pcoil+cap-Pmosfet-Premaining circuit
Pworkpiece≈Pinput-Pidle-Pmosfet

The mosfet losses can be assumed to be relatively small, probably under 100W with that heat sink. These depend on the Input current/voltage and switching frequency.

The 48A is already a seriously big current that's why I bought some new mosfet with a higher voltage rating. A heating power of effective 2kw at the workpiece is most likely enough for most applications, but you can't always reach this with the standard configuration for specific shapes like bolt heads.
« Last Edit: June 17, 2019, 09:44:01 AM by Bert911 »

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[Voltage Multipliers]
rustedone
October 16, 2019, 04:03:58 PM
post Analog Panel Meter Shunt Calculation and Custom Scale Design
[Beginners]
Mads Barnkob
October 16, 2019, 07:56:20 AM
post Re: Mysterious Chinese HV capacitors
[Capacitor banks]
MRMILSTAR
October 16, 2019, 05:40:55 AM
post Re: Mysterious Chinese HV capacitors
[Capacitor banks]
davekni
October 16, 2019, 03:33:52 AM
post WTS [US]: pole transformer, SRSG, PTs, NSTs, capacitors, variacs, [MORE]
[Sell / Buy / Trade]
acobaugh
October 15, 2019, 09:36:55 PM

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