Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"

[petespaco]

I have been experimenting the the popular "12-48 Volt 1000 Watt ZVS Induction heaters" for a year or two and have many videos and web pages describing that work, as many of you may know.
   More recently, an improved version has become available and is being sold by well over a dozen vendors.  Instead of one pair of IRFP260N's driving the coil, they doubled up on them and added 2 fans on top.  The also added 50% more capacitance to the  tank circuit and increased the number of turns of the output coil from 7 to 10.  These tank changes should lower the oscillation frequency which is good for many things that people would want to heat.

  Just recently, I ordered one of them, a complete kit, called "Combo 2" by seller Aliexpress.
I had to wait quite a while for an analog ammeter and it’s here now.  I still haven’t connected it all up yet, but I have spent a lot of time unraveling the various  descriptions and pseudo instructions that I see on the vendor offerings.  These units are seldom soldi n as complete a kit form as the one the I got from Aliexpress.
Some vendors call them 1800 watt, some even call them 2500 watt, but I’m pretty sure they are all the same.
  Yesterday I put up a new web page to help new buyers understand what they just bought and how to set it up with a minimum of disappointment.
I tell you all this, because I’d like to get this link to others, since I am already getting inquiries anyway.
There are two web pages referenced here on this cover page:
 https://spaco.org/Blacksmithing/ZVSInductionHeater/ZVS1800Watt/1800-2500WattZVSInductionHeaterNotes.htm

Both pages are pretty messy, but, due to the apparent popularity of these devices, I wanted to get something out there.
Time will tell.

I will add to that page and to my youtube channel once I get my system up and running.

Pete Stanaitis
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[Mads Barnkob]

You got my attention with this, there has for a long while been small ZVS drivers available, but these "high" power seems more interesting as the price-tag is getting closer to what you could build a similar unit for yourself.

I looked at "1800W 40A ZVS Induction Heating Board" on ebay and it seems to be the exact same unit as your 1800W model, on some pictures for the 2500W model it looked like it was 120mm fans on top and it had a 3rd heat sink in the middle, so just from the pictures it must been built bigger for then higher power rating.

I placed a best offer on one of them and will see how cheap I can get one from China, as I got a few different "cheap" power supplies that I wanted to test on a ZVS induction heater before telling the world about it is a possibility

[petespaco]

Good eye, Mads.
   Yes, I now see the extra heat sinks and additional pair of gate resistors.  So now it looks like 3 Mosfets in parallel on each side.
And I also now see that the 1800 watt model  has 90mm fans, versus the 120mm fans for the 2500 watt model..
I can only say that I did some  sloppy investigation!
I'll already updated  my pages to reflect this difference.

I will look forward to your comments when you get your board.
By the way, we have all heard the warnings about NOT connecting these zvs heaters directly to a switched mode power supply and then plugging the power supply in.  They say that the slow start characteristics of the SMPS cause it to start slowly and cause the mosfets to lock up.
And I am sure that is generally true.  But the server power supply that I got with my Aliexpress heater (Emerson 48-2900U Switched mode Power Supply)
doesn't even turn on until about 7 seconds after power us applied.  I will probably set my system up to power the supply first anyway, just to be safe.

(a bit red-faced),
Pete Stanaitis
   

[petespaco]

Hello, Mads.
I hope I am not getting ahead of myself here, but I see a new issue with both the 1800 watt and the 2500 watt versions of these ZVS heaters.
  It has to do with the little buck converter that runs the fans, and in the case of the one the I bought, the pump.
Here's what I have to say:
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Important note if you intend to run your heater on 48 Volts:
You can NOT use the little power supply (buck converter) for the fans! You will have to provide a separate 12 volt supply at a couple of amps.
That is because the maximum rating of the regulator chip on the buck converter board is 40 volts. Don't ask me why they did that, but, hidden in the Chinglish, is a warning that operation at voltages higher than 36 will "burn" the fans and/or pump.
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I'm getting closer to powering the thing up.  I checked the no load current draw of the pump and its only about 300ma, but I will need to connect it to the actual system and fill it with water to see how much current it will draw,  Then, same for the fans.  Then find or make a simple power supply for them.

Have you noticed this situation, and what is your feeling about using that buck converter?

Pete Stanaitis
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[Mads Barnkob]

Thats a pretty important detail you discovered there, thank you for sharing.

I am still waiting for my mine to arrive, hopefully I wont get hit by the Chinese new year in February as ebay has it stated as shipped off on 25th December 2018. But still it says Estimated delivery: Tue, 08 Jan - Tue, 19 Feb

[flyrod]

What is the chip on the DC-DC converter?  I'm guessing it's a LM2596.  It could be a high voltage version of the same thing: LM2596HV which would take 60v or so.  Does it look like this:?



From here:

https://www.ebay.com/itm/123560506283

[petespaco]

Thanks for your question, flyrod.
  Yes, the chip IS the "LM2596HVS" version.
That makes the Chinglish warning about not using the converter when the input is over 36 volts even more confusing..
When I looked up the datasheet a couple of days ago, i googled "LM2596" and got this:
http://www.ti.com/lit/ds/symlink/lm2596.pdf
I didn't look beyond the first few pages when I found the max input voltage to be 45.
I even found another datasheet when it was spec'd at 40:
https://www.onsemi.com/pub/Collateral/LM2596-D.PDF

It didn't occur to me that to investigate the "HV".  Sorry, I hope I didn't cause too much confusion.  I guess I was biased by the warning that I mentioned earlier.
http://hmsemi.com/downfile/LM2596HV.PDF

  By the way, my buck converter doesn't have the pot.  There's a fixed resistor in its place.

I did fire the system up yesterday and it worked, BUT the idle current (current flow with nothing in the work coil) is at 26 amps.  I think it should only be about 6 amps.  It IS oscillating. When I put a graphite crucible into the work coil the current does increase to 40 amps.  Frequency is about 77Khz, by the way.
I have attempted to contact the vendor through aliexpress.  We will see how that goes.

For that initial test, I did add a radiator and  unplugged the buck converter and powered  the fans and pump from a separate supply, just in case.

Sorry for jumping to conclusions,
Pete Stanaitis
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[flyrod]

Can you tell what the gate drive is on your new board?  Is it the same pull-up resistors as on the little boards?

How are you measuring 26A?  Could you be using a different shunt that needs calibration maybe?  If 26A is accurate, that's a lot of power going somewhere.  Does anything besides the work coil heat up quickly?  For example if one of the caps is defective, 1000w should pop it in short order and make the problem clear.  A shorted turn in the work coil could also explain it.

Good luck in your experiments.

[petespaco]

i just checked the current by adding a direct reading ammeter in series with the shunt meter.  The readings are the same, within a couple of amps, since the scale on the new meter is fairly coarse.
  Haven't yet dismantled the board to look at circuitry, or to scope the gates.  The way this thing is made, you can't see inside much because the 4 heat sinks cover the sides and the fans cover the top.  when I do dismantle it, I probably should bring out a couple of test points.
I was hoping that I wouldn't have to dig into the thing at all.
No feedback from the Chinese vendor yet.  Is it Chinese new year right now?

[petespaco]

Today I examined the heater by eye and with an ohmmeter.  Can't yet see any reason why the idle current should be so high.
   Circuit components are identical to the 1000 watt board, Just twice as many.  Except that there are 9 of the 0.33 ufd capacitors and a 10 turn 60+ mm ID work coil.
Stumped.
   I did see one video where the guy was testing an 1800 watt board with an ammeter in the ckt.  That's where I got MY "expected" 6 amps idle current from.  That and the fact that my 1000 watt heaters do about the same.
  I may try a smaller diameter work coil just to see what happens.
But I am still hoping for some sort of feedback from the vendor.  Chinese new year for 2019 (year of the pig) apparently does not start for a few weeks yet:
Jan 28 to Feb 19.
  I now see that I can get the gate signals from the bottom of the board, so I can look at them once I get my courage up.

[petespaco]

Yesterday I added a short lead to each gate of the Mosfets so I could scope them.  I didn't change anything else, but when I fired it up, the idle current is only  about 14 amps instead of the 26 amps that I had previously!  Then, when inserting the crucible, the current went up to  36 amps instead of the previous 40 amps.
 The gate signals are all pretty good looking square waves and they are all the same.
Why the change???---  I don't know, but all I did was to solder those gate leads in place.  Bad joints???

The aliexpress vendor didn't seem to pay any attention to my problem description.  They emailed me back to say:
"friend , can you tell us in aliexpress message ?"
Aliexpress customer service, by the way, seemed very concerned when I chatted with them about the issue earlier.  But all they did was to pass my concerns on to the vendor.

I did make a short video of the the above and may put it up on youtube as a troubleshooting aid.
If anybody who is viewing this message has one of these 1800 watt or 2500 watt ZVS heaters running, please tell me what YOUR idle current is.

Thank you,
Pete Stanaitis
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[petespaco]

Well, it is finally up and running properly.
 Drawing about 4 amps idle current (still using 48 volt power supply), then goes to about 35 amps with crucible fully inserted.  Now need to mount a fan on the radiator and do a few other things.  Hate to say it, but I am not certain what caused the difficulties.  Later in my troubleshooting, I discovered that two adjacent turns of the work coil were touching, but separating them didn't help.  I took the fans off to get at the coil so I could insulate it with high temperature fiberglass sleeving.  When I put it back together, it works fine.
Maybe a cracked foil on the board?  Don't know for sure.

Next steps if it continues to work properly:
  Shoot for max current of about 40 to 45 amps.
Place fire brick below coil
  Try some steel  (to max out current) and to see how quickly it heats things to 1200° C.
1" Sq.
3/4" pipe  (pipe heats real fast since its a one turn "coil"
Melt some copper.
   Make a crucible cover. 
   Find/make tongs for pouring.
   Make a simple open face mold?

[Mads Barnkob]

My first impression of the 1800 Watt IH is not great.

- The whole PCB is bent in a curve due to the fans+mount is bigger than the holes for it on the board.
- One of the input inductors had broken off the PCB from rough shipping.
- Connector to the fan controller was destroyed and broken off the board.

Returning the product is more expensive for me than its worth, so I filed for a refund and seller only gave me a laughable 5$ refund out of 50$. For that he will earn a negative review. For others warning, I bought from "Gowin Electronic" ( http://www.ebay.co.uk/usr/gowin_electronic?_trksid=p2057872.m2749.l2754 ): https://www.ebay.co.uk/itm/1800W-40A-ZVS-Induction-Heating-Board-Module-Driver-Heater-With-Heat-Sink-Kit/312211105813?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Shipping was fast, seller communicates fast aswell, but they are not giving up any money without a fight.


I will repair and test it later.

[the_anomaly]

I have also just purchased one, Yosoo 1000W by huhushop on Amazon.  Bought it Sunday morning, got it delivered Sunday evening.. man I love Amazon haha.

Looks ok except one of the FETs is not fully secured to its heatsink; the screw is only part way threaded in.  Also no thermal compound, Mads does your unit have thermal compound on the FETs?

As long as I can use it to heat stuck bolts on this outboard engine I am repairing I will be happy.  I've been tempted to build Uzzors PLL induction heater http://uzzors2k.4hv.org/index.php?page=pllinductionheater1 but I took this gamble to hopefully save time and money. 

One thing I've been warned about using ZVS induction heaters is you need a power supply with a fast turn on transient otherwise oscillation may fail to start and resulting in both FETs turning on at the same time.  Probably best to connect the power supply to the induction heater through a relay so you can turn on the power supply, let it fill its output filter caps and then activate the relay.

[petespaco]

Mads-  Sorry to hear about your shipping issues.  I did get one or two of the 1000 watt units where one lead of  the 470 5 watt resistor had broken off the board.   The buck converter terminal on your board is different from any I have seen.  That makes me wonder how many actual manufacturers are in this game, and how much actual thought goes into each one's design variations.

the_anomaly-  I assume you will need to have some flexible way to get power and water cooling to your work coil if you plan to heat stuck bolts.  Please keep us/me informed on how you do that. 

[petespaco]

It's working fine now:

/>
Pete Stanaitis
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[the_anomaly]

Nice video Pete!  I am actually not planning to use water cooling, probably 12-14ga solid copper wire.  I am hoping that using it only for a minute at a time will be sufficient to get a 7/16" bolt red.  Hopefully this will be a short enough duty cycle to keep the coil from melting.  If I do need water cooling I was planning to go to the auto store; they usually stock 1/8" copper tube for oil pressure gauges.  Since space is tight for my application, I need to use a smaller coil.

Is that a South Bend lathe in the background?

[petespaco]

Thanks for the kind words.
  I should have gotten back to you sooner.
I don't think the coil will melt in 30 seconds or so, but it will transfer a lot of heat back to the standoffs that it is connected to.
When you say "get a 7/16 inch bolt red", do you meant just the head or a whole bolt?  And, how hot is "red"?   If it just needs to glow a low to medium read color to the naked eye, you should be okay,  But if you need it to be bright red or orange. it can take quite a while, once the bolt's temperature passes the "curie point", becoming nonmagnetic.  That's because the heating rate will slow considerably.
  if you plan to use a work coil of less than 7 or 8 turns, please let me know how it works out. 

That's an Atlas 10F lathe in the background.  Wish it was a South Bend, but it works for me.

Pete Stanaitis
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[Mads Barnkob]

I finally got around to get the IH out of the box and repair it, here is part 1 of a series of videos on this IH.

The future parts will be power supply building and testing.

[petespaco]

Hello Mads.
  Putting the standoffs on the bottom is a good Idea.  I wish I'd have thought of that.

It is interesting to see how many slightly different implementations of these devices exist.  Your device is the first one I've seen where the work coil is oriented horizontally.
On my 1800 watt unit, there was no heat sink compound, but they did have piece of thin, white material sandwiched between the Mosfets and the heat sink.  I thought about replacing that material with heat sink compound, but so far it hasn't been a problem.  I did blow up one Mosfet, but that was my own fault for paralleling one gate with too low of a resistance.  I knew better, but did it anyway.  Such is the life of a novice!

By the way, I just powered  up my 2500 Watt ZVS induction unit and did a youtube video of it yesterday.
It is here:

/>You will see my messy method of getting the water away from the board.

Pete Stanaitis
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