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120W induction heater - a typical gadget or a useful workshop tool?

bestler 20943 41
This content has been translated » The original version can be found here
  • Some time ago I bought 2 induction converters in China, hoping that despite the simple-looking structure and a really small number of elements, it will be possible to use this device in a workshop, e.g. as an aid in unscrewing stuck screws or, for example, in the process of hardening small metals. 120W of power is unfortunately very little for this type of construction, but the device is really decent.

    120W induction heater - a typical gadget or a useful workshop tool? 120W induction heater - a typical gadget or a useful workshop tool? 120W induction heater - a typical gadget or a useful workshop tool?

    You can see at first glance that the number of elements is limited to the necessary minimum. The system consists of two mosfet transistors, two fast diodes, two inductances, resistors and resonant elements, i.e. an external coil and high capacity. During the first attempts, and basically when squeezing "as much as possible", I managed to damage the circuit, the transistors burned out. At first I inserted the IRFR120, but due to the low maximum current, they lasted only a moment. Then I soldered the IRFR2905 - 50A low voltage transistors, which seem to be appropriate - the heater works better than on the original mosfets, the marking of which is unfortunately not visible. The photos show a burning transistor.

    120W induction heater - a typical gadget or a useful workshop tool? 120W induction heater - a typical gadget or a useful workshop tool? 120W induction heater - a typical gadget or a useful workshop tool?

    Let's move on to the tests.
    After connecting the 12V DC voltage, the device consumes about 1.8A. As soon as the metal element is brought closer to the coil, the current begins to increase. At its peak, I managed to achieve a current of about 12A, which gives almost 150W, which is more than the manufacturer declares. During the idle run, despite the power consumption of about 20W, nothing heats up, rather a little bit of everything, which may prove the correct operation of the entire structure. At first, I connected the device to a universal power supply, which in its design has several taps on the transformer and relays that activate the appropriate voltage. Unfortunately - the heater most likely generates large disturbances that destabilize the operation of such a power supply, causing its chaotic switching. I built a simple transformer power supply quickly in order to be able to further test the device.
    I tested three elements: a 6.5mm screwdriver, a figure-eight screw, and the same screw with two nuts. All three cases can occur in reality, so let's check how our heater will meet the set bar.

    120W induction heater - a typical gadget or a useful workshop tool? 120W induction heater - a typical gadget or a useful workshop tool? 120W induction heater - a typical gadget or a useful workshop tool?

    Screwdriver:


    Link

    120W induction heater - a typical gadget or a useful workshop tool?

    As you can see, a medium-sized screwdriver can be heated to redness with this device within 2 minutes. This is a pretty decent result in my opinion. If we can harden the tip of a screwdriver at home, then such a heater will be a great help here!

    Eight screw:


    Link

    120W induction heater - a typical gadget or a useful workshop tool?

    It takes about 3 minutes to make this screw red hot - it also seems to be a good result, of course considering the simplicity of the device. Also in this case, we can use this device to harden to a diameter of 8mm.

    Bolt with nuts:


    Link

    120W induction heater - a typical gadget or a useful workshop tool?

    In this case, it took 4 minutes to warm up such a kit to a barely visible redness - a long time. The device under test can be used in this way to heat the baked cap in order to unscrew it easier, but the process will be long and inconvenient. In addition, in our case, we could put the heated elements inside the coil - in the real case it may not be possible, which will significantly reduce the efficiency of such an operation.

    Summarizing...

    one piece of "induction heater" cost about $ 9, which is less than PLN 35. In my opinion, this is a low amount for a device that is able to heat efficiently with low power, but small metal objects. Of course, this heater cannot be compared to company equipment for a few thousand zlotys, but it is also not just a worthless gadget and it will work for home, hobby or even small workshop applications.

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    About Author
    bestler
    Admin of DIY, Automation
    Offline 
    bestler wrote 5117 posts with rating 594, helped 254 times. Live in city Siedlce. Been with us since 2002 year.
  • #2
    domel1
    Level 12  
    On Allegro, they once cost PLN 50, I was wondering whether to buy such something, but I was always curious about the maximum temperature that can be obtained. The seller said that there is no possibility of temperature regulation in this converter. There are such large induction furnaces every 2000-3000 W for hardening metals The melting point of aluminum is some 660 C, gold 1 064 C, iron 1 538 C. Films like such a heater can melt aluminum. https://pl.wikipedia.org/wiki/%C5%B The red color is about 900 C. But forge at home it is unlikely to do so to melt iron :) . I wonder if it is possible to obtain such a temperature with a similar converter :) The second thing to precisely measure the temperature at home is to have an industrial sensor :)
  • #4
    domel1
    Level 12  
    But nowhere in these converters does it write what maximum temperature can be obtained only from the maximum power. Maybe the maximum temperature depends not only on the power but also on the physical structure of the metal?
    Aluminum may melt, but steel will not :)
  • #5
    robokop
    Moderator of Cars
    For the workshop, it is a rather useless toy. He's already writing why before Comrade Admin launches a counteroffensive :) :
    Contrary to appearances, iron conducts heat quite well, so when heating you need to bring excess heat - which requires quite a lot of power, and you need to do it in a relatively short time - so that the applied heat acts on the object pointwise, does not spread around the area - analogy to soldering - you can solder small things with a small soldering iron, with low power and low thermal capacity of the tip, for larger ones you need to have a bigger one - because the soldered detail will cool the tip, and the small heater will not heat it up. Similarly here - the idea of "electric unscrewing" is thermal shock - breaking corrosion at the joint, and two - thermal expansion of metals - what if the nut will heat up and expand in the same way as the screw on which it is screwed? If it expands quickly first before giving heat to the bolt, chances are it will come loose. Hence my opinion. The one with the link seems interesting @ xray81 - 1000W gives a wider range of possibilities. For this you can add a larger and more refined shape inductor, including the possibility of cooling it with water, for heavier work.
    @bestler Didn't you rummage around the pattern?
  • #6
    bestler
    Admin of DIY, Automation
    robokop wrote:
    For the workshop, it is a rather useless toy.

    Just remember that there are very different industries and therefore different workshops. As for 120W - which I noted in many places - the device does the job. In most small elements, a popular 5A power supply is enough to power it, you just need to add a large capacity to the power supply.

    I will try to use this device as the primary side of the Tesla coil - maybe I can create something nice.
  • #7
    robokop
    Moderator of Cars
    bestler wrote:
    robokop wrote:
    For the workshop, it is a rather useless toy.

    Just remember that there are very different industries and therefore different workshops.

    Not sure, just note that the heating power of this device is about the same as a better lighter. For PLN 5 or a small burner for PLN 20.
    Quote:
    As for 120W - which I noted in many places - the device does the job.

    In the "entertainment" application - in professional applications, as "unscrewing devices", these are devices of much greater power, and in addition made not as a Mazilla converter, but with PLL control - to obtain maximum performance regardless of the "charge" or type the inductor used. Even for hardening, the heating time is important - the shorter the better - especially the surface one, where the surface of the workpiece is improved by hardening, without demolishing the interior structure (saw blades, shaft journals, etc.).
    Quote:

    In most small elements, a popular 5A power supply is enough to power it, you just need to add a large capacity to the power supply.
    A cheap power source for such low-voltage inventions are demobilized server power supplies - even 12V / 100A for pennies on the Allegro.
    120W induction heater - a typical gadget or a useful workshop tool?
  • #8
    nici
    Moderator of Car Maps
    120W induction heater - a typical gadget or a useful workshop tool?


    I made a spider from what was in the box. It worked elegantly. I had a video somewhere.

    Imbus 6 heated up to redness in half a minute, took a lot of electricity and powered about 14V
  • #9
    robokop
    Moderator of Cars
    And tell me, good people - will the mosfet-to-igbt conversion work directly for this application? I would do it too. But from the mosfets I have the most powerful at 17A, and the welding "igiebets" are probably even 60A ...?
  • #10
    nici
    Moderator of Car Maps
    It seems to me that the system will work, the isolated gate will probably not be an obstacle.
  • #11
    vodiczka
    Level 43  
    domel1 wrote:
    Maybe the maximum temperature depends not only on the power but also on the physical structure of the metal?
    Ignoring the heater's power, the maximum temperature that the heated element can reach depends on its magnetic properties, mass and intensity of heat exchange with the environment. In practice, it looks like this that the longer you warm it up to the temperature of cherry heat, the lower the final temperature you will get.
  • #12
    nici
    Moderator of Car Maps
    vodiczka wrote:
    that the longer you warm it up to the temperature of cherry heat, the lower the final temperature you will get.
    he? Can you brighter? The longer I warm up, the colder it will be?
  • #13
    robokop
    Moderator of Cars
    nici wrote:
    vodiczka wrote:
    that the longer you warm it up to the temperature of cherry heat, the lower the final temperature you will get.
    he? Can you brighter? The longer I warm up, the colder it will be?

    No - it's just that the speed of heat emission from the heated object is too high to obtain high temperature. Something like an analogy for the heat balance so briefly.
  • #14
    vodiczka
    Level 43  
    nici wrote:
    Can you brighter? The longer I warm up, the colder it will be?
    I can brighter. The temperature of cherry heat of iron is approx. 770 C, if you reach it within e.g. 10 seconds, the achievable end temperature will be much higher than if you reach 770 C after 60 seconds.
  • #15
    robokop
    Moderator of Cars
    I don't feel like it anymore, because for this project, as shown in the picture above, I would have everything without getting up from the table - the problem would probably only be 5-watt, 12V zener. I don't like winter as such (because it's cold and dark), but I love long winter evenings at home at my desk with a soldering iron.

    Added after 4 [minutes]:

    @bestler see - 120W induction heater - a typical gadget or a useful workshop tool?
    http://kaizerpowerelectronics.dk/high-voltage/mazilli-zvs-flyback-driver/
  • #16
    TechEkspert
    Editor
    What is the radio interference level in the vicinity of a working heater?

    Is it possible to make the air coil with a shorter length and will this allow for better heating efficiency?

    What is producing that popping sound in IR movies?
  • #17
    bestler
    Admin of DIY, Automation
    TechEkspert wrote:
    What is producing that popping sound in IR movies?

    The thermal imager is probably calibrating - I don't know exactly, but I worked with different cameras and this effect was visible, but here it is quite clear.

    TechEkspert wrote:
    Is it possible to make the air coil with a shorter length and will this allow for better heating efficiency?

    You can definitely, it must be calculated in such a way that, together with the capacitance, the resonant frequency of the system is ... appropriate :)

    TechEkspert wrote:
    What is the radio interference level in the vicinity of a working heater?

    Rather big :) I do not have the appropriate tools to perform such a measurement.

    robokop wrote:
    Will this application work directly to replace transistors from mosfet to igbt?

    Igbt work usually in slower applications, and most of all, they always use at least a minimum of elements shaping the impulse - most often dedicated drivers are used. It is important because igbt transistors have slower switching times than mosfets and in this particular system they may "not make it".
  • #19
    bestler
    Admin of DIY, Automation
    I have rtl-sdr - I forgot about it, I will do tests in the evening.
  • #20
    CMS
    Administrator of HydePark
    As for the maximum temperature, it will depend on the metal being heated. There is something like the Curie temperature above which ferromagnets lose their properties and cannot heat up any further.
    Aluminum, as it is not a ferromagnetic material, will not heat up in such a heater. Unless it has ferromagnetic additives in its composition, and in a large amount. To melt aluminum in an induction furnace, this metal must be placed in a suitable crucible.
  • #21
    Arek_v1
    Level 14  
    @ these capacitors will not work for a long time, put WIMA MKP10 there, they are designed for high currents.
  • #22
    nici
    Moderator of Car Maps
    It was just a prototype. Already dismantled long ago.
  • #23
    _lazor_
    Moderator of Designing
    CMS wrote:
    As for the maximum temperature, it will depend on the metal being heated. There is something like the Curie temperature above which ferromagnets lose their properties and cannot heat up any further.
    Aluminum, as it is not a ferromagnetic material, will not heat up in such a heater. Unless it has ferromagnetic additives in its composition, and in a large amount. To melt aluminum in an induction furnace, this metal must be placed in a suitable crucible.


    A ferromagnetic element is not really needed, on the contrary, when I gave the heater a ferromagnetic element (transformer core) it did not heat up at all, this is due to the fact that such material has very little eddy current losses.

    Well, eddy currents, it depends on them whether the material will heat up or not.
    https://www.researchgate.net/publication/2811...ndryczna_wzory_na_parametr_tlumienia_i_dobroc

    Here we have the formula for the batch resistance (2) and as you can see it is not related to the magnetic permeability, but the batch reactance (3) is so, which is so important that you need to adjust the resonant frequency of the system a little more.
    In addition, materials in induction heaters can be melted to a liquid state, which significantly exceeds the Curie temperature.


    I am the one who praises the work on the induction heater, but in series, controlled by the UC
    https://www.youtube.com/watch?v=vEs7U1ZIvWg

    Currently only 60W, but the current algorithm worked great, so a 1kW model is already in preparation. When I'm finished, I'll put it in the DIY section with the full schematic in the circuit maker (full schematic with a 3d model :) )
  • #24
    CMS
    Administrator of HydePark
    _lazor_ wrote:
    ferromagnetic element (transformer core)


    I guess it wasn't metal.
    I did not specify here. I mean the ferromagnetic material being a metal.

    _lazor_ wrote:
    In addition, materials in induction heaters can be melted to a liquid state, which significantly exceeds the Curie temperature.



    I am asking for evidence in the form of films.
  • #25
    _lazor_
    Moderator of Designing
    Proof, please:
    https://www.youtube.com/watch?v=ZHxrFzZlFBw

    It looks to me like copper, which is actually a diamagnet.

    As for the magnetic core, it was metal, but these ferromagnetic materials are so strange, anyway, the meter showed zero resistance (i.e. below 1mohm).


    There are also interesting dielectric heaters that heat the insulators, but unfortunately such heaters must already work in MHz :( but there are already GaN mosfets available in detail, it would be necessary to fix some prototype ^^

    edit:

    As for this ferrite core, I must have lied a bit, because the problem is more complex. It is possible that it would heat up just as well, but by introducing a much larger inductance into the system, I changed the L / C ratio, which changed the goodness of the system, and because I have a goodness limiter, it meant that less energy was flowing to the core, so my mistake
  • #26
    robokop
    Moderator of Cars
    CMS wrote:
    I am asking for evidence in the form of films.
    Marcin, but why do you need evidence? For a long time, metallurgical furnaces have been either induction or arc furnaces - initially built with a tube generator, then a thyristor one - with a capacity of several, several hundred kW. During my school days, I repaired the furnace inductor, and in school workshops - he worked in a cast iron foundry, melting scrap metal into pig iron for casting heaters, etc. A coil about a meter in diameter, made of a copper profile with a cross-section of about 3x3 cm (from memory, because it was a quarter of a century ago).
  • #27
    CMS
    Administrator of HydePark
    And now I have to educate myself on this topic, instead of focusing on a new article :) .
  • #28
    pskal32
    Level 13  
    Hello. I have a question. In place of these two coils on toroidal cores, could a transformer from a UPS be connected? These coils probably have a common center, as in the transformer from the ups.
  • #29
    _lazor_
    Moderator of Designing
    It is impossible, because these chokes are not to be magnetically coupled. Another thing is that the main function of transformers is not to store energy.
  • #30
    TechEkspert
    Editor
    _lazor_ wrote:
    Proof, please:

    Link


    It looks to me like copper, which is actually a diamagnet.



    The owner of the channel specializes in heaters quite well and they have their Polish products with different powers, I did not expect that a 3kW stove could be so compact. They have more such curiosities on the channel: https://www.youtube.com/channel/UCBeRJGj1zp1m60mtdEWW2wQ
    Could add some comment to the stove videos.

    You can see that they are still in such a development of the company that they have some time for entertainment, and this is a good development of the team:


    Link



    Link



    For me, all this induction heating is black magic, see what happens here,
    directional field winding?


    Link