Monday, October 28, 2013

Simple Induction Heater Circuit - Hot Plate Cooker Circuit

The proposed induction heater circuit exhibits the use of high frequency magnetic induction principles for generating substantial magnitude of heat over a small specified radius.


The discussed induction cooker circuit is truly simple and uses just a few active and passive ordinary components for the required actions.

According to the involved principle when a change in magnetic field is forced around a metal, electrons inside the metals get agitated and begins flowing across the metal, this is termed as eddy current. This flow of current in the metal or the introduced conductor causes a heat to be generated in the metal making it warmer.
The generated heat is proportional to (current)^2 x resistance of the metal.

The above heat is also directly proportional to the induced frequency and that's why ordinary iron stamped transformers are not used in high frequency switching applications, instead ferrite materials are used as cores.

However here the above drawback is exploited for acquiring heat from high frequency magnetic induction.

Referring to the proposed induction heater circuit below, we find the concept utilizing the ZVS or zero voltage switching technology for the required triggering of the mosfets. The technology ensures minimum heating of the devices making the operation very efficient and effective.
Further to add, the circuit being self resonant by nature automatically gets sets at the resonant frequency of the attached coil and capacitor quite identical to a tank circuit.

The circuit fundamentally makes use of a Royer oscillator which is marked by simplicity and self resonant operating principle. However the main downside of the design is that it employs a center tapped coil as the transformer, which makes the winding implementation a bit trickier. However the center tap allows an efficient push pull effect over the coil through just a couple of active devices such as mosfets.

As can be seen, there are fast recovery or high speed switching diodes connected across the gate/source of each mosfet. These diodes perform the important function of discharging the gate capacitance of the respective mosfets during their non-conducting states thereby making the switching operation snappy and quick.

You can use IRF540 as the mosfets which are rated at good 110V, 33amps. Heatsinks could be used for them, although the heat generated is not to any worrying level, yet still it's better to reinforce them on heat absorbing metals.

The inductor L2 terminating from center of the main induction coil is a kind of choke for eliminating any possible entry of the high frequency content into the power supply and also for restricting the current to safe limits.

Relatively the value of L2 should be high enough, a 2mH will do the job well. However it must be built using high gauge wires for enabling high current usage through it safely.

C1 and L1 constitute the tank circuit here for the interned high resonant frequency latching. Again these too musts be rated to withstand high magnitudes of current and heat.

Here we can see the incorporation of a 330nF/400V metalized PP capacitors.




Now comes L1, which is the most crucial element of the whole circuit. It must be built using extremely thick copper wires so that it sustains the high temperatures during the induction operations.
The capacitor as discussed above must be ideally connected as close as possible to the L1 terminals. his is important for sustaining the resonant frequency at the specified 200kHz frequency.

For the induction heater coil L1, many 1mm copper wire may be wound in parallel or in bifilar manner in order to dissipate current more effectively causing lower heat generation in the coil. Even after this the coil could be subjected to extreme heats, and could get deformed due to it therefore an alternative method of winding it may be tried.

In this method we wind it in the form of two separate coils joined at the center for acquiring the required center tap.

In this method lesser turns may be tried for reducing the impedance of  the coil and in turn increase its current handling capability. The capacitance for this arrangement may be in contrast increased in order to pull down the resonant frequency proportionately.
In all 330nF x 6 could be used for acquiring a net 2uF capacitance approximately.





Parts list for the above induction heater circuit or induction hot plate circuit

R1, R2 = 330 ohms 1/2 watt
D1, D2 = FR107 or BA159
T1, T2 = IRF540
C1 = 10,000uF/25V
C2 = 2uF/400V made by attaching 6nos 330nF/400V caps in parallel
D3----D6 = 25 amp diodes
IC1 = 7812

L1 = 2mm brass pipe wound as shown in the following pics, the diameter can be anywhere near 30mm (internal diameter of the coils)

L2 = 2mH choke made by winding 2mm magnet wire on any suitable ferrite rod 

TR1 = 0-15V/20amps

POWER SUPPLY: Use regulated 15V 20 amp DC power supply.



Using BC547 transistors in place of high speed diodes

In the above induction heater circuit diagram we can see the mosfets gates consisting of fast recovery diodes, which might be difficult to obtain in some parts of the country.

A simple alternative to this may be in the form of  BC547 transistors connected instead of the diodes as shown in the following diagarm.

The transistors would perform the same function as the diodes since the BC547 can operate well around 1Mhz frequencies.





112 comments:

  1. Dear sir which diode can i put in place of FR107

    ReplyDelete
    Replies
    1. You can use BC547 transistor in place of the diodes. Connect base and collector together with the gate of the mosfet, and emitter to the drain of the other mosfet.

      Delete
  2. can i take L1 from another induction cooker ?

    ReplyDelete
    Replies
    1. No, only the specified type will work.

      Delete
    2. Hello sir can I use it for boiling a moving water from pipe.

      Delete
    3. Helo Salman,

      Yes you can do it, but the pipe should be made of iron or steel (magnetic material)

      Delete
    4. Thank you for the quick response,
      So pipe that Water flow inside, is a metal to be heated or as a induction metal(L1)?

      Delete
    5. The iron water pipe should pass through the center of the coil L1 as shown in the last diagram.

      Delete
  3. so do I calculate the power using the formula: VOLTAGE X CURRENT?

    ReplyDelete
  4. Not worked swgtm. the material not even heat up & both mosfets burnt out. it specified 200kHz frequency. So can i use Astable multivibrator to set frequency 200Khz to drive the coils.

    ReplyDelete
    Replies
    1. Hi Max,

      What did you use for D1/D2 and L2?

      Delete
    2. FR302 & 40 turns on a ferrite bead as L2

      Delete
  5. hello swagatam.
    Plz suggest a circuit to run cooling fan externally. i bought a amplifier unit the heat sense fan stops automatically after 1 minute. need a solid state cheap circuit to run fan directly from mains. (fan rated 12vdc 0.25amp 2.5w)

    ReplyDelete
    Replies
    1. Hello Max,

      The only solution is to a use a readymade 12V ac/dc smps adapter rated at 500mA or 1amp current, because you won't get below this rating.

      Delete
  6. Hello Swagatam,
    I have built my one successfully with DC power source of 18V connected to L2 while the other side keep 12V to drive MOSFET. I am also connecting ammerter in series to L2 to monitor the current. With some bolts and nuts or steel rod. They can turn red hot without problem. Current goes up from original L1 coil without anything inside to some level according to the object inside the coil. Somehow, I try this with 1/2" diameter steel pipe with 0.5mm thickness. Current goes up and increasing. After a while when pipe is in red hot, current suddenly increase very rapidly and FET burn-out. At this point, everything stop. I have to change FET as it was shorted Drain-Source. I used IRFP250N and diode BYV26E, pretty high rated voltage and current but still failed. Do you have any idea what I did wrong? Is this due to FET or Diode? Thanks.

    ReplyDelete
    Replies
    1. Helo Sitti,

      Try the following circuit, set Rt, Ct for getting 200khz, use L2 in place of "L" and the L1 for RL.

      http://homemadecircuitsandschematics.blogspot.in/2013/09/half-bridge-mosfet-driver-ic-irs21531d.html

      This circuit will never allow your mosfets to blow off, according to me.

      Delete
  7. Is there any alternative power supply? Cause its too expensive to buy a 20 A transformer then make it DC supply. By the way, could I use a power supply with adjuster in order to control the temparature of the induction coil?

    ReplyDelete
    Replies
    1. sorry there's no direct alternative for high current. You can reduce it proportionately by increasing the voltage, but that would also require modifications in the work coil, the turns will need to be increased while the gauge will need to reduced accordingly.

      Delete
    2. thanks for the quick reply, I really want to learn more about induction heating. Where I can find a choke coil required L2 because I can't find one of it in some electronics store here in my place, is it okay not to put L2? I want to share my idea to you, I have a circuit design that I found in the internet to control temperature, how can I share it to you?

      Delete
    3. You won't get the coils readymade, you will have to hand make it as per the details shown in the images and the article info.

      You are welcome to share your ideas, please send it to hitman2008@live.in

      Delete
    4. can we use the psu of computer

      Delete
  8. is it safe that my transformer that is rated 6A only is giving me up to 10A of current. Because i connected it to a bridge rectifier and a 4700uF caps to make a dc power supply, then i successfully make the circuit work but when I measured the current flowing to the transformer using a clamp meter, it gives me up to 10A depending on the metal to be heated. is it still safe for the transformer producing greater current than its rating?

    ReplyDelete
    Replies
    1. if it's showing more than the specified amps of the transformer means the voltage is being dropped proportionately in the course....so ultimately the total power is never being exceeded.

      as far as the above circuit is concerned, the coil would handle current depending upon its thickness, if it's correctly dimensioned it would be safe.

      Delete
  9. Replies
    1. It's 15V/20amp, that's equal to 300 watts

      Delete
    2. sir, i mean can i use 150v 2amp?

      Delete
    3. no, it should be @15V, amps is not important can be of any value (not less than 20amps)

      Delete
    4. Sir, both terminal will be +ve? if yes then; where is -ve terminal? And in MOSFET source will be grounded or -ve?

      Delete
    5. only the mosfet sources will go to the negative of the supply, no other point of the circuit is connected to the supply negative.

      Delete
    6. Sir, this kind of power supply(15v, 20a)is not esily available in the market.So, at which minimum voltage and current the circuit will be run?

      Delete
    7. Vinay, you can use a 12V, 20 amp transformer

      Delete
  10. Hello Swatam
    what changes I should make in the circuit to operate at 220V , two phases, each 110 V and a power of 6kW.
    and I'm thinking to cool L1 and L2 with water that circulates inside
    this is possible.

    ReplyDelete
    Replies
    1. Hello Paul,

      Sorry, I think that may not be recommended and could require more number of turns for L1/L2...I do not have the data for calculating those.

      Delete
  11. thank you very much.
    the number of turns can prove, but the electronic elements can recommend me what changes should be do.

    ReplyDelete
    Replies
    1. The configuration will remain as is. The resistors could be increased to 1K 10 watt (wirewound) each, everything will need to be done through trial and error, though.

      For the mosfets you can use IRF840, however since mains voltage is involved, the risks of an untoward could be on the cards, I am not recommending use of 220V for this project.

      Delete
  12. i have built one successfully but my capacitors tanks become very hot....
    i am using parallel cap at single point and where the all cap meet(at single point) they get very hot.
    should i mount capacitors on pipes at some distance?

    ReplyDelete
    Replies
    1. yes preferably the caps must be p;aced slightly away from the coil, may be a 6 inches distance will do.

      Delete
  13. One more thing
    At the start current go up very high without anything inside..

    ReplyDelete
    Replies
    1. you can use a 1000 watt halogen lamp in series with the mains input to the transformer, this will ensure that the initial amp intake does not exceed to dangerous levels.

      Delete
  14. Thanks Swagatam
    I made my induction heater successfully now i want to increase its power..
    Can i increase power of this induction heater using more mosfets in parallel?
    Please scheme a circuit for parallel combination.
    Thanks

    ReplyDelete
    Replies
    1. Thanks Waqar, to increase power you may try increasing the input current and also the voltage, and upgrade the mosfet with other higher rated ones, parallel combination may not be recommended.

      You can select an appropriate mosfet pair from the following article

      http://easydatasheets.blogspot.in/p/mosfets.html

      Delete
  15. Can i pass the iron or steel tube(from which water which is to be heated) three to four times from the coil L1.

    ReplyDelete
  16. sir we are making induction heater ckt for academic project purpose so could u tell us about the length and turns of L1,L2

    ReplyDelete
    Replies
    1. you can find it in this video: https://www.youtube.com/watch?v=pVYMLnXW9uo

      Delete
  17. can i use a high rated transformer and then minimize the current and voltage by a rheostat.

    ReplyDelete
    Replies
    1. you may have to do it through a variac, a rheostat will not do.

      Delete
    2. ty sir.
      can i fed the circuit with directly 20 amp or i have to increase it gradually because the insulation of my wire which are use for connection are burning along with mosfet.
      what is the reason for the same

      Delete
    3. increase it gradually, but if the mosfets are also burning it means the circuit is malfunctioning and there could be a fault in the circuit

      Delete
    4. sir plz help me out.
      when i increase the voltage with the variac my bridge rectifier burned out at 7 volt and if i fed the circuit directly my mosfet burned out.
      what should i do..

      Delete
    5. Pratik, it means the circuit is drawing huge currents without load, something is incorrect in your circuit.

      try a bridge driver type of circuit instead of the above self resonanat design for reliable results

      Delete
  18. Dear Swagatam, thank you very much for the details of the construction of this circuit. I built the heater and works well. I have a question related to the possibility to change the frequency of the system. I need differents frequencies. And I am thinking of if possible to change Capacitor and L at the same time to get any frequency. This is possible? Like for example 200Khz , 300 Khz, 400 and soon.
    Also I would know how I can calculate the magnetic intensity of the system.
    Thank you very much.

    ReplyDelete
    Replies
    1. Thanks Guillermo, the above circuit is a self resonant type of configuration so frequency cannot be changed manually....you may have to incorporate an external oscillator circuit for implementing an adjustable resonance, the following half bridge circuit could tried with the coil network explained in the above article for achieving the same:

      http://homemadecircuitsandschematics.blogspot.in/2013/09/half-bridge-mosfet-driver-ic-irs21531d.html

      Delete
  19. Thank You again, i will try the this circuit and let You knoe my progress. Cheers

    ReplyDelete
  20. dear sir I have a old induction heater coil . i want to use that coil . how can i use that coil for heat the panel. please tell me with using simple words. thank you...,...

    ReplyDelete
    Replies
    1. Dear Kamaljeet, without seeing the coil it would be difficult to suggest anything, anyway a commercial induction coil will require a sophisticated circuitry, much complex than the above published design...

      Delete
  21. sir
    L1 copper wire gauge # kia hay

    ReplyDelete
    Replies
    1. L1 should be preferably a copper pipe having a outer diameter of about 1cm, using a pipe will enable water to be circulated through it in order to keep the coil temp within limits

      Delete
    2. thanks sir for reply.
      kia ma ap ko urdu ma b question kr sakta hun

      Delete
    3. yes, but my replies will be in English.

      Delete
  22. hello
    what is the exact use of transformer? it is impedance matching only? what can we use instead of transformer

    ReplyDelete
    Replies
    1. which transformer...TR1?

      It's for supplying power to the circuit.

      Delete
  23. Hello sir,
    what power has to be given to heat a coil?

    ReplyDelete
    Replies
    1. hello jayalaxmi,
      the power specs are approximately 20V 15amps

      Delete
    2. Sir,
      Cant we heat the coil with Dc source using driver circuit??

      I did an oscillator circuit of a supply of 24Vdc and 0.3A and got an output of 46MHz and 19v as peak to peak voltage.
      Can we heat the coil with that frequency ?? what are the possible ways??

      Delete
    3. Jayalaxmi, the coil is not supposed to heat, the vessel is supposed to get hot.

      0.3A will not produce any result...it should be at least 10 to 15 ampere

      Delete
  24. Hi there,

    Its a very nice technology. Thanks for the circuit.
    What is the value of L1 and can i use pan cake coil of the same inductance?

    ReplyDelete
    Replies
    1. The inductance value is not crucial, you can make it as per the given instructions in the diagram, yes with little modifications it can be converted for the pan type implementation.

      Delete
  25. Hey, great thread. I was wondering what changes would need to be made to the schematic and the induction coil to work using 3.7vdc max 30amp load. This would obviously be used in a micro induction coil to heat small objects such as a sewing needle. And suggestion on coil size, wrapping and component change on the schematic would be greatly appreciated.
    Thanks!
    Dan

    ReplyDelete
    Replies
    1. thanks Dan, I think it may have to be done through some trial and error since I do not have a formula for calculating the coil.

      The only thing I know is that as the turns increase and the diameter decrease the operating frequency and the current consumption also decrease proportionately, so on this basis you could probably do some experimentation.

      L2 and the other components except the voltage may not require a change as per my knowledge

      Delete
    2. hi sir...we try the circuit using the power supply of the computer as the power supply to the circuit....in our first try....the metal that we put on the middle of the working coil gets hot....but the mosfets gets hot too.....so we decided to change the heatsink with bigger one......after changing we try it again.......and the metal dont get hot......why is it happen sir??thanks for the reply

      Delete
    3. Hi Christian, I guess this could be related to some frequency variations due to the introduction/removel of the metal plate.

      heating up of the msgfets might be hampering the generation of the resonance frequency which might be getting corrected with the addition of the larger hetasink and resulting in an automatic correction of the frequency.

      Not sure though, this could be the reason.

      by the way you are not supposed to put a metal inside the working coil, this might seriously affect the functioning of the circuit

      Delete
    4. but, is it ok that we use a power supply of a computer as the supply for this circuit?

      what could you suggest sir for us to make this induction warmer work.?

      Delete
    5. I'm sorry sir... the metal that we put inside the working is a screw driver just to test if it is working already,if the working coil produce induction heat
      .

      Delete
    6. oh... that was quite silly of me, I completely forgot that a metal (magnetic) needs to be inserted inside the work coil for implementing the design, make sure the heatsinks are perfectly aloof and are not touching anything in the circuit....

      any power supply will do as long as it's able to generate 15 to 20 amps for the circuit.

      Delete
    7. good day sir.....in the 2 small diagram above.....the c1 and c2 are in different position...which capacitor do we need to parallel in the l1?

      Delete
    8. we use a power supply of a computer....if we use the bridge driver type circuit...do we still needed to parallel a capacitor with the + and - of the power supply??

      Delete
    9. C1 value needs to be arranged by putting many MKT capacitors in parallel.

      If you are using a pure DC from an SMPS in that case C2 can be eliminated....

      Delete
    10. ....I am referring to C1 which is in parallel with L1, and C2 at the bridge...

      Delete
  26. sir may iuse it to cooking purpose

    ReplyDelete
    Replies
    1. It won't be possible with the shown coil dimension

      Delete
  27. am working on this circuit from last few weeks but its not working as i expect it too. am using a coil of 12 gauge 9 turns center taped mosfet irfz44n ,22uf 4 caps in parallel adn the voltage suply is 15 v 12 amps its from a transformer ( battery charger) as i turn on the circuit the the mosfets blows up within seconds seeps like shor circuted help pe am not using any choke .

    ReplyDelete
  28. am working on this circuit from few weeks and am facing the same proble as soon as i turn on the supply the current increses upto 40-70 amps and the mosfets blows up . am using irfz44n and 17v 10 amps power supplt from a transformer( its basically a battery charger) am not using any choke please help me out, ? :(

    ReplyDelete
    Replies
    1. the choke (L2) is specifically introduced to limit current and to optimize resonance frequency, if you remove it the circuit is bound to fry immediately.

      Delete
  29. Hello,

    My application requires that the object being heated (will be very thin) can be inserted and removed through the side of the coil, as both ends of that object will be fixed and unable to be pulled through the center of the coil. Are you able to tell me if there is any way to construct this without a completely closed heating coil (i.e. with a C-like cross-section instead of an O-shaped cross-section) to allow for side entry of a thin (~2mm diameter) object?

    ReplyDelete
    Replies
    1. Hello, I don't think that's feasible, one method could be by creating a flat spiral coil and then by introducing the object close to the surface of the spiral.

      An example spiral coil image may be witnessed in the third diagram below:

      http://www.homemade-circuits.com/2014/08/making-small-induction-cookware.html

      Delete
  30. Hello! Very intersting article!! But i need some help! Can you give me specific models for the D3-D5 (rectifier diodes), C1 capacitor & IC1 on the 1st circuit ?? Ampseres/volts for the IC1 voltage regulator??

    ReplyDelete
    Replies
    1. Hi thanks, D3---D6 can be any rectifier diode capable of handling 25amp current, you can inquire about it with your local component dealer, he will know better and will guide you with the correct number.

      Delete
  31. Ok! Something else...the Maximum DC current for the L2 (1st circuit) it's critical?? Let's say that we have a choke with Max. DC current 15A...it will be ok?? Or we need a higher value?

    ReplyDelete
    Replies
    1. if 15amp is the breakdown limit of the choke then it will not do, if it's the optimal rating then it won't be a problem.

      I think the choke wire should be at least 2mm thick or made by using 2 strands of 1mm wire to be able to withstand 15amps

      Delete
  32. i not get o/p plz i can't get output in proteou7s plz help me

    ReplyDelete
  33. Replies
    1. sorry can't figure out the issue...

      Delete
    2. plz let me know that which circuit diagram is right . as i run both but not working a single and i used 12v,10A supply .

      Delete
    3. i used cooker capacitor of 2uf instead of 330nf ,6pcs how much turns in coil L2 .

      Delete
    4. both the circuits are correct, but the first one is better recommended.

      there are many related youtube videos, you can refer any of those for a detailed help.

      Delete
    5. coil which generate heat is either l2 or l1 and how many turns are there for heat coil.

      Delete
    6. let me know about the frequency of this as i want to calculate value of inductor

      Delete
    7. L1 is the heating coil...

      details are given in the article

      Delete
    8. let me know about the l1 coil turns and i have to use same wire or other bcoz temporary i used different copper wire and let me know that can ckt run on 12v 10a

      Delete
    9. i want to ask you that either this circuit is run in PROTEOUS 7 simulator becoz i m not getting output in that as well as in real time circuit

      Delete
    10. I have updated the coil data in the parts list.

      I have no idea regarding the simulation details, however the circuit has been already tested practically successfully with no issues whatsoever

      Delete
    11. hey swagatam i would like to thank you for updates but how many wound i have to take for
      l1 and directly can i use 12v 10a power supply last question is iff i use ditto component then i get output otherwise no t

      Delete
    12. as you can see in the image, L1 consists of two separate coils made by curling two turns each of brass pipes and then then by joining the center together.....so total it becomes 4 turns, but you can try 3 turns each to make 6 turns.

      power supply should be 15V minimum and 15 amps

      please check the youtube videos you'll able to see these circuits in real and how these are configured and tested to produce heat.

      Delete
  34. My requirement is heating water ,approx 170ml, upto 90○C. Would it be possible using above circuit?
    If not what changes are required? Also would it be possible to run the above circuit on battery power?

    ReplyDelete
    Replies
    1. yes, the above circuit can be used for the purpose.

      Delete

Readers are requested not to include external links while commenting. For consulting a diagram, upload it on Google Drive and provide the link here.

Readers are advised to proceed with the construction of the presented circuits only after understanding the concepts from the core. Not adhering to this can lead to failures and frustrations.
Copyright © Swagatam Innovations. All rights reserved

Popular Posts