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Induction Heater Circuit Using IGBT

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In this post we comprehensively discuss how to build a high power induction heater circuit using IGBTs which are considered to be the most versatile and powerful switching devices

Induction Heater Working Principle

The principle on which induction heating works is very simple to understand.

A magnetic field of high frequency is produced by the coil present in the induction heater and thus in turn eddy currents are induced over the metal (magnetic) object which is present in the middle of the coil and heats it.

In order to compensate the inductive nature of the coil, a resonance capacity is placed in parallel to the coil.

Written By Surbhi Prakash

The resonant frequency is the frequency at which the resonance circuit (also known as coil-capacitor) needs to be driven.

The current flowing through the coil is always much larger than the excitation current. The IR2153 circuit is used to enable the working of the circuit as a “double halfbridge” along with the four controlled IGBT STGW30NC60W.

An equal amount of power is delivered by the double halfbridge as to the full bridge, but the gate driver in the case of the former is simpler.

Using Anti-Parallel Diodes

The large sized double diodes STTH200L06TV1 (2x 120A) are used in the form of anti-parallel diodes. Even if the smaller diodes of 30A size will be enough for this.

In case you use the built-in diodes of IGBT such as STGW30NC60WD, then you will not be required to use the smaller diodes or large double diodes. A potentiometer is used in order to tune the operating frequency into resonance.

One of the best indicators of the resonance is the LED’s highest brightness. You can certainly build drivers which are more sophisticated depending on your requirement.

You can also use automatic tuning which is one of the best things to do, which is the course adopted in the professional heaters; but there is one drawback that the simplicity of the circuit will be lost in this process.

You can control the frequency which falls in the range of approximately 110 to 210 kHz. An adapter of little size which can be either transformer type or smps is used to provide 14-15V of auxiliary voltage which is required in the control circuit.

The Isolating Transformer

An isolating transformer and a matching Choke L1 are the electrical equipment which are used to connect the output to the working circuit.

Both these inductors are present in the air-core design.

On one hand where a choke consists of 4 turns on a 23cm diameter, the isolating transformer on the other hand consists of 12 turns on a 14 cm diameter and these turns are made up of double wired cable (as shown in the figure given below).

Even when the output power reaches to a scale of 1600W, you will find that there is still a lot of scope for improvement.

The work coil of the proposed IGBT induction heater is made up of a wire which is 3.3 mm in diameter.

Using Copper for the Coil

A copper wire is considered more suitable to make the work coil as it can be connected easily and effectively to the water cooling.

The coil consists of six turns along with the dimensions of 23 mm height and 24 mm diameter. The coil can get hot in case it is subjected to prolonged operation.

Resonance capacitor is made up of and consists 23 pieces of capacitors of small size which has a total capacity of 2u3. You can also use capacitors of 100nF in the designs such as Class X2 and 275V MKP polypropylene.

You can use them for this purpose even when they are basically not intended or made for such purposes.

The frequency of resonant is 160 kHz. EMI filter is always recommended to be used. A soft start can be used in order to replace the variac.

I would always strongly recommend you to use limiter which is connected in series with the mains such as halogen lamps and heaters of approximately 1 kW when it is being turned on for the first time.

Warning: the induction heating circuit being used is connected to the mains and contains voltage of high level and can be lethal.

In order to avoid any accident due to this you should use a potentiometer which has a plastic shaft. The electromagnetic fields of high frequency are always harmful and can have a damaging effect on the storage media and the electronic devices.

A significant level of electromagnetic interference is caused by the circuit and this in turn can also cause electric shock, fire, or burns.

Every task or process which you carry out is at your own risk and the responsibility will lie with you and I will not be responsible for any kind of harm which comes by in carrying out of this process.

Circuit Schematic

The Choke L1

The design of the choke L1 used in the above full bridge IGBT induction heater circuit can be witnessed in the below given image:

The following image shows the double coiled air cored isolation transformer design:

 

 

The work coil may be build as per the following instruction

 

UPDATE

Adding a Current Limit

The following diagram suggest how a simple current limiting feature can be added to the above explained induction heater design.

IGBT induction heater with current limit

Here Rx becomes the current sensing resistor, which develops a small voltage across itself to the desired point when the current begins exceeding the safe limits.

This voltage across Rx is used for triggering the LED inside the attached opto-coupler. The output transistor inside the opto responds to the LED triggering and quickly conducts grounding the Ct, pin#3 of the main driver IC IR2153.

The IC shuts down immediately prohibiting any further rise in current. When this happens the current drops which in turn eliminates the voltage across Rx, thereby switching OFF the opto LED. This reverts the situation towards earlier normal situation, and the IC starts oscillating again. This cycle now repeats rapidly ensuring a constant current consumption for the load, within the predetermined safe limits.

Rx = 2/Current Limit

Feedback from one of the dedicated readers:

Dear Sir- I have successfully made induction heater 1/2 bridge with 4 IGBTs and i want to know that the 1000 watts heater that you have suggested should be permanently connected to the circuit or only upto testing for the 1st time.

Awaiting your reply at the earliest. Regards- Manish... Mob:09820660450(for Techweld Industries- Mumbai)

Solving the Circuit Query

Dear Manish,
while operating the induction heater do you see any glow on the series lamp?
If yes then probably it cannot be removed, if the lamp is in the non-illuminated state then it can be removed
Regards
 

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About Me
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Swagatam is an ardent electronic researcher, inventor, schematic/PCB designer, manufacturer, and an avid publisher. He is the founder of https://homemade-circuits.com/where visitors get the opportunity to read many of his innovative electronic circuit ideas, and also solve crucial circuit related problems through comment discussion.

Reader Interactions

Comments

  1. Dear Swagatam:
    I am really upset with my circuit. it has quite little heat,just as hot as making a wrench head red and not more. and when i boost the wattage of the lamp in series to get more heat, i lose two of my IGBTs (gw35hf60wd). i used these IGBTs , as i could not find the one mentioned in the schematic. on the other hand i am after melting iron and making it red. please help me what i should do so that my IGBTs remain safe on the hand and i can get as much heat as to melt iron on the other.
    meanwhile, i was waiting to get to the heat and shoot a film, but …..could not yet
    thanks a lot Saeed Mahdavi Asl

    Reply

    • Dear Saeed, I am really sorry I do not have much idea regarding the design since it was created and tested by another person, according to whom the circuit worked perfectly. It is the frequency which actually affects the heat, so make sure it is best optimized perfectly while the load is placed in the coil

      Reply

  2. Dear Swagatam:
    just a health concerning question,
    as you have mentioned in your post, this circuit makes so powerful radiation. do you think it might be dangerous for its operator or it is quite safe??
    have you ever researched about it??
    thanks a lot
    Saeed Mahdavi Asl

    Reply

    • Saeed, as per my assumption the radiations may not be harmful to the user, because we have mobile towers at every corner of our cities and those radiations are much powerful than this, so if those are not a concern then this situation can be also ignored.

      Reply

  3. Dear Swagatam:
    first of all, i thank you for all useful information you kindly gave me. concerning the induction heater with 4 IGBTs in your webpage , i should say I made it at last successfully. thanks God. it was all OK having little illumination in the 1200 watt lamp in series. while working, the coil got so hot and the bolt in it got quite red. however, i was intending to see the bolt melt, so i increased the wattage of the lamp to 1800 which caused one of my IGBTs to burn out after a few minutes.
    1-Now would you please tell me if i have to keep the 1200 watt lamp in the circuit for good , which in this case i would have just a moderate heat not able to melt iron.
    2- what else i should do to get to that heat?
    3- if i could omit the isolater coil, which is contained of 12 turns of wire?
    4- if i could change the 4 turn choke with an air cored one to a smaller one with feritte core?
    thanks a lot
    Saeed Mahdavi Asl

    Reply

    • Dear Saeed,

      I am glad you could make it successfully.

      However since this was not designed by me,providing perfect solutions may not be possible for me.

      I would recommend you to keep the circuit as it is, and add a current limiting stage as shown in the updated diagram above.
      Once you configure the current limiting stage, you can try removing the 1200 watt series lamp and check what happens.
      The current limit should be set with regards to the breakdown limit of the IGBTs and other relevant components.

      Reply

  4. Hello Dear..
    First of all thanks for making such a nice & informative website 🙂
    In the article above i found this line..

    "In case you use the built-in diodes of IGBT such as STGW30NC60WD, then you will not be required to use the smaller diodes or large double diodes."

    TO my understanding the above line means if i have IGBT with internal(built-in) diodes then i can change my circuit to
    https://drive.google.com/file/d/0B3Pn7Yg7DiqkTURzRWxpdm5peE0/edit

    means i can skip big antiparallel diodes?
    Am i right?

    Reply

    • Thanks Waqaar, I am glad you liked my site.

      yes that's right, however I would not recommend removing the external protection diodes, after all the IGBTs are too important for the circuit and we would want to provide extreme protection for these device even if it costs little more to us.

      Reply

    • Hi Carlos, I don't have mush idea regrading your device so it would be difficult for me to analyze the integration, however if you can provide more details regarding the specs and the operating principle of the device, I may try to suggest my views

      Reply

    • Hi Saketh, everything is furnished in the above article, please copy them on a notepad accordingly…

      please try a smaller one first and then attempt this one

      Reply

    • Hi Aris, if the datasheet says 50% then it should be 50%

      Please build it only if you are an expert with switching circuits, and high voltage circuits, otherwise not, because this design is not suitable for the newcomers.

      Reply

  10. Dear Swagatam Majumdar,

    Of course you cannot troubleshoot my circuit from a picture but you may see something wrong. The resistors and capacitors may be to far or to close, or the coils and transformer may be not good for example.

    I did a test now. I fill the work coil with metal and turn it on. The lamp still lights constantly at any position I turn the frequency potentiometer. It is obviously that my circuit works as a short circuit for a reason.

    IR2153 looks to be working because it is shutting down the IGBTs when I short pin 3 Ct to ground.

    Reply

  11. Dear Swagatam Majumdar,

    Fist of all, thank you for spending time to help all of us here.

    I knew the correct behavior of the lamp but after so many failed tests I start doubt.

    Most probably my problem here is that I am not in the resonant field.
    I made a circuit board and I can take a few pictures of my circuit that I can send them to you to have a look. You may see something that I am missing.

    Is it possible to send a file to you? If yes can I have an email address to send?

    Reply

    • Dear Nicos,

      you can send the images to my email: admin @ homemade-circuits.com

      however just by looking at the pictures I don't think I would be able to troubleshoot the fault, because there are so many parameters involved and pinpointing the fault could be difficult.

      Reply

  12. Dear Swagatam Majumdar,

    I am trying to get through this circuit but looks impossible. I burned up to 20 IGBTs and still going and some times the large diodes. I power up the system and IGBTs start get hot until burn. If I power up, shut down and then power up again, immediately burns and crack the IGBTs. I check the circuitry over a hundred times and it is all the way correct.

    Could you please define the correct state of the halogen lamp? It should illuminates once or always illuminates?
    In my circuit I used a 250W halogen and it is always illuminates. It is illuminate once only if I power the system without IGBTs.

    Then the 4.7K potentiometer for the frequency should be at the correct place corresponding to the LC tank? If it is not could be damage the IGBTs? If can damage how can I set it to the correct position?

    Please I spent a lot of time and money for this one and I definitely have to make this circuit work. Please help!!

    Reply

    • Dear Nicos,

      It could be difficult for me to troubleshoot your circuit without seeing it practically, please understand that this is a resonant based circuit which can be extremely unpredictable and sensitive, unless you are an expert dealing with such concepts it could be very difficult to make these work.

      first of all, resonant circuits do not have a standard working condition, they will work satisfactorily only while they are within the resonant zone, however the moment this zone is disturbed or shifted the circuit will turn into a "short circuit" therefore maintaining a perfect resonant condition is the key to keep this circuit working.

      Another thing I see is that you are asking what should be the state of the lamp, which indicates that you are a newcomer in the field.

      anyway the answer is, obviously the lamp should be completely shut-off or glowing dimly, and this should happen only while the metal within the work coil is heating up nicely.
      If your lamp is glowing constantly it means your circuit is not in the resonant zone, rather behaving as a "short-circuit"

      remember resonance condition will occur when you hit the exact right frequency and while a ferromagnetic metal is placed inside work coil.

      always keep a metal inside the work coil while testing and adjusting the frequency, as soon as you strike the resonant frequency you might find the lamp instantly getting dimmer and the metal inside the work coil beginning to heat up.

      I would recommend you to first try other smaller circuits and then comeback to this one once you have learned all the aspects of the design

      Reply

  13. Dear Swagatam Majumdar,

    I want to change the work coil to 80mm inner diameter, 260mm long, 23 terns. That mathematically means approximately 11.25uH. Also mathematically means that I need to place capacitors in parallel approximately 56nF for frequency 200KHz. (please let me know if I did something wrong in mathematics). Now, doing those changes do I need to change anything else in the circuitry in order to work?

    Thank you Nicos

    Reply

    • Thank you dear Swagatam.

      Now I want to make this circuit more proportional. I want to control the power output by adjusting a potentiometer.

      From my experience that could be achieved by controlling the gates of IGBT.

      Is there any pins of IR2153 where I can place an extra circuit to control the gates? Or can be achieved by simply adjust the voltage input of IR2135?

      Do you suggest anything else?

      Also, after initial starting, can I short the 1000W halogen to get the maximum abilities of the circuit and also extend the halogen's lamp lifetime? Or it is not recommended?

      Thank you
      Nicos

      Reply

    • Dear Nicos, the pin Ct of the IC is the shutdown pin, if you ground this pin the IC and the IGBTs will shut down.

      If you apply a PWM (negative pulse) at Ct and adjust this pWM then the circuit power can be controlled by varying this PWM.

      the 1000 watt bulb can be bypassed but if the input voltage fluctuates then the IGBTs could get damaged, to protect again the Ct pin can be used and configured with a current limiter stage which may ground the Ct pin each time the output consumption goes above a certain safe value.

      Reply

  15. Hello Sir,Is there any possibility or way to check this circuit if we didn't connect part after L1.

    I am looking forward to use this circuit for Induction Cooker and for that If i purchase ready made coil out there in market.So how can I select resonant capacitors for same ?

    Plz guide me sir That would be great Help.

    Reply

    • dear waqar, you can probably attach a series bulb with the circuit, as long as this is illuminating would indicate no resonance, and as its glow begins decreasing you can anticipate a resonance taking place.

      Reply

  18. When the load and the 100 Watt series lamp was connected we got an output of 0 Volt at the 6*2u2 capacitor terminals.
    Then we removed the load, and applied voltage by the variac instantaneously we got almost same output that of the input at the 6*2u2 capacitor terminal. But gradually it damped up to 2 Volt.
    We tried to measure the frequency at that terminal, but when we connected it with CRO, the MCB tripped down.
    We also checked voltage input into the 20Amp bridge rectifier, but it showed only 2 Volt, when 100 Volt was given from variac, and the series bulb was glowing almost brightly.
    Till then IGBTs were working properly. At last we removed the series bulb, and applied only 7V from the variac, the voltage input at the bridge rectifier was also 7V. But suddenly 2 IGBTs got damaged.
    Through out the whole process, the current reading in the clamp meter was showing 0.02Amp

    Reply

    • the coils must resonate with the applied frequency, until this does not happen the circuit will keep getting damaged and not work.

      there could be a few related videos on youtube which you can see for more info.

      Reply

  20. During the circuit test, 5 IGBTs are gone….
    Are you sure about the authenticity of the German circuit?
    Please tell me ASAP.
    Now I am totally dependent on your reply,If you can assure me,that the circuit is correct,then only I can proceed.

    Reply

    • this circuit is a tested and verified design, but said that the design will require extreme knowledge of switch-mode circuits from the user, because if there's a slightest mismatch between the inductors and the frequency could cause an instant damage for the devices, and so the circuit has to optimized by your self expertise in the field, this circuit is not one of those which will start working just by building it correctly as per the diagram.

      the AC mains is shown with a 1000watt halogen lamp for dropping current, did you include that in your circuit?

      You can try a 400 watt bulb initially just to make things safer and see the effects on the output, whether the work coil heats up of not

      Reply

  21. How will i make double coiled wire with 3/20 wires for the isolating transformer? will i take 2 .. wires and wound it as per the specification? please explain it a bit sir…..

    Reply

    • the idea is shown in the image using white wires. Use two double-core wires as used for irons or heaters etc…coil them together as shown in the image

      each wire should have two internal isolated wires (2-core wire but thick ones)

      Reply

  24. Hello sir, I have made this circuit but even I give the 60 volt to the circuit after 30 second the igbt burnt out…what is the problem? I use buitin antiparallel igbt

    Reply

    • sorry abhijit, it will be difficult for me to troubleshoot your circuit from here because I don't know what fault you might have done in circuit connections

      Reply

  25. my dear such a good contribution thanks in advance for asking a favor quisera see waves resonate to compare circuit because my gives a pure sinusoid and the output of the coil have the same waves thanks

    Reply

    • Sarath, if you are asking about the voltage and current handling capacity, the answer could be found in the datasheet of the specific device.

      however a 25amp diode could become hot at 20amp current, so a heatsink may be required for it.

      Reply

  28. Dear swagatam
    Based on this I have reached to Induction heating but now I am using water cooled copper coil and Want to melt small amount of aluminum inside 30mm inside dia of coil but present circuit is not able to supply more than 1A power so i want circuit with 2kw power and 200khz frequency ..but I don't know how to design that circuit please help me.

    Reply

    • It may be the voltage rating of the resistor, because normally resistors are designed to tolerate 300V max, you can use two 220K resistors in series in its place

      k=0.4mm could be the maximum distance between the winding which should not be exceeded for maintaining optimal performance

      Reply

  32. Dear sir swagatam
    At last I did the sstc based on this schematic sstc4.png – https://docs.google.com/file/d/0B8xT7Q4vaK-bYVRTTnRseHZqb1U/edit?usp=docslist_api

    Its worked well for 10minutes with 1inch spark output on secondary coil .but after 2nd start the igbts blow out like crackers suddenly .
    I have know idea what went wrong with it .I checked the entire circuit for ani short connections.. But its all well.
    Plz suggest any trouble shoot
    Thanks
    Regards
    Raj

    Reply

    • Dar Raj, just like mosfets an IGBT can be susceptible to high gate voltages or high load currents and also transient spikes, troubleshooting can be difficult without a lot of practical effort….
      try driving the IC with 9V or 12V and use a 200 watt bulb in series with the mains input line while checking, check the response.. how it goes.

      makes sure the IGBT gate links with the IC is very close, and not too far away

      Reply

  36. Hello. I see many that apply the working coil into water for cooling. If i do so, will matter if I apply the transformer coil leads into water too? ( only the leads connected to working coil not all the transformer coil)

    Reply

    • I don't think it would cause any problems but make sure the wires are insulated and do not short circuit into the water which could result in a disturbance in the generated frequency and resonance.

      Reply

  39. Hello. I have a couple of questions. If I replace the 15V supply by 12V would the controller working properly? And the diode BA519, is it a simple diode or zener? Because the symbol on the schematic confuses.Thank you

    Reply

    • hello, 12v would proportionately reduce the output power of the heater (by about 3×20 = 60 watts)

      BA159 is a fast switching rectifier diode, it's not a zener diode

      Reply

  42. Please tell me whether there is any relation between the choke L1 and 6 X 2u2 capacitors used, like any resonance or not. What for the choke is used and how it's value selected?

    Reply

  43. Hello. some help please. Can I apply a single 6.6uF 450V capacitor (one to the top and one to the bottom) in place of 6x 2.2uF? Second, what should be the value of the resonant capacitors?
    Thank you.

    Reply

  45. I am in the process of designing a circuit for analysis purposes and might some some help. Do you consult on electronics matters?

    Best Regards

    Paul

    Reply

  46. Can you publish a circuit automatically controlling a ceiling fan according to room temperature. I mean it should increase / decrease speed according to variation in room temperature.

    Reply

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