Written By Surbhi PrakashThe 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.
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.
Both these inductors are present in the air-core design.
The work coil of the proposed IGBT induction heater is made up of a wire which is 3.3 mm in diameter. 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.
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 work coil may be build as per the following instruction
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.
If yes then probably it cannot be removed, if the lamp is in the non-illuminated state then it can be removed