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Simple Induction Heater Circuit

This article explains how to construct a circuit that heats iron items using magnetism.

We call this induction heating.

WARNING: Creating circuits with high currents and voltages can prove harmful.

Do this only under adult supervision and using the right safety equipment.

For beginners this project is not advised.

What is a Induction Heater Circuit:

An electrical device known as an induction heater circuit generates heat in the specified region by using the electromagnetic induction principle.

Eddy currents are frequently generated in conductive materials like metal objects by applying a high frequency magnetic field.

This causes the substance to heat up quickly.

Induction warmers are used in metal hardening, research experiments and cooking equipment.

Circuit Working:

Parts List:

CategoryDescriptionQuantity
ResistorsAll 1/4 W CFR
220Ω2
Capacitors
PPC 330nF2
Semiconductors
MOSFET IRF5402
Schottky Diode UF40072
Coils As specified in diagram above3

Induction Heater Working Principle:

To create eddy currents in iron or ferromagnetic metals an induction heater uses a high frequency magnetic field.

Eddy currents along with heating are caused by this mechanism which limits the flow of electrons within the metal.

When considering iron in this situation the heat produced is exactly equal to the square of the current I2 times the metals resistance R.

Because iron has a resistance of 97 nΩ*m high frequency switching applications require perfect designs that use ferrite materials rather than standard iron stamping transformers.

Formula:

Below formula explains how resistance current and heat generation interact in an object like an iron.

It is an example of Joules Law an essential electrical concept.

Heat = I2 × R (Iron)

where,

The formulas operation:

When the iron is plugged in and switched ON electricity is conducted by the heating element.

This element offers an important level of resistance to the electrical circuit due to the high resistance material used in its making.

Heat or thermal energy is the result of this fight between electrical and thermal energy.

Zero Voltage Switching Technology:

The circuits for the mentioned induction heaters use ZVS technology to activate the MOSFETs.

ZVS delivers low device heating increasing the operations overall effectiveness.

The circuit is naturally self resonant matching the resonant frequency of the capacitor and coil that are connected to it much like a tank circuit.

Using Oscillator:

A Royer oscillator famous for its simplicity and self resonant working principle is included into the circuit.

MOSFETs are turned ON in sequence with one starting conduction before the other because of inbuilt differences in electronic device parameters.

ZVS Technology and Its Advantages:

With little to no current flowing to their drains ZVS or zero voltage switching assures safe MOSFET activation.

Because of this feature the circuit is capable of handling heavy loads of up to 1 kVA without the need for big heatsinks.

The following formula provides the inductance L1 and capacitance C1 values which directly affect the circuits resonant frequency:

Formula:

Following are the formulas for Simple Induction Heater Circuit:

f = 1 / 2π × √L × C​

where,

How the formula works:

The capacitance C is equal to the weight of the person sitting on a swing set and the inductance L is comparable to the swings length.

With these changes one can modify the swings fundamental oscillation frequency.

The formula basically states that the resonant frequency of the LC circuit is calculated in an adverse form by the square root of the product of capacitance C and inductance L.

Component Specifications:

For the induction heater circuits MOSFETs with recommended ratings of 110V and 33A like the IRF540 can be used.

Heat generation is kept within control by the design even though heatsinks are used.

It is also possible to use N channel MOSFETs with enough ratings without any particular restrictions.

Inductor and Tank Circuit:

By acting as a choke the inductor connected to the main heater coil keeps high frequency content out of the power supply and restricts current to safe levels.

It should be built with large gauge wires to safely carry high currents and its value should be much higher than the work coil usually about 2mH.

For high resonant frequency latching the tank circuit which consists of C1 and L1 needs to be rated to deal with large current and heat magnitudes.

Powerful Induction Heater Design:

An effective ZVS induction idea based on the Mazzilli driver theory is the first design shown here.

This design which has two current limiter coils and one work coil does not require a central tap and ensures quick and efficient heating of heavy loads using a complete bridge push pull action.

Power Output:

With an input voltage of 48V and a current of up to 25A this design can produce up to 1200 watts of electricity.

When the system is working it can melt a bolt that is 1 cm thick in under one minute showing such a level of power.

Because the module for this design is readily available online which is affordable.

How to Build:

To build a Simple Induction Heater Circuit following are the steps one should follow:

Keep the inductor ready:

Put together the tank circuit:

Construct the oscillator:

Join MOSFETs:

Put Schottky Diodes in Place:

Include Quick Recovery Diodes:

Check for Connections:

Connection to the Power Supply:

Testing:

Modifications:

Connection for Loading:

Conclusion:

Connecting skills and electronics understanding are necessary for building electronic circuits.

If one is not familiar with these than think about checking thorough circuit diagrams and instructions or asking an experienced person for help.

When making modifications always turn OFF the circuit and ensure that all safety rules are followed.

References:

Induction heater

PMW control of a 5-12v ZVS induction heater?

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