The working principle of induction heating furnace

What is the working principle of medium-frequency induction heating furnace ？

The relationship between the induction heating coil and the work-piece (metal) is analogous to that between the primary and secondary coils of a transformer.

As shown in the diagram, high-frequency current flowing through the heating coil generates magnetic flux lines that are concentrated on the work-piece; electromagnetic induction then creates eddy currents, thereby heating the material. By selecting the appropriate AC frequency, power, heating duration, holding time, and coil geometry based on the specific type and shape of the steel, the desired material properties can be achieved. 

A medium-frequency induction heating furnace is a power supply unit that converts standard 50Hz AC power into medium-frequency power (ranging from above 300Hz to 20kHz). It rectifies three-phase mains AC into DC, then converts that DC into an adjustable medium-frequency current. This current flows through a circuit comprising Capacitors and an induction coil, generating high-density magnetic flux lines within the coil. These lines cut across the metal material placed inside, inducing strong eddy currents within the metal. These eddy currents exhibit the characteristics of medium-frequency current—specifically, the flow of free electrons through the resistive metal body generates heat. For instance, if a metal cylinder is placed inside an induction coil carrying medium-frequency AC, the cylinder does not touch the coil directly; while the coil itself remains cool, the surface of the cylinder heats up until it glows red or even melts. Furthermore, the rate of heating and melting can be controlled simply by adjusting the frequency and current intensity. If the cylinder is positioned at the center of the coil, the temperature distribution around its circumference remains uniform. Additionally, the heating and melting process produces no harmful gases or intense light pollution. Medium-frequency induction heating furnaces are widely used for melting ferrous metals (such as steel, alloy steel, specialty steel, and cast iron) and non-ferrous metals (such as stainless steel, zinc, copper, and aluminum). They are also employed for heating, holding, and temperature maintenance, and can operate in tandem with blast furnaces. ...forging heating [applications include through-heating, reheating, and online heating prior to shearing or "blue quenching" for bars, round/square steel, and plates; local heating; online forging of metal components (such as precision forging of gears, axle shafts, connecting rods, bearings, etc.); extrusion; hot rolling; pre-shearing heating; heating for spraying; thermal assembly; as well as through-hardening and tempering, annealing, and tempering of metal materials]; heat treatment [primarily for surface heat treatment of various mechanical and automotive/motorcycle parts—such as shafts (straight, stepped, camshafts, crankshafts, gear shafts), gears, sleeves/rings/discs, machine tool lead screws, guide rails, flat surfaces, ball joints, hardware tools, etc.—and for through-hardening and tempering, annealing, and tempering of metal materials], etc.

Medium-frequency melting furnaces VS Medium-frequency through-heating furnaces

1. Features of Medium-Frequency Melting Furnaces:

(1) High melting efficiency and energy-saving performance; compact structure with strong overload capacity.

(2) Low ambient temperature around the furnace, minimal smoke and dust, and a favorable working environment.

(3) Simple operating procedures and reliable melting performance.

(4) Uniform metal composition.

(5) Rapid heating, easy temperature control, and high production efficiency.

(6) High furnace utilization rate and convenient alloy/material switching.

(7) Arc-shaped magnetic yokes shield against magnetic flux leakage and reduce external magnetic reluctance; they also shield leakage at the coil ends. The arc-shaped cross-section ensures the inner side fits seamlessly against the outer wall, increasing the effective magnetic permeability area and providing superior support for the lower coil sections. A unique forward-and-reverse winding coil design significantly boosts system efficiency.

2. Features of Medium-Frequency Through-Heating Furnaces:

• Rapid heating speed; minimal oxidation and decarburization

Based on the principle of electromagnetic induction, heat is generated internally within the work-piece. This method allows for rapid temperature rise, resulting in minimal oxidation, high heating efficiency, and excellent process repeatability.

• High degree of automation; fully automatic operation possible

Equipped with automatic loading and unloading/sorting devices, and utilizing our company's proprietary control software, the system enables fully automatic operation.

• Uniform heating and high temperature control precision

Induction heating easily achieves uniform heating with minimal temperature difference between the core and the surface. Precise temperature control is ensured through the application of advanced temperature control systems.

• Easy replacement of induction furnace bodies

The medium-frequency induction through-heating system features a split-unit design, consisting of a medium-frequency power supply and the heating furnace body. Drawing on years of practical experience, we design and manufacture "one-power-supply, two-furnace" systems tailored to specific user requirements. This configuration pairs a single power supply with two furnace bodies; depending on workpiece dimensions, furnace bodies of different specifications can be selected for alternating or simultaneous heating. Each furnace body is equipped with quick-connect couplings for water and electricity, making the replacement process simple, rapid, and convenient. This setup not only saves the cost of an additional power supply but also minimizes downtime during furnace body changes. Our company manufactures "one-to-three" through-heating electric furnaces that represent state-of-the-art technology in China, positioning us as a leader in the industry. To meet specific customer requirements, the power supply and furnace body can be integrated into a single, unified electromechanical unit.

• Low energy consumption and zero pollution

Compared to other heating methods, induction heating offers high efficiency, low energy consumption, and zero pollution, with performance metrics that fully meet user requirements. For through-heating applications, the electricity consumption required to heat material from room temperature to 1,100°C is less than 360 kWh per tonne.

With advantages such as compact size, light weight, high efficiency, superior thermal processing quality, and environmental friendliness, medium-frequency electric furnaces are rapidly replacing coal, gas, and oil-fired furnaces as well as conventional resistance furnaces; they represent the new generation of metal heating equipment.

Medium-frequency electric furnaces are essential equipment in casting, forging, and heat treatment workshops; their operational stability, reliability, and safety ensure the smooth and consistent functioning of continuous production lines. 

Are you looking to replace or deploy Capacitor Bank for induction furnace?

Flair Electronics specialized in Power Capacitors for induction heating installations: water-cooled and air-cooled set up type.

If you are looking to replace or layout capacitor banks, please tell me:

What is the power rating (kW or kVar) of your furnace?

What is the operating frequency (Hz or kHz)?

Is it an air-cooled or water-cooled setup?

We will be happy to provide with the best optimal capacitor bank arrangement.