Induction heating equipment

Technical Principles and Characteristics of Induction Heating

Electromagnetic Induction and Eddy Current Heating

Induction heating utilizes the heat effect generated by induced currents (eddy currents) in a conductor placed in an alternating electromagnetic field to heat the conductor itself. Depending on the heating process requirements, induction heating uses power supplies with frequencies of power frequency (50～60Hz), medium frequency (60～10000Hz), and high frequency (above 10000Hz). The object to be induction heated must be a conductor. Induction heating can directly generate heat inside the object being heated, resulting in high thermal efficiency, fast heating speed, and easy achievement of overall uniform heating or local heating (including surface heating).

Induction heating uses alternating current to establish an alternating magnetic field, generating eddy currents to inductively heat metal workpieces. The basic working principle is shown in Figure 1, where A is the induction coil (also known as the load coil), and B is the metal workpiece being heated. If an alternating current i ₁ passes through coil A, a time-varying magnetic field is generated within coil A. The workpiece B placed in the alternating magnetic field will generate an induced electromotive force e ₂ , forming eddy currents i ₂ . These eddy currents cause the metal workpiece to heat up, consuming electrical energy. From the above, it can be seen that induction heating relies on the induction coil to transfer electrical energy to the metal workpiece to be heated, which is then converted into thermal energy within the metal. The induction coil and the heated metal are not in direct electrical contact; energy is transferred through electromagnetic induction.

Diagram of Basic Induction Heating Principle

Three effects exist in induction heating: skin effect, proximity effect, and ring effect.

Skin effect: When alternating current passes through a conductor, the current distribution across the conductor's cross-section is not uniform; the maximum current density appears in the surface layer of the conductor. This phenomenon of current concentration is called the skin effect.

Proximity effect: When two conductors carrying alternating current are very close to each other, they mutually influence each other, causing the current in the two conductors to redistribute. When the currents in the two conductors are in opposite directions, the maximum current density appears on the inner side of the conductors; when the currents in the two conductors are in the same direction, the maximum current density appears on the outer side of the conductors. This phenomenon is called the proximity effect.

Ring effect: When alternating current passes through a ring-shaped coil, the maximum current density appears on the inner side of the coil conductor. This phenomenon is called the ring effect.

Induction heating utilizes these three effects comprehensively. A metal workpiece is placed in the induction coil, and an alternating voltage is applied to the two ends of the induction coil, generating an alternating current I ₁ , which induces a current I ₂ in the workpiece. The directions of these two currents are opposite, similar to the situation where two parallel busbars have currents flowing in opposite directions. When the current I ₁ and the induced current I ₂ are close to each other, the coil and the workpiece exhibit a proximity effect. As a result, the current I ₁ concentrates on the inner surface of the coil, and the current I ₂ concentrates on the outer surface of the workpiece. At this time, the coil itself exhibits a ring effect, while the workpiece itself exhibits a skin effect.

Xi'an Aobang Technology Co., Ltd. is one of the earliest manufacturers in China to mass-produce medium-frequency furnaces. Main products include medium-frequency power supplies, IGBT power supplies, melting furnaces, heating furnaces, and a full range of induction heating equipment. Long-term focus on induction heating equipment research and development and manufacturing Based in Xi'an, Aobang Technology's mission is to "drive industrial heating innovation through technology." Leveraging core technologies accumulated from early mass production, we provide customers with full-cycle services ranging from equipment selection and installation and commissioning to process optimization.

Ancient City Welcomes Guests, Sharing Aobang's Feelings We look forward to collaborating with more industry partners to explore the innovative boundaries of induction heating technology. 13891865812 　Mr. Luo