Principle of electromagnetic heater:

An electromagnetic heater is a device that converts electrical energy into heat energy using the principle of electromagnetic induction. The electromagnetic controller converts 220V/380V, 50/60Hz AC power through a rectifying circuit to DC power, which is then transformed into a high-frequency current of 10-40kHz via a control circuit. The current flowing through the coil generates a varying alternating magnetic field. When the alternating magnetic flux lines pass through ferromagnetic metals (such as iron, cobalt, and nickel), numerous tiny eddy currents are induced within the metal, causing the metal to heat up rapidly, thereby achieving the purpose of heating the metal material.

Variable-frequency drives are the core components of high-frequency electromagnetic heaters, utilizing the on-off action of power semiconductor devices to convert AC power supply to another frequency of electrical energy control device. The variable-frequency drives currently in use mainly adopt AC-DC-AC method, first converting the AC power supply to DC power through a rectifier, and then converting the DC power to AC power with controllable frequency and voltage to supply the motor. The circuit of the variable-frequency drive generally consists of four parts: rectification, intermediate DC link, inversion, and control. The rectification part is a three-phase bridge uncontrolled rectifier, the inversion part is a IGBT three-phase bridge inverter with PWM waveform output, and the intermediate DC link is for filtering, DC energy storage, and reactive power buffering.