The induction melting furnace is determined by the five major links of the circuit
① Rectification link (AC-DC), in the rectifier circuit, through the three-phase bridge-type fully-controlled rectifier circuit, the AC power of 50 Hz power frequency can be rectified into pulsating DC power, and the DC voltage U of the circuit can be changed to change the load current; The load of the intermediate frequency power supply rectifier circuit is an inverter, and the active power output by the inverter is provided by the rectifier circuit. The DC output voltage of the rectifier circuit is required to be continuously smooth and adjustable;
②FILTER, in the filter circuit, the power frequency and the intermediate frequency network are separated through Ld, and part of the unsmooth current is filtered at the same time, and then the DC current is filtered into a flat waveform through the filter capacitor Cd-smooth DC current .
③Inverter link (DC-AC), the inverter circuit is a fully controlled bridge inverter circuit composed of IGBTs, which converts DC current into AC current through the inverter link, and then passes it to the load. The output frequency of the inverter circuit is It is controlled by the oscillation frequency of the load circuit and works at a frequency higher than the oscillation frequency of the load.
④ Load and resonant tank circuit (RESONANT TANK), the load part is a series oscillation circuit composed of induction heating coil L and compensation intermediate frequency capacitor C; in this case, the adaptability of the load is significantly increased and when the workpiece is running, Its reliability has also increased.
⑤Control and protection link (CONTROL AND PROTECT), through it to adjust the power output, and provide system security protection. This link mainly uses changing the firing angle of the rectifier bridge to change the output voltage of the rectifier bridge, thereby changing the output power of the power supply.
The working principle is that the three-phase 50Hz alternating current is rectified into a pulsating direct current with adjustable voltage through a thyristor three-phase fully controlled rectifier bridge, and then the pulsating direct current is filtered into a smooth and stable direct current through a smoothing reactor and a filter capacitor, and then passed The conduction frequency of the IGBT is controlled, and then sent to the single-phase inverter bridge, and finally the DC power is converted into a single-phase intermediate frequency AC power to the load through the inverter bridge.
For the induction heating process, electricity is usually delivered by an induction coil, and then the current is delivered to the load for heating. The induction coil can be classified as a power inverter. Therefore, the induction coil and the load become an equivalent load.
