What causes the rapid heating of metal workpieces in a medium-frequency melting furnace?
2022-04-11
The medium-frequency melting furnace is incredibly simple to install and operate. Through continuous research and innovation, it has successfully achieved energy efficiency, high melting efficiency, and uniform heating temperatures. The operating principle of the medium-frequency melting furnace relies on medium-frequency electromagnetic induction heating. Once activated, the heated workpiece is placed inside a sensor, enabling non-contact, rapid heating. This process works because the medium-frequency current passes through an inductor, generating an alternating magnetic field that induces currents of the same frequency within the workpiece. These induced currents are unevenly distributed—stronger at the surface and weaker toward the interior—leveraging the skin effect to facilitate swift and efficient heating of the workpiece’s outer layer.
After practical experience, we have summarized specific precautions for the safe operation of medium-frequency melting furnaces:
1. The medium-frequency melting furnace should be used regularly and not left idle for extended periods. If the furnace has been stored unused for a long time, before first use, run a fan for 1 hour to remove any moisture and dust inside, then power it on for a low-power test run. Only after confirming that everything is functioning properly should you proceed with normal operation.
2. Always monitor water temperature and pressure carefully. All water channels—especially the thyristor cooling channels—must remain unobstructed, with no leaks or blockages allowed.
3. Closely monitor the readings of all instruments on the medium-frequency melting furnace. Readings should remain stable and free from fluctuations or mixing. If any instrument is damaged, it should be replaced promptly. The control cabinet is equipped with a fan that effectively cools and dehumidifies the interior. Always keep an eye on the fan’s operation, and replace it immediately if it becomes damaged.
4. Regularly check the engagement status of the main contactor and air switch, as well as the temperature and color of the main contacts. If you notice any contact erosion or loosening, address the issue promptly by repairing or replacing the components.
5. During the yellow mold season and rainy season, it is essential to ensure that condensation is promptly removed from the thyristors and the main control board.
6. When observing the main circuit waveform, disconnect the ground wire of the oscilloscope's cathode-ground power supply to prevent electrical components from being damaged due to ground loops. Please pay extra attention to safety—note that the oscilloscope casing is currently energized.
7. Before energizing, connect three 20–30A fuses in series on the incoming side of the three-phase power grid and implement arc protection measures to effectively prevent any short circuits in the medium-frequency power supply from causing damage—such as burning out—entire main circuits and components like thyristors. It is crucial to prevent short-circuit currents from spreading beyond the medium-frequency unit itself, safeguarding other connected equipment like distribution cabinets and power transformers. All maintenance personnel must be thoroughly trained in these procedures.
8. Disconnect the main inverter circuit (remove the connecting cable from the smoothing reactor to the common anode of the inverter bridge), and connect six 200W/220V light bulbs (or three 2kW heating elements) in a configuration of three in series and two in parallel across the output terminals of the rectifier bridge, ensuring the rectification stage operates under low-current conditions. This approach allows distributed testing to directly pinpoint whether the fault lies in the rectifier or inverter section, thereby eliminating unnecessary maintenance efforts and minimizing the risk of introducing human-induced errors.
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2025-09-17