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About Medium-frequency induction furnace Regarding safety protection, this section focuses solely on the safety measures adopted in terms of equipment structure. In particular, the medium-frequency power supply, induction coil, water cables, and other components in the water-cooling system all require water for cooling; thus, water is critically important to the furnace equipment. The incidence of furnace equipment damage caused by cooling-water failures is relatively high. Since most of the cooled components—such as thyristors, induction coils, and water cables—are energized, the conductivity of the cooling water directly used to cool these components must be kept below specified limits. Moreover, the connecting hoses must be carbon-free rubber hoses. In addition, the inlet temperature, outlet temperature, water pressure, and flow rate of the cooling water must all comply with the design specifications. The cooling-water system of the electric furnace is equipped with various sensors to monitor the relevant parameters of the cooling water. When any cooling-water parameter deviates from normal conditions or exceeds the set values, an alarm will be triggered, or the operation of the equipment will be automatically halted. The cooling-water pump station for the medium-frequency electric furnace should be equipped with two identical main pumps—one serving as the primary unit and the other as a backup. Furthermore, an emergency cooling-water system must be provided. Should the main power supply to the grid fail and cause the main pumps to stop functioning, the emergency cooling-water system can continue to provide cooling to the furnace body, thereby preventing damage to the furnace.

In the hydraulic system of a medium-frequency coreless induction furnace, the hydraulic system is used for tilting the furnace to pour out the molten metal, as well as for opening and closing the furnace. To ensure reliable operation, the furnace’s hydraulic station should be equipped with two identical main pumps—one serving as the primary pump and the other as a standby. The inlet end of the tilting furnace hydraulic cylinder must be fitted with a throttling valve to prevent the furnace body from suddenly dropping in the event of a pressure loss in the hydraulic system. Under conditions where the power grid outage lasts for an extended period, the molten metal inside the furnace could cool down and solidify, potentially damaging the furnace lining. Moreover, attempting to melt the solidified metal by running the furnace itself would be extremely dangerous. Therefore, the furnace’s hydraulic system must be equipped with an emergency system. When the power grid fails, this emergency system can be activated, if necessary, to safely pour out the molten metal from the furnace, thereby preventing it from solidifying and leaking. During the operation of a coreless medium-frequency induction furnace, if the furnace lining is damaged, it could lead to a furnace leakage accident.

If molten metal leaks through the furnace lining, it can damage the insulation of the induction coil, the coil supports, and the magnetic yoke. If such leakage goes undetected for too long, it could lead to severe damage. Moreover, if the molten metal burns through the copper tubing of the coil, the water inside the tubing could come into contact with the molten metal, potentially causing an explosion and resulting in a serious accident. Hence, it is absolutely essential to install a furnace lining leak detection alarm system. Currently, a particularly effective type of leak detection system is the DC injection-based alarm system. In this system, the center tap of the secondary winding of the transformer is not grounded; therefore, a DC circuit can be connected in parallel with the AC power supply circuit of the induction coil. The molten metal inside the furnace is grounded via the bottom electrode, while the induction coil is connected in series with the DC power source and a milliammeter, and all are grounded as well. As a result, the molten metal, furnace lining, induction coil, and milliammeter form a closed DC circuit. When the furnace lining is in good condition, its resistance is very high, so the milliammeter reading remains very low. However, if the furnace lining deteriorates and molten metal starts leaking into the lining near the induction coil, the resistance of the lining will decrease, causing the milliammeter reading to rise significantly. Once the current exceeds the preset threshold, the alarm will be triggered, and the main power supply will be automatically cut off, thereby preventing furnace leakage accidents from occurring.

4. The modern induction furnace is equipped with a computer management system that features automatic fault diagnosis.

The system scans all setting points of the equipment. When it detects abnormal parameters at a setting point, it triggers an alarm and can display and record detailed fault information. Thanks to its rapid scanning speed—up to hundreds of scans per minute—the system can identify faults in their very early stages, thus preventing them from causing serious damage to the equipment. Information about any detected faults is stored in the computer for future reference. In addition to those mentioned above, there are other safety measures in place: for instance, when the cabinet door of the intermediate-frequency power supply is opened, a mechanical interlock will automatically disconnect the incoming power supply. Furthermore, each capacitor is equipped with a pressure switch; if the internal pressure of a capacitor exceeds the preset value, an alarm will be triggered and the power supply will be cut off, thereby preventing the capacitor from exploding due to excessive internal pressure.

Although various safety measures have been implemented on electric furnace equipment, to ensure safety, it is also essential to have a corresponding management system in place and to enhance personnel’s safety awareness.