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What is a medium-frequency induction furnace?
Aug 12,2020
◆ Definition: What is a medium-frequency induction furnace?
Medium-frequency induction furnace It is a process that first rectifies three-phase power-frequency AC into DC, and then converts the DC into an adjustable current to supply a circuit composed of capacitors and induction coils. In this way, high-density magnetic flux lines are generated in the induction coil, which cut through the metal material housed within the induction coil, inducing large eddy currents in the metal and thereby heating it up.
The operating frequency of medium-frequency induction furnaces typically ranges from 200 Hz to 1,000 Hz, depending on the furnace’s tonnage and power rating. For an 8-ton medium-frequency induction furnace, the operating frequency falls within the range of 200 to 400 Hz—roughly around 350 Hz.
◆ Composition of the Medium-Frequency Induction Furnace Melting System
I. High-Voltage Distribution Section
The 10,000-volt power supply is distributed to the electric furnace transformer via a high-voltage switchgear, and then the electric furnace transformer steps down the 10,000-volt power supply to the operating voltage required by the electric furnace equipment (rectifier cabinet). The operating voltage for electric furnaces manufactured by the U.S.-based Yida Company is 575 volts; the operating voltage for electric furnaces manufactured by Zhenwu Company is also 575 volts. As shown in the figure:
High-voltage switchgear, transformer—rectifier cabinet—inverter cabinet—furnace body
(1) Rectification section: Converts the 50 Hz AC power supply into a DC power supply.
(2) Inverter Section: Converts the DC power supply into a medium-frequency AC power supply with a high voltage of 3000 volts and a frequency of 200–400 Hz, which is then supplied to the furnace.
The 8-ton electric furnace operates at a frequency of around 350 Hz.
III. Water cooling system
Includes: a power supply unit, a circulating water cooling system, and a furnace body circulating water cooling system.
IV. Furnace Body and Auxiliary Systems
Includes: furnace structure system, emergency tap water system, hydraulic system, and dust removal system.
◆ Daily Operation Step 1: Pre-Furnace Inspection
(1) Inspect and repair the lining condition of the furnace promptly every day, especially at the furnace mouth and the junction between the furnace wall—areas where molten iron tends to leak—and strictly prevent slag from falling into the gaps.
(2) Inspection of the hydraulic system, including the opening and closing of the furnace lid and the lifting and lowering of the furnace body.
(3) Start the circulating water pumps for both the furnace body and the power cabinet, and check whether the water pressure reaches 5.5 kg, the water temperature and flow rate are normal, and there are no leaks in the pipelines. Pay special attention to inspecting the connections of the cooling water pipes inside the power cabinet and on the furnace body for any signs of dripping, leaking, or seepage. If leaks are detected, take appropriate measures—such as replacing the pipe or tightening the pipe clamps—and then use a hot air blower to thoroughly dry the leaking areas.
(4) The spray and emergency pump control switches for the cooling tower should be set to the “Automatic” position.
(5) Set the generator key switch to “ON” and adjust the operating mode to “Automatic.” Manually open the gate valve to check whether emergency tap water is available. If there is no tap water, absolutely do not start the furnace and promptly report the situation to your supervisor.
(6) Turn on the supply and exhaust fans in the transformer room to provide cooling and ventilation for the transformer. (This is especially important during summer.)
(7) Before starting the furnace each day, check whether the “R” and “N” indicator lights on the AT1 panel of the dual-power switching cabinet are lit. If neither light is on or only one is lit, it indicates that the emergency power supply is malfunctioning. Report this to the workshop supervisor, identify the cause, and then proceed with starting the furnace.
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Kangda Electric Furnace specializes in the manufacture of the following equipment: KGCL series medium-frequency power supplies, KGPS series medium-frequency power supplies, GTR series medium-frequency induction heating furnaces...
Contact Information
Address: Yuhe Industrial Park, Weicheng District, Weifang City, Shandong Province
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