Medium frequency furnace USES medium frequency power supply for induction heating, melting and heat preservation. Medium frequency furnace is mainly used for smelting carbon steel, alloy steel, kind of steel, but also can be used for copper, aluminum and other non-ferrous metal smelting and temperature raising.Small size, light weight, high rate, low power consumption, fast melting, easy to control furnace temperature, high productivity.Intermediate frequency furnace is generally used in factory casting and heat treatment. Intermediate frequency furnace has gradually replaced coal burning furnace, gas furnace, oil furnace and ordinary resistance furnace, and has become a new favorite in factory casting and heat treatment.One, medium frequency furnace working principleIntermediate frequency furnace through silicon controlled rectifier inverter to generate intermediate frequency power, sent to the furnace body coil, furnace (coil) in the middle of the medium frequency electromagnetic field, so that the metal in the furnace body produce eddy current, eddy current and then make the metal produce a large amount of heat so that the metal melting.Intermediate frequency furnace is mainly composed of power supply, induction ring and crucible made of refractory material in induction ring.Within the crucible containing metal furnace charge, equal to each winding transformer, induction coil, when on ac power, to produce alternating magnetic field in the induction coil, the magnetic force line in the crucible furnace charge, metal is produced in the furnace charge induction electromotive force, due to burden itself form a closed loop, the point of this vice winding is only turn and is closed.Therefore, inductive current is generated simultaneously in the charge. When the induced current passes through the charge, the charge is heated to make it melt.The working process of the intermediate frequency furnace is also a kind of induction cooker, as follows: first, through an inverter power supply, the three-phase alternating current rectifier (SCR) into a single phase dc, then by the inverter bridge inverter into a kind of alternating current (ac), 500-1000 hz frequency pulse through copper ring formation in the furnace magnetic field, make the circle steel produces eddy current magnetic field, eddy current flows through the heated steel, generate heat, so as to achieve the goal of smelting steel.The general frequency of intermediate frequency electric furnace is 800-20000Hz.Two, medium frequency furnace working principle diagramThe main circuit block diagram of the machine is shown in the figure.The rectifier adopts three-phase bridge controlled rectifier circuit, the inverter adopts single-phase bridge inverter circuit, the load is parallel resonant form, the DC filtering link is large inductance filtering, so as to meet the input requirements of parallel inverters. 
Ac - DC - AC converter
Three phase bridge controlled rectifier circuit
The output voltage of the three-phase bridge controlled rectifier circuit is:Ud = 2.34 U2cosa...(1)Ud is the average value of the output DC voltageU2 -- Grid phase voltageA -- Trigger phase shift AngleThe waveform of the output voltage at different A angles (under inductive load and non-intermittent current).The a>The state of 90° is called the inverting working state of rectification, whose essence is that the load feeds back energy to the power grid.
