Why Low Frequency is Needed for Core Type Induction Furnaces

Low frequency power supply is essential for certain types of induction furnaces, specifically direct core type induction furnaces, primarily to manage two critical factors:

1. Controlling Stirring Action

• Normal frequency AC supplies induce strong electromagnetic forces within the molten metal.
• These forces result in vigorous stirring or agitation of the molten bath.
• Excessive stirring can cause operational issues such as splashing, increased wear on furnace refractories, and difficulty in controlling the melt.
• Using a low frequency supply significantly reduces the intensity of these electromagnetic forces, thereby minimizing unwanted stirring and allowing for more stable operation.

2. Optimizing Magnetic Coupling

• The design of a core type induction furnace involves a magnetic core to direct flux.
• The efficiency of magnetic coupling—the transfer of energy from the primary coil to the molten metal (secondary)—is dependent on frequency and furnace geometry.
• In some direct core type designs, operating at normal frequencies might result in suboptimal or undesirable magnetic coupling characteristics.
• Low frequency operation is required to achieve the necessary magnetic coupling for efficient induction heating in these specific furnace configurations, possibly influencing the depth and distribution of induced currents.

Therefore, the necessity of a low frequency supply stems from the need to both avoid excessive electromagnetic stirring and ensure appropriate magnetic coupling for effective and stable operation of direct core type induction furnaces.