Introduction to Coreless Induction Furnace by Stead Fast Engineers Pvt Ltd

Introduction:

The coreless induction furnace is considered as the most prevalent sort of the induction furnaces in view

of its suitability for all metal industries. The coreless induction furnace is a basic unit comprising of a

helically twisted curl encompassing an unmanageable cauldron containing the liquid charge and joined

with a rotating excitation system. At the point when the curl is energized by a rotating current it create a

hub exchanging attractive field. The variety of attractive field creates an electric field and swirl streams

along ways concentric with the hub. The electromagnetic field weakens quickly inside the charge. The

profundity at which the impelled thickness tumbles to (1/e) of its surface worth is normally alluded to as

skin profundity.The skin depth δ is given by: δ = under root 𝜌/ 𝜇𝜋𝑓 (m).

eddy currents are amassed at the external surface of the charge due to skin impact and heat is created

by the routine ohmic misfortunes. Some portion of the created heat is lost to the encompassing

medium, and the remaining part is conveyed through the mass of the charge by impact of warm

conductivity. The skin impact is additionally spread in the coil conductor. In addition, the conveyance of

the surface current density over the coil is non-uniform, the best current density is to be found in the

segments of the coil lying nearest to the charge, this marvels is known as the vicinity impact. The

induction furnace is, in this manner, in view of four standards: Electromagnetic induction, skin impact,

heat exchange and vicinity impact

Design Steps of the Coreless Induction Furnace:

The proportionate circuit technique is general routines that can be connected to investigation and

outline of all induction heating applications, the coreless furnace is surely one of them. The identical

circuit technique is viewed as general technique in light of the fact that this system doesn't decide the

measurements, recurrence or the force prerequisites of the particular application examined and

composed by this strategy. Despite what might be expected, the utilization of proportionate circuit

technique requires this data as essential, so to set up a complete outline of the coreless induction

furance, these data are :

i- Outline of cauldron which incorporate the determination of stature to distance across

proportion (Lw/Dw), coil breadth to charge breadth Dc/Dw, and the cauldron divider thickness.

ii- Frequency determination: The physical particular of the workpiece and its measurement decide

the recurrence of the force supply for heat process. This frequency must be greater than critical

frequency given in the following equation[3]: fc = 6.45𝜌/ 𝜇𝐷*D

iii- Determination of the required power: the power supply is chosen in light of power and

frequency required for dissolving procedure. The required power comprises of : the relative

power to dissolve the charge and the heat misfortunes went with the dissolving process.

iv- Induction coil design: which it consists of number of copper conductor with proper cross-section

to satisfy the required cooling.

v- Determination of the required cooling. A complete study of performance of furnace is

performed from the calculation of the equivalent circuit resistances and inductances.

The equivalent circuit is shown in fig.1, where :

Xg = KR 𝐷𝑐 2− 𝐷𝑤 2 4𝐿𝑐 Z

w = Rw + jXw = KR 𝜇𝑟𝐷𝑤 2 4𝐿𝑐 (q + jp)

Zc = Rc + jXc = KR 𝐾𝑟 𝛿𝑐 𝐷𝑐 2𝐿𝑐 (1 + j)

Xr = KR 𝐷𝑐 4(0.45+ 𝐾𝑔) Where KR = ωμoπ𝑁𝑐 2

This relationship was derivate after knowing the reluctance of magnetic field paths.