SU1753628A1 - Inductor for induction heating of a metal strip by a travelling magnetic field - Google Patents

Abstract

SUMMARY OF THE INVENTION: The inductor comprises magnetic cores with windings mounted with a working gap for the strip. The winding is made in the form of sections of various configurations — central spiral and extreme flat, which allows for uniform heating. 3 il.

Description

The invention relates to the heat treatment of metals and is intended for eddy current heating of a metal strip or sheet.

Single-phase inductors are known for induction heating of flat metal bodies by eddy currents of industrial or increased frequency. Their disadvantages are uneven heating due to the impossibility of using the central space of the coils, the poor use of the coil frontal parts, the increased size, the uneven network load, low efficiency.

In an inductor made of three windings, these disadvantages are partially eliminated, however, the heating efficiency is insufficient due to the arrangement of the coils in two parallel planes.

To heat a metal strip, it is proposed to use three-phase inductors of a traveling magnetic field, the windings of which are laid in the grooves of steel magnetic circuits, which face their active surfaces to each other and form a narrow slit for placing or passing a metal strip in it.

Closest to the present invention is a three-phase transverse magnetic field heater for heating sheet material, comprising two groups of sections, between which a heated sheet is placed. Each section is made in the form of a U-shaped magnetic circuit with a single-phase winding on its middle rod. The sections in the groups are installed in rows, with the ends of the magnetic cores to each other so that the axial lines of the active parts of their windings are on the same straight line. The windings of the sections of the first group are connected to a three-phase power source according to the star circuit. The windings of the sections of the second group are connected to two phases of a three-phase source.

When applied directly to the windings of the sections, they create a transverse traveling magnetic field in the working gap, which penetrates the heated sheet and inductife

SP

so about yu

00

It generates eddy currents in it, heating a narrow zone under the active branches of the windings.

A disadvantage of the known induction heater is the low efficiency due to the large scattering of the magnetic flux and the impossibility of heating the strip across its entire width. In addition, this design can provide a narrow-zone heating only at some specific ratio between the air gap and the pole distance. In other cases, the expected effect is not achieved.

The aim of the invention is to increase the efficiency of the device.

This goal is achieved by the fact that in an inductor for induction heating of a metal strip by a running field containing identical sections installed opposite each other to form a working gap, each of which is made in the form of a magnetic conductor with a three-phase winding placed on it, the magnetic conductors of the sections are made in the form of a central package with a longitudinal straightening and at least two side packages with transverse charge-. This three-phase winding is made in the form of at least one covering the central package of the spiral coil of the middle phase and covering its flat rectangular coils of the extreme phases laid on the surface of the magnetic conduits in such a way that their frontal sections are located on the side packages.

Figure 1 shows the inductor, a general view; figure 2 is the same cross section; on fig.Z - placement of a three-phase combined winding (type A in figure 1)

The magnetic conductors of a two-sided inductor are sectioned and contain central sections 1 and side sections 2 on which combined windings are laid, consisting of concentric coils 3 extreme phases and ring coils 4 of the middle phase. The magnetic cores are mounted on a fixed base by means of the brackets 5 and 6, the winding is attached to the magnetic core by means of a pressure plate 7. The heated strip 8 is placed in the gap of the inductor. The longitudinal magnetic conductor is blended in the direction of a traveling magnetic field; annular coils of the middle phase of a three-phase winding and straight lines of concentric coils of the extreme phases are placed on it. Bo-

The magnetic cores are blended in the transverse direction and located under the frontal parts of the coils of the outer phases.

The inductor works as follows.

Each of the two three-phase windings of a two-sided inductor is connected into a star or delta and is connected to the three-phase current network. In this case, the direction of the currents in the opposite conductors of a two-sided inductor should be such that a transverse magnetic flux is formed in the gap, which would penetrate the metal strip 8, inducing eddy currents in it, which are sources of heat that heat the metal. In this case, the central part of the strip is heated under the action of the traveling magnetic field of the three-phase windings, and the side sections are heated by the eddy currents formed by the pulsating currents of the frontal parts of the extreme phases of the windings. These flows are approximately doubled due to lateral lengths of the magnetic cores. Thereby, uniform heating of both the central part of the strip and its side parts is achieved. The proposed design of the inductor has a good modularity for the purpose of both sequential and parallel placement with respect to the heated strip, in which the advantages noted do not depend on the width of the latter.

Forms of the invention: Inductor for induction heating of a metal strip by a running magnetic field, which are installed opposite one another to form a working gap of the same section, each of which is made in the form of a magnetic circuit with a three-phase winding placed on it, characterized in that , the magnetic cores of the sections are made in the form of a central package with a longitudinal laminating and at least two lateral packages with a transverse laminating, and the three-phase winding is made in the form of at least one Noah covering the central package of the spiral coil of the middle phase and the extreme phases covering its flat rectangular coils, laid on the surface of the magnetic cores so that their frontal areas are located on the side Packs.

Oo 3

U

i

&

i

-

Jl @

f-ri

j

SL CO 01

to

CO

Ni

/

X, 4

Type A

Fig.Z

Claims (1)

Claim An inductor for induction heating of a metal strip by a traveling magnetic field, containing identical sections mounted one opposite the other with the formation of a working gap, each of which is made in the form of a magnetic circuit with a three-phase winding placed on it, so that that, in order to increase the efficiency, the magnetic circuits of sections 45 are made in the form of a central package with a longitudinal charge and at least two side packages with a transverse charge, and the three-phase winding is made in the form of at least one covering st, | the central package of the spiral coil of the middle phase and the flat rectangular coils of the extreme phases surrounding it, laid on the surface of the magnetic cores _: · so that their frontal sections are Fig 2