JPS61279093A - Induction heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an induction heating device that heats billet material, bar material, wire material, etc. by continuously passing it through an induction heating coil.

[Technical background of the invention and its problems]

This type of induction heating device is generally configured to heat and raise the temperature of a material to be heated by passing it through a plurality of induction heating coils that are continuously wound in a solenoid shape. In this induction heating device, each induction heating coil arranged in a straight line is energized by each independent power source.

By the way, when multiple induction heating coils are operated with power supplied from their respective power sources, the magnetic flux generated in the heating coils may interfere with adjacent coils, preventing them from evenly heating the material to be heated. Depending on the situation, the power supply may be affected and operation may be disrupted. For this reason, the distance between the heating coils should be kept large to prevent the influence of magnetic flux between adjacent coils, but methods such as installing a magnetic shield plate or iron core on the heating coil to eliminate the influence of magnetic flux have been adopted. ing.

However, among these conventional measures, the former method of separating the heating coils by a large distance requires a large space for installing the heating coils.

In addition, in the latter case, which includes a magnetic shielding plate, the magnetic shielding plate constitutes a kind of heat dissipation part, resulting in poor thermal efficiency.
Moreover, the loss generated in the magnetic shielding plate also increases, and the energy saving effect is also reduced.

[Purpose of the invention]

An object of the present invention is to provide an efficient and compact induction heating device that is not affected by mutual induction between adjacent heating coils even when a plurality of heating coils are arranged close to each other.

[Summary of the invention]

The induction heating device according to the present invention is characterized in that a plurality of induction heating coils are each connected to an individual power source, and each adjacent power source is operated with its frequency shifted within a certain range. .

[Embodiments of the invention]

The present invention will be explained below with reference to embodiments shown in the drawings.

In FIG. 1, a plurality of induction heating coils la, lb
... are arranged in a straight line at predetermined intervals, and the heated material 2 is passed through each of the heating coils la and lb.
The temperature is increased by passing through it. The heating coils la and lb are connected to individual power sources 4a and 4b via power factor improving capacitors 3a and 3b, respectively. FIG. 2 shows an equivalent circuit of the heating coils la, lb and capacitors 3a, 3b connected to the respective power sources 4a, 4b.

C1y capacitor 3 to capacitance of capacitor 3a with 2N
The capacitance of b is C1ot, the inductance of heating coil la is L□, the inductance of heating coil lb is Lift, and further L(・CL～L,+,・Ck+
Set to 1.

Now, in the equivalent circuit of FIG. 2, the relationship between the frequency f□ and the load in each power source 4a, 4b for efficiently operating the heating coils la, lb connected to the power sources 4a, 4b will be shown.

becomes.

Now, to change the frequency of the adjacent power supplies 4a and 4b, change the CL of the connected capacitor 3,
or changing the heating coil 2, or both. That is, adjacent heating coils La, lb
The circuit condition is to set Li'ct''FLt+x・C1+t.This means that the impedance 2 when looking from one coil to the adjacent coil is 2πf l)''LL・C1=1.

Therefore, the more the frequencies f and j' Lax differ, the smaller the impedance Z of the adjacent coil viewed from one side becomes, and the less interference due to mutual induction becomes. However, in order to reduce interference, the difference in frequency should be set to a certain level, but it is recommended to set the difference to approximately 10 to 40%, taking into account temperature distribution and electrical impedance matching. good. In order to change the frequency of each power source 4a, 4b, if an inverter capable of variable frequency is used for the power source 4a, 4b, the frequency can be adjusted arbitrarily.

〔Effect of the invention〕

As described above, according to the present invention, the frequency of the power supplies individually connected to a plurality of MR heating coils is operated by shifting them within a certain range, thereby shortening the distance between the arrangement intervals of each heating coil. However, interference due to mutual induction is reduced, and heat radiation loss is reduced with a minimum installation space, which has the advantage of achieving a sufficient energy saving effect.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of an induction heating device according to the present invention, and FIG. 2 is an equivalent circuit diagram of FIG. 1.

Claims (3)

[Claims] (1) An induction heating device characterized in that a plurality of induction heating coils are each connected to an individual power source and are operated by shifting the frequency of each adjacent power source by a certain range. (2) Frequency deviation range between adjacent power supplies is 10~
Claim 1 characterized in that it is about 40%.
Induction heating device as described in section. (3) The induction heating device according to claim 1, wherein the power source is a variable frequency inverter.