Electric heating – Inductive heating – Specific heating application
Patent
1997-02-13
1998-10-06
Leung, Philip H.
Electric heating
Inductive heating
Specific heating application
219646, 219661, 219662, 219675, H05B 610, H05B 644
Patent
active
058180133
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a device for inductive cross-field heating of flat metallic material, for example strips and plates, having at least one pair of inductors which form a gap for the material to pass through and whose inductors each have an iron core which has grooves running in the transport direction and each receiving a lead, the grooves and leads of the inductors of a pair of inductors each being mirror symmetrical, and to a process for applying the device.
From DE-A 39 28 629, a device for inductive heating of flat metallic material is known, in which a plurality of independently switchable conductor loops are provided, which each have two conductor parts, the right hand conductor part in each case being just as far away from the right hand edge of the inductor as the left hand conductor part is from the left hand edge of the inductor. By connecting or disconnecting said conductor loops, the effective width of the inductor can be adapted to the width of the material. All the conductor loops switched on are effective at the same time, there is no synchronization.
A device for inductive heating having two lead systems for each inductor is known from PCT/GB 92/02212. In this case, viewed over the width of the metallic material, one lead system generates an approximately sinusoidal course of the induced current flux, the period corresponding to the width of the material. To obtain the desired course and thus to achieve the associated pole width, current flows through a number of adjacent leads of this lead system in the same direction. Owing to the desired matching of the period length and width of the material, the width of the poles is determined by the latter. Said first lead system thus generates an approximately sinusoidal course of the temperature in the material to be heated. The second lead system then likewise generates a sinusoidal course of the induced current flux over the width of the material to be heated, but offset by about .pi./4 compared to the first lead system, with the result that particularly those places of the metallic material which were previously minimally heated by the first lead system are subjected to the greatest heating by said second lead system. For this purpose, the two lead systems can be switched one after the other in time. In this case, operating only one lead system would result in a widely differing temperature distribution and would not be able to be accepted.
The disadvantage of this arrangement consists in the fact that the sinusoidal distribution of the induced current flux predetermined by the inductor only matches a specific width of the metallic material to be heated. Moreover, in this device, complex measures must be taken to avoid overheating of the edges in the metallic material.
SUMMARY OF THE INVENTION
The object of the present invention is now to specify a device of the type mentioned at the beginning and a process for operating this device, with which a temperature course which is as uniform as possible is achieved in the metallic material to be heated and overheating of the edges is avoided.
In a device of the type mentioned at the beginning, the solution of this object is achieved in that the leads of an inductor each have two independently switchable lead systems, each lead system having lead sections which run in the transport direction and whose centre lines are arranged symmetrically with respect to an axis which is central in relation to the inductor and runs parallel to the transport direction, in that the individual poles of the lead systems are formed by a maximum of two leads, and in that a pole of one lead system is arranged in each case between the poles of the other lead system.
According to the invention, the procedure applied with this device is that the two lead systems are switched synchronously and offset in time with respect to one another.
Since a maximum of two leads form one pole, the poles can be of narrow design so that the temperature distribution, viewed over the width of the metallic ma
REFERENCES:
patent: 4122321 (1978-10-01), Cachat
patent: 4788394 (1988-11-01), Vanneste et al.
patent: 5308946 (1994-05-01), Mohr
patent: 5336868 (1994-08-01), Schluckebier
Leung Philip H.
Otto Junker GmbH
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