SU1315497A1 - Induction heating arrangement - Google Patents

Abstract

The invention relates to the field of induction heating products in induction furnaces. The purpose of the invention is to reduce energy consumption. The cost of the invention is that during the heating process, temperature sensors 5 measure the temperature of the product along its length. If there is a mismatch between the measured temperature and the given sensor 7, the resistance of the corresponding regulator 8 and the current in one of the additional windings 4 change. Thus, the field from is added to the main field of the inductor 2. additional winding, which ultimately leads to temperature equalization along the length of the product. In addition, the adder 10 summarizes the signals proportional to the currents in all additional windings 4 measured by sensors 9, which leads to a change in the signal at its output and, accordingly, to a change in the power supply of the inductor 2. 1 Il. (L D L ffi i U U Ui 00 SP 4i CO vl

Description

one . .

The invention relates to mechanical engineering and metallurgy and can be used mainly in induction furnaces for heat treatment and brazing of metal products.

The aim of the invention is to reduce power consumption.

The drawing shows a block diagram of the system.

The power source 1 is connected to the main winding of the inductor 2, inside which is heated workpiece 3, covered, in addition, by additional windings 4, each of which is located above the part of the workpiece, the temperature of which is monitored by a corresponding sensor

5temperatury. Each of the temperature sensors is connected by its output to the first input of the corresponding node.

6 comparison. The second inputs of the comparison nodes are given a reference signal from setpoint 7, and the outputs of these nodes are connected to control inputs of current regulators 8, which are located in the circuits of windings 4. In series with each regulator, the sensor of current 9 of the corresponding winding is connected. The signals from the current sensors are fed to the inputs of the adder 10, the output of which is connected to the control input of the power supply 1.

V. Thermoelectric thermometers can be used as temperature sensors 5. Comparison units 6 can be made according to the subtractor circuit, and current regulators 8 - according to one of the thyristor controllers. The sensors 9 current can be performed on the basis of current transformers.

The current in the additional windings flows due to the EMF of mutual induction induced in the additional windings by the magnetic field of the main winding of the inductor 2.

The device works as follows.

When the power source 1 is turned on, an electric current begins to flow through the inductor 2. By the electromagnetic field of the inductor, the workpiece 3 is heated and the emf of mutual induction in the additional windings 4 is induced. However, until the temperature at the controlled points has reached a predetermined level, from the output of the nodes 6 comparison

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The control inputs of the current regulators 8 receive negative signals, the resistance of the current regulators 8 is high, so the current through the additional windings 4 does not flow. If the temperature at the controlled points reaches a predetermined level at the same time, the ejector operates, and the workpiece is discharged from

0 inductor (pusher and control circuit are not shown).

However, the temperature at one or several points can reach a predetermined level earlier than at the rest. When the temperature in any of the monitored points exceeds a predetermined level, a positive signal appears at the output of the corresponding comparison node 6; Resistance

7P

 current regulator 8 decreases as a current starts to flow along the corresponding additional winding, causing the emf of mutual induction to flow. There is own electromagnetic field of this additional winding. By the force of the law of electromagnetic inertia, the appearing electromagnetic field of the additional winding is directed opposite to the main inductor GEO. Thus, the appearance of the current of this additional winding calls for a local decrease in the intensity of the resulting electromagnetic field in a certain vicinity

35 of the additional winding, and consequently, a decrease in the intensity of heating of the workpiece 3 near this additional winding. Moreover, the more the temperature of a certain point of the surface is greater than a predetermined level, the lower the resistance of its current regulator 8, and therefore, the greater the current of this additional winding 4, thus creating the prerequisite for equalizing the temperature along the length of the workpiece 3.

However, under the action of deep disturbances, leading to significant

5Q temperature drops along the length of the workpiece 3, the action of only additional windings 4 either does not bring the desired result or is associated with significant losses. In order

with; In order to effectively reduce the significant overheating of any zone of the workpiece 3, it is necessary to reduce the resulting field (the sum of the inductor floor and the fields of the additional windings) in

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This zone is below the heat loss power level. This means that the own field of additional windings located in this zone should be comparable in intensity with the inductor field, and this is possible only with significant additional windings, respectively, there are large losses in the windings. Therefore, it is proposed to maintain power control of power supply 1 as a function of the sum of the currents of all additional windings. The sum of the currents of the additional windings acts as an indirect, but easily measurable, criterion of temperature uniformity along the length of the workpiece 3.

As follows from the description of the operation of the regulators 8 of the current strength of the additional windings 4, the current of the winding 4 is maximum at the maximum deviation of the temperature of this zone of the workpiece 3 from the specified level. Current appearance

 in any of the additional windings 3 is registered by the corresponding current sensor 9. The sum of the signals of all current sensors 9 from the output of the adder 10 is fed to the control input of the power source 1. The larger the signal at the output of the adder 10, the

 the temperature of the workpiece 3 exceeds the required level by a large amount and in a greater number of points, the more the currents of the additional windings 4 and the greater the loss in them.

When a signal arrives at the control input of the power supply 1, the power supply capability is reduced. The main disturbance leading to uneven temperature field

Editor N. Gunko

Order 2318/27 Circulation 549 Subscription VNIIPI USSR State Committee.

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

974

the length of the workpiece 3, is the uneven distribution of the heating power along the length of the inductor, therefore, with a decrease in the power of the power source, the unevenness of the temperature field also decreases, and more intensively than with the action of additional windings. The non-uniformity of heating in this case decreases the currents of the additional windings also decrease. This makes it possible to reduce energy losses in the windings, and, consequently, to increase the efficiency of the device as a whole.

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Claims (1)

Invention Formula An induction heating device containing an inductor connected to a power source and inductively connected with it additional windings, in series with each of which the current regulator is connected, as well as. According to the number of additional windings, temperature sensors and comparison nodes, the temperature sensor outputs are connected to the first inputs of the comparison nodes, the second inputs of which are connected to the temperature sensor, and the outputs - to the control inputs of current regulators, reducing energy consumption, it is equipped with an adder, current sensors connected in series with current regulators, and the inputs of the adder are connected to the outputs of sensors. current, and the output is connected to the control input of the power supply. Compiled by A.Abrosimov Tehred M. Khodanich Proofreader S. Shekmar