JPS6335516Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a high frequency induction heating device, and particularly to a high frequency induction heating device that can efficiently heat conductors such as power cables and communication cables.

Until now, when metals were to be heated by induction using high-frequency high-power waves of 100KHz to 1000KHz, a step-down transformer was connected to a vacuum tube oscillator, and a low-voltage, high-current water-cooled bare copper pipe coil was used for induction heating. However, when a step-down transformer is used, high frequency power is wasted corresponding to the loss. Furthermore, leakage inductance causes an increase in the number of compensation capacitors. On the other hand, when converting to a low voltage with a step-down transformer,
This is particularly advantageous in terms of safety when using bare copper pipe coils. However, when using such a low-impedance method, the high-frequency power supplied to the coil decreases due to the impedance or effective resistance of the lead wire between the transformer and the coil, which reduces the overall induction heating efficiency. There was a problem.

Generally, when supplying a certain amount of power to a load, power transmission efficiency tends to be higher if the voltage at which the power is transmitted is higher within a range that does not pose safety or insulation problems. Therefore, in this case as well, it is desirable to supply the high voltage of the vacuum tube oscillator to the induction heating coil as is unless there is a safety or insulation problem.

The object of the present invention is to provide a high-frequency induction heating device that can directly supply high-frequency high voltage from a vacuum tube oscillator to an induction heating coil, thereby increasing the induction heating efficiency of the entire system.

High efficiency can be achieved if it is safe to apply high frequency and high voltage to the induction heating coil and has sufficient insulation.

For this reason, a plastic film or other insulating paper with low dielectric loss at high frequencies is wrapped around the outside of an insulator, ceramic, or other insulating cylinder to serve as the main insulation, an induction heating coil is wound around the outside, and the whole is housed in a housing. The housing is impregnated with insulating oil to insulate high frequency and high voltage.

The material of the insulating cylinder is selected depending on the temperature of the metal to be heated and other factors.

For example, if the temperature is below 100°C, FRP, Bakelite, hard vinyl, or other organic insulating tubes can be used. If a higher temperature is required, a tube made of heat-resistant insulator, ceramic, or the like with high specific electrical resistance can be used.

In order to prevent the risk of high frequency and high voltage coming into contact with the metal to be heated due to the deterioration of the insulation performance of the induction heating coil, it is sufficient to apply an electrostatic shield to the surface of the insulating cylinder and perform main insulation on top of this.

The main insulator is preferably a material with high dielectric strength and low dielectric loss, such as various low dielectric loss plastic films or plastic fiber papers, low dielectric loss kraft paper, or a combination thereof. These are sufficiently dried and impregnated with insulating oil before use.

An example of the device of the present invention is shown in the accompanying drawings. Insulation tube 1
is an insulator tube with an inner diameter of 80 mm and a thickness of 5 mm, and an electrostatic shield 2 made of wire mesh is applied to the surface of the insulator tube. Main insulator 3
is a semi-synthetic paper made by laminating polypropylene film with insulating paper, and is wrapped to a thickness of 5 mm. A solenoid coil 4 is formed by connecting three 10 mm diameter copper pipes in parallel on the outside and winding them 11 times. The total length of coil part 4 is 50
cm. This was housed in a housing 7 with flanges 8 attached to both ends, and after vacuum drying, it was completely impregnated with insulating oil 5. Both ends of the coil 4 are bushings 6
The vacuum tube oscillator 1 is connected to both ends of the
0 and apply a high frequency voltage of 400KHz, 100KW, 8KV to the inside of the insulating tube ¹ .
was moved at a speed of 10 m/min and heated.
A temperature increase of 100°C was obtained. If the coil 4 is operated continuously in this state, the coil 4 will overheat, so cooling water is made to flow into the pipe 4. Here, coil 4
The voltage is insulated by the main insulator 1 between the electrostatic shield 2 and the coil 4, but even if the main insulator 1 were to break down, it would be shielded by the grounded electrostatic shield 2. There is no fear that the coil voltage will be applied to the twisted conductor 9, which is the metal to be heated, and it is safe. The rated voltage of this coil is 8KV, which matches the output voltage of the vacuum tube oscillator 10 and can be directly connected. This eliminates the need for a step-down transformer, and the high impedance load results in high efficiency.

In the above explanation, the frequency was 100 to 1000KHz,
In principle, it is also effective outside this range.

In addition, if the output of the vacuum tube oscillator is an unbalanced type, the main insulation should be tapered in the length direction of the coil, and the insulation thickness on the ground potential side should be thinner to make the diameter of the coil smaller. It is also good to increase efficiency by improving coupling.

It is also a good idea to install a ferrite core or a dust core on the outside of the induction heating coil to reduce magnetic resistance and improve efficiency, or to reduce magnetic field leakage to the outside to reduce induction disturbances. It is also a good idea to cover the outside of the housing with a copper or aluminum cylinder to reduce the induced interference to the outside.

As explained above, the device of the present invention has a coil with sufficient dielectric strength, which makes it possible to directly connect a high-frequency power oscillator to the coil, greatly improving efficiency. It is possible to reduce the size and cost of the device.

[Brief explanation of the drawing]

The accompanying drawings are explanatory diagrams of one embodiment of the present invention. 1... Insulating tube, 2... Electrostatic shield, 3... Main insulator, 4... Solenoid coil, 5... Insulating oil, 6
...Bushing, 7...Housing, 9...Heated object, 10...Vacuum tube oscillator.

Claims (1)

[Scope of utility model registration request] This is a high-frequency induction heating device that induces an induced current in a continuously traveling conductive filament, and the device includes a hollow insulating cylinder that penetrates the filament in the length direction;
A main insulator with low dielectric loss at high frequencies is provided on the outer periphery of the insulating cylinder, a solenoid coil is further wound around the outer periphery of the main insulator, and the whole is housed in a housing, and electrical insulating oil is filled in the housing. A high frequency induction heating device characterized in that a vacuum tube oscillator is directly connected to the solenoid coil.