EP0248090A1 - Aperiodic generator - Google Patents

Abstract

Improvement to inductive heating generators, termed "aperiodic generators", with a view to simplifying their construction, and to reducing the size of the adaptation casings related to the technology of these generators. The improvement consists in using, in the aperiodic transformer, two separate secondary windings each connected to an energy- transporting cable and switched in series or in parallel into the application circuit. <IMAGE>

Description

The present invention relates to an improvement made to induction heating generators, called "aperiodic generators".

In generators constructed according to this technique, there is in the generator itself an adaptation transformer of the aperiodic transformer carrying mainly active energy and whose object is to adapt the operating impedance of the electronic tube used in these generators to the power line. In practice, these transformers consist of a primary and a secondary or of several primary windings and of multiple secondary; these are always identical and interconnected. The transformation ratios usually used are between 5 and 7.

The consequence of this way of doing things is to locate the voltage applied to the energy transport cable at values between 500 and 1200 volts, according to the transformation ratios used as well as according to the voltages applied to the electronic tube of these generators.

As a practical example, for a generator using an operating voltage of 8000 volts, and a transformation ratio of 6, the effective voltage supplied by the lamp would be 8000 s 2 or 5660 volts, which leads to the transformer secondary and, consequently, on the energy transport cable a voltage of 5660 s 6 = 943 volts.

As the frequency of these generators is usually between 50 and 300 KHz, it is necessary to use materials with low dielectric losses for cable insulation.
The multi-conductor cables used for the transport of energy are usually insulated with polyethylene and are the subject of special projects.

In addition, the practical operating voltages used on induction generators are usually between 300 and 500 volts; these voltages being determined by the limit voltages of the capacitor banks usable for low-voltage induction heating.

We are therefore led in practice to have a second transformer usually located at the end of the cable, and which divides the voltage by two. This transformer usually has intermediate sockets allowing the voltage to be adjusted to plus or minus 20% around the ratio of the matching transformer located at the end of the cable.

The object of the present invention is to obtain directly from the aperiodic transformer the practical operating voltages between 300 and 500 volts. For this purpose, on the aperiodic transformer described above each of the secondary and divided into two separate half aecondaries.
tincts each connected to an energy transport cable.

The voltage of energy transport has glued only half of what it was previously. Dielectric losses are divided by four and it is no longer necessary to use special cables.

At the end of these cables, on the use side, these cables can be connected either in series or in parallel so as to obtain exactly the same possibilities as in the case described above. One can add, always on the use side, a transformer or an autotransformer of complementary adaptation allowing an adjustment of the tension to more or less 20% of the power to the maximum and can be reduced in a volume from 1 to 4 approximately compared to the embodiment previously described.

It is thus possible to manufacture adaptation boxes whose volume is itself in a ratio of 1 to 4 compared to previous embodiments. At the same time, this results in a reduction in cost and an improvement in conditions of use since it is desirable to give the user an adaptation box of dimension and weight as reduced as possible.

In the invention patent to which this certificate refers, it is planned to use 2 secondary connected in series or in parallel, in order to simplify the production of adaptation boxes for the generator called "aperiodic generator".

The present invention further simplifies both the production of the aperiodic transformers and the adapter boxes.

The invention consists in making an aperiodic transformer comprising at least one primary winding connected in alternation between the anode of the tube and the cathode and one or more secondary comprising at least three sockets; these three sockets being, one the reference potential, the second the minimum operating voltage, the third the operating voltage.

It is obviously possible to have intermediate sockets between the two sockets in question, but in practice, the voltages per turn used in the high frequency aperiodic transformers being of the order of 150 V; it appears more advantageous to have between the sockets 1 and 2 a separate autotransformer intended to carry out a fine adaptation of the generator to its load.

In the diagram illustrating the device which is the subject of the present invention, the tube VI is connected to the aperiodic transformer Tl where the primary winding is represented at El and the secondary winding E2.

The taps 1 and 2 of this winding are connected to an auxiliary autotransformer T2 intended to carry out a voltage division in order to adapt the generator to its load.

The energy transport line L1 connects this device to the adaptation box, the composition of which is limited to a battery of capacitors CI associated with the inductor N1. 1

A second line L2 brings the voltage drawn across the oscillating circuit CI-NI to the excitation autotransformer T3. The resistance RI is the gate self-polarization resistance which is associated with the decoupling capacitor Cl; C2 is the decoupling capacitor of the anode voltage.

Such a device makes it possible to limit the adaptation box to the single capacitor bank; all the adaptation and excitation transformers found in the generator and no longer as previously in the adaptation box.

In the case of medium frequency generators where the voltages per turn are much lower than at high frequency, (between 30 and 60 V per turn usually), the transformer T2 is no longer necessary because it can be provided directly on the secondary of the aperiodic transformer, the number of sockets allowing the desired adaptation.

If the generator is connected to several adaptation boxes, it is possible to provide switching by contactor, as in the known embodiments, but the same excitation transformers T3 and adaptation T2 are used independently of the number of cabinets while in known embodiments each adapter cabinet required an autotransformer and a separate grid transformer.

Claims (4)

1 ° - Aperiodic transformer consisting of one or more primary windings and characterized by two or more separate windings each connected to a separate energy transport cable for which switching in series or in parallel takes place at the end of use of energy carried by cables. 2 ° - Improvement according to claim (1) characterized by the use of the adaptation transformer located at the end of use of the current carried by the cables and where the said "transformer or" autotransformer allows a variation of more or minus around 20% around the average voltage value expected for this transformer. 3 ° - Aperiodic transformer Tl consisting of one or more separate secondary windings E2 comprising at least 3 sockets on each of the windings. 4 ° - Improvement according to claim (3) characterized by the use of a T2 autotransformer connected between the sockets 1 and 2 of the secondary winding E2; this autotransformer is intended to carry out a fine adaptation of the generator to its load.

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