SU140671A1 - Unipolar current pulse generator for electrical discharge machining of materials - Google Patents

Description

Unipolar current impedance generators for electrical discharge machining of materials are known, which contain a storage capacitor connected to a DC source through resistance.

The proposed generator differs from the known ones in that it contains a transformer with a saturated core or a core of a material with a rectangular magnetization curve, the primary winding of which is connected through the limiting resistance parallel to the storage capacitor, the secondary winding is connected in series with the erosion gap, and the bias winding is connected to the source direct current.

Such an embodiment of the generator simplifies the design and allows to increase its average power at a given pulse energy.

The drawing shows a schematic diagram of the proposed generator.

The generator contains a storage capacitor / charged from a DC source, and a transformer 2, the primary winding 3 of which is connected in parallel with the storage capacitor, and the secondary winding 4 is connected in series with an erosion gap of 5 .:

To improve transformer operation, limiting resistance 6 is included in the primary winding circuit, and the transformer core is made of a material with a rectangular magnetization curve, for example, permallo or ferrite.

To remagnetise the core, the transformer is provided with a bias winding 7. connected to a direct current source.

No. 1406712 The use of a transformer 2 allows the counter-emf to be introduced into the discharge circuit, which varies according to the law of voltage variation on the capacitance of the working circuit, in order to create interruptions in the supply of voltage to the erosion gap at the time of capacitor charging. The interruptions in the supply of voltage to the erosion gap improve deionization conditions in it and make it possible to increase the charging rate of the capacitor without the risk of the spark process moving into an arc process. This circumstance makes it possible to significantly increase the generator frequency at a given pulse energy and, therefore, increase the average power of conventional relaxation generators.

In order to create interruptions in the supply of voltage at the erosion gap 5, the secondary winding 4 of the transformer 2 is turned on in such a way that the emf is induced in it. had a reverse polarity relative to the voltage on the storage capacitor, the value was equal to or close to it.

With such switching on, the voltage across the erosion gap during the period of charging of the capacitor / will be practically zero. As the capacitor charges, the rate of change of voltage on it decreases and, consequently, the voltage induced in the secondary winding of transformer 2 decreases. As a result, at the end of the process of charging the capacitor, the voltage on the erosion gap sharply increases.

In order to limit the current in the primary winding 3 of the transformer, after the end of the transient process, the ballast resistance 6 or the semiconductor triode, which does not allow the current to rise above the magnet current of the transformer, turns on.

In order to reduce the counter emf in the secondary winding of the transformer, when discharging the capacitor, the core of the transformer must be made of magnetic materials with a rectangular namag loop; piping and performing its magnetic circuit so that by the end of the process of charging the capacitor its saturation occurs.

After charging the capacitor for normal operation of the generator, it is necessary to remagnetize the transformer core. This is done by changing the polarity of the voltage on the capacitor when it is recharged by the electromagnetic energy of the discharge circuit, or by means of the bias winding 7. Due to the fact that when the core is re-magnetized in the secondary winding 4, the transformer induces e. DS opposite to the polarity of the voltage on the capacitor when it is recharged, the proposed generator will not have a negative half-wave current in the discharge circuit, which is observed in conventional relaxation generators.

The duty cycle of the voltage pulses can be adjusted by selecting the appropriate transient process in the primary circuit of the transformer, as well as by measuring the time at which its core becomes saturated relative to the moment when the capacitor starts charging.

The proposed method of interrupting the supply of voltage to the erosion gap 5 can be applied to generators with a storage capacitor charged in the general case through some resistance 8 or some interrupter.

Subject invention

A generator of unipolar current pulses for electrical erosion of material processing, containing a storage capacitor connected to a DC source through resistance, so that, in order to simplify the design and increase the average power of the generator at a given pulse energy , it contains a transformer with a saturated core or with a core of a material with a rectangular magnetization curve, the primary winding of which is connected through the limiting resistance parallel to the accumulative at the condenser, the secondary winding is connected in series with the erosion gap, and biasing coil is connected to a DC source.

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No. 140671