SU1449269A1 - Apparatus for exciting electric arc in plasmatron - Google Patents

Abstract

The invention relates to engineering and is intended to energize an electric arc during plasma welding. The goal is to increase the excitation reliability of the main plasma arc. The device contains a welding power source, supply -. protective output capacitor, a serial-type oscillator and a plasma torch. The plasma torch nozzle is connected to a welding power source through a high-frequency choke and a limiting resistor connected in parallel with a shunt capacitor. A high-frequency choke, whose impedance is in the range of 0.2-0.7 to the oscillator impedance, ensures that the stand-by arc potential is maintained relatively to the product being welded. The device allows you to increase the reliable excitation distance from the plasma torch to the product by providing a high duty arc potential. 1 hp f-ly, 1 ill. (L

Description

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The invention relates to mechanical engineering and is intended to initiate an electric arc during plasma welding.

1The invention is to improve the reliability of the excitation of an OCHOBJ plasma arc.

The drawing shows a circuit diagram of a device for initiating an electric arc in a plasma torch.

The device contains a welding power source 1, an oscillator 2, a plasma torch 3 containing an electrode 4 and a nozzle 5, a protective capacitor 6, a shunt capacitor 7, a limiting resistor 8, a high-frequency inductor 9 and the welded product 10 The first output of the welding power source 1 is connected to a protective capacitor 6 and through an oscillator 2 of the sequential type with the electrode 4 of the plasma torch 3.

The second output of the welding power source 1 is connected to the product to be welded 10. The nozzle 5 of the plasma torch 3 is connected to a high-frequency choke 9, the other end of which is connected in parallel to the duty arc current limiting resistor 8 in parallel and the shunt capacitor 7 to the product to be welded 10. The device operates as follows.

When the oscillator 2 is turned on, a high-voltage high-frequency voltage across the circuit: a protective capacitor 6, a welded product 10, a shunt capacitor 7, a high-frequency wire; a sel 9 is applied to the gap of the nozzle electrode. A gap breakdown occurs, in which the current depends on the magnitude of the internal oscillator resistance jfa 2, the magnitude of the impedance of the high-frequency throttle 9 and the resistance of the spark gap

 Spark breakdown of the electrode-nozzle leads to the arming of the pilot arc, which is supplied from the welding source 1 through the limiting resistor 8 and the high-frequency choke 9, whose resistance to direct current is negligible.

When a pilot arc arises, the resistance of the gap electrode-nozzle drops sharply and becomes

1-2 times less than the total internal resistance of the oscillator, which leads to a redistribution of the voltage generated at the output of the oscillator 2.

Taking into account the high conductivity of the pilot arc, the high-frequency potential of the arc torch is relatively

The welded product 10 is proportional to the ratio of the impedance of the high-frequency choke (Z dr) and the total internal resistance of the oscillator (Z o) and should be 5,17–0.41 of the no-load voltage of the oscillator. When using standard oscillators, this potential is 600–3000 V. High potential

0 plasma torch relatively

the welded product allows to destroy oxide films on the surface of the product, additionally ionizes the gas gap between the plasma

5 by the torch and the product, which significantly increases the stability of the excitation of the main arc and the distance of the reliable excitation.

After exciting the main arc

 oscillator 2 is turned off.

The magnitude of the inductance of the high-frequency choke is chosen from the following considerations.

Z AR

With respect to -; - 0.2 potential

the pilot arc torch decreases below 600 V, which is not enough to destroy oxide films on the surface

Z Ap

0 products, and at 7 0.7 the corresponding

the throttles already significantly reduces the spark current, which reduces the excitation reliability of the duty

5 arcs. And, as a result, the main arc. The use of the device makes it possible to significantly increase the reliability of the excitation of the main arc, especially reverse polarity, to increase the distance between the nozzle and the product when the arc is excited, which increases the reliability of the plasma torch as a whole, since the probability of double arcing is reduced.

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Claims (2)

1. A device for initiating an electric arc in a plasma torch. Contains a welding power source, in parallel with which a protective capacitor is connected, the first output of the welding power source is connected to a sequential type arc exciter, the output of which is connected to the plasma torch electrode, the second output of the welding power source is connected to parallel connected limiter resistor and shunt capacitor that are connected to the plasma torch nozzle characterized in that, in order to increase the excitation reliability of the main plasma arc. between the nozzle of the plasma torch and parallel connected limiting resistor and shunt capacitor installed high-frequency droop-: sel. I 2. The device according to claim 1, which is the fact that the inductance value of the high-frequency throttle is chosen such that at the oscillation frequency of the oscillator, the impedance of the high-frequency throttle is 0.2 0.7 of the total internal resistance of the oscillator .