SU1669657A1 - Method for measurement of voltage drop at closed part of compressed arc of plasma generator of direct effect - Google Patents

Abstract

The invention relates to welding production and can be used to increase the efficiency of controlling the energy parameters of an arc in the development of plasma torches of direct action. The purpose of the invention is to improve the accuracy of measuring the voltage drop in a closed area of a column of a compressed arc of direct action on a plasma torch. A probe is inserted into the arc column in the open area at the exit section of the nozzle channel. The potential between the probe and the electrode is measured at the forward and reverse polarity of the current. The voltage drop across the closed arc column portion is calculated by U formula _c = (U _s + U _s) - (U _a + U _a) / 2 where U _s and U _s - probe potentials relative to the electrode on the forward and reverse polarity respectively

U _a and U _a - cathode and anode voltage drop for the electrode material. The method makes it possible to increase the reliability of the measurement of the voltage drop in the closed section of the arc column and thereby more accurately calculate the probability of the occurrence of the emergency mode of the plasmatron.

Description

The invention relates to welding production and can be used in the design of plasma torches of direct action.

The purpose of the invention is to improve the accuracy of measuring the voltage drop in a closed area of a column of a compressed arc of direct action on a plasma torch.

The method is carried out as follows.

To measure the voltage drop in a closed section of a direct-acting arc column, a probe is preliminarily inserted into a compressed arc column in an open area near the exit section of the nozzle channel, and the potential between the probe and electrode is measured.

the plasmatron, then an additional measurement of the potential between the electrode and the probe is made when the polarity of the arc changes and the voltage drop across the closed section of the column is determined by the formula

Uc (U3p + U 6pHUK + Ua) / 2.

where is the potential between the probe and the electrode at the direct polarity of the arc;

U ° is the potential between the probe and the electrode at the reverse polarity of the arc;

Uk Ua, respectively, cathode and anode voltage drop for electrode material.

Oh oh

u o ate

vj

The potential between the electrode and the probe with the direct polarity of the current is determined by the formula

U2P -UK + Uc-er,

where UK is the cathode voltage drop for the electrode;

Uc is the voltage drop on the closed section of the arc column;

er is the potential difference between the plasma and the probe.

The potential between the electrode and the probe on the reverse polarity of the current is determined by the formula

US6p Ua + Uc + ef,

where Ua is the anodic voltage drop for the electrode material.

The voltage drop across the closed section of the arc column Uc in the direct and reverse polarity is the same, since the processes in the column of the compressed arc are little associated with near-electrode voltage drops. The magnitude of er in this case is taken positive, since the probe is negatively charged relative to the plasma and in this case, the potentials of the arc and the potential er are added. After adding the expressions get

USP + U 6p 2UcHJK + U3

From where

Uc4JSp + U§6p- (UK + Ua) / 2.

In the formula, there is no magnitude er, that is, its influence on Uc is strange.

The measurement accuracy is increased by the same measurement of the voltage drop in the open arc area. For this, the potential of each probe and electrode is measured on the forward and reverse polarity. The values UK and Ua are selected for the part material. If the material of the part and the electrode are the same, then the condition

и§эч + U0 + U + Ua + Ug

The last expression allows you to refine the understanding of Uc and Uo, since they are verified by an accurate measurement of the arc voltage Ug.

Example. The voltage drop was measured at the closed portion of the column of a three-phase compressed alternating current arc at the moment when the maximum current value was reached in the part. Tungsten was used as the material of the electrodes of the two-electrode plasma torch. The arc burned onto a tungsten rod 10 mm in diameter, sealed in a copper water cooled cylinder. The diameter of the nozzle outlet channel mm, dl; 1 on the channel mm Length of the open section of stopba

arc mm The effective value of the current in part A. The maximum instantaneous value of the current is 1 Max. 212 A. The consumption of plasma argon was 18 g / s. A probe of tungsten wire with a diameter of 0.5 mm at a distance of 0.5 mm from the nozzle was placed in the plasma of the open portion of the column of the compressed arc. When measured, the probe was moved through the pole at a speed of 20 mm / s. During the passage of the probe through the pole for 0.25 seconds, the waveform was photographed. In the measurements, the potential of the probe relative to the electrode was first recorded on an electron-beam oscilloscope, and then the experiment was repeated and the potential of the probe was recorded relative to the part. The maximum potential value of the probe voltage was taken as the probe potential at the moment of flow max. By probe waveform

U5P is measured in both direct and reverse polarity. They were made by probe measurements relative to the electrode.

USPH5.4 BU ° 63P 16.4 V. For probe measurements relative to the part, the result was

, 5 V; US3M3.5 V. Voltage at

dependent duguesh was ЈЈaKC 29.5 V. Direct polarity was considered the one at which the probe was connected to the negative electrode. The value of the sum for tungsten electrodes was taken to be 10 V. As a result of calculations, we obtained

UcMO, 9B;

U0 8B;

UЈ8C4 Uc + Uo + UK + U3 28.9 V.

The calculated voltage id differs from the measured one by 0.6 V or by 2%, which confirms the high accuracy of the proposed method of measuring Uc and U0.

The proposed method makes it possible to increase the accuracy of measuring the voltage in a closed section of a column by a factor of 2–3, which makes it possible to effectively take into account the influence of various mode parameters on the energy release in the channel and control the energy characteristics of the arc.

Claims (1)

The invention The method of measuring the voltage drop in a closed section of a direct-acting plasma torch arc column, in which a probe is inserted into an arc column in an open area near the exit section of the nozzle and measured directly in the polarity of the plasma torch, that, in order to improve the measurement accuracy, the potential between the electrode and the zone is additionally measured at the reverse of the current, while The magnitude of the voltage drop at the closed probe and electrode and near the electrode parts of the arc column is determined as the mean voltage of the electrodes at the forward received values of the potential of the inter- and reverse polarity.