CN101126774A - Arc root current density distribution test method and device - Google Patents

Abstract

The utility model discloses a testing method and device for electrical arc root ampere density distribution, comprising an anode and a cathode; wherein the cathode comprises a first cathode and a second cathode which are arranged on the same plane; a narrow gap of 50 to 200 Mum is arranged between two cathodes which are separately connected with a current transmitter. The current transmitter is also connected with the broadband oscilloscope. Driven by the outer magnetic field Bext or air current, the electric arc passes through a narrow gap which is arranged at motion direction Vx of vertical electrical arc root between the cathodes. Current signal is collected by the oscilloscope. The speed of the electrical arc root passing through the narrow gap is tested by measuring the self-magnetic field of the electrical arc or by high-speed photographic instrument. A mathematical model, which is for the relationship for the current I2 passing through the cathode and the arc root circuit region ampere density distribution (Jr) and for the arc root circular region center and the cathode edge distance x, is made when the electrical arc root passes through the narrow gap. The integral equation of the mathematical model is analyzed and value solution is given. Current signal is processed by the value method and the curve is given for the electrical arc root ampere density distribution.

Description

A kind of electric arc arc root current density distribution test method and device

Technical field

The invention belongs to electrical equipment electric arc technical field of measurement and test, be specifically related to a kind of electric arc arc root current density distribution test method and device.

Background technology

Arc phenomenon is the fundamemtal phenomena that occurs in the device such as various alternating current-direct current isolating switchs, contactor, arc heated and arc welding, thereby the degree of going deep into of the research of electric arc parameters is being determined the height of the research and development level of this type of device.

Electric arc arc root under the atmospheric gas pressure is the zone that electric arc contacts with electrode, it is generally acknowledged that the cathode arc root is flocked together by spot small, high brightness many and that deposit to form, and promptly electric arc arc root is the zone of the cathode protection sub-circular of assembling.According to the arc root ablation pit on high-speed camera and the SEM scanning electron microscopic observation electrode surface, the result shows that electric arc arc root is rounded.Electric arc arc root current density is an important parameters of electric arc, and the heat flow density of its decision electric arc, the temperature in arc root zone and electric arc are to the parameters such as erosion ratio of electrode.Electric arc arc root current density distributes and is meant current load zone current distributions in the electric arc arc root circle, it is determining that arc root zone energy flux density distributes, the Temperature Distribution in arc root zone and electric arc is to the distribution parameters such as erosion ratio distribution of electrode, therefore, the distribution of arc root current density is an important parameter of electric arc equally.

In recent years, along with the develop rapidly of computer hardware technology and becoming stronger day by day of fluid software for calculation function, by this magnetic fluid of electric arc being carried out emulation under the electric switch environment to explain and to predict its all The Characteristic Study, and the application of result that this research institute is obtained is in the electric switch new product development, the expensive experimental cost can be saved, product development cycle can be accelerated again.

In naval vessel live power equipment field, increase along with shipping capacity, the direct current power system capacity that needs further increases to satisfy its power requirement, therefore needs further researching DC high-current on-off technology, cut-offs technology as middle straightening stream current limiting of breaker.But centering straightening stream isolating switch interrupting process electric arc simulation analysis needs electric arc arc root current density distribution boundary condition, and does not have convenient and practical electric arc arc root current density method of testing and device respectively at present.

The distribution of electric arc arc root current density all is the focus that people pay close attention to all the time, also is simultaneously one of difficult point of electric arc research.In the past, electric current distribution boundary condition to electric arc arc root is rule of thumb to be set to axisymmetric exponential distribution with the radial distance decay, rather than be provided with according to the experiment test result, and the experiment test result has higher confidence level, and therefore testing the distribution of electric arc arc root current density by experiment can be for providing necessary reliable basis for the electric arc simulation study.Distribution is tested thereby is become important task in the electric arc experimental study to electric arc arc root current density.

In general, the method of measuring the arc root current density has high-speed photography to take the method for the instantaneous form of electric arc arc root and the SEM scanning electron microscopic observation method through electric arc arc root ablation rear electrode surface microscopic form, and these two kinds of methods can only be used for finding the solution the average current density of electric arc arc root.During electric current distribution, exist more insoluble problem in these two kinds of methods analyst arc roots circle territories, therefore seeking a kind of test electric arc arc root current density location mode rational and simple to operate has very important realistic meaning.

Summary of the invention

The object of the present invention is to provide a kind of making simple, cost is low, and testing procedure, numerical value are handled simple, and has the electric arc arc root current density distribution test method and the device of higher accuracy and confidence.

For achieving the above object, the inventive system comprises: comprise anode and negative electrode, this negative electrode comprises and is arranged on conplane first negative electrode and second negative electrode, the slit that 50-200um is arranged between two negative electrodes, two negative electrodes are connected with current transducer respectively, and this current transducer also is connected with data acquisition equipment.

Be provided with insulation polyester lacquer in the slit of the present invention; Data acquisition equipment is a wide band oscilloscope tube.

Method of testing of the present invention is: trigger electric arc between first negative electrode and the anode externally under the effect of transverse magnetic field Bext or air-flow, to second cathode motion, the current signal that flows through first negative electrode and second negative electrode send sensor to be collected by wide band oscillograph by electrorheological respectively, when triggering electric arc arc root circle territory by the time, flow through the electric current I of two electrodes perpendicular to the slit of two negative electrodes of electric arc arc root direction of motion ₁And I ₂Along with the state by slit changes, variation tendency obtains the time of electrode arc root by slit thus, with this mistiming, is used in combination high-speed camera or measures the arc motion speed that the method for electric arc self-magnetic field records, obtain electrode arc root radius and diameter, and then according to 2R _s=v _sΔ t obtains current density value; Wherein, v _sBe electric arc arc root speed by slit under magnetic field or air-blowing effect; Δ t is that electric arc arc root is from arriving second cathode-side edge to entering second cathode zone time constantly fully; R _sIt is electric arc arc root radius; Mathematical model when setting up the arc root by slit according to current density value is by the electric current I of second negative electrode ₂Promptly be exactly the integration of the lap of the electric arc arc root circle territory and second negative electrode, set up current density $I\left(x\right)=2\underset{x}{\overset{R_s}{\∫}}J\left(r\right)\·\arccos \left(\frac{x}{r}\right)\·\mathrm{rdr},$ The measuring current Density Distribution is converted into finds the solution integral equation, by I ₂Variation tendency obtain the electric current distribution curve.

Test unit of the present invention is made simple, and cost is low, and the testing equipment performance requirement is not high, and test procedure, numerical value are handled simple, and have higher accuracy and confidence.

Description of drawings

Fig. 1 is that driving electric arc arc root of the present invention is by isolating negative electrode slit measuring current Density Distribution method schematic diagram;

Fig. 2 is that electric arc arc root of the present invention is by slit signal and two electrode current changing trend diagrams between two negative electrodes;

Fig. 3 is the graph of a relation of electrode current of the present invention with x variation tendency and electric current distribution;

Fig. 4 is a test arc root current density distribution implementation process original state of the present invention;

Fig. 5 is a test arc root current density distribution implementation process starting the arc state of the present invention;

Fig. 6 is the electric arc arc root of test arc root current density distribution implementation process of the present invention state when crossing slit;

Fig. 7 is the state of test arc root current density distribution implementation process electric arc of the present invention when running slit.

Embodiment

Below in conjunction with accompanying drawing the present invention is described in further detail.

Referring to Fig. 1, the present invention includes anode 1 and negative electrode, this negative electrode comprises and is arranged on the slit 6 that 50-200um is arranged between conplane first negative electrode 2 and second negative electrode, 3, two negative electrodes, is provided with insulation polyester lacquer in the contact slit 6 of two negative electrodes.Two negative electrodes are connected with current transducer 5 respectively, and this current transducer 5 also is connected with wide band oscilloscope tube 9.The electric arc 4 of triggering is arranged between two negative electrodes and anode 1, and this triggers externally transverse magnetic field B of electric arc 4 _ExtOr under the effect of air-flow 8, to 3 motions of second negative electrode, the current signal that flows through first negative electrode 2 and second negative electrode 3 send sensor 5 to be collected by wide band oscillograph 9 by electrorheological respectively.When triggering electric arc 4 arc roots circle territory by the time, as shown in Figure 2, flow through the electric current I of two electrodes perpendicular to the slit 6 of two negative electrodes of electric arc arc root direction of motion ₁And I ₂Along with the state by slit 6 changes, variation tendency obtains the time of electrode arc root 7 by slit thus, with this mistiming, be used in combination high-speed camera or measure the arc motion speed that the method for electric arc self-magnetic field records, can be in the hope of electrode arc root radius and diameter, and then try to achieve current density value.

2R _s＝v _sΔt (1)

In the formula (1), v _sBe electric arc arc root speed by slit under magnetic field or air-blowing effect; Δ t is that electric arc arc root 7 is from arriving second negative electrode, 3 edges to entering the 3 zone times constantly of second negative electrode fully; R _sIt is electric arc arc root radius.

Can be by formula (1) in the hope of electric arc arc root watt current regional diameter, the result who tries to achieve is an electric arc arc root average current density.

On this basis, mathematical model when setting up the arc root by slit, as shown in Figure 3, by the electric current I of second negative electrode 3 ₂Promptly be exactly the integration of the lap of the electric arc arc root 7 circle territories and second negative electrode 3, set up this relation as the formula (2), therefore by I to current density ₂Variation tendency in can obtain the electric current distribution curve, promptly measuring current Density Distribution problem is converted into the problem of finding the solution following integral equation:

$I\left(x\right)=2\underset{x}{\overset{R_s}{\∫}}J\left(r\right)\·\arccos \left(\frac{x}{r}\right)\·\mathrm{rdr}---\left(2\right)$

Integral equation is the integral equation with weak singularity, satisfies the existence of Solution of Integral Equation and the necessary condition of uniqueness.

According to concrete test event, as flame current and voltage magnitude, and the factors such as volume of tested device, according to the mode of Fig. 4, in addition suitable adjustment just can be formed the test platform that distributes with the electric arc arc root current density based on this principle.

Referring to Fig. 4,5,6, shown in 7, the present invention also is provided with the fuse 11 that is attached thereto between the anode 1 and first negative electrode 2, anode 1 links to each other with power supply 15 respectively with two negative electrodes, and the circuit that anode 1 is connected with power supply is provided with contactor 12, the circuit that negative electrode is connected with power supply 15 is provided with thyristor units 16, this crystalline substance brake gear 16 links to each other by the high-speed camera 10 of controller with observation electric arc arc root movement velocity, and anode 1 and two negative electrodes are respectively arranged with and drive in the arc field coil 13, this coil 13 links to each other with coil excitation current rectifier assembly 14, on perpendicular to the arc motion direction, with two cathode isolation, should avoid the contact of negative electrode two parts with the slit 6 of 50um-200um.The race cambered surface of two negative electrodes should keep at grade, run the test result that the cambered surface surface quality helps obtaining preferably, therefore will run cambered surface to electrode before experiment carries out necessary surface treatment, remove surface filth and oxide layer, after perhaps after repeatedly running arc, the surface being handled, remake official testing by electric arc.Keeping under the discontiguous situation of two negative electrodes, slot distances is more little, and is littler to electric arc arc root current interference, and test result is also just good more.The mode of opening with fuse 11 or contact between first negative electrode 2 and anode 1 triggers electric arc 4, as shown in Figure 5, triggers externally transverse magnetic field B of electric arc 4 _ExtOr under the effect of air-flow, to slit 6 motions.When the arc root was crossed over slit 6, as shown in Figure 6, the current signal that flows through first negative electrode 2 and second negative electrode 3 changed, and the electric current that flows through first negative electrode 2 descends rapidly and the electric current of second negative electrode 3 rises rapidly.When electric arc arc root 7 arrived second negative electrode, 3 surperficial going up fully, as shown in Figure 7, the electric current of first negative electrode 2 was zero, and the electric current of second negative electrode 3 equals total flame current.The information that is containing the electric current distribution of pointing out by above-mentioned model in the variation tendency of electric current.The electric current that flows through negative electrode obtains by oscillograph 9 or other recording apparatus collecting of current transducer 5 by the frequency band broad.In addition, when test, should guarantee that first negative electrode 2 and second negative electrode 3 are in same current potential.

In the experiment, require power supply 15 current output signals output level and smooth as far as possible, contain or do not contain high-frequency interferencing signal less, help the processing of data like this and reduce the error of experimental result, thereby obtain test findings more accurately.Because electric arc arc root 7 is very short by the time of slit 6, therefore can should when building, experiment porch be avoided reducing the passband of test macro by complete acquisition for guarantee information; In addition, in order to improve resolution, when test, adopt the oscillograph 9 of broader bandwidth to obtain fast-changing current signal with the contained useful information of complete acquisition current signal to signal frequency domain.

Velocity amplitude when the electric arc arc root 7 that the current signal that collects is used in combination high-speed camera 10 observation is by slit 6 at last, by handling accordingly, can draw the electric current distribution curve of electric arc arc root when motion based on the numerical algorithm of above-mentioned mathematical model principle.

Claims (4)

1. electric arc arc root current density distribution tests device, comprise anode (1) and negative electrode, it is characterized in that: this negative electrode comprises and is arranged on conplane first negative electrode (2) and second negative electrode (3), the slit (6) that 50-200um is arranged between two negative electrodes, two negative electrodes are connected with current transducer (5) respectively, and this current transducer (5) also is connected with data acquisition equipment (9).

2. electric arc arc root current density distribution tests device according to claim 1 is characterized in that: be provided with insulation polyester lacquer in the said slit 6.

3. electric arc arc root current density distribution tests device according to claim 1, it is characterized in that: said data acquisition equipment is a wide band oscilloscope tube 9.

4. the method for testing of a device according to claim 1 is characterized in that: trigger externally transverse magnetic field B of electric arc (4) between first negative electrode (2) and the anode (1) _ExtOr under the effect of air-flow (8), move to second negative electrode (3), the current signal that flows through first negative electrode (2) and second negative electrode (3) send sensor (5) to be collected by wide band oscillograph (9) by electrorheological respectively, when triggering electric arc (4) arc root circle territory by the time, flow through the electric current I of two electrodes perpendicular to the slit (6) of two negative electrodes of electric arc arc root direction of motion ₁And I ₂Along with the state by slit (6) changes, variation tendency obtains the time of electrode arc root (7) by slit (6) thus, with this mistiming, be used in combination high-speed camera or measure the arc motion speed that the method for electric arc self-magnetic field records, obtain electrode arc root radius and diameter, and then according to 2 R _s=v _sΔ t obtains current density value; Wherein, v _sBe electric arc arc root speed by slit under magnetic field or air-blowing effect; Δ t is that electric arc arc root (7) is from arriving second negative electrode (3) edge to entering second negative electrode (3) the zone time constantly fully; R _sIt is electric arc arc root radius; Mathematical model when setting up the arc root by slit (6) according to current density value is by the electric current I of second negative electrode (3) ₂Promptly be exactly the integration of the lap of electric arc arc root (7) circle territory and second negative electrode (3), set up current density $I\left(x\right)=2\underset{x}{\overset{R_s}{\∫}}J\left(r\right)\·\arccos \left(\frac{x}{r}\right)\·\mathrm{rdr},$ The measuring current Density Distribution is converted into finds the solution integral equation, by I ₂Variation tendency obtain the electric current distribution curve.

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