Testing electrical contact connections

External inspection of contact connections

External control controls: the quality of metal coatings on the details of the contact joints, the tightness of the contact surfaces of the flat folding electrical contact joints (with such a test between the connection planes of conductive parts, the probe with a thickness of 0.03 mm should not enter outside the area under the perimeter of the washer or nut; if the washers are of different diameters, the area is determined by the diameter of the smaller washer); geometric dimensions of the pressed part of non-detachable electrical contact joints, absence of cracks, undercuts, unmelted craters in welded or soldered electrical joints. The quality of such compounds is controlled selectively, but not less than on three samples.

Measurement of electrical resistance of contact connections

Electrical resistance measured between the points, that is, in areas conventionally equated to the length of the electrical contact connection.For other cases, the measurement points are set at a distance of 2 — 5 mm from the contact connection along the current path. If necessary, the resistance of the contact connections of the package of busbars or parallel wires of wires and cables is measured separately for each pair of elements.

When measuring the resistance of multi-core wires of wires and cables, they are previously pressed with sleeves or a bandage of three to four turns of tinned copper wire 0.5 — 1.5 mm is applied. The resistance of the joints of stranded conductors with a cross-section of up to 6 mm2 is measured by piercing the insulation without pressing the sleeve or applying a bandage. The resistance of electrical contact connections is measured by the voltmeter method - ammeter for direct or alternating current, micrometer, etc. at an ambient temperature of 20 ° C. For drilling, use probes with sharp needles that destroy the oxide film.

If the electrical resistance measurements of the contact joints are carried out at other temperatures, the resulting resistances lead to the calculated temperature.

Testing the contact connections by the ammeter-voltmeter method

Non-detachable contact connections and collapsible wire connections of wires and cables with sockets and clamps and flat terminals and terminals with shaped washers are subjected to tests by the voltmeter - ammeter method

Mechanical testing of contact connections

Welded joints are tested for static load on standard samples or contact joints made by soldering, crimping and detachable contact joints.If a stranded conductor is being tested, use roller grippers or some other device that ensures even distribution of the load on the individual conductors of the conductor.

To evaluate the strength of the connection, a method is used to compare static axial loads that break the connection and the entire wire. If the connection is made of wires of different cross-sections or different materials, the assessment of its strength is made by comparison with a whole wire of lower strength.

Flat terminals with threaded holes and pins are subjected to such tests to determine their ability to withstand the effects of torque. After these tests, the contact connections must not be damaged, permanent deformations, loosening of bolts, screws and nuts that interfere with the normal operation of the devices, increase in resistance and temperature when heated with rated current.

Thermal resistance tests of contact connections

The heat resistance test is carried out on contact connections as part of a product or individual blocks of linear connections after measuring the insulation resistance. Heating is possible with both direct and alternating current, while the linear contact connections for testing are collected in a series circuit. The stationary temperature of the joints must meet the requirements of GOST or standards and specifications.

The heating cycle test is performed on the contact connections after the electrical resistance measurement and the rated current heating test.It consists in alternating cyclic heating of the contact joints with current up to 120 ± 10 ° C, followed by cooling to ambient temperature, but not higher than 30 ° C. There should be at least 500 such cycles.

The test current is set empirically based on the heating time for 3 to 10 minutes. After each cycle, the test link is allowed to cool by blowing. Every 50 cycles, the insulation resistance of the contact joints is measured and the average resistance of a group of homogeneous joints is determined.

Test tests for durability of contact connections

The passing current check is carried out on the joints after measuring the electrical resistance. Contact connections are considered to have passed such tests if they meet the requirements of GOST.

Climatic tests of contact connections

The need for climatic tests, the types and importance of climatic factors from the influence of the external environment are established by standards and technical conditions. After the tests, there should be no foci of corrosion on the contact surfaces and an increase in resistance above the permissible value.

Reliability test of contact connections

The reliability test is carried out by heating the contact connections with the rated current under conditions and regimes close to the working ones. Its duration is usually at least 1500 hours under current, while periodically, every 150 hours, the temperature of the contact joints is measured.