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DC resistance tester operation

time:2021/4/24   source:华天电力  reading:399 time

In the measurement process of the DC resistance tester, in addition to strictly complying with the electrical safety regulations and equipment test regulations, special attention must be paid to the measurement under the condition of stable coil temperature. The temperature difference between the upper and lower parts of the transformer tank is required to be no more than 3 ℃. Due to the inductance of the transformer coil, the charging current during measurement is not stable, so the counting must be performed after the current is stable, and measures to shorten the charging time should be taken if necessary. Try to reduce the contact resistance of the wires in the test circuit. The transformer taps in operation are often affected by oil film and other contaminants to make their contact poor. Generally, it is necessary to switch several times before measuring to avoid judgment errors. When measuring the low-voltage side of the transformer, all personnel should keep a proper safe distance from the high-voltage side.


Transformer DC Winding Resistance Tester.png


The DC resistance tester should be protected from strong vibration, direct sunlight and magnetic fields during transportation, storage and work. When storing the instrument, pay attention to the ambient temperature and humidity. It should be placed in a dry, ventilated, and non-corrosive place. Don't be exposed to damp, rain, or insolation. When using it, handle it with care, and don't drop it. It can check whether the conductive circuit of the equipment has defects such as poor contact, poor welding, coil failure, and wiring errors. In the actual measurement of medium and small transformers, the DC bridge method is mostly used. When the resistance value of the tested coil is above 1 ohm, it is generally measured with a single-arm bridge, and when the resistance value of the tested coil is below 1 ohm, it is measured with a double-arm bridge. When using double-arm bridge wiring, the potential pile head of the bridge should be close to the resistance to be measured, and the current pile head should be connected to the potential pile head.


Before measuring the DC resistance tester, you should first estimate the resistance value of the tested coil, place the bridge magnification button in the appropriate position, short-circuit the non-tested coil and ground, then turn on the power switch to charge, and press the test after it is fully charged. The current meter switch quickly adjusts the measurement arm to make the galvanometer pointer move to the zero line in the middle of the galvanometer scale for fine adjustment. When the pointer stops at the zero position steadily, the resistance value is recorded. At this time, the measured coil resistance Value=number of magnifications×measurement arm resistance value. After the measurement is completed, first open the galvanometer button, and then release the power switch.


Before measuring the DC resistance tester, you should first estimate the resistance value of the tested coil, place the bridge magnification button in the appropriate position, short-circuit the non-tested coil and ground, then turn on the power switch to charge, and press the test after it is fully charged. The current meter switch quickly adjusts the measurement arm to make the galvanometer pointer move to the zero line in the middle of the galvanometer scale for fine adjustment. When the pointer stops at the zero position steadily, the resistance value is recorded. At this time, the measured coil resistance Value=number of magnifications×measurement arm resistance value. After the measurement is completed, first open the galvanometer button, and then release the power switch.


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