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Measuring method of DC resistance tester

time:2021/3/29   source:华天电力  reading:292 time

Measurement method of DC resistance tester:


Due to the difference in the quality of the transformer manufacturing, the maintenance level of the operating unit, the accuracy of the instruments used by the testers, and the measurement connection method, the measured resistance values are also different.


1. In the actual measurement of small and medium-sized transformers, the DC bridge method is mostly used for measurement.


Transformer DC Winding Resistance Tester.png


2. When the resistance value of the tested coil is above 1Ω, it is generally measured by a single-arm bridge, while the resistance value of the coil under 1Ω is measured by a double-arm bridge.


3. When using double-arm bridge connection, the potential terminal of the bridge should be close to the coil under test, and the current terminal should be connected to the potential terminal. Before measurement, the resistance value of the coil under test should be estimated. Place the bridge magnification knob in the proper position. Then, turn on the power switch to charge. After fully charged, press the galvanometer switch and quickly adjust the measuring arm to move the galvanometer pointer to the zero line in the middle of the galvanometer scale, and make fine adjustments until the pointer stops at zero steadily. Record the resistance value when the bit is up. At this time, the measured coil resistance value is the product of the multiplying factor and the resistance value of the measuring arm. After the measurement is completed, first press the galvanometer button, and then turn off the power switch. The measured data should be filled in the record sheet faithfully in order to correctly analyze and judge the fault of the transformer.


4. Through measurement, it is possible to check whether the conductive circuit of the equipment has defects such as poor contact, poor welding, coil failure, and wiring errors.

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