DC resistance is mainly for DC resistance testing of inductive loads such as transformers, motors, CT/PT, etc. The measurement unit is mΩ. For example, the measurement of the DC resistance of the winding of the transformer is a convenient and effective test to investigate the connection condition of the winding insulation and the current loop. It can reflect the welding quality of the winding, the winding turn-to-turn short circuit, the winding break or the lead wire break, the tap changer and Faults such as poor wire contact, in fact, it is also an effective means to judge whether the DC resistance of each phase winding is balanced and whether the voltage regulating switch gear position is correct.
The DC resistance measurement methods include: current-voltage method, DC bridge method, and simultaneous compression of three-phase windings. Now DC resistance testers are all using the DC bridge method, which requires the test current to be no less than 1A, and the measurement resistance value is small. High, test currents are common: 1A, 3A, 10A, 20A, 40A, 50A, 100A, these are only used for single-phase measurements. For three-phase simultaneous measurement, the JYR-10S/20S and JYR-40S/50S three-channel DC winding resistance testers are available.