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DC and loop resistance test

time:2021/1/14   source:华天电力  reading:290 time

The DC resistance test is generally the DC resistance of windings such as transformers and motors. Since inductance and or capacitive reactance exist in the circuit of such equipment, it is impossible to test if large current is applied, except for the test device with large capacity. (Such as battery packs, etc.), but it is not very economical, so the current dedicated DC resistance tester,

Transformer DC Winding Resistance Tester.png

The loop resistance is generally very small in the micro-ohm level, which refers to the on-contact resistance of disconnecting switches and circuit breakers. However, the contact points of these devices are easily oxidized, so large current must be applied to destroy the oxide film when making it detectable. In this way, the real DC resistance value of the loop can be obtained. This kind of loop does not have impedance (inductive reactance and capacitive reactance), so the resistance value can be measured very quickly by passing current.

Micro Ohmmeter.png

Both testers are used to test resistance, and they also use the DC voltage drop method. Many people think that they are the same and can be used alternately. In fact, there are still differences between the two. The main resistance load is resistive load, and they are all micro-resistance tests. The DC resistance tester tests mainly inductive loads, and the resistance range is relatively large. The two cannot be used interchangeably. If there is a loop resistance tester to measure the inductive load, it is extremely The equipment may be damaged. At present, there is no composite type of two instruments on the market, because if the two equipment is combined into one equipment, it will not only meet the high current, but also meet the inductive load with relatively large resistance, which is very costly. , The equipment volume is also very large.

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