Winding Resistance Meters  | Detailed introduction of technical principles

The core principle of a transformer winding resistance tester is the DC voltage drop method. A constant DC current is injected into the winding, and the DC resistance is calculated based on Ohm's law (R=U/I) by precisely measuring the voltage drop across the winding.

Due to the extremely high inductance of the winding, the instrument employs a "constant current-sampling" operating mode: first, a constant DC current (typically several to hundreds of amperes) is output to charge the winding. Once the current stabilizes and the inductive effect is largely eliminated, the instrument simultaneously and rapidly acquires the current (I) and the voltage (U) across the winding. The DC resistance of the winding under the test current can then be precisely calculated.

This test is one of the most fundamental and important tests for transformers. By measuring the DC resistance of each phase winding and comparing the unbalance rate between the three phases, as well as the deviations from factory data and historical data, defects such as poor welding of internal winding wires, loose lead connections, tap changer contact faults, and inter-turn short circuits can be effectively diagnosed. Transformer winding resistance tester, transformer winding resistance ohmmeter, 20mA-20A transformer winding resistance tester. This three-channel DC resistance tester enables simultaneous three-phase power application, independent current and voltage sampling, and simultaneous measurement and display of three-phase resistance values and three-phase unbalance rate. This significantly shortens the testing time for transformer DC resistance and solves the problem of long testing times for the DC resistance of various tap windings in power transformers.

1. The instrument can select the appropriate output current value for testing based on the tested object, mainly suitable for measuring the inductive resistance of transformers, instrument transformers, etc.

2. For large transformers with a five-limb core and a delta-connected low-voltage winding, the instrument can use a high-low voltage series excitation method for testing. The instrument automatically connects the winding's auxiliary magnetizing circuit internally, enabling fast and accurate testing of the low-voltage winding's DC resistance.

3. The instrument has a three-channel testing function to complete three-phase DC resistance measurement with a single connection for star-connected windings, automatically calculating the three-phase unbalance rate, greatly saving measurement time and improving work efficiency. The instrument can also perform phase-by-phase testing for transformers with YN or D(Y) connections until the test is complete.

1. The instrument can select the appropriate output current value for the tested object, primarily suitable for measuring the inductive resistance of transformers and instrument transformers.

2. For large transformers with a five-limb core and a delta-connected low-voltage winding, the instrument can use a high-low voltage series excitation method for testing. The instrument automatically connects the winding's auxiliary magnetizing circuit internally, enabling rapid and accurate testing of the DC resistance of the low-voltage winding.

3. The instrument has a three-channel testing function to complete three-phase DC resistance measurement with a single connection for star-connected windings. It automatically calculates the three-phase imbalance rate, greatly saving measurement time and improving work efficiency.

The instrument can also perform phase-by-phase testing for transformers with YN or D(Y) connections until the test is complete.

4. The winding material can be set according to the winding material of the tested object, selecting copper or aluminum to differentiate the temperature coefficients of different materials.

5. The instrument is equipped with a function to detect the resistance of the neutral point lead of the transformer YN winding, which allows the three-channel test data to be closer to the single-phase test value.

1. Output current three-phase test: 20A+20A; 10A+10A; 5A+5A; 1A+1A; 200mA+200mA; 20mA+20mA;

2. Single-phase test: 40A; 20A; 10A; 5A; 1A; 200mA; 20mA;

3. Range:

(1) Three-phase test:

20A+20A: 0.5mΩ-0.3Ω; 10A+10A: 1mΩ-0.6Ω; 5A+5A:

2mΩ-1.2Ω; 1A+1A: 10mΩ-6Ω; 200mA+200mA:

100mΩ-30Ω; 20mA+20mA: 10Ω-200Ω;

(2) Single-phase test:

40A: 0.25mΩ-0.5Ω; 20A: 0.5mΩ-1Ω; 10A: 1mΩ-2Ω;

5A: 2mΩ-4Ω; 1A: 10mΩ-20Ω;

200mA: 100mΩ-100Ω; 20mA: 10Ω-20KΩ;

4. Accuracy: ±(0.2%+2 digits)

5. Minimum resolution: 0.1μΩ

6. Operating temperature: -10-40℃

7. Ambient humidity: ≤80%RH No condensation
8. Operating power supply: AC220V±10% 50Hz±1Hz
9. Dimensions and weight: 428mm (L) * 350mm (W) * 230mm (H) 12.8kg

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MS-520S winding resistance tester, transformer winding resistance ohmmeter, transformer winding resistance tester