40A Transformer Winding DC Resistance Tester

Product Overview

To meet the demand for rapid DC resistance measurement, our company has developed the HM5002S-40A three-channel assisted magnetic DC resistance tester for large power transformers. This instrument integrates three-phase simultaneous testing, assisted magnetic function, and demagnetization capability. This instrument enables simultaneous three-phase energization, independent current and voltage sampling, and concurrent measurement and display of three-phase resistance values and three-phase imbalance rates. It significantly reduces transformer DC resistance testing time and resolves the issue of lengthy DC resistance testing for each tap winding of power transformers.

Application Scenarios

1.Power Transformer Manufacturing and Commissioning:Final quality control check on new power transformers before they leave the factory or are energized on-site.
2.Preventive Maintenance in Electrical Substations:Routine diagnostic testing on transformers and reactors in utility and industrial substations.
3.Assessment after a Fault:Testing a transformer after it has experienced a short-circuit or lightning strike.
4.Reactor and Shunt Testing:Measuring the DC resistance of current-limiting reactors, smoothing reactors, and shunt windings.

1. This instrument can select the corresponding output current value for testing based on the test specimen, primarily suited for measuring inductive resistances such as transformers and instrument transformers.

2. For large transformers with five-column cores and low-voltage windings connected in delta configuration, the instrument employs a high-low voltage series excitation method for testing. The internal auxiliary excitation circuit automatically connects the windings, enabling rapid and accurate measurement of the low-voltage winding's DC resistance.

3. This instrument features a three-channel testing function to perform three-phase DC resistance measurements on star-connected windings with a single primary connection, automatically calculating the three-phase imbalance rate. This significantly reduces measurement time and improves efficiency. Alternatively, the phase-by-phase testing function can be used for transformers with YN or D(Y) connections, testing each phase sequentially until completion.

4. The winding material (copper or aluminum) can be set based on the tested winding material to distinguish the conversion temperature coefficients for different materials.

5. The instrument includes a detection function for the resistance of the neutral point lead-out wire of the transformer's YN winding, allowing the three-channel test data to more closely approximate single-phase test values.

6. The instrument features a transformer demagnetization function to effectively reduce residual magnetism.

7. Comprehensive protection circuits and audible discharge alarms are included, with clear discharge indicators to minimize operational errors.

8. Equipped with a 7-inch color touchscreen, the interface displays test data in real time with a clear and aesthetically pleasing layout.

9. Optional Chinese or English operating interfaces available based on customer requirements.

10. Equipped with an RS232 communication interface for transferring test data to a host computer via control software.

11. Features a USB port for saving test data to a USB drive.

12. Built-in calendar clock with capability to store, retrieve, and print up to 100 sets of test data.

13. Enhanced parameter settings allow configuration of transformer test windings, tap positions, test phases, specimen temperature, and equivalent temperature.

14. Industrial plastic enclosure design ensures portability and extended service life.

15. AC380V overvoltage protection prevents internal component damage from accidental high-voltage connections during operation.

Temperature: 10°C–40°C

Humidity: ≤80% RH (non - condensing)

Power Requirements:

Input Voltage:AC 220V ±10% or specified DC input

Frequency:50/60 Hz ±1%

Grounding:Reliable earth ground connection mandatory

Power Stability:Stable voltage supply without sharp fluctuations

Package Contents

Main Test Unit×1

HM5002S-40A DC Resistance Tester

Built-in three-channel measurement system

Test Leads and Cables:

High-current test clips (3 sets - for 3-phase simultaneous measurement)

Sensing leads (fine measurement probes) ×3 sets

Power cord ×1

Grounding cable ×1

Communication cable (if applicable) ×1

Accessories:

Safety discharge rod ×1

Fuse set (spare fuses) ×1 set

Cable reel or organizer ×1

Test report software (CD/USB) ×1

Q1: What is the main purpose of this tester?

A: It is designed to measure the DC winding resistance of transformers, reactors, and other electrical equipment quickly and accurately. It is especially useful for detecting issues like loose connections, broken strands, and faulty tap changers.

Q2: What does "three-channel" mean?

A: The tester can measure three phases (e.g., A, B, C) of a transformer simultaneously, reducing testing time by up to 70% compared to single-phase testers.

Q3: What is "magnetic assistance"?

A: After testing, the device automatically demagnetizesthe transformer core to prevent residual magnetism, which can cause high inrush currents or relay trips when re-energizing the transformer.

Q4: What is the maximum test current?

A: The maximum output current is 40A DC, suitable for testing large power transformers and reactors.

Q5: Can it test single-phase transformers?

A: Yes. The tester supports single-phase, three-phase, and other winding configurations (e.g., star or delta connections).

Q6: Is specialized training required to operate it?

A: Basic knowledge of transformer testing is recommended. The device includes an intuitive interface, but users should follow safety procedures and the operation manual.

Q7: What safety features does it include?

A:

Automatic discharge after testing.

Overcurrent and over-temperature protection.

Alerts for improper connections.

Earthing requirement reminders.

Q8: How is data stored and exported?

A: The tester can store results internally. Data can be transferred via USB or Bluetooth to a computer for analysis and reporting.

Q9: What industries use this device?

A: Power utilities, transformer manufacturers, repair workshops, and heavy industries (e.g., steel, mining) for commissioning and maintenance.

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