Working Principle and Testing Advantages of ZXR-20A+ Three-Channel DC Resistance Tester

1. Introduction

The ZXR-20A+ Three-Channel DC Resistance Tester is an essential instrument for various tests related to transformers, such as semi-finished and finished product factory tests, installation, handover tests, and preventive tests in the power sector. It can effectively detect manufacturing defects in transformer coils, including material selection, welding issues, loose connection parts, strand shortages, and open circuits, as well as potential hidden dangers during operation.

2. Working Principle

2.1 Current Output and Selection

The tester can output different currents according to the requirements of the tested product. For three-phase testing, it offers current combinations of 10A + 10A, 5A + 5A, and 1A + 1A. For single-phase testing, the available current values are 20A, 10A, 5A, 1A, and 200mA. The instrument selects the appropriate current based on the characteristics of the tested object to ensure accurate measurement.

2.2 Measurement of Resistance

When conducting measurements, the tester uses independent three-channel current sampling and voltage sampling methods. For star-connected windings, it can measure three-phase resistances simultaneously through the three-channel test function. For YN, D(Y) connected transformers, it can also perform single-phase measurements. The instrument calculates the resistance value by measuring the current flowing through the winding and the voltage across it, using Ohm's law (R = U / I).

2.3 Special Testing Methods for Large Transformers

For large transformers with five-column cores and low-voltage windings in a delta connection, the tester adopts a high-low voltage series excitation method. The instrument automatically connects the magnetizing circuit of the windings internally. This method can quickly and accurately measure the DC resistance of the low-voltage windings.

2.4 Data Processing and Display

The tester is equipped with a built-in microprocessor that processes the measured data. It can calculate the three-phase resistance unbalance rate when performing three-phase measurements. The measurement results, including resistance values, unbalance rates, and other relevant data, are clearly displayed on a 7-inch color touch screen. The display not only shows the real-time test data but also provides an intuitive and user-friendly operation interface.

3. Testing Advantages

3.1 Time-Saving

• Three-Channel Simultaneous Measurement: The three-channel test function allows for one-time wiring to complete the measurement of three-phase DC resistances for star-connected windings. This significantly reduces the measurement time compared to traditional single-channel measurement methods. For example, when testing a three-phase transformer, the traditional method may require multiple measurements for each phase, while this instrument can complete all three-phase measurements at once, saving a great deal of time and improving work efficiency.
• Quick Testing for Large Transformers: For large transformers with complex winding structures, such as those with five-column cores and low-voltage windings in a delta connection, the high-low voltage series excitation method enables fast and accurate measurement of the low-voltage winding resistance. This effectively solves the problem of long testing times for these types of transformers.

3.2 High Accuracy

• Precise Current Output: The tester can output accurate currents within a wide range, ensuring that the measured resistance values are reliable. The specified current accuracy and stability contribute to the precision of the measurement results.
• Advanced Sampling and Calculation: The independent three-channel current and voltage sampling techniques, combined with accurate data processing algorithms, enable the instrument to measure resistance values with high precision. The accuracy of the instrument is ±(0.2% + 2 digits), and the minimum resolution is 0.1μΩ, which can meet the high-precision measurement requirements of various applications.

3.3 Versatility

• Multiple Winding Connection Types: The instrument can handle various winding connection types, including star (YN) and delta (D or Y) connections. It can perform both three-phase simultaneous measurements and single-phase measurements, adapting to different testing needs of transformers with different connection methods.
• Applicable to Multiple Inductive Resistors: In addition to transformers, the tester is also suitable for measuring the resistance of other inductive components such as mutual inductors, meeting the diverse testing requirements in the electrical field.

3.4 User-Friendly Operation

• 7-Inch Color Touch Screen: The 7-inch color touch screen provides a clear and beautiful interface display. The intuitive operation menu allows users to easily set parameters, start tests, and view test data. Real-time display of test data enables users to monitor the measurement process and results at any time.
• Optional Language Interfaces: The instrument offers both Chinese and English operation interfaces, which can be configured according to customer requirements. This makes it convenient for users in different regions to operate the instrument.

3.5 Data Management and Communication

• Data Storage and Retrieval: The built-in calendar clock and the ability to store, retrieve, and print 100 groups of test data provide convenience for data management. Users can easily access historical test data for analysis and comparison.
• Communication Interfaces: With RS232 and USB interfaces, the tester can communicate with upper computer control software. The RS232 interface can transfer test data to the background for further analysis and management, while the USB interface allows users to transfer test data to a U disk for easy storage and sharing.

3.6 Protection and Durability

• Perfect Protection Circuit: The instrument is equipped with a perfect protection circuit, which can effectively protect against various potential problems such as back EMF, disconnection, and power failure. This ensures the safety and reliability of the instrument during operation and reduces the risk of damage to the instrument.
• Industrial Plastic Shell: The industrial plastic shell not only makes the instrument easy to carry but also improves its service life. It can withstand certain impacts and environmental challenges, ensuring stable performance in different working conditions.

In conclusion, the ZXR-20A+ Three-Channel DC Resistance Tester combines advanced working principles and multiple testing advantages, making it an ideal choice for accurately and efficiently measuring the DC resistance of transformers and other inductive components.