Instrument Overview

DC Resistance Rapid Tester (0-40A) Product



Measuring the DC resistance of transformer windings is a very important test item. In the "Regulations for Power Equipment Testing," it ranks second among transformer test items. The regulations stipulate that during transformer handover, major repair, minor repair, tap changer position changes, fault inspection, and preventive testing, the DC resistance of transformer windings must be measured. The purposes are: [1]



① Check the welding quality of internal winding conductors and leads



② Check whether the contact at each position of the tap changer is good



③ Check for any breaks in the windings or leads



④ Check the correctness of parallel branches, whether there is a situation where one or more breaks occur in windings made of several parallel conductors



⑤ Check for short circuits between layers and turns



This product complies with the requirements of national standards GB6587-86 "General Outline for Environmental Testing of Electronic Measuring Instruments" and GB6593-86 "Quality Inspection Rules for Electronic Instruments."



Other names for the DC Resistance Rapid Tester:



DC Resistance Rapid Tester, Transformer DC Resistance Tester, Transformer Winding DC Resistance Tester, Transformer DC Resistance Rapid Tester, Transformer DC Resistance Quick Tester, Inductive Load DC Resistance Rapid Tester, Inductive Load DC Resistance Quick Tester, Inductive Load DC Resistance Tester



Overview



Transformer DC resistance testing is a mandatory item for power equipment manufacturers and power generation and supply departments in transformer factory inspection, handover testing, and preventive testing. It effectively improves product quality and prevents power accidents. The Transformer DC Resistance Tester consists of a high-power switching power supply circuit, precision small-signal measurement circuit, protection circuit, high-speed microcontroller control circuit, etc., with functions such as instrument self-check, signal measurement, data processing, rapid discharge, and print results.



2 Main Features of the Instrument

1. Uses a high-speed 16-bit A/D converter, providing stable measurement data and good repeatability.



2. Automatic program-controlled current source technology, with a total of 1000 current gears set in the current source, automatically controlled by the internal microcontroller based on the measured resistance, achieving a wide measurement range and optimal measurement state without manual current gear switching.



3. Fast response speed; the tap changer can be directly switched during measurement, and the instrument will automatically prompt, with the new resistance value displayed quickly.



4. Highly intelligent design with clever and advanced function settings, capable of automatically detecting faults such as loose test leads or disconnection.



5. Comprehensive protection functions, reliably protecting against back EMF impacts, with automatic discharge indication.



6. Can display measurement current and measurement time.



7. Intelligent power management technology effectively reduces internal heating.



8. Can store 120 measurement data sets, which are not lost after power failure.



9. All Chinese menu and operation prompts, intuitive and convenient.







3 Structural Characteristics and Working Principle

This tester adopts a typical four-wire measurement method to improve the accuracy of measuring resistance (especially low resistance). The program-controlled constant current source, program-controlled preamplifier, and A/D converter form the main body of the measurement circuit. The central control unit applies a constant, high-precision current to the external load under test by controlling the constant current source, then processes the obtained data (including test voltage, current test current, etc.) to obtain the actual resistance value.



This instrument can store 255 test data sets and can print all stored test data. The stored data is not lost upon instrument reset or power failure.



[Instrument Technical Specifications] (Taking HT-40A as an example)



1. Output four gear currents: 40A, 20A, 10A, 5A



2. Resolution: 0.1μΩ



3. Range: 20mΩ - 4Ω (5A gear); 10mΩ - 2Ω (10A gear);



0.2mΩ - 1Ω (20A gear); 0.1mΩ - 0.5Ω (40A gear);



4. Accuracy: 0.2%



5. Ambient temperature: 0～40℃



6. Ambient humidity: <90%RH



7. Working power supply: AC220V±10%, (50±1)HZ



8. Dimensions: 400×200×350mm



9. Weight: 13kg



Test current 5A, 10A, 20A, 40A



Measurement range



5A: 1μΩ~4Ω



10A: 1μΩ~2Ω



20A: 1μΩ~1Ω



40A: 1μΩ~0.5Ω



Measurement accuracy ±0.2% (full scale)



Display method 128×64 dot matrix display, resistance displayed as 4 1/2 digits



Maximum resolution 0.1μΩ



Power supply AC 220V±22V, 50Hz±2 Hz, fuse 5A



Maximum power consumption 600W when test current is 40A



Working environment Ambient temperature: 0°～40°



Relative humidity: ≤80%



Volume 400╳200╳425(mm)



Weight 12kg with accessories



Features:



① Microcomputer-controlled intelligent instrument, can store test results;



② AC powered, portable design, easy to use and carry;



③ Uses advanced constant current power technology, greatly reducing the instrument's size, weight, and power consumption, further shortening measurement time, and ensuring more stable and reliable measurement data.



④ Built-in micro printer, directly outputs printed results



⑤ This instrument is suitable for measuring and analyzing inductive, low-resistance values such as various power transformer and instrument transformer windings.



[Instrument Precautions]



1. Before measuring an on-load tap changer transformer and switching the tap, be sure to reset. After discharge ends, the discharge prompt sound ends, and the prompt information disappears before switching the tap changer.



3. After the test, press the "Reset" button, and be sure to wait until the discharge indicator light goes out and the prompt information disappears before turning off the power and disconnecting the wires.



4. During the test, avoid power outages or test clamp detachment.



5. Connect the ground wire before turning on the power, and disconnect the ground wire last after the test.