Instrument Overview

DC Resistance Quick Tester (0-40A) Product



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



① Check the welding quality of internal wires and leads in the winding



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



③ Check whether there are any broken points in the winding or lead-out wires



④ Check the correctness of parallel branches, whether there is a situation where a winding made of several parallel wires has one or more broken wires



⑤ Check for short circuits between layers and turns



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



Other names for the DC Resistance Quick 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 test item for power equipment manufacturers and power generation and supply departments during factory inspection, handover tests, and preventive tests. It can effectively improve product quality and prevent 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 result printing.



2 Main Features of the Instrument

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



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



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



4. Highly intelligent design with clever and advanced function settings, can automatically judge faults such as loose test leads or broken wires.



5. Complete protection functions, reliably protecting the instrument from back EMF impact, with automatic discharge indication.



6. Can display measurement current and measurement time.



7. Intelligent power management technology effectively reduces internal heating of the instrument.



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



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







3 Structural Characteristics and Working Principle

This tester adopts the 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 and can print all stored test data. The stored data is not lost upon 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 Adopts advanced constant current power supply technology, greatly reducing the volume, weight, and power consumption of the instrument, further shortening measurement time, and ensuring more stable and reliable measurement data.



④ Comes with a built-in micro printer for direct output of printed results



⑤ This instrument is suitable for measurement and analysis of inductive, low-resistance values such as various power transformer and mutual inductor windings.



[Instrument Precautions]



1. Before switching the tap changer of an on-load tap changer transformer, be sure to reset. After discharge, wait until 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, please minimize 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.