The DC resistance quick tester measures the DC resistance of transformer windings, which is a very important test item. In the "Regulations for Power Equipment Testing Procedures", it ranks second among transformer test items. The regulations stipulate that during transformer handover, major repairs, minor repairs, tap changer position changes, fault inspections, 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 the winding or leads have any broken points
④ Check the correctness of parallel branches, whether there are one or more broken wires in a winding made of several parallel 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 Testing for Electronic Measuring Instruments" and GB6593-86 "Quality Inspection Rules for Electronic Instruments".
Other names for the DC resistance quick tester:
DC resistance quick tester, transformer DC resistance tester, transformer winding DC resistance tester, transformer DC resistance quick tester, transformer DC resistance fast tester, inductive load DC resistance quick tester, inductive load DC resistance fast 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 tests, and preventive tests. 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 self-test, signal measurement, data processing, fast discharge, and print results.
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 a total of 1000 current gears set by the internal microcontroller automatically based on the measured resistance, achieving a wide measurement range and optimal measurement state without manual current gear 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 protect against back EMF impact on the instrument, with automatic discharge indication function.
6. Can display measurement current and measurement time.
7. Intelligent power management technology effectively reduces internal heat generation.
8. Can store 120 measurement data, not lost when power is off.
9. All Chinese menus 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 will not be lost when the instrument is reset or powered off.
[Instrument Technical Indicators] (Take 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 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 print 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 is complete, the discharge prompt sound ends, and the prompt information disappears before switching the tap changer.
3. After the test, press the "Reset" button, and 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.
