In the early 20th century, transformer DC resistance testing primarily relied on basic bridge circuits. Due to the very low resistance and high inductance of transformer windings, the Kelvin double bridge became the standard method for measuring sub-ohm resistances and eliminating the effects of lead resistance, these early "testers" were not single devices but assemblies made of brass and wooden components, including sensitive galvanometers, large-capacity batteries, and manual sliding resistors, operators had to wait several minutes until the transformer core's large inductance saturated before obtaining stable readings. By the mid-20th century, these components were integrated into portable wooden box bridge devices. While more convenient, they still required manual balancing and complex temperature correction. The digital revolution of the 1980s introduced the "current-source" method, utilizing stable DC power supplies and microprocessors to calculate resistance through Ohm's Law (R = V/I). Modern testers are now equipped with high-speed discharge circuits that safely dissipate stored magnetic energy, along with automatic temperature compensation and multi-phase testing functions, transforming the cumbersome manual process into a quick one-button diagnostic.

JYR-10S/20S/40S/50S incorporate the multi-core CPU from ARM (Advanced RISC Machines, USA), offering stable performance and high computational accuracy. It also adopts third-generation constant current source technology, with a maximum output current of 50A (40A), a range of 0Ω to 20kΩ, and an output voltage of up to 24V. The instrument features a built-in channel conversion matrix. With the JYR-40S/50S, various tests on power transformers can be performed without rewiring. The instrument can complete three-phase simultaneous tests, phase-by-phase tests, magnetic assistance tests, and single-phase DC winding resistance tests.

The JYR-40S/50S three-phase winding resistance tester supports routine and diagnostic testing for power transformers of all levels. It is also suitable for factory laboratory and acceptance (FAT) testing.

Function Introduction:

1.The output current can be set manually or automatically selected based on the resistance of the tested product.

2.High Voltage YN Three-Phase Simultaneous Testing: Includes compensation testing (including O-phase resistance) and phase-by-phase testing functions. Features automatic magnetization assistance for YND11 transformers, high and low voltage D/Y three-phase phase selection measurement, and automatic calculation of the three-phase resistance balance rate for high voltage.

3.Measuring range: 0～20kΩ. The instrument can measure the DC resistance of inductive products such as transformers and instrument transformers.

4.Auxiliary data stabilizing function: Automatically calculates the percentage deviation of resistance values at 5s, 15s, and 30s, accurately determining the reliability of data and preventing misreading.

5.Temperature conversion can be made according to the material (Copper/Aluminum) of the tested products, facilitating comparison with historical data.

6.Equipped with transformer demagnetization function to reduce residual magnetism in transformers.

7.With a permanent calendar, 99 sets of data storage, Chinese and English interface selection, power failure protection (no data loss), mini printer, and U disk interface.

8.6-inch color touch LCD display screen.

9.Dual RS485 (RS232) communication interface with PC control software, enabling remote measurement. The instrument can be fitted with an optional built-in Bluetooth module for wireless Bluetooth communication.

10.Discharge alarm with sound and clear discharge indication to reduce misoperation.

11.AC380V misconnection protection, perfect back EMF protection, and anti-arcing function.

12.Features dustproof, shockproof, moistureproof, high precision, good repeatability, and portability.

Technical specification

Wiring diagram for the transformer test leads of the JYR-50S winding resistance tester

Kingrun Transformer Instrument Co.,Ltd.

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