Test and operation method of DC resistance tester

The DC resistance of transformer is a must test item in transformer manufacturing, including semi-finished products, finished products factory test, installation, handover test and preventive test of power department. It can effectively find manufacturing defects such as material selection, welding, loose connection parts, missing strand, broken wire and other manufacturing defects and hidden dangers after operation. In order to meet the needs of rapid measurement of transformer DC resistance, our company developed this DC resistance tester by using its own technical advantages. The new power supply technology is adopted in the instrument, which has the characteristics of small volume, light weight and large output current. The whole machine is controlled by single-chip microcomputer, which can automatically complete self-test, data processing, display and other functions, and has the function of automatic discharge and discharge indication. The instrument has the advantages of high precision and easy operation, which can realize the rapid measurement of transformer direct resistance.

1. Wiring: connect the tested object with the test terminal of the machine through special cable, and connect the ground wire well.
 
For the wiring of single channel direct measurement, see Figure 1.
DC resistance tester
Quick test R_AO

Figure 1
 
2. Range selection: turn on the power switch, and the display screen will display as shown in Fig. 2. At this time, the resistance range of the tested product can be selected through the select / test key. Each range, 10a, 5A, 1a, 100mA, < 4mA, will scroll on the display screen.
 

Figure 2 main menu of power on
 
3. Speed selection: when the “speed” menu is selected, press the selection key to select the “fast” and “slow” speed. The default mode of the instrument is “fast”. When the data of the low voltage side of the large capacity transformer is not stable, it is recommended to use the slow speed mode to enhance the stability.
 
4. Test: after selecting the menu content, press the test key under the “test” menu to start the test. The display screen indicates the charging current value and prompts “charging please wait”. When the current is stable, the display screen displays the test current used, and prompts “testing, please wait”. At the same time, the word “test” starts to flash, and then the current value and resistance value are displayed Press the test key to re measure, but the current remains unchanged.
 
During the test, when the selected current is too low, it will prompt “please change the high current”, because the resistance is too small, the instrument measurement cannot meet the requirements, so the high current should be replaced and retested.
 
When the selected current is too large, it will prompt “please change the small current”. Because the resistance is too large, the instrument cannot charge the measured current. At this time, the small current should be replaced to retest.
 
5. After the test is finished, press the “reset” key, the power supply of the instrument will be disconnected from the winding, and the instrument will discharge at the same time. Then, the display screen will return to the initial state. After the sound is discharged, it can be rewired for the next measurement or the test line and power line can be removed to finish the measurement.