25KVA/50KV High Voltage AC Test Transformer
Darni Electric recommends for you
Working Principle
The working principle of the AC/DC dual-purpose high-voltage test transformer is shown in Figure 3. In the figure, a rectifier silicon stack is installed inside the high-voltage bushing, connected in series in the high-voltage circuit for high-voltage rectification to obtain DC high voltage. When a short-circuit rod is used to short-circuit the high-voltage silicon stack, AC high voltage can be obtained, and its state is AC output; conversely, when the short-circuit rod is pulled out, its state is DC output.
Figure 3: Schematic diagram of the working principle of a single SSB AC/DC high-voltage test transformer
In the test transformer: a, x are the low-voltage input terminals; A, X are the high-voltage output terminals; E, F are the instrument measurement terminals.
1- High-voltage rectifier silicon stack; 2- Silicon stack short-circuit rod.
Usage Methods and Precautions
According to the power frequency withstand voltage test wiring shown in Figure 6, connect the working circuit, pull out the short-circuit rod. The X terminal (high-voltage tail) of the high-voltage winding of the test transformer, the F terminal of the instrument measurement winding, the shell of the test transformer, and the shell of the power control box (console) must be reliably grounded.
Before connecting the power supply, the voltage regulator of the power control box (console) must be adjusted to the zero position (the zero position indicator light is on). After connecting the power supply, the red indicator light is on. Press the start button, the green indicator light is on, indicating that the test transformer has been connected to the control power supply and starts to boost voltage.
Starting from the zero position, rotate the voltage regulator handwheel clockwise at a uniform speed to boost the voltage. (The boosting methods include: fast boosting method, i.e., 20S step-by-step boosting method, slow boosting method, i.e., 60S step-by-step boosting method, and extremely slow boosting method for selection) The voltage starts from zero and rises at the selected boosting speed to 75% of the rated test voltage you need, then rises at a speed of 2% of the rated test voltage per second to the required test voltage, and closely monitor the indication of the measuring instrument and the condition of the test object. After the time of applying voltage to the test object is reached, the voltage regulator should be returned uniformly within a few seconds, and the high voltage should be reduced to below 1/3 of the test voltage. Press the stop button, the high-voltage and low-voltage outputs stop, then cut off the power cord, and the test is completed.
Figure 6: Schematic diagram of wiring for DC leakage test
R- Current limiting resistor; C- High-voltage filter capacitor; Zx- Test object; G- Silicon stack short-circuit rod;
FRC- Resistive-capacitive voltage divider; V- High-voltage meter of the voltage divider; uA- Microammeter; D- High-voltage rectifier silicon stack.
Precautions for DC Leakage Test Operation
(1) Test personnel should divide responsibilities, set the safety distance of the test site, carefully check the grounding of the test object and the test transformer, and arrange special personnel to monitor safety and observe the condition of the test object.
(2) Before testing the test object, all external connections should be removed, and fully discharged. The main parts should be cleaned and kept dry to avoid damaging the test object and causing errors in test values.
(3) For large-capacity test objects (capacitors, ultra-long cables, etc.), the voltage should be raised slowly during the test to prevent the charging current of the test object from being too large and burning out the microammeter. If necessary, the voltage should be applied in stages, and the stable readings of the microammeter at each voltage should be recorded separately.
(4) During the test, the test object, microammeter, and test device should be closely monitored. Once flashing, breakdown, or other phenomena occur, the voltage should be immediately reduced, the power supply cut off, and the cause investigated.
Note: The above information and technical parameters are compiled and released by Yangzhou Darni Electric Co., Ltd.
|
