The non-exciting tap changer, also known as a no-load tap changer, is an essential component in power transformers used to adjust the transformer's voltage ratio and output by changing the number of turns in the winding when the transformer is not energized. This type of tap changer is designed for manual operation only and does not require arc suppression due to its low capacity. However, improper maintenance, poor quality switches, or incorrect operation can lead to serious damage, such as short circuits, overheating, and even total transformer failure.
One of the main causes of failure is oil leakage, which exposes the tap changer to air and leads to moisture ingress. Over time, this dampness reduces insulation performance, causing short circuits. Additionally, poor manufacturing quality can result in unreliable contact, misalignment, and insufficient pressure, all of which contribute to internal faults. When the tap changer is operated under high temperatures or overload conditions, especially in remote areas with unstable voltage, the contacts may become carbonized or oxidized, increasing resistance and leading to overheating and arcing.
Incorrect adjustments by untrained personnel, such as village electricians, can also cause damage. For example, adjusting the tap from position "2" to "1" when the voltage is too low, or failing to fully seat the tap during operation, can create short circuits between windings or to ground. Poor installation practices, like loose bolts or neglected maintenance, further increase the risk of failure.
To detect issues early, regular testing is crucial. Insulation resistance and DC resistance measurements should be taken using a megohmmeter and bridge, respectively. The DC resistance error should be within 4% for three-phase systems. Oil sampling and checking the actual oil level are also important to avoid false readings. Before and after switching, DC resistance values must be measured and compared to ensure consistency.
When measuring DC resistance, it’s essential to account for temperature variations. The resistance value should be converted to a standard temperature (usually 20°C) using a specific formula. Proper wiring and good contact are necessary to avoid measurement errors. After measurements, the transformer coil must be discharged to prevent electrical hazards.
During inspection and repair, the tap changer should be carefully examined for signs of wear, discoloration, or deformation. If the contact pressure is insufficient, springs should be replaced. The connections should be checked for tightness, and any damaged parts should be repaired or replaced. After repairs, the DC resistance and insulation resistance should be tested again to ensure everything is functioning correctly.
In summary, proper maintenance, regular inspections, and correct operation are vital for ensuring the reliable performance of a no-load tap changer and preventing costly transformer failures.
The mechanical Buzzer uses a magnet to move a reed up and down quickly to emit a lower-pitch buzz! It's quieter than the piezoelectric buzzer but uses more power, so you the terminals will have to be closer to the battery packs. To use them, you'll need to match the wire colors to the wires from the battery pack.
Piezo Beeper,Mechanical Buzzer,Piezo Mechanical Buzzer,Low Frequency Mechanical Buzzer
Jiangsu Huawha Electronices Co.,Ltd , https://www.hnbuzzer.com