Adjustment of power voltage tap changer

Changing the tap position means changing the number of turns of the transformer, that is, changing the transformer ratio. The ratio K = W1/W2 = U1/U2, it is easy to see: the tap is on the primary side, changing the number of turns of the primary coil changes K, and once the K value changes, the secondary voltage U2 = U1/K will naturally change when the same voltage U1 is applied, which plays the role of regulating the voltage.

What types of tap switches are there? They are divided into on-load voltage regulators and off-load voltage regulators.

• On-load voltage regulator: Suitable for occasions where frequent voltage adjustment is required, such as arc furnaces. This type of switch can be adjusted during operation and usually has automatic and manual adjustment functions.
• No-load voltage regulator: Mainly used for transformers for power distribution, it can only be adjusted during power outages. Common ones are 3-position and 5-position.

The steps for adjusting the tap changer are to first shut down the power and ensure that the transformer is completely de-energized to avoid any electrical accidents.

To disconnect the load, use an insulating rod to pull out the high-voltage drop-out fuse to ensure that the transformer is completely disconnected from the grid;

Unscrew the transformer's tap changer cover and place the positioning pin in the neutral position.

You also need to adjust the gear position. According to the output voltage, adjust the tap switch to the corresponding position. When the voltage is too low, adjust it to the low voltage gear; when the voltage is too high, adjust it to the high voltage gear.

Finally, measure the resistance. After adjusting the gear, use a DC bridge to measure the DC resistance of each phase winding to check whether the DC resistance between each winding is balanced. If the resistance difference between each phase is greater than 2%, readjustment is required.

Note:

Safety comes first. During the entire process, make sure all operations are performed under power outage and use appropriate personal protective equipment such as gloves and glasses.

During the adjustment process, record all operation data and results for subsequent monitoring and comparison;

Regular inspections should be carried out to check and adjust the transformer tap changer regularly, especially when there are large load changes.

By following the above steps and precautions, you can effectively adjust the tap changer of the power transformer to ensure that the transformer can maintain optimal performance and safety under various operating conditions.