Many electricians have asked: What is the adjustment method of the tap changer of a power transformer? What is a transformer tap changer? What is its function? The following will answer these questions in detail.
Because even within the same voltage level of the power grid, the voltage varies at different points due to factors such as line voltage drops, transformers installed in different locations will have different primary voltages. To ensure that all transformers can output the rated voltage, multiple taps are installed on the high-voltage winding of the transformer. These taps are connected to tap changers, which in turn connect to the power grid. Thus, by adjusting the tap changers, the turns ratio of the high-voltage and low-voltage windings can be changed, thereby adjusting the transformer's output voltage.
There are two types of transformer tap changers: on-load tap changers and off-load tap changers. On-load tap changers can adjust the tap position while the transformer is running. They are generally used on transformers for special purposes, such as electric arc furnaces. Common types in China include 17-tap, 11-tap, and 9-tap tap changers, all of which have automatic and manual adjustment mechanisms.
Transformers used for general power distribution typically employ no-load tap changers. No-load tap changing can only be done after the transformer is disconnected from the power grid. Common tap changers have 3 or 5 positions. Today, we'll discuss how to adjust a no-load tap changer.
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For example, a three-phase transformer with 10KV/0.4KV:
First gear: 10500V
Second setting: 10000V
Three speed settings: 9500V
Obviously, level one is the highest, and level three is the lowest. "High to high": "High" means if the low-voltage side voltage is too high, "higher" means adjusting the tap changer to a higher setting. "Low to low": "Low" means if the low-voltage side voltage is too low, "lower" means adjusting the tap changer to a lower setting. Why adjust it this way? For example, if the output voltage is too high in level two, the switch is adjusted to level one. This is because a higher setting means more turns in the primary winding. Adjusting to a higher setting increases the number of turns in the primary winding while keeping the number of turns in the secondary winding unchanged, thus increasing the turns ratio. Since the primary power supply voltage remains constant, the increased turns ratio lowers the secondary output voltage.
Similarly, if the switch is in position two and the secondary voltage is too low, to reduce the voltage from low to low, the switch is moved to position three. This reduces the number of turns in the primary winding while keeping the number of turns in the secondary winding unchanged, thus decreasing the turns ratio. The primary power supply remains unchanged, while the secondary output voltage increases.
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