Tap changers are devices used in transformers to adjust the turns ratio between the primary and secondary windings, thereby changing the voltage ratio. They are employed to regulate the voltage levels and compensate for variations in the supply voltage or load conditions. Tap changers allow transformers to adapt to changing system requirements and maintain a desired voltage output.
There are two main types of tap changers:
- On-Load Tap Changer (OLTC): On-load tap changers, also known as diverter switch or under-load tap changers, are designed to change the tap position while the transformer remains energized and connected to the power system. OLTCs are typically used in power transformers where continuous voltage regulation is required, such as in distribution networks or large industrial systems. They allow for step changes in the voltage ratio by redirecting the current flow through different tapping points on the windings. OLTCs are controlled by a motor-driven mechanism that switches the tap position.
- Off-Circuit Tap Changer (OCTC): Off-circuit tap changers, also known as no-load tap changers, are designed to change the tap position when the transformer is disconnected from the power system. OCTCs are commonly used in smaller distribution transformers. To change the tap position, the transformer must be de-energized, and the connections are manually adjusted using a mechanical switching mechanism. Once the tap position is changed, the transformer is reconnected to the power system.
Tap changers provide several benefits and functions:
- Voltage Regulation: By changing the tap position, tap changers enable voltage adjustment to compensate for variations in the supply voltage or load conditions. This helps to maintain a stable and desired voltage level at the secondary side of the transformer.
- Load Compensation: Tap changers can accommodate changes in the load demand by adjusting the voltage output accordingly. This ensures that the voltage delivered to the load remains within an acceptable range even under varying load conditions.
- Voltage Control: Tap changers allow for voltage control during periods of high or low supply voltage. By changing the tap position, transformers can either boost or buck the voltage to maintain a desirable voltage level at the load.
- Power Quality Improvement: Tap changers help to improve power quality by regulating the voltage levels and minimizing voltage fluctuations. This enables better control over voltage-sensitive equipment and reduces the risk of equipment damage or performance issues.