A Load Tap Changer (LTC) is a device used in electrical power transformers to regulate the output voltage by changing the turns ratio of the transformer winding. It allows for the adjustment of the transformer's secondary voltage to maintain a consistent voltage level within acceptable limits, despite fluctuations in the input voltage or changes in the load connected to the transformer.
The primary purpose of an LTC is to ensure that the voltage supplied to the distribution network or the connected equipment remains within a specified range, as overvoltage or undervoltage conditions can have detrimental effects on electrical equipment and systems.
Here's how an LTC works to regulate transformer voltage:
Tap Changer Mechanism: The transformer winding usually has several taps along its winding. These taps are points along the winding where connections can be made to vary the effective turns ratio. By changing the tap connection, the ratio of the primary to secondary turns is adjusted, which directly affects the output voltage.
Voltage Sensing: The LTC system includes sensors that continuously monitor the output voltage. This feedback information is used to determine whether the voltage is within the desired range or if it needs adjustment.
Control System: The LTC is controlled by a sophisticated control system that receives information from the voltage sensors. This control system decides whether the tap needs to be changed based on the discrepancy between the measured voltage and the desired voltage setpoint.
Tap Changing: When the control system detects a deviation from the desired voltage, it triggers the LTC mechanism to make the necessary tap change. The tap changer mechanism can be operated either manually or automatically.
Tap Change Process: Changing the tap involves physically shifting the connection point along the winding. This alters the turns ratio and subsequently adjusts the output voltage. Tap changes can be done by mechanical means (such as motor-driven mechanisms) or electronically (using power electronics).
Voltage Regulation: With tap changes, the transformer's secondary voltage is adjusted to bring it back to the desired level. If the output voltage is too high, the tap is lowered to reduce the voltage; if the output voltage is too low, the tap is raised to increase the voltage.
Overall, an LTC enables the transformer to adapt to changing load conditions and fluctuations in the input voltage, ensuring a stable and consistent output voltage. This is crucial for maintaining the reliability of the power distribution system and protecting the connected electrical equipment from voltage-related issues.