How does a tap changer work?
1 Answer
A tap changer is a device used in transformers and voltage regulators to adjust the turns ratio of the winding and thereby regulate the output voltage. It is commonly used to maintain a desired voltage level under varying load or input voltage conditions. Tap changers are crucial in electrical systems to ensure a stable and consistent power supply.
There are two main types of tap changers: on-load tap changers (OLTC) and off-load tap changers (OLTC).
On-Load Tap Changer (OLTC):
An on-load tap changer allows adjustments to be made to the transformer's turns ratio while the transformer is energized and under load. OLTCs are used in applications where a continuous power supply is essential, and interrupting the power flow is not feasible. Here's how an OLTC typically works:
Diverter Switch: An OLTC employs a diverter switch mechanism that redirects the current flowing through the winding to a different tap position. This switch is equipped with various tap positions, which correspond to different numbers of turns in the winding.
Motor Drive: The tap changer is controlled by a motor drive system. This motor is responsible for rotating the diverter switch to the desired tap position. The motor drive can be automatic, controlled by a regulating system based on voltage or load feedback, or it can be manually operated by an operator.
Transition Process: When a tap change is initiated, the motor drive system activates and moves the diverter switch from one tap position to another. During this transition, the transformer's winding momentarily experiences a change in turns ratio, which in turn adjusts the output voltage. The transition is designed to be smooth and gradual to minimize voltage and current transients.
Off-Load Tap Changer (OLTC):
An off-load tap changer, as the name suggests, requires the transformer to be de-energized (turned off) during tap changes. While this type of tap changer is less versatile than the on-load version, it is simpler and can be more reliable due to its reduced complexity.
No Load Condition: In an off-load tap changer, the transformer is taken out of service (no load) before the tap change process begins. This prevents the risk of arcing or other complications associated with changing taps under load.
Manual Adjustment: An operator manually adjusts the tap changer by physically moving a mechanical link or lever to the desired tap position.
Re-Energization: After the tap change is completed, the transformer is re-energized, and power flow is restored.
Both on-load and off-load tap changers play a crucial role in maintaining stable voltage levels in electrical systems, especially when dealing with fluctuating loads or input voltages. The choice between the two types depends on the specific application requirements, cost considerations, and the degree of permissible downtime for maintenance and tap changes.
There are two main types of tap changers: on-load tap changers (OLTC) and off-load tap changers (OLTC).
On-Load Tap Changer (OLTC):
An on-load tap changer allows adjustments to be made to the transformer's turns ratio while the transformer is energized and under load. OLTCs are used in applications where a continuous power supply is essential, and interrupting the power flow is not feasible. Here's how an OLTC typically works:
Diverter Switch: An OLTC employs a diverter switch mechanism that redirects the current flowing through the winding to a different tap position. This switch is equipped with various tap positions, which correspond to different numbers of turns in the winding.
Motor Drive: The tap changer is controlled by a motor drive system. This motor is responsible for rotating the diverter switch to the desired tap position. The motor drive can be automatic, controlled by a regulating system based on voltage or load feedback, or it can be manually operated by an operator.
Transition Process: When a tap change is initiated, the motor drive system activates and moves the diverter switch from one tap position to another. During this transition, the transformer's winding momentarily experiences a change in turns ratio, which in turn adjusts the output voltage. The transition is designed to be smooth and gradual to minimize voltage and current transients.
Off-Load Tap Changer (OLTC):
An off-load tap changer, as the name suggests, requires the transformer to be de-energized (turned off) during tap changes. While this type of tap changer is less versatile than the on-load version, it is simpler and can be more reliable due to its reduced complexity.
No Load Condition: In an off-load tap changer, the transformer is taken out of service (no load) before the tap change process begins. This prevents the risk of arcing or other complications associated with changing taps under load.
Manual Adjustment: An operator manually adjusts the tap changer by physically moving a mechanical link or lever to the desired tap position.
Re-Energization: After the tap change is completed, the transformer is re-energized, and power flow is restored.
Both on-load and off-load tap changers play a crucial role in maintaining stable voltage levels in electrical systems, especially when dealing with fluctuating loads or input voltages. The choice between the two types depends on the specific application requirements, cost considerations, and the degree of permissible downtime for maintenance and tap changes.