Tap Changer
Q. Explain the purpose of equipments in AC locomotive : Tap changer.
Q. Explain the purpose of equipments in AC locomotive : Tap changer.
- Tap changers are of many types such as On-Load tap changers and Off-Load tap changers.
- In traction power circuit mainly on load tap changers are preferred.
- On load tap changers are capable of changing the taps quickly without interrupting the flow of current.
- On-load tap changer is provided on 25kV (High Tension) regulating transformer for controlling the voltage input to winding of locomotive the main transformer.
- The Tap Changer is operated with the help of elaborate mechanism which uses an air driven servo motor and a bevel gear arrangement.
- With the help of precision adjustment and provision of transition resistance it is confirmed that there is no break of load current inside the selector which is oil filled and the load current is broken by the load switches in required condition.
- The on-load tap changer currently used on locomotives for speed control requires more maintenance on account of its inherent design and the construction.
- The flashovers that are taking place at various locations are some of the factors affecting to reliability of the locomotives.
- This problem is taken sophisticated devices such as thyristor converters care of by using and silicon diode rectifier units etc.
- The Figure shows the working of On Load Tap Changer (OLTC) to control the speed of the - DC traction motor.
- Taps provided on the secondary side of the transformer which is further connected to the rectifier circuit and rectifier to the DC motor.
- The main transformer secondary is so designed that it has two windings. The one winding is connected to tap changer and the other winding is connected to the auxiliary circuit.
