Choke transformer is a special transformer which is located in the rail insulation of dual track circuit in electrified section and can insulate the signal current in the track circuit.The characteristic is that it can not only separate the signal current in the adjacent track circuit, but also make the traction current flow from one track circuit section to another track circuit section through it without being separated by the rail insulation.
Choke transformer is installed on the connection between traction reflux and rail and is used to conduct traction current, or it is installed on the upper and lower track circuit to balance traction current so that it does not affect the normal operation of the track circuit.Choke transformer's function in rail circuit is to make use of traction current and match the supply transformer and the receiving end.
Since there is no insulation between the track and the ground, part of the traction current flows through the ground and back to the transformer from the grounding grid buried under the traction substation.At the same time, the rail and the suction line are not directly connected, but a choke transformer is added at the insulation section of the track circuit, and the two are firmly connected with the transformer's terminal post and neutral point respectively, so that the traction current loop and the track signal loop form the conduction loop respectively and do not interfere with each other.
When choke transformer has fault, it should be further determined whether it is a wire break fault or a mixed fault. If choke transformer coil has voltage but no current, it is a wire break. If it has current but no voltage, it is a choke transformer hybrid.Sometimes a single mixed coil of the traction coil of the choke transformer may not produce red band of the track circuit, but at this time, the voltage measured at both ends of the traction coil and the neutral connection point should be deviated for further investigation and treatment.