2004 Track Circuit Calculations

[jenni.joseph9]

Hi,

Thanks for the reply.

As per the bullet no.1 mentioned in the question, I have taken the value as 0.7v. Please let me know if am wrong while considering the values.

Here is the question, for your reference please.

A d.c. track circuit is provided with an additional resistance at the relay end, connected in series with the relay coil. The characteristics of the track circuit are as follows.
Feed transformer rectifier output: 5.0 Volt
Relay coil resistance: 9.0 Ohm
Relay pickup current: 40.0 mA
Ballast resistance: 2.5 Ohm km
Length of track circuit 600 m
1. Calculate the value of the additional relay end resistance that will ensure a minimum rail to rail voltage of 0.7V when the track circuit is clear of trains.
2. Calculate the value of the feed resistance that will ensure reliable operation of this track circuit.
3. Calculate the drop shunt when the feed and relay end resistances have the values you have calculated.
4. Explain briefly the advantage of the additional relay end resistance.

Thanks in advance.

Regards,
Jenni.