08-01-2010, 09:50 PM
(08-01-2010, 09:05 PM)Peter Wrote:(08-01-2010, 08:43 PM)Archie Wrote: Hello again, for the purposes dc track circuit, am I right in saying the lower the resistance, the higher the voltage and as a train cannot shunt all the voltage away from the relay,it would leave to much voltage on the relay coil meaning TR would not drop, causing a 'wrongside failure.'
If someone could just verify this then it would be greatly appreciated.
If by "the resistance" you mean the drop shunt value, yes, what you have written is essentially correct. The current being supplied will go one of thee ways - through the relay, through the ballast leakage or through the shunt (shunt box or the train). A low value of shunt resistance indicates that you are having to "divert" a lot of the current away from the relay hence a train needs to emulate that low value to guarantee dropping the track.
Now that you have grasped that bit, what will be the effect on the drop shunt value (all other things being equal for a given setup of track circuit) of altering the value of the ballast resistance?
Many thanks for the quick reply, sorry I don't quite understand the question, maybe I have got it wrong, but if I increase the resistance, which will lower the voltage, and increase the drop shunt, or is this nothing to do with what you are asking me.