12-08-2010, 11:27 AM
(12-08-2010, 09:44 AM)shivi Wrote: For the second part of the question, which is for calculating Minimum Drop Shunt Value, why should we consider Minimum Ballast Resistance?
I think if we consider minimum ballast resistance, then there is chance that under DRY conditions the train may not shunt the track circuit because of more current passing through relay.
I was always thinking that we should consider Maximum ballast resistance (Infinity if not given) for calculating Drop Shunt Value.
Can anybody clarify this doubt?
Shivani Singh.
Your point is a very interesting one and adds to the discussion about what is being asked for when the term is used "calculate the minimum drop shunt". Taking your interpretation, if you use "good" ballast conditions (ie infinity) then you will come up with a value of DS which is lower than the one shown in the example answer, hence coming up with the value of drop shunt that is the lowest value that MAY be neeeded to drop the track in all the foreseeable conditions.
Perhaps there are other comments that people have.
Peter