05-10-2009, 09:15 AM
I looked at this question too and actually attempted it thinking that I would somehow manage to work it out.
The questions gives you -
Feed Voltage - 50V
Feed Resistance - 100ohm
Rail Resistance - 33ohm/km
Shunt Resistance - 12ohm
Pick Up Current - 500mA
Track Circuit Length - 2400m
I couldn't see how to calculate the Rail-to-Rail voltage over the relay coil without being given the coil resistance. I attempted to assume it was 9ohm but soon realised this was unworkable.
The couple of people I have asked about this have asked if I was given the realy resistance and seemed surprised when I said no.
I was also curious as to the wording of the question as to find the ballast resistance in ohms per km as usually the units for ballast resistance is ohm km which isn't exactly the same thing.
I really want to know how this is done so if anyone has any ideas...
The questions gives you -
Feed Voltage - 50V
Feed Resistance - 100ohm
Rail Resistance - 33ohm/km
Shunt Resistance - 12ohm
Pick Up Current - 500mA
Track Circuit Length - 2400m
I couldn't see how to calculate the Rail-to-Rail voltage over the relay coil without being given the coil resistance. I attempted to assume it was 9ohm but soon realised this was unworkable.
The couple of people I have asked about this have asked if I was given the realy resistance and seemed surprised when I said no.
I was also curious as to the wording of the question as to find the ballast resistance in ohms per km as usually the units for ballast resistance is ohm km which isn't exactly the same thing.
I really want to know how this is done so if anyone has any ideas...