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| Re: Differences between types of track circuits? 20/12/2011 at 00:48 #25842 | |
Firefly
521 posts |
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| Re: Differences between types of track circuits? 20/12/2011 at 00:55 #25843 | |
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Prof Jolly
61 posts |
" said:With and Without a trainI'm getting attachment not found 
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| Re: Differences between types of track circuits? 20/12/2011 at 14:50 #25889 | |
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kbarber
1719 posts |
" said:With and Without a train Is it actually 0V with the track occupied? Or perhaps more like 0.3V - nowhere near enough to hold up the relay? Log in to reply |
| Re: Differences between types of track circuits? 20/12/2011 at 15:54 #25892 | |
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Firefly
521 posts |
You'll possibly have a few millivolts but not much. It does vary with the type of track circuit. AC 50hz track circuits as used on 3rd Rail areas can have larger voltages on the relay due to their characteristics. Also worth mentioning is that it takes more voltage to pick a relay than it does to hold a relay. Therefore in my example of the relay having a pick up voltage of 0.8v, it's drop away voltage will probably be something like 0.6v Log in to reply |
| Re: Differences between types of track circuits? 23/12/2011 at 07:06 #26090 | |
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maxand
1637 posts |
See also IRSE_Green_Book_-_No_9_Track_Circuits_(British_Practice)_-_1951.pdf Links to this publication and other IRSE Green Books here. Log in to reply |
| Re: Differences between types of track circuits? 23/12/2011 at 11:44 #26093 | |
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Firefly
521 posts |
Bit of light reading for you :) I'll expect a report back later! (or 50 questions!!) That book is obviously very old, although the characteristics of AC and DC track circuits hasn't changed the technology has moved on. Modern trains have different electrical equipment onboard that can interfere with certain types of track circuits. From the book:- Quote: a.c. asynchronous, three phase and inverter drives, e.g. Networker, Class 373, Class 323 and Class 92, has created new track circuit interference risks arising from the wide frequency spectrum over which such units are capable of generating interfering current.Some track circuits that are installed these days include:- TI21(EBI 200)- Frequency based, DC traction immune and they don't require block joints when used in plain line. They're also used extensively on non-electrified areas taking advantage of the fact that IBJ's are not required. Can only be used on AC electrified areas if the structures are not bonded to the rail (so in reality only new electrification schemes) HVI - HVI stands for high voltage impulse. These track circuits are only generally used in point work, however due to the fact that they are immune to both AC and DC traction currents can be used in dual electrified areas. DC - Medium Voltage - As per my original drawing except power supply is a transformer and not a battery. They are immune to AC traction current and therefore used extensively on AC electrified areas provided there is no DC electrification nearby. Other track circuit types exist but these are the main 3 in use today. FF Last edited: 23/12/2011 at 11:45 by Firefly Log in to reply The following user said thank you: maxand |
