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1.Why 1st TPR [DC track circuit] and USR'S made slow to pick up?
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Believe I have answered this in b and k of first post
Sounds like relay puely to drive route lights on a panel- why shouldn't be neutral relay- this is the dafault unless there is a reason for it not to be
As per Peter's answer re back emf for AWS; it provides a path for the current to decay slowly and whilst so doing it maintains some magnetic effect in the relay coil thus delaying the time when the force of the spring overcomes it
As I stated before, it is best that you have a go at working that out for yourself; you'll learn more by doing so than if I give you answer every time. As a hint, work on the basis that if it was fast acting then the circuit wouldn't work and the points could not respond to the operastion of the switch. Then consider what advantage making the WZR slower to release would give.
Ask yourself what is the purpose of theNZLPR circuit by investigating in what circuits its contacts are used and this should give you your answer
Indeed the centre light associated with a points control switch generally does flash when neither of the Normal or Reverse lights are illuminated, so I expect that such a circuit is shown in the typicals; pretty basic though so doesn't take much working out anyway!
Similarly whilst the (S)R = start relay for a signal is energised and the push button ring is looking for another button to be pressed as an exit then the fist button light is to flash.
Basically whereas an electrical circuit has components witi it of different resistance, the magnetic circuit has components of different reluctance. The ac component of the incoming voltage induces eddy currents within the copper which is a good conductor and this opposes tosome extent the build up of magnetic flux across the airgap and instead provides an alternative path for the magnetic flux to divert it away.
I haven't ready acess to the circuits; I guess that it might be a means of preventing a backfeed. Use of diodes in this manner is not permissible for vital circuits, but it would be ok in a push-button ring and may be more economical than using more contacts as an altenative means of avoiding backfeed.
I don't think that this would make it slow to pick up; give me a hint what made you ask this.
These are far too big a subject to give answer here.
I don't believe that new TDs have utilised relay circuitry in the UK for at least 40 years; they became an early application of electonics and hav been computer based for at least 20 years.
Overrides also are very much a thing of the past as the reduction in price of transmission systems means that it is invariably cheaper and better to duplicate these rather than provide an override system. They also tended to be quite bespoke for each particular signalbox, reflecting the technologhy available to achieve, the design of the usual interlocking and the operational requirement.
1.Why 1st TPR [DC track circuit] and USR'S made slow to pick up?
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Believe I have answered this in b and k of first post
Quote:2.Why UKR made neutral relay?
Sounds like relay puely to drive route lights on a panel- why shouldn't be neutral relay- this is the dafault unless there is a reason for it not to be
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3.To make the relay slow to release what is purpose of diode?
As per Peter's answer re back emf for AWS; it provides a path for the current to decay slowly and whilst so doing it maintains some magnetic effect in the relay coil thus delaying the time when the force of the spring overcomes it
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4.Why WZR made slow to release?
As I stated before, it is best that you have a go at working that out for yourself; you'll learn more by doing so than if I give you answer every time. As a hint, work on the basis that if it was fast acting then the circuit wouldn't work and the points could not respond to the operastion of the switch. Then consider what advantage making the WZR slower to release would give.
Quote:5.In NZLPR/RZLPR circuit: Purpose of WZR contact parallel with NLR/RLR contact?
Ask yourself what is the purpose of theNZLPR circuit by investigating in what circuits its contacts are used and this should give you your answer
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6.Is there any typical circuit to give flashing indication for the following action:
. Point CR relay not picked up
. Once entrance button is pressed
Indeed the centre light associated with a points control switch generally does flash when neither of the Normal or Reverse lights are illuminated, so I expect that such a circuit is shown in the typicals; pretty basic though so doesn't take much working out anyway!
Similarly whilst the (S)R = start relay for a signal is energised and the push button ring is looking for another button to be pressed as an exit then the fist button light is to flash.
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7.Magnetic shunt (with CU slug) making the relay to achieve AC immunized and slow to pick up function, Please explain the working?
Basically whereas an electrical circuit has components witi it of different resistance, the magnetic circuit has components of different reluctance. The ac component of the incoming voltage induces eddy currents within the copper which is a good conductor and this opposes tosome extent the build up of magnetic flux across the airgap and instead provides an alternative path for the magnetic flux to divert it away.
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8.what is the advantage of giving the supply to relay front/back contact? [But in indian railway circuit the supply will be given to arm contact]
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Generally signalling relays do not utilise changeover contacts but have an arm and either a front or a back. Where carbon-metal contacts are in use then putting the positive to the carbon (and therefore the front of a F-A pair) and the negative to the metal is supposed to discourage the deteriration of the carbon contact material. However the Western Region historically fused the negative of the circuit and still wired the supply to the contact rather than the arm; I know of no evidence that in practice it hasmade any difference to contact life, although I stand to be corrected. I believe in India that whereas British style relays are used, so too are Geran ones with metal-metal contacts which presumably this is not a consideration. Also where changeover contacts are used it is often needed for circuit reasons to put the supply from the fuse to the common arm contact.
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9.In (S)R and (D)R circuit, what is the purpose of forward biased diode?
I haven't ready acess to the circuits; I guess that it might be a means of preventing a backfeed. Use of diodes in this manner is not permissible for vital circuits, but it would be ok in a push-button ring and may be more economical than using more contacts as an altenative means of avoiding backfeed.
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10.Please explain how the relay is working as Slow to pick up When we connect the reverse biased diode across the relay?
I don't think that this would make it slow to pick up; give me a hint what made you ask this.
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11.Explain the working principle [With circuitry] of TD & override ?
These are far too big a subject to give answer here.
I don't believe that new TDs have utilised relay circuitry in the UK for at least 40 years; they became an early application of electonics and hav been computer based for at least 20 years.
Overrides also are very much a thing of the past as the reduction in price of transmission systems means that it is invariably cheaper and better to duplicate these rather than provide an override system. They also tended to be quite bespoke for each particular signalbox, reflecting the technologhy available to achieve, the design of the usual interlocking and the operational requirement.
Quote:I am not sure how these compare, but I doubt whether they are very much different as the same laws of physics apply, although the environment may differ slightly (e.g. considerations of heat dissipation may depend a bit on ambient temperature). The actual voltages are not regarded as important as the currents (to which of course they are related) and when setting up a track it is the pick up and drop away shunt values achieved that are the dominant consideration.
12.DC Track circuit: [In india]
Relay terminal voltage is not more than 300% of Pick up voltage
After train shunt,
Relay terminal voltage should be less than 85% of drop away voltage
what is the parameter for the same in UK railway and how it is achieved in TFU?
PJW