relays for railway signaling
DESCRIPTION
Teaching notes on Relays used for railway signalingTRANSCRIPT
1
TEACHING NOTES
ON
RELAYS
SIGNAL & TELECOMMUNICATION TRAINING CENTRE, BYCULLA, MUMBAI
( I S O 9001-2000 CERTIFIED )
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CONTENTS PAGE NO.
1. INTRODUCTION 04
2. Axle Counter 04
3. Components of the system 04
4. Basic function 07
5. Installation procedure. 08
6. Cable connection 11
7. Power Supply Arrangements. 12
8. Initial adjustment and commissioning 14
9. Adjustment of wheel dip 14
10. Testing of the system working 18
11. Typical failure and trouble shooting 22
12. Isolation of defective card 25
13. Input and output voltages of each card 26
14. Universal axle counter 31
INTERMEDIATE BLOCK SIGNALLING
1. INTRODUCTION 43
2. Requirement of IBS 44
3. Use of axle counter for IBS 46
4. Resetting Procedure 47
5. Description of Relays and Circuitry 49
6. Power Supply Arrangement for IBS 54
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7. RELAY:
A relay is an electromagnetic device, which is used to open or close electrical
circuits. It is so called because it relays information from one circuit to
another circuit.
CLASSIFICATION OF RELAYS:
Relays may be classified into various ways depending upon the following
factors.
1. Type of mounting – Shelf type and plug in type.
2. Supply used – DC relay and AC relay
3. Contact arrangement - Proved and non-proved.
4. Application – Track relay, Line relay and special relays.
DC RELAYS:
DC Relay works on DC current.
DC NEUTRAL RELAY: A neutral relay is one which operates irrespective of
direction of current,. It is so called because it is magnetically neutral.
DC SHELF TYPE RELAY: (As shown in fig.)
PRINCIPLE OF WORKING: DC neutral relay works on electromagnetic
principle. Each relay has two coils, core, Yoke, armature contacts and
binding post.
When current is applied through the coil, it sets up magnetic flux through the
core, yoke and armature. This flux causes armature to get attracted towards
the pole face. Armature picks up and front contact closes. When current is
interrupted magnetic flux collapses causing armature to drop due to its gravity
and front contact opens.
PLUG IN TYPE RELAY: Plug in type relays, which are plugged into prewired
terminal board. The relay may be proved type (metal to metal) and non-
proved type (metal to carbon)
USAGE: The relays are used to control signaling circuit and signalling
apparatuses. The relay also protects the signaling equipment.
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DIFFERENCE BETWEEN SHELF TYPE AND PLUG IN TYPE RELAYS
SN. SHELF TYPE PLUG IN TYPE
1. These are heavy and large These are light and compact
2. These occupy more space These occupy less space
3. Their replacement takes more
time
Their replacement is quick and easy.
4. Controlled circuit must be
tested before putting a
replaced relay to use
Controlled circuit need not be tested
after replacing the relay as the wiring
does not get dislocated.
5. No coding arrangement is
needed in the relay
Some coding is needed on the relay to
avoid inter changeability with that of
different contact position.
TRACK RELAYS AND LINE RELAYS
The relays, which are directly connected to the track/rail to detect its
occupation, are called track relays. The relays, other than track relays, which
are connected to supply lines through necessary controls, are called line
relays.
SN. TRACK RELAY LINE RELAY
1. The relay directly connected
with track relay
Other than track relay
2. Functions with less or more
current
Functions either with normal supply
voltage or with no supply at all.
3. More sensitive,% age release
should be high
Comparatively low percentage release
4. For front contact non fusible
contact are necessary
Not necessary
5. Less nos. of contacts due to
low power operation.
These can have more contacts due to
sufficient power application.
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PARAMETERS OF SHELF TYPE TRACK & LINE RELAYS
SN. FEATURE LINE RELAY TRACK RELAY
1. Working
Voltage
Normally 12 VDC Min. 125% of Relay PU
Max. 250% of relay PU
2. Coil
Resistance
Two coils each of 500 ohm.
1000 ohms when coils are
connected in series and
250 ohms when coils are
connected in parellel
Two coils each of 4.5
ohms. 9 ohms when coils
are connected in series
and 2.25 ohms when coils
are connected in parellel
3. Contact 4F/B, and 6F/B 2F/B, 2F 2F/B, 4F/B
4. Contact
current
rating
(a) For
front
(b) For
30
sec.
(c) For
back
3 amps.
5 amps.
3 amps.
3 amps.
5 amps.
3 amps.
5. Minimum%
Release
50% 68%
6. AC
immunity of
relay
300 VAC 50 VAC
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Initial Pick up current for Track Relay:
Relay
Resistance
2F/B 2F 2F/B 4 F/B
Min
mA
Max.mA Min
mA
MaxmA Min.mA Max.mA
9 ohms 37 39 39 41 44 49
2.25 ohm 74 78 78 82 88 98
9 ohm AC
immune.
Relay min
66mAmax
72 mAmax
For line relay
Coil Resistance Max. Max. Max.
250 ohms 10.5 ma 12 ma 14.0 ma
1000 ohms 5.25 ma 6 ma 7.0 ma
IMPORTANT DEFINITIONS:
1. Non-fusible Contacts: A pair of contact in which one contact element
comprises of non-fusible material, which present practically no risk of
welding of contact.
2. Carbon Contact: “Carbon” in the expression “carbon to metal contact” is
used as a general term covering graphite and compound and mixture of
carbon and metal. Contact resistance should not be more than 0.2 ohms.
3. Metal Contacts: Metal in expression “metal to carbon” “metal to metal” is
used as general term covering the use of silver, silver cadmium oxide,
tungsten platinum or any other suitable material to an approved
specification. Contact resistance should not be more than 0.05 ohms
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4. Front Contact: That contact which is made with the arm contact when
the relay is energized.
5. Back Contact : That contact which is made when relay is de-energized.
6. Arm Contact (or Armature Contact) : That contact which is movable
part of the pair of contact and makes with front contact when relay is
energized and with back contact when the relay is de-energized.
Dependent Contact: The condition in which a movable arm contact
connects a front contact when the relay is energized and the same arm
contact connects to a back contact when the relay is de-energized.
Independent Contact: The arrangement in which the Arm contact connects
to either a front or a back contact but not to both.
Pick up Value: the value of current or ampere-turns, which is just sufficient
to close all the front contact of relay under specified condition.
Drop Away Value: The value of current or ampere-turn at which all the front
contacts of the relay get open under specified condition.
% Release: It is ratio of DA value to pick up value.
% Release = DA X 100 PU
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Proved Type Relay: Means a relay having metal-to-metal contacts. The
relays are called proved type since in this relay it is ensured that the release
of these relays after each previous operation is proved before any function is
controlled through their operated contacts.
Non Proved Type Relay : Means a relay having metal to carbon contacts as
front contact. These are used for controlling vital circuits.
Polarized relay: It works on Dc supply. This relay is sensitive to the
direction of current and makes different sets of contacts for different direction
of current flowing though the coil.
Working Principle: a permanent magnet is placed in between the pole faces
of electromagnet. In the center position of the magnet, the flux divides equally
on both side and there is no force of attraction towards any side. When the
coil is energized the electromagnetic flux causes a variation in the amount of
flux on either side of armature. In one side flux is strengthened and other side
weakened and armature is attracted on any one side depending upon the
polarity of supply.
When (+) on R1 (-) on R2 the normal contacts make
(-) on R1 (+) on R2 the reverse contacts make.
Operating Characteristics of IRS 31-80 Relay
1. Coil Resistance – 77 ohms (38.5 ohm + 38.5 ohm)
2. Pick up current (15ma to 18 ma)
3. Rated current – 25 ma
4. Contact gap – 1.5 mm.
Use: used in Non RE and RE area in B/Instt.
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‘Q’ Style Relay (Plug in type)
These are miniature non-proved/proved plug in type relays
Q’ Style Relay: is a non-proved type relay
Special Feature:
1. Non proved type, independent contact, relay
2. Plug and socket type connection between relay base and relay. Board.
3. Plug board for all ‘Q’ type relays is standard.
4. The line relay is provided with max. 16 nos. of contact (with different
contact combinations)
5. The track relay is provided with max. 2F contacts
6. Pre-wiring facilities are available for each type of relay, Relay replacement
is easy.
7. All relays are provided with registration device with specified coding
combination to prevent plugging of wrong relay.
8. Armature is biased by helical spring.
9. A retaining clip is provided to hold the relay firmly in its plug board.
10. A gasket is provided to make the relay dust proof and waterproof.
OPERATING CHARACTERISTICS OF SOME MOST COMMONLY USED
Q1 STYLE RELAY.
SN. Description Style Contact
arrangement
Rated
voltage
Usage
1. Neutral Line
Relay
QN1 12F.4B,
8F.4B,
6F.6B,
8F.8B
24v DC
400
ohms
For indoor and outdoor ckt in
non RE area and Indoor ckt.
in RE area
2. AC-immunized
DC Neutral
Relay
QNA1 12F.4B,
8F.8B,
8F.4B
24v DC
195
ohms
For external ckt in RE area
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3. Magnetically
Latch Relay
QL1 8F.6B,
11F.4B
24v DC PU-145
ohms
TD-680
ohms
IRS push-
button block
TGTR/TCFR
4. Lamp Checking
Relay
QEC1 4F.2B 1 amp 4.5 Ohms For lamp
proving
5. Thermal time
relay
QJ1 2F.1B 24 v DC Thermal 43
ohms
Neutral 380
Ω
For time delay
ckt. 30 sec to
120 sec.
6. Biased AC
immunized
contactor relay
QBCA1 2F(HD).4B 24 v DC 208 ohms Point m/c
control in RE
area
7. Slow pick up AC
immunized line
relay
QSPA1 8F.4B 24 v DC 195 ohms Repeater of
QTA2 & QBAT
8. DC neutral
sensitive line
relay
QS3 4F.4B 12 v DC 1000 ohms In place of
shelf type relay
9. DC Track Relay QT1 2F 0.5 v DC 4 ohms In non RE area
10. AC Immunized
Track Relay
QTA2
2F.1B
1.4 v DC
9 ohms
In RE area up
to 450m
11.
ACI biased DC
track relay
QBAT
2F.2B
1.75 v
9 ohms
T/Ckt. length
up to 750 mtrs.
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K.50 Relays (METAL TO METALPLUG IN RELAYS)
This relay comes in category of proved type relay. These relays are
manufactured by Siemens’ India Limited under code K.50
Special Features:
1. All movable contacts are rigidly coupled to ensure simultaneous making
and breaking of contact.
2. Double break series contact arrangement provided ensures high
switching speed and more gap between the contact.
3. Contacts are designed to have self-cleaning feature.
Characteristics:
1. Coil Resistance – 1260 ohms to 1840 ohms
2. Rated voltage – 24v DC, 60 v DC
3. Operating Power – 1.3 watt to 2.5 watt
4. Max. Nos. of contact – 8
5. Contact combination – 4f/4B 5F/3B 6F/2B
6. Max. Switching contact current – 2A
7. Max. Continuous load of closed contact – 5A
8. Pick up time – 25 to 60 sec.
9. Drop Away time – 7 to 15 m sec.
Contact Numbering : Relay Base Pin numbering can be seen in figure.
K.50 Inter locked Relay: This is also known as latch relay consist of two
K.50 neutral relay arranged one above the other on a common base plate.
The armature of the relay being made interdependent by an additional
mechanical latching device such that one relay in its resting position latches
the other in the operating position.
In normal condition of latch the bottom relay armature is latched in its
operated position.
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In reverse condition of latch the top relay armature is latched in its operated
position.
Coil Resistance – 615 ohms.
Max. Nos. of contact – 8
K.50 ’E’ Relay: (Lamp proving Relay) K50 ‘E’ relay is a special relay for
proving that the signal lamp at site is lit or not.
The characteristics of the K.50 ‘E’ type relay are different for proving the Red
Aspect, and green/yellow double yellow aspect. Junction type route indicator
with lamp in series, junction route indicator with lamp in parallel and multiple
route indicator.
Coil Resistance - 64.1 OHM
Max. No. of Contacts - 6 Nos.
Contact Combination - 3F/3B
- 5F/1B in case of UECR.
K-50 relays are available in-group or one relay with a current transformer.
Maintenance of K-50 Relay: K.50 Relay does not require periodical
maintenance. Adjustment of contact or contact spring should not be done
only contacts can be cleaned when any failure occurs.
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Important symbols of K.50 Relays
Neutral Relay Coils
common relay relay controlling relay controlling relay controlling relay controlling a signal a point a route a track
Track repeater relay Locking relay for signal Locking relay for point Locking relay for route
Signal lamp checking relay Point detection relay Route checking relay
Normally closed contact of a normally dropped neutral relay
(or a back contact).
Normally open contact of a normally dropped neutral relay
(or a front contact).
Normally closed contact of normally picked up relay
(or a front contact).
Normally open contact of a normally picked up relay
(or a back contact).
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AC IMMUNISED RELAY
AC immunized relays are used in 25 KV AC electrified area. AC immunization
is done by means of two copper slug on core near pole face. A magnetic
shunt between the cores above the copper slug.
PROCESS: induced current in copper slugs oppose the alternating flux, most
of alternating flux diverted through magnetic shunt. Flux through air gap is
not sufficient to pick up the relay
AC IMMUNISATION LEVEL:
1. DC shelf type line relay 300 V AC
2. DC shelf type Track relay 50 V AC
3. DC polarized relay 10 V AC
4. QNA1 300 v AC
5. QTA2 50 V AC
6. QBAT 80 v AC
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AC RELAYS
The AC relay works on AC supply:
Principle of Working: AC relay works on the principle of Induction motor.
Magnetic circuit completes through core and vane. When any current
carrying conductor is placed in a magnetic field it experiences a force.
In AC relay the armature is called vane it is made of aluminum when the relay
is energized the vane rotates.
To produce a torque to rotate the vane two fluxes with a phase difference
between them is required. These two fluxes produce eddy currents in the
vane.
Flux Ø1 produce eddy current I1
Flux Ø2 produce eddy current I2
Ø1 interacts with I2 & produce torque T1
Ø2 interacts with I1 & produce torque T2
Resultant of T1 and T2 rotates the vane
Using two coils and feeding them AC voltage with phase difference achieve
two fluxes with phase difference. The phase difference between two voltages
is achieved by
1. In case of single-phase supply – Feeding one coil directly and another coil
through a condenser/reactance.
2. Design the coil with different power factor.
In case of 3Φ or different supply.
1. By feeding the coil with different phase of 3 phases supply.
2. By feeding the coil with different source of supply. The two coils are called
Local coil and control coil local coils are fed directly and control coil
through reactance/condenser etc.
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Types of AC Relay
Single Element Relay Motor type double coil Double element relay Use only for Track relay it is double coil relay
Used as only line relay used for both track and line relay
Single Element Relay Double Element Relay
1. Source of supply is only one 1. Different source of supply. 2. No. of coil may be one or two 2. Nos. of coil are two 3. Phase angle is low 3. Phase angle is high 4. Less torque 4. More torque 5. Designed to work as line relay 5. Designed to work as track and line
relay. 6. Can give only two positions Designed to give two as well as three
positions. Motor type AC Track relay (Siemens make) Contact 2F/2B
Frequency Local Voltage Control Voltage 50 Hz 130 18.5 V 83 1/3 Hz 165 22.2 V
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TIME ELEMENT RELAY
In signalling, for the purpose of safety, a time delay is require to be
maintained between initiation and actual operation of certain circuit /
equipment to achieve the time delay, time element relay is used.
Types of Time element Relay
1. DC Thermal Type.
2. DC Clock Work Type
3. Motor Type
4. Electronic Type
1. DC Thermal Type (QJ1): - this is a thermal time element relay. It has a
heating element and a neutral relay, which together energizes an external
time relay after a pre-set time delay. Circuit is shown in figure.
1. Rated voltage – 24 v DC
2. Heating Coil Resistance – 40 ohms
3. Neutral Time Relay – 400 ohms
4. Time – 30/60/120 sec.
DC clock work Type:
Working voltage – 60 v DC
Time – 1 minute to 3 minutes.
Motor Type Timer:
Working voltage – 110 v AC
Time: 1 to 5 minutes.
Electronic Type Timer:
Working voltage – 12v, 24v, or 60 v DC
Time: 60sec, 120sec, 180 sec.
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SLOW ACTING RELAY
Slow acting relays are so called because their operation is delayed for a
period of a few seconds or milli seconds to keep circuit controlled by them live
even after their own feed is cut off. This is necessary to maintain certain
operational sequences.
Slow acting relays are classified as
1. Slow to pick up and slow to release.
2. Slow to pick up relay.
3. Slow to release relay.
Slow to pick up and slow to release: to make slow to pick up and slow to
release relays, Copper sleeves are provided on the core of relay.
Slow to Pick Up
Slow to release relay: Relays are made slow to release by following
methods
1. By connecting a diode in reverse biased.
2. By connecting a condenser across relay
\/\/\/\/\/\
3. By proving the front contact of relay in series of condenser.
\/\/\/\/
Copper sleeve
Magnetc shunt
RELAY
RELAY
RELAY
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Flasher Relay: These relays are normally used for giving flashing indications.
When supply is connected its armature makes normal and reverse contacts
alternately. The contacts when connected with indication circuit the indication
will flash.
Contactor Relay: These relays having heavy-duty contacts are used to
control high current for point machines etc to reduce the Arc due to high
breaking current permanent or electromagnets are used near heavy-duty
contact for spark quenching.
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Maintenance Check:
During Maintenance visit relays should be checked visually for the following.
1. There is no loose connection on the terminals. Plug in relays are fitted
tightly and the sealing is intact.
2. Metal contacts are not blackened due to arcing
3. There is no pitting of carbon contacts.
4. No foreign materials are inside the relay.
5. There is no rusting or sulphation on the parts.
6. Removing the transit lock screw, hole has been closed by dummy screw
fitting, before connecting a shelf type relay in circuit.
7. Relays are not due for POH.
8. Track relay drops properly with 0.5 ohms TSR.
9. Over energisation is not more than 250 % of its PU value.
As per SEM:
01. All vital relays should be inspected visually once in every two and three
years for track and line relays respectively in following respect.
a. Movement of Armature and current carriage.
b. Wiping of contacts arcing of contacts if any
c. Pitting or charring of contacts.
d. Dust on contact.
e. Electro plating
f. Corrosion rusting of contact.
g. Presence of fungus
h. Charring of cover near contacts
i. Corrosion of label.
j. Presence of seal.
Overhauling: Track relay:
Track relay of all type should be overhauled after every 10 to 12 years.
Shelf type line relays: Shelf type line relays shall be over haled after every
15 years
All other non-proved type relays, when removed from service after failure.
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