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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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