Page 523 - IRSEM_Main Book

(d) QBCA1 Relay: This is similar to QBA1 relay but having two heavy-duty front contacts. It can
carry 30 A inductive current at 110 V through its front contact. The back contact can carry
3 A continuous and 2 A switching current like any other relay. Its Specification is BR
specification no. 943.Usage: These relays are used as Point contactor relays.

(e) QSPA1 relay: Only this relay is permitted to be used as the repeater for immunised
‘Q’ series track relays (QBAT & QTA2), due to its slow to pickup character. Provision of
a copper slug between the core and the heel piece behind and a magnetic shunt
between the core and the armature at the front contact make this relay slow to
pickup. Features of QSPA1 relay are: (i) Slow to pick up by 540 /600 milli seconds.(ii)
Less slow to release by 140/200 milli seconds and immune to AC. This made to BR
specification no. 933A.

(f) QL1 relay: This is a magnetically latched DC line relay. This relay remains in full operated
condition though the feed to the relay is cut off. This relay has two coils namely operate coil
(R) and release coil (N) and a permanent magnet. This made to BR specification no.
935A.Usage : these relays are used as latch relays in block instruments etc.

4.0 Track Relays

Track relays shall always be of metal to carbon contact type & normally be of plug in
type, unless otherwise specially permitted. In non electrified area, the following
relays shall be used: 9 ohm DC non-AC immunized (plug-in type). In electrified area,
the following relays shall be used: 9 ohm DC neutral, AC immunized.9 ohm DC biased,
AC immunized. Double element motor type relay, operating on 83 & one third Hz in
AC traction area and 50 Hz in DC traction area shall be used. Vane type relays may
continue in use till replacement. Relays for track circuit provided with coded, pulsed,
electronic (audio frequency or high frequency track circuit), shall be of an approved
type of track/line relay or as recommended by manufacturer.

(a) QT2: The construction of this relay is similar to that of a Q - Series line relay except that its
contact load is reduced drastically. The relay is more sensitive and workable on a low
voltage. QT2 relay has only one core and 2F - 1B contacts. The back contact is used for cross
protection for TPR circuit. This has a single coil unlike the shelf type relay, which has two
coils with open ends. Usage: it is used as track relay in Non-RE area.

(b) QTA2: Copper slug is provided on the core to achieve AC immunity. It's pick up
voltage is 1.4v and pick up current is 140 ma approximately. QTA2 relays are available
in 9 Ohms coil resistance with 2F/1B contact configuration. This relay requires more
D.C. operating power and it take more time to pick up and drop due to the copper
slug. New Installations: This can be used Upto 450 meters track Circuit Lengths in RE
Areas with Choke at both ends. ii. Existing installations: This can be used Upto 450
meters track Circuit Lengths in RE Areas with Choke at the Relay end with high
traction return current of 1000 Amps and up to 350 meters track circuit length
without choke at the Relay end with low traction return current of 600 amps. Usage:
used as track relay in RE area.

Chapter 21: Relay & Electronic Interlocking Page 466 of 535