Type B Vital Relays - Alstom

Theory of Operation
2.2.2.1. Contact Combinations
A B1 relay has space for three contact groups. For example, a relay with 6 front-back
dependent contacts has three groups, each with 2 front-back contacts. A relay with 4
front-back dependent contacts and 2 front and 1 back independent contacts also has
three groups, two with 2 front-back dependent contacts, and one with 2 front and 1 back
independent contacts.
A typical B2 relay has space for six contact groups. For example, a relay with 12 frontback
contacts has six groups, each with 2 front-back contacts. The B2 AC Vane relay
has a different configuration with space for four contact groups.
Table 2–1 shows the contact combinations normally furnished with B relays. For the
configuration of specific arrangements, see Section 7.
Table 2–1. Typical Relay Contact Combinations
Type
B1 Relays
(3 Contact Groups)
B2 Relays
(6 Contact Groups)
B2 Vane Relays
(4 Contact Groups)
Neutral 2FB, 4FB, 4F-2B, 12FB
4FB-2F-1B, 6FB
Biased-Neutral 4FB-2F-1B, 6FB 8FB-4F-2B, 12FB
Magnetic-Stick 4 NR
Power-Transfer 2FB, 6FB
Light-Out 4FB, 4F-2B, 6FB
AC Vane
2FB, 4FB
FB
Front-Back Dependent Contact
F
Front Independent Contact
B
Back Independent Contact
NR
Normal-Reverse Dependent Contact
P1457, Rev. Nov/07 2–5 Alstom Signaling Inc.