Type B Vital Relays - Alstom

Theory of Operation
2.4.2. Biased-Neutral Line Relay
The biased-neutral line relay is basically a relay with a neutral structure. It is, however,
equipped with a permanent magnet and a leakage strip bridging the cores and placed
between the coils and the armature. The effect on the operation is to allow the relay to
pick up only if voltage of the proper polarity is applied.
In other respects, the relay is essentially like a regular neutral relay. It is built in Sizes 1
and 2.
Figures 2–14 through 2–16 how the relay works.
-
S
VOLTAGE OF
CORRECT
POLARITY
+
N
ARMATURE
PICKS UP
Figure 2–14. Voltage of Right Polarity Applied
P1457, Rev. Nov/07 2–16 Alstom Signaling Inc.