Type B Vital Relays - Alstom

Theory of Operation
Figure 2–38. VTB Relay Energized
A simplified operating diagram of a VTB polar-biased relay with two armatures is shown
in Figure 2–39.
COIL B
CORE B
COIL A
CORE A
Figure 2–39. VTB Relay, Two Armatures De-energized
These armatures are biased in opposite directions, armature A against the left-handed
pole piece, and armature B against the right-hand pole piece. This provides a
symmetrical magnetic path. The permanent magnet flux divides equally between the
two armatures and cores and reinforces the effect of the biasing springs on both
armatures.
P1457, Rev. Nov/07 2–41 Alstom Signaling Inc.