Type B Vital Relays - Alstom

Theory of Operation
2.5.2. Power-Transfer Relay
A Type B power-transfer relay, built in Size 1 only, is essentially a DC neutral line relay
operating on rectified alternating current. The rectifier (P/N 59899-005-03) is shown in
Figure 2–27.
B RELAY 1E POST
RECTIFIER
B RELAY 1E POST
FRONT
PLUGBOARD
Figure 2–27. Type S1/4 Half-Wave Rectifier for Power-Transfer Relay
While AC energy is on, the relay stays energized. If AC energy fails the relay armature
drops and automatically transfers the circuits to local battery. The percent of release
voltage, found by dividing the DROP AWAY voltage by the PICKUP voltage, is about 75
percent at 70 degrees F. Power-transfer relay coil wiring is shown in Figure 2–28.
P1457, Rev. Nov/07 2–30 Alstom Signaling Inc.