Type B Vital Relays - Alstom

Preventive Maintenance
4.5.3. Biased-Neutral Relay Test
Use the procedure in Table 4–9 to verify biased-neutral relay performance.
Table 4–9. Biased-Neutral Relay Test Procedure
Step
Procedure
1 Perform the B1 relay visual inspection procedure in Table 4–2.
2 Saturate the relay coils with current at the value shown on the Relays ED sheet.
Coils are connected in series unless otherwise indicated.
3 Slowly decrease current and obtain DROPAWAY, which is the value at which
the back contacts just make.
4 Open circuit.
5 Close circuit and slowly increase the current to obtain PICKUP, which is the
value at which the front contacts just make.
6 Continue to slowly increase the current to obtain WORKING current, which is
the value at which the armature is against the front stop. Frequently the PICKUP
and WORKING current values are the same.
7 All biased-neutral relays are designed to ensure that they will not pick up when
50 times normal WORKING voltage is applied in the reverse direction.
Apply 50 times the normal WORKING voltage in the reverse direction. Relay
should not pick up.
If the relay picks up, remove it from service.
P1457, Rev. Nov/07 4–13 Alstom Signaling Inc.