Alstom MCAG 34 - Section 5. PROBLEM ANALYSIS; Troubleshooting Relay Failure to Operate

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Section 4. MECHANICAL SETTINGS
4.1 General
Armature gap measurements should be made with the top of the feeler gauge level
with the centre line of the core.
Contact pressures are measured with a gramme gauge at the contact tips.
In general, contact gaps and follow through are defined by quoting an armature gap
at which the tips should be just closed or just open.
The relay contact state is always defined with the relay in the unenergised position,
unless otherwise specified on the appropriate circuit diagram.
4.1.1 With the armature closed the clearance between the back of the armature and the
back stop should be 0.003"/0.008".
4.1.2 Nominal armature gap open 0.050"/0.060" for all types.
4.2 Contact settings
4.2.1 Normal duty make contacts
With the armature closed onto a 0.011" feeler gauge the make contacts should be
closed, but should be open using a 0.013" feeler gauge.
Force to just close the make contacts 11/16 grammes.
4.3 Mechanical flag settings
4.3.1 Settings for self reset units
With the armature closed onto a 0.013" feeler gauge the flag should be free to fall,
but should not fall using a 0.018" feeler gauge. Adjustment is made to the catch
spring on the flag.
Section 5. PROBLEM ANALYSIS
5.1 Failure to operate
Check diagram for correct input connections.
Check tap current, this is marked above or below the plug bridge on the front of the
module.
Flag spring may be jammed between armature and core face, preventing armature
closure.
Check internal wiring.
Check continuity – result open circuit
– transformer open circuit
– internal wiring damaged
Check continuity – result short circuit
– transformer short circuit – relay takes excessive current
– shorting switch not opening