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4.2 Cleaning contacts
Contacts should be cleaned with the burnishing tool, supplied in relay tool kits.
On no account should cleaning fluids, knives, files or abrasive materials be used.
4.3 Contact settings
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. Follow through should be
measured at the centre of the armature. Some mechanically operated contact gaps
must be measured directly with feeler gauges at the contact tips.
The relay contact state is always defined with the relay in the reset position unless
otherwise specified on the appropriate circuit diagram.
Symbols used on diagrams
Contact type Normal duty
Make (normally open) M
Break (normally closed) B
4.4 Settings
Settings should be within those specified in the following tables.
4.4.1 Relay types MVAJ05
Standard armature gap 1.5 to 1.25 mm
Make Follow through – just closed 0.5 mm
– just open 0.6 mm
Force to make 25 to 30 grammes
Break Contact gaps 1.25 to 1.5 mm
Force to break 25 to 30 grammes
Break Cut off contact (top left-hand viewed from front)
Force to break 25 to 30 grammes
Contact gap 0.2 to 0.5 mm
(measured at armature)
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