A contactor is used to switch larger amounts of electrical power through circuit contacts of 10 amps or higher.
Contacts, carrying such a load are called ‘Main Contacts’.
These are always NO (normally open) contacts and designated by single digits in pairs: 7-2, 3-4, 5-6 (for three pole contactors), and 7-8 (for four pole contactors). In addition to reference numbers, the following reference letter code is used: Li, L2, (.This is shown on the top of the contactor, representing three-phase power supply terminals and T1, T2, T3, from the bottom of the contactor, representing the load side terminals.
Ship electrical contactor arrangement
The main contacts marked with (1) are movable, but the main contacts marked with (2) are fixed.
The auxiliary contacts, (3) fixed and (4) movable, are only used in control circuitry for monitoring purposes.
If the contactor coil is designed to be energized with AC (alternating current), aluminum or copper (shading) rings are crimped to both ends of the magnetic core creating an out-of-phase current that increases the minimum pull on the armature during the AC cycle.
Maintenance of ship electrical contactors
Modern ship electrical contractors are extremely reliable but may have common faults. Worn main contacts due to the arc-effect is a known problem. The operating coil should be opened for internal inspection under recommended routine maintenance systems.
A high standard of maintenance on contactors is paramount to the efficient operation of a vessel. High standards of preventive maintenance will minimize ship inefficiency and related downtime.
