MECHANICAL AND ELECTRICAL LATCHED VACCUM CONTACTORS

See the answers:

Mechanically latched contactor:

There are two springs used in this system: one is closing spring and the other is tripping spring. The closing spring is stronger than the tripping spring. Once the breaker is closed, a mechanically latched system holds the breaker in closed position. When the contactor needs to be opened, the latch is released by the tripping coil. For detail mechanism, see the previous thread: http://cr4.globalspec.com/thread/39932

Electrically latched contactor:

In this mechanism, the contactor is held at closing position by an electrical Holding coil. As long as the holding coil is energized, the contactor remains closed (against tripping spring). When the contactor needs to be opened, the holding coil is de-energized and the contactor is opened with the action of the tripping string. There are two categories of this type of contactor: (1) the first category has single closing coil which is used for both closing and holding, all small size and low voltage contactors fall in this category, (2) the other category has separate closing coil and holding coil. Closing coil is stronger than holding coil. Once the contactor is closed by the closing coil, it is latched by the low power holding coil. Larger size and medium voltage contactors fall in this category. Generally DC power is used for the energizing coils.

- MS

An electrically latched relay or contactor is held in the actuated position by maintaining power to its coil, typically via an auxiliary NO (normally open) contact. The coil consumes a small amount of power and generates a small amount of heat.

A mechanically latched relay or contactor has two coils. With a brief signal, the actuating coil operates the relay, but then the relay stays in the actuated position until the deactuating coil (brief signal again) turns the relay back "off." Neither coil is energized for very long; this minimizes power usage and heat generation.

[Note, that should be "vacuum", not "vaccum". The concept applies to regular contactors as well as vacuum contactors.]

(Sorry to be redundant, but msamad must have posted just as I was writing this. My apologies for the near echo.)