Contactor

A contactor is a electrotechnical apparatus intended to establish or stop the passage of the current, starting from an electric drive or pneumatic. It with the same function as a electromechanical Relais, with the difference that its contacts is designed to support a running much more important. Thus, they are used in order to feed from the industrial engines of great power (more 0,5  kw) and in general of the consumers of strong powers.

They are also used in domestic medium to feed from the electricals appliance like the heating or the water-heater, because the control units (thermostat, switch-schedule and other contacts of order) would be likely to be quickly deteriorated by the too important current.

Construction

They can be unipolar, bipolar, tripolar or four-pole, in other words they have one, two, three or four contact S of power.

On the contactors of high power the reels are often interchangeable, making it possible to order the contactor with various tensions (24  V, 48  V, 110  V, 230  V).

The three pole switches comprise an auxiliary contact most of the time, while the four-pole contactors do not have any in general (the place of the auxiliary contact being occupied by the fourth contact of power 7-8 not represented on the diagram below).

The difference between contact in power and auxiliary contact lies in the fact that the contact of power is designed to resist during the appearance of a Electric arc, when it opens or firm the circuit; so it is this contact which has a breaking capacity. The auxiliary contact is equipped only with one very weak breaking capacity; it is compared to the part orders circuit whose currents remain weak vis-a-vis the power part.

Thus, the only difference which exists between an electromechanical relay and a contactor is the presence or not of contacts of power, being able to establish or stop strong currents. One can regard a contactor as being a “relay of power”, or a relay as being a “contactor deprived of contacts of power”.

Location of the terminals

Each terminal is located by a number. Only one figure for the terminals of power and two for the terminals of the auxiliary contacts. Each terminal of power has an odd figure for the hight delimiters, and an even figure for the lower limits. The terminals of the auxiliary contacts have two digits: the figure of the units indicates the type of the contact: 1-2 for a NC (Normaly Closed), 3-4 for NO (Normaly Opened), 5-6 and 7-8 for special contacts, in particular on the time-lag blocks), the figure of tens allowing to identify each contact (there is one contact 13-14, 23-24…).

1 3 5 13 | | | | \ \ \ \ | | | | 2 4 6 14

Auxiliary contacts

It is possible to associate additional auxiliary contacts with the contactors, via the assembly of an additive block. This block can comprise contacts NO, NC or time-lag. An association of 2  in general is found; NC + 2  NO per additive block. The blocks of time-lag contacts comprise two contacts in general: NC and NO.

According to the model used, one can add of one to several additive blocks per contactor (on the top, and the sides).

See too

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