Last edit: 22/08/2023
They are also called Auxiliary Relays or Contactor-relays and are used in the control part of the electrical equipment of Machinery.
They have two parts only:
- The control part: it is the coil that moves the auxiliary contacts. The terminals are indicated as A1 and A2.
- The Auxiliary contacts: some are normally open and some are normally closed.
Figure 4.28 {4.12.2.2.2} shows a schematic of the contactor. The auxiliary contacts are shown when the coil is de-energised. That means:
- Normally open contacts means that when the coil is de-energised, the contacts are open. They are normally indicated as 13, 14, 43, 44.
- Normally closed contacts means that when the coil is de-energised, the contacts are closed. They are normally indicated as 21, 22, 31, 32.
When the auxiliary contacts are indicated as Mechanically linked, it means that it is not possible that a NO contact has the same position of and NC one. They are designed according to IEC 60947-5-1 [32] Annex L.
[IEC 60947-5-1] Annex L: Special requirements for mechanically linked contact elements
L.2.1 mechanically linked contact elements. Combination of n Make contact element(s) and m Break contact element(s) designed in such a way that they cannot be in closed position simultaneously under conditions defined in L.8.4.
Note 1 to entry: One control circuit device may have more than one group of mechanically linked contact elements
The mechanical linkage shall be identified in circuit diagrams by a double parallel line connecting a filled circle on each of the mechanically linked contact symbols.
