Last edit: 22/08/2023
They are used as motor controllers in Branch Circuits.
They have three parts:
- The control part: it is the coil that moves both the power and the auxiliary contacts. The terminals are indicated as A1 and A2. When the coil is energised, the power contacts close.
- The Power contacts: normally there are 3 input and 3 output terminals, numbered from 1 to 6. Those are used for the power lines L1, L2 and L3
- The Auxiliary contacts: they indicate the status of the power contacts. Those contacts are called Mirror contacts and they are designed according to IEC 60947-4-1  Annex F.
The Mirror contacts have the characteristics of being guaranteed that if the power contacts are all in the open position, the Mirror contacts are closed.
[IEC 60947-4-1] Annex F: Requirements for auxiliary contact linked with power contact (mirror contact)
F.2.1 mirror contact. Normally closed auxiliary contact which cannot be in closed position simultaneously with the normally open main contact under conditions defined in Clause F.7
NOTE One contactor may have more than one mirror contact.
The symbol of a mirror contact is hereafter