The term 'safety contactor' does not appear to have any clear definition within the Safety of Machinery standard IEC (BS EN) 60204-1 or within IEC (BS EN) 60947-4-1, the standard associated with contactors.
However, Schneider Electric does have contactor products with 'mirror contacts' that can be used to switch off the supply to a motor as part of a machine safety system.
Mirror Contacts
Mirror contacts are defined within IEC (BS EN) 60947-4-1. The essence of the mirror contact function (refer to the standard for a full explanation) states that the N/C auxiliary contact on each contactor will not close when one of the power contacts is closed and can therefore be connected to a safety monitoring relay.
Schneider Electric's TeSys D contactors and TeSys U combined contactor circuit breaker ranges incorporate N/C mirror contacts in accordance with IEC (BS EN) 60947-4-1.
Mechanically linked or guided contacts
It is worth mentioning that prior to the introduction of mirror contact terminology, the requirement for reliable signaling from a N/C contactor auxiliary has, in some instances, been referred to as mechanically linked or guided contacts.
Using this terminology to describe the requirements of a contactor can be misleading, as the definition of a mechanically linked or guided contact is the non overlap of all N/O and N/C contacts. This terminology was originally used with respect to relays used in a variety of applications including railway signal interlocking. To claim this feature for a contactor without clarification is unwise as it implies that the condition of a very small auxiliary contact can influence the status of a potentially very large power contact controlled by a powerful electromagnet. Thus the introduction of the mirror contact specification that only considers the influence of the power contacts on the auxiliary and not the auxiliary on the power contacts.
This FAQ is intended as a brief explanation for information purposes only. For further details refer to the product literature and the relevant standards.
However, Schneider Electric does have contactor products with 'mirror contacts' that can be used to switch off the supply to a motor as part of a machine safety system.
Mirror Contacts
Mirror contacts are defined within IEC (BS EN) 60947-4-1. The essence of the mirror contact function (refer to the standard for a full explanation) states that the N/C auxiliary contact on each contactor will not close when one of the power contacts is closed and can therefore be connected to a safety monitoring relay.
Schneider Electric's TeSys D contactors and TeSys U combined contactor circuit breaker ranges incorporate N/C mirror contacts in accordance with IEC (BS EN) 60947-4-1.
Mechanically linked or guided contacts
It is worth mentioning that prior to the introduction of mirror contact terminology, the requirement for reliable signaling from a N/C contactor auxiliary has, in some instances, been referred to as mechanically linked or guided contacts.
Using this terminology to describe the requirements of a contactor can be misleading, as the definition of a mechanically linked or guided contact is the non overlap of all N/O and N/C contacts. This terminology was originally used with respect to relays used in a variety of applications including railway signal interlocking. To claim this feature for a contactor without clarification is unwise as it implies that the condition of a very small auxiliary contact can influence the status of a potentially very large power contact controlled by a powerful electromagnet. Thus the introduction of the mirror contact specification that only considers the influence of the power contacts on the auxiliary and not the auxiliary on the power contacts.
This FAQ is intended as a brief explanation for information purposes only. For further details refer to the product literature and the relevant standards.
Released for:Schneider Electric UK
