Is there a difference between contacts described as positive-break and those described as force-guided? I believe there is a construction difference but I am confused by the literature I have reviewed.

 

Force Guided Contacts (Linked contacts):
All-or-nothing relay with at least one break contact and at least one make contact designed in such a way that it is made sure by mechanical means that make and break contacts can not be in closed position simultaneously. Also known as: forced contacts, positively activated contacts, guided contacts, and linked contacts.

Positive Opening Operation (of a contact element):
The achievement of contact separation as the direct result of a specified movement of the switch actuator through non-resilient members (e.g.: not dependent on springs).The term Positive Opening is used throughout NFPA 79, and in IEC 60947-5-1, and EN 60947-5-1. Direct Opening is the term referred to in NEMA ICS-5, part 6 (direct opening action). The terms Positive Opening and Direct Opening identify the same contact action and characteristics.

 

A major difference is that Positive Opening Action contacts can open a contact weld, or other failure, but force-guided relays cannot. Conversely, Force guided relays can monitor them selves through the auxiliary contact (with an external Category 3 or 4 Safety Module) whereas Positive Opening contacts cannot.

Therefore, manufacturers should not use the Positive Opening Action symbol (a 3-o'clock arrow with a circle around it) on Force-Guided Relays.

Positive Opening Action contacts are best for Category 1 applications; Force-Guided Relays are best for Category 3 or 4 solutions.