IEC/EN 50205 Section 3.1:
Switching Relays with Force Guided Contacts:
Switching relays with at least one NC (Normally Closed) contact and one NO (Normally Open) contact, exhibit a mechanical design preventing simultaneous closing of the NO and NC contact at all times. Force guidance is defined as a condition in which contacts are mechanically connected in such a way that the NC contact and NO contact can never be closed at the same time.
What is a Force Guided Contact Set?
IEC/EN 50205 Section 3.2:
Contact Set with Force Guided Contacts, all exhibit mutual force guidance.
A force guided contact consists of at least 1 NC + 1 NO contacts.
A force guided contact set consists of 1 (n+1) NO + (m+1) NC contacts, which all exhibit mutual force guidance.
(n and m =>0)
Additional Requirements (1)
ZH1/281 Section 3.9.2
Contact spacing of at least 0.5 mm must be ensured over the entire service life and even in the event of disturbances.
IEC/EN 50205 Section 4.1
It must be ensured that even in the event of disturbances, the contact spacing is at least 0.5mm.
UIC 736 & VDE 0831 Signal Relays
It must be ensured that even in the event of disturbances the contact spacing is at least 1.2mm.
This means:
The requirement is valid throughout the entire individual service life.
A failure analysis must ensure that the requirement is fulfilled.
A contact is considered closed if its spacing is <0.5 mm.
IEC/EN 50205 Section 5.3.2
The stipulations set forth in IEC 61810.5 valid for air gap and creepage distances. The respective rules according to IEC 6064-1: 1992 or, respectively VDE 0110-1: 1997, will remain to be valid until the date of issue of IEC EN 61810-5. The content of UL standard 840 is identical.
IEC/EN 50205 Section 5.3.3
The suitability of solid insulation is verified by means of test using AC voltage 2*U +750 V-1
Remark:
Definitions refer to the minimum requirements for switching relay components. Apart from the basic requirements, any further requirement with regard to device standards must be taken into consideration. (IEC/EN 50178)