Unlike other relays, safety relays ensure
the safety function even if contacts are welded together because they have
forcibly guided (linked) contacts (EN 50205).
Note: Welding cannot be pulled apart.
(1) Main Safety Relay
Requirements
-
The gap between contacts must be at least 0.5 mm during normal operation
or when a fault occurs.
-
Contact load switching must conform to AC-15 and DC-13 (IEC 60947-5-1).
-
The mechanical service life must be at least 10 million operations.
(2) Forcibly Guided (Linked)
Contact Structure (G7S Safety Relay)
If at least one normally open contact is welded, when the coil is
de-energized, all normally closed contacts maintain a gap of at least 0.5
mm. Even if a normally closed contact is welded, all normally open
contacts maintain a gap of at least 0.5 mm in the coil energized mode (in
accordance with EN 50205).
Relays that use forcibly guided contacts for all of the contacts are
called Class A and indicated by the
 mark.
(3) Structural Comparison of
General Relays and Relays with Forcibly Guided Contacts
|
A. General
Relay |
B. Relay with
Forcibly Guided Contact |
|
Example: G2R
PCB Relay
 |
Example: G7SA
Relay with Forcibly Guided Contact
 |
|
(a)
When contact welding occurs
(Coil: Not
energized) |
(a)
When contact welding occurs in the NO contacts
(The NO contacts will not close if contact welding occurs in the NC
contacts.)
(Coil: Not energized)
|
|
(b)
When a movable spring is broken
(Coil: Not energized)
A
broken movable spring may cause a short-circuit between electrodes. |
(b) When a
contact spring is broken (broken NC contacts)
(Coil: Not
energized)
The above
shielded structure protects other contacts from being affected by the
failure.
|
Recommended Products
|
Safety Relay
G7SA
Compact, Slim Relays with guided
contact structure ensures safety and conforms to EN standards. |
|
Relays with
Forcibly Guided Contacts
G7SB
Low profile Relays with low power
consumption. |
|
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