SD2D-DC5V Datasheet, PDF (4/5 Pages) Nais(Matsushita Electric Works) – POLARISED, MONOSTABLE SAFETY RELAY

THE OPERATION OF SF RELAYS (when contacts are welded)
SF relays work to maintain a normal operating state even when the contact welding occur by overloading or short-circuit
currents. It is easy to make weld detection circuits and safety circuits in the design to ensure safety even if contacts weld.
Internal Contacts Weld
If the internal contacts (No. 2, 3, 6, and 7) weld of 4a4b type, the armature becomes non-operational and the contact gaps of each of
the four form “a” contacts are maintained at greater than 0.5 mm .020 inch. Reliable isolation is thus ensured. The 2a2b type operates
in the same way.
No.8
No.7
No.6
No.5
Non-energized
No.1
No.2
No.3
No.4
No.8
No.7
No.1
No.2
No.6
No.5
No.3
No.4
Energized (when no. 2 contact is welded)
If the No. 2 contact welds.
Each of the four form “a” contacts (No. 1, 3, 5,
and 7) maintains a gap of greater than 0.5 mm
.020 inch.
External Contacts Weld
If the external contacts (No. 1, 4, 5, and 8) weld of 4a4b type, gaps of greater than 0.5 mm .020 inch are maintained between adjacent
contacts and the other contacts return by an non-energized.
No.8
No.7
No.6
No.5
Energized
No.1
No.2
No.3
No.4
No.8
No.7
No.1
No.2
No.6
No.5
No.3
No.4
Non-energized (when no. 1 contact is welded)
If the No. 1 contact welds.
The adjacent No. 2 contact maintains a gap of
greater than 0.5 mm .020 inch. The other
contacts, because the coil is not energized,
return to their normal return state; each of
form “a” contacts (No. 3, 5, and 7) maintains a
contact gap of greater than 0.5 mm .020 inch;
each of the form “b” contacts (No. 4, 6, and 8)
return to a closed state.
Weld
If external connections are made in series.
Even if one of the contacts welds, the other contacts
Energized
operate independently and the contact gaps are
maintained at greater than 0.5 mm .020 inch.
Non-energized
Contact gap
min 0.5 mm .020 inch
Contact Operation Table
The table below shows the state of the other contacts. In case of form “a” contact weld the coil applied voltage is 0 V.
In case of form “b” contact weld the coil applied voltage is nominal.
No.8
No.7
No.1
No.2
No.6
No.5
No.3
No.4
Contact No. No.1 No.2 No.3 No.4 No.5 No.6 No.7 No.8
Terminal No. 20–19 12–11 8–7 16–15 13–14 5–6 9–10 17–18
Contact No.
State of other contacts
Contact No.
12345678
Welded
contact
No.
1
>0.5 >0.5 ≠ >0.5 ≠ >0.5 ≠
2 >0.5
>0.5
>0.5
>0.5
>0.5: contact gap
is kept at min. 0.5
3
>0.5
>0.5
>0.5
>0.5 _{mm .020 inch}
4 ≠ >0.5 >0.5
≠ >0.5 ≠ >0.5 ^{≠: contact closed}
5 >0.5 ≠ >0.5 ≠
>0.5 >0.5 ≠
Empty cells: either
closed or open
6 >0.5
>0.5
>0.5
>0.5
7
>0.5
>0.5
>0.5
>0.5
8 ≠ >0.5 ≠ >0.5 ≠ >0.5 >0.5
Note: Contact gaps are shown at the initial state.
If the contact transfer is caused by load switching, it is necessary to check the actual loading.
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