262

SF

If the two form “a” contacts (Nos. 2 and 4) weld, the armature becomes non-operational and the gap between the two form "b"

Form “a” Contact Weld

If the No. 2 contact welds.

Each of the two form "b" contacts (Nos. 1 and 3)

No.4

No.3

No.1

No.2

Energized

No.4

No.3

No.1

No.2

Non-energized (when no. 2 contact is welded)

No.4

No.3

No.1

No.2

Contact No.

No.1

No.2

No.3

No.4

Terminal No.

11–12

7–8

5–6

9–10

State of other contacts

1234

Welded

terminal

No.

1

>0.5

>0.5

2

>0.5

>0.5

3

>0.5

>0.5

4

>0.5

>0.5

Note: Contact gaps are shown at the initial state.

If the contacts change state owing to loading/breaking

it is necessary to check the actual loading.

Empty cells: either closed or open

Contact No.

Contact No.

The table below shows the state of the other contacts when the current through the welded form “a” contact is 0 V and the rated

voltage is applied through the form “b” contact.

Contact Operation Table

1) 2a2b Type

If the form “b” contacts (Nos. 1 and 3) weld, the armature becomes non-operational and the contact gap of the two form “a” contacts

Form “b” Contact Weld

If the No. 1 contact welds.

tained at each of the two form "a" contacts (Nos.

2 and 4).

No.4

No.3

No.1

No.2

Non-energized

No.4

No.3

No.1

No.2

Energized (when no. 1 contact is welded)

THE OPERATION OF SF RELAYS (when contacts are welded)

SF relays work to maintain a normal operating state even when overloading or short-circuit currents occur. It is also easy to include

weld detection circuits and safety circuits in the design to ensure safety even if contacts weld.