User Manual

Publication 1000-UM001B-US-P - July 2000
4-2 SLS Sequence of Op er ation
D. If an operator moves the SLS switch from ON to OFF, the following
will happen:
1. The safety relay circuit between terminals S10 an d S11, and S21 and
S2 will open up to de-energize the safety relay, causing the safety
conta c ts termina ls #1 3 and #1 4 between wires #1 a nd #3 to ope n
up. In addition, safety relay auxiliary contacts between terminals #33
and # 34 and #43 and #44 will open droppin g out 1CR. This w ill
cause IC to open up.
Note: If one of the contacts on the SLS switch does not open, or if
there is a short in the cable to the SLS switch, only one of the safety
relay contacts K1 or K2 will drop out IC. But, the safety relay will
lock up and not allow a re-start. Now, since one of the safety relay
auxiliary contacts K1 or K2 will remain closed, 1CR will remain
energized, preventing the SAFE pilot l ight from i lluminating. Also, if
the contact s IC and 1CR between term inals S41 and S42 on the
safety relay have not re-closed, the safety relay will not allow a restart.
2. After IC has dropped out, the VSR will check for voltages greater
than 10V on the load sid e of IC through its redundan t and broken
wire sensing cir cuit. The VSR will also check to see that the N.C.
positively guided auxiliary contact between wire #7 and #8 on IC is
closed. If these two conditions are met, the VSR will close the safety
co nta c ts betwe en its ter m inal s #1 3 an d # 14 .
3. Since the auxiliary contact of IC between ++ and wire #10 is closed,
the 1CR contact between wires #10 and #11 is closed, the safety
contacts between wire #1 1 and #12 are closed, and the SLS s witch
contact between wire #12 and the SAFE pilot light is closed, the
SAFE pilot light will illuminate. The TB led between wire #12 and –
is on.
E. The SAFE pilot light will not come on with the SLS swit ch in the off
posi tion if:
1. The VSR detects a voltage greater than 10V on the load side IC.
2. The VSR detects that the positively guided N.C. auxiliary IC contact
betw een wires #7 and #8 has not re-c losed.
3. A sa fety rela y aux ilia ry cont act does not allow 1C R to drop ou t and
close circuit between wires #10 and #11.
4. The IC auxiliary contact between wires PLUS and #10 does not
re-close.