Cooper Lighting S260-75-1 - Manual (Page 18)

Automatic Transfer, Preferred to
Alternate
The following assumptions are made:
• OPERATION SELECTOR switch (S3) is in AUTO.
• SOURCE PREFERENCE and RETURN MODE
switch (S4) is in PREF l-P (Terminal 2 of each deck
connected).
• CONTROL MODE switch (S5) is in NORMAL.
• S control is in a quiescent state.
• Source I high-voltage transfer switch (SW-I) is closed
and Source II high voltage transfer switch (SW-II) is
open.
Note: The actuators of both high-voltage transfer switch-
es are shown in the switch open position on the
schematic diagram. Following each opening opera-
tion, the motor recharges the actuator springs and
the cutout switch returns to the position shown in
the schematic. However, when the high voltage
transfer switch is closed, the selector switch of the
actuator mechanism is opposite to that shown in
the schematic.
If one or more phases of the preferred source (Source I)
are lost, R2 will drop out and the SOURCE I ENER-
GIZED lamp (L1) will go out. N.C. contacts 1-7 of R2
close completing the circuit to the PREFERRED TO
ALTERNATE TlMER (TM1) through 4-7 of R6 (which is
energized), 7-4 of R1, and deck J of S4. When TM1 times
out, its 5-6 contacts close to energize the coil of R1 in the
reset direction causing R1 to transfer. Diodes in the cir-
cuit of this single-coil magnetically held relay determine
whether “latching” or “resetting” occurs.
The transfer of R1 energizes the trip coil of Source I high-
voltage transfer switch (SW-I) as follows:
Transfer bus voltage passes through terminals 5-1 of S3,
contact 9-3 of energized R1, and terminals 4-3 of S5. It
is then impressed on N.C. contact 7-2 of R4 and passes
through deck B of S4 to output terminal 13 of TB-1.
Terminal 13 is connected to the internal selector switch in
the actuator of SW-I (which is closed when SW-I is
closed), through the trip coil to ground (terminal G).
After SW-I has opened, the selector transfers to connect
terminal 3 to terminal 4, which energizes terminal 16 of
TB1. In turn contacts 2-6 of S3, deck C of S4, and termi-
nal 25 of TB-1 are energized to operate the close coil of
SW-II and close the switch.
SW-I will now remain open and SW-II closed until Source
I voltage is restored.
Return Transfer, Parallel Transition
When Source I power is restored on all three phases, R2
will pick up and Source I Energized lamp (L1) will light.
Contact 9-6 of R2 closes to energize ALTERNATE TO
PREFERRED TIMER (TM-2) through contact 8-2 of R1,
and deck K of S4. After TM2 times out, its contacts 5-6
close to energize the coil of R1 through diode DL in the
latching direction causing R1 to transfer.
The transfer of R1 energizes the close coil of SW-I as follows:
Transfer bus voltage passes through terminals 5-1 of S3,
contacts 9-6 of latched R1, and terminals 5-6 of S5. It is
then impressed on N.C. contact 7-2 of R5 and passes
through deck A of S4 to output terminal 15 of TB-1. This
activates the close coil in SW-I. When SW-I closes, its
auxiliary contact “a” closes to energize R5 (via TB1-24
and deck E of S4). Contact 7-5 of R5 closes to energize
TB1-23 through deck D of S4. Voltage at TB1-23 will
actuate the trip coil of SW-II to open the Source II high-
voltage transfer switch.
Note: The Source I high-voltage switch (SW-I) closes before
the Source II high-voltage switch (SW-II) opens to
effect a parallel return transition. SW-I will now remain
closed and SW-II open until Source I voltage is lost or
a change of control settings is made.
Return Transfer, Non-Parallel
Transition
The following assumptions are made:
• SOURCE PREFERENCE and RETURN MODE
switch (S4) is in PREF l-NP (Terminal 3 of each
deck connected).
• Source I has lost one or more phases and the load
has been transferred to Source II as previously
described (SW-I open and SW-II closed).
• Control is in a quiescent state with latching relay R1
in the reset position (contacts 9-3 and 8-2 closed)
and R2 is deenergized.
When Source I power is restored on all three phases, R2
will pick up, closing its contact 9-6, and energize the
ALTERNATE TO PREFERRED TIMER (TM-2) through
contact 8-2 of R1, and deck K of S4. After TM-2 times
out, its 5-6 contact closes to energize the coiI of R1
through diode DL in the latching direction causing R1 to
transfer, closing its 6-9 contact.
In this case, the trip coil of SW-II is immediately ener-
gized through the following circuit:
Terminals 5-1 of S3, N.C. contact 9-6 of R1, terminals 5-
6 of S5, N.C. contact 7-2 of R5, and deck D of S4 to out-
put terminal TB1-23 to activate the trip coil of SW-I I and
open to Source II high-voltage transfer switch.
When SW-II opens, its selector switch transfers to
impress the voltage at TB1-23 onto TB1-26 which, in turn,
energizes TB1-15 through terminals 3-7 of S3 and deck A
of S4. Voltage at TB-15 will actuate the quick-close coil of
SW-I to close the Source I high-voltage switch.
Note: In this instance, the Source II high voltage switch (SW-
II) opens before the Source I high voltage switch clos-
es, to effect a non-parallel return transition. SW-I will
now remain closed and SW-II open until Source I volt-
age is lost or a change is made in the control settings.
Type S Automatic Load-Transfer Control Installation, Operation, and Maintenance Instructions
18