15
Zenith Automatic Transfer Switch | new.abb.com/low-voltage
Delayed Transition
Source 1 Power Failure:
When the test is initiated, the controller initiates the Time
Delay Source 2 Start (Engine Start Timer “P”) cycle. A manual
CANCEL button is provided to cancel the test if desired. Upon
completion of the (P) time delay, an Engine start Signal is sent
to Source 2. When Source 2 voltage and frequency reach the
preset “Restore” values, the time delay to open Source 1 timer
(W) begins its timing cycle to ensure voltage and frequency
stabilization before retransfer. A manual pushbutton BYPASS is
provided to bypass the “W” time delay if desired. After the (W)
time delay, the MX controller initiates a transfer signal through
the Relay Driver Module to operate the main transfer operator.
The load is now transferred to the Open position. The time delay
to Source 2 timer (DW) begins its timing cycle. After the (DW)
time delay, the MX controller initiates a transfer signal through
the Relay Driver Module to operate the main transfer operator.
The load is now transferred to Source 2 line. The transfer
switch is mechanically locked. SN limit switch awaits the next
operation to Source 1.
Restoration of Source 1 Power:
Deactivating the test switch initiates re-transfer to Source 1
sequence. The delay to open Source 2 Timer (T) begins its timing
cycle to ensure voltage and frequency stabilization before
retransfer. A manual pushbutton BYPASS is provided to bypass
the “T” time delay if desired. After the (T) time delay, the MX
controller initiates a transfer signal through the Relay Driver
Module to operate the main transfer operator. The load is now
transferred to the Open position. The time delay to Source 1
timer (DT) begins its timing cycle. After the (DT) time delay, the
MX controller initiates a transfer signal through the Relay Driver
Module to operate the main transfer operator. The load is now
transferred to Source 1 line. The transfer switch is mechanically
locked. SE limit switch awaits the next operation to Source 2.
Immediately after re-transfer, the S2 Stop Delay Timer (Delay
to Engine Stop “U”) begins its cycle to allow Source 2 Engine
to run unloaded. A manual pushbutton BYPASS is provided to
bypass the “U” time delay if desired. Upon completion of the
(U) timing cycle, the controller sends an Engine stop signal.
ATS TYPE
P
W
DW
T
DT
U
Standard Transition
Time Delay
S2 Start
Time Delay
S2 Stable
Time Delay S1
Stable
S2 Stop Delay
Delayed Transition
Time Delay S2
Start
Time Delay S2
Stable
ATS Open Time
to S2
Time Delay S1
Stable
ATS Open Time
to S1
S2 Stop Delay
Source 1 Fails
Transfer to Source 2
Engine
Cooldown
Timer Designations as they appear in the SET menu
Transfer to Source 1
Source 1 Returns
S4-11 Showing timer set menu
