Operator’s Manual
ASCO Series 300
381333-453
ASCO Power Technologies
Page 7
Operating Mode(s)
This ASCO Series 300 PCS is designed to start up
to 4 engine-generator sets upon receipt of a signal
that emergency power is required from any of the
automatic transfer switches (ATS).
Emergency Mode
Whenever the individual engine generator control
switches are placed in their automatic position, the
engine generator system is on standby in readiness
for automatic starting and synchronization in the
event of a power failure signal.
In the event of a power failure, all generator(s)
automatically start and come up to speed. The first
generator set to achieve 90% of nominal voltage
and frequency shall be connected to the bus.
Electronic interlocks permit the connection of only
one engine generator to the dead generator bus in
the event of simultaneous generator relay
operation. Upon sensing the availability of
emergency power, the priority-1 load block will be
able to transfer to the emergency bus. Priority 1
loads cannot be shed from the emergency bus and
are always allowed to transfer
.
(Note: If priority 1 loads are not calling for an
engine start because they have not lost normal
power, a priority-pass along feature will be
activated.
Generally, if no loads in any priority block are
calling for an engine start, all loads in lower
priority blocks will be shifted up to a higher
priority for block load add/shed purposes.)
The synchronizer will automatically adjust the
frequency of the on-coming generator to
synchronize with the bus. When synchronism is
achieved, the on-coming generator is paralleled to
the bus. When the second generator’s paralleling
contactor is closed the priority-2 load block will be
allowed to transfer their loads to the emergency
bus. As each generator parallels to the bus, another
block of load is allowed to add, until all generators
and all loads are online.
Upon sensing that normal utility power has been
restored to acceptable limits, a sequence shall
begin to transfer the load back to the utility source.
The re-transfer shall be initiated after the retransfer
to utility time delay has expired (adjustable at each
ATS from 0 minute to 30 minutes) allowing an
open transition transfer return to utility. After all
the transfer switches have re-transferred their loads
to the normal source, the generator circuit
paralleling contactors are simultaneously opened
and the engine generators run for an adjustable no-
load cool-down period (adjustable at the local
generator controls if provided by the generator
controller manufacturer). The controls are
released and the generators placed in readiness for
the next power failure.
