Bryant ASPAS1BBA015 - Manual (Page 22)

Page 22
SECTION 1.7
AUTOMATIC OPERATING PARAMETERS
INTRODUCTION
When the prepackaged generator is installed in
conjunction with a prepackaged transfer switch, either
manual or automatic operation is possible. Manual
transfer and engine startup, as well as manual
shutdown and retransfer are covered in Section 1.6.
Selection of fully automatic operation is also
discussed in that section. This section will provide a
step-by-step description of the sequence of events
that will occur during automatic operation of the
system.
AUTOMATIC OPERATING SEQUENCES
PHASE 1 - UTILITY VOLTAGE AVAILABLE:
With utility source voltage available to the transfer
switch, that source voltage is sensed by a circuit
board in the generator panel and the circuit board
takes no action.
Electrical loads are powered by the utility source and
the Auto-Off-Manual switch is set to AUTO.
PHASE 2- UTILITY VOLTAGE DROPOUT:
If a dropout in utility source voltage should occur
below about 60 percent of the nominal utility source
voltage, a 15 second timer on the circuit board will
start timing. This timer is required to prevent false
generator starts that might be caused by transient
utility voltage dips.
PHASE 3- ENGINE CRANKING:
When the circuit board's 15 second timer has finished
timing and if utility source voltage is still below 60
percent of the nominal source voltage, circuit board
action will energize a crank relay and a run relay.
Both of these relays are mounted on the circuit board.
If the engine starts, cranking will terminate when
generator AC output frequency reaches
approximately 30 Hz.
PHASE 4-ENGINE STARTUP AND RUNNING:
The circuit board senses that the engine is running by
receiving a voltage/frequency signal from the engine
run windings.
When generator AC frequency reaches approximately
30 Hz, an engine warm-up timer on the circuit board
turns on. That timer will run for about ten (10)
seconds.
The engine warm-up timer lets the engine warm-up
and stabilize before transfer to the "Standby" source
can occur.
NOTE: The engine can be shut down manually at
any time, by setting the Auto-Off-Manual switch to
OFF.
PHASE 5- TRANSFER TO "STANDBY":
When the circuit board's engine warm-up timer has
timed out and AC voltage has reached 50 percent of
the nominal rated voltage, circuit board action
completes a transfer relay circuit to ground. The
transfer relay is housed in the prepackaged transfer
switch enclosure.
The transfer relay energizes and transfer of loads to
the "Standby" power source occurs. Loads are now
powered by standby generator AC output.
PHASE 6- "UTILITY" POWER RESTORED:
When utility source voltage is restored above about
80 percent of the nominal supply voltage, a 15
second timer on the circuit board starts timing. If utility
voltage remains sufficiently high at the end of 15
seconds, retransfer can occur.
PHASE 7- RETRANSFER BACK TO "UTILITY":
At the end of the 15 second delay, circuit board action
will open a circuit to a transfer relay (housed in the
transfer switch). The transfer relay will then de-
energize and retransfer back to the utility source will
occur. Loads are now powered by utility source
power. On retransfer, an engine cool-down timer
starts timing and will run for about one (1) minute.
PHASE 8- GENERATOR SHUTDOWN:
When the engine cool-down timer has finished timing,
and if the minimum run timer has timed out, engine
shutdown will occur.
PART 1
GENERAL INFORMATION