PART 1
GENERAL INFORMATION
SECTION 1.7
AUTOMATIC OPERATING PARAMETERS
Page 28
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
The generator’s control panel houses a control logic
circuit board. This board constantly monitors util-
ity power source voltage. Should that voltage drop
below a preset level, circuit board action will signal
the engine to crank and start. After the engine starts,
the circuit board signals the transfer switch to activate
and connect load circuits to the standby power supply
(load terminal lugs T1/T2 connect to terminal lugs E1/
E2). Refer to the Electrical Data section.
The generator must run at 50 Hz or greater for the
transfer output to be activated. Once activated, it will
remain active even if the frequency dips below 50 Hz.
Upon restoration of utility source voltage above a
preset level, generator circuit board action signals the
transfer switch to transfer loads back to that power
supply. After retransfer, the engine is signalled to shut
down.
The actual sequence of operation is controlled by
sensors and timers on a control logic circuit board, as
follows:
A. Utility Voltage Dropout Sensor
• This sensor monitors utility source voltage.
• If utility source voltage drops below about 65 percent
of the nominal supply voltage, the sensor energizes a
10 second timer.
• Once the timer has expired, the engine will crank and
start if utility is still low.
B. Engine Warm-up Time Delay
• This mechanism lets the engine warm up for about
five (5) seconds before the load is transferred to the
standby source.
C. Standby Voltage Sensor
• This sensor monitors generator AC output voltage.
When the voltage has reached 50 percent of the
nominal rated voltage, transfer to standby can occur.
D. Utility Voltage Pickup Sensor
• This sensor monitors utility power supply voltage.
When that voltage is restored above 75 percent of the
nominal source voltage, a retransfer time delay starts
timing.
E. Retransfer Time Delay
• This timer runs for about 15 seconds.
• At end of a 15-second delay, circuit board action de-
energizes transfer relay in the transfer switch if utility
is still present.
• Retransfer to utility power source then occurs.
F. Engine Cool-down Timer
• When the load is transferred back to utility power
source, the engine cool-down timer starts timing.
• The timer will run for about one minute, and the gen
-
erator will then shut down.
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