Alpha Technologies AlphaGen 5.0kW Auxiliary Power Unit - Manual (Page 19)

1. System Overview
19
031-132-B0-001 Rev. A TM ©2000
1.5.1 Normal Operating Condition
Under normal operating conditions (no alarms) the ECM's Run-Auto-Stop
(RAS) three-position rocker switch will be in the "center" or AUTO position .
The ECM has complete control over the APU while in the AUTO mode. Also,
each time the RAS switch is moved from the STOP position, to the center or
AUTO position, the ECM will run the APU for one minute after a short delay.
This is an indicator to the system operator that the ECM is truly in the AUTO
mode and is fully capable of starting and stopping the APU automatically.
The APU can be controlled manually by placing the RAS switch in the “down”
or RUN position and the “up” or STOP position. If a system controller is
attached to the ECM via the RS-485 bus, the APU can be controlled remotely.
Similarly, the APU can be started via the transponder interface on the ECM.
In the AUTO mode, the ECM continuously monitors the AC line voltage, and
DC bus voltage, enclosure sensors, and the APU status. If a fault occurs, the
ECM will determine whether to start or inhibit the APU based on the type of
failure.
1.5.2.Standby Operating Condition (less than 10 minutes)
If an AC line disturbance or outage is less than 10 minutes, the ECM will not
start the APU unless the battery bus voltage drops below a programmable
threshold (Low DC Bus Level) which defaults to 1.95 Volts per cell or 35.1/46.8
Volts for 36/48 Volt systems respectively. However, the ECM will notify the
system operator of a line failure via the front panel LED’s (see alarm section).
Otherwise, the ECM will appear to be in a “normal” operating condition.
1.5.3.Standby Operating Condition (more than 10 minutes)
If an AC line disturbance or outage is greater than 10 minutes, the ECM
start delay timer will expire and the ECM will attempt to start the APU. The ECM
will attempt to start the engine 9 times with either a 30 second or a 60 second
pause between attempts (See table 1-1). If the engine fails to start, the ECM
will report an “Engine Over-crank” alarm. Otherwise, the ECM will start and
continue to run the APU until either a normal shutdown or Major alarm occurs
(refer to Alarm section 1.7).
1.5 Generator Modes of Operation