Alpha Technologies AlphaGen PN-6x-T 7.5kW 48VDC - Installation and Operation Manual - Manual (Page 39)

745-020-B0-003, Rev. C 39
4.0 The Engine Control Module, continued
4.1 Theory of Operation
Under normal operating conditions (no alarms) the ECM Run-Auto-Stop (RAS) switch is in
the AUTO (center) position. The ECM has control of the APU while in the Auto mode. When
the RAS switch is switched from the STOP position to the AUTO position the ECM will run the
APU for one minute, after a short delay. This indicates the ECM is in the Auto mode and is
capable of starting and stopping the APU automatically.
The APU can be controlled manually by placing the RAS switch in the RUN (up) position or
the STOP (down) position. If a system controller is attached to the ECM via the RS-485 bus,
the APU can be controlled remotely. In Auto mode, the ECM continuously monitors the AC
line voltage, DC bus voltage, enclosure sensors, and APU status. If a fault occurs, the ECM
determines whether to start or inhibit the APU based on the type of failure.
4.1.1 Standby Operating Condition Less Than Three Minutes
If an AC line disturbance or outage lasts less than three minutes, the ECM will not
start the APU unless the battery bus voltage drops below the default threshold (Low
DC Bus Level) of 49V. The ECM will notify the system operator of a line failure via the
front panel LED’s (see Fig. 4-2a).
4.1.2 Standby Operating Condition More Than Three Minutes
If an AC line disturbance or outage lasts more than three minutes, the ECM start
delay timer expires 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 4-1). If the engine fails to start, the ECM will report an “Engine
Over-crank” alarm. Otherwise, the ECM starts and runs the APU until either a normal
shutdown or major alarm occurs.
Crank Cycle
Crank
Attempt
Cranking
Engine
Pause
(no crank)
15 Sec 15 Sec 15 Sec 15 Sec 15 Sec 15 Sec 15 Sec 15 Sec 15 Sec
Engine
Over-crank
30 Sec 30 Sec 60 Sec 30 Sec 30 Sec 60 Sec 30 Sec 30 Sec
1 2 3 4 5 6 7 8 9
Table 4-1, Engine Crank Cycle