Alpha Technologies AlphaGen PN-6x-T 7.5kW 48Vdc - Manual (Page 56)

56 042-288-B0-001, Rev. A2
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 a one minute self-test 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. 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 indicates line failure locally using the front panel
LEDs (see Fig. 4-2a), and remotely by the appropriate Terminal block 2 terminal posi-
tions (see Fig. 3-21 and 3-22.
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 attempts 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 reports an Engine
Over-crank alarm. Otherwise, the ECM starts and runs the APU until either a normal
shutdown, or major alarm, occurs.
Table 4-1, Engine Crank Cycle
Crank Attempt
Crank Duration
Pause (no crank) 30 Sec
15 Sec
Crank Cycle
15 Sec 15 Sec 15 Sec 15 Sec 15 Sec 15 Sec 15 Sec 15 Sec
30 Sec 30 Sec 30 Sec 30 Sec 30 Sec 60 Sec 60 Sec
Engine
Over-crank
Alarm
1 2 3 4 5 6 7 8 9