Alpha Technologies ECM - Manual (Page 19)

19 TM 744-862-C0-003 Rev.C
Engine Control Module (ECM)
1.2.6. ECM Operating Mode Summary
The ECM monitors the status of the AC line and DC bus to make a
determination when to start and stop the generator. The ECM also monitors
APU status while the engine is running and will immediately shut down the unit
if certain alarm conditions are detected. The ECM reports status information
via a parallel data interface and/or an Alpha-Bus serial data (RS-485)
interface.
Any of the following conditions can cause the ECM to start the generator:
1. Loss of AC line for a period of time in excess of Start Delay
(programmable).
2. DC bus voltage drops below 1.95 Volts/cell (35.1/46.8/93.6 VDC
for 36/48/96 Volt systems, respectively).
3. Manual run switch is activated.
4. Software run command received.
5. Engine run is commanded via the transponder interface.
6. A self-test is initiated manually.
7. An automatic self-test is initiated.
The following conditions are required for normal engine shutdown:
1. AC line is qualified.
2. DC bus voltage is greater than nominal +2 Volts (i.e., 50V for a
48V system).
3. Cool-down period has expired.
4. Engine Run command is not active.
5. Engine has run for a minimum of 30 minutes if it started due to low
DC bus voltage.
The following conditions will cause immediate engine shutdown:
1. Manual engine stop switch is activated.
2. Software engine stop switch is received.
3. Any of the following engine alarms become active:
· Low oil
· Engine over-temperature
· Low fuel
· Over-speed
· Over-crank
· Overvoltage
4. Any of the following system alarms become active:
· Gas hazard
· Pad shear
· Water intrusion
· General APU failure
1.2 Theory of Operation, continued