Alpha Technologies AlphaGen PN-6x-T 7.5kW 48Vdc - Manual (Page 57)

042-288-B0-001, Rev. A2 57
4.0 The Engine Control Module, continued
4.1
Theory of Operation, continued
4.1.3 Normal APU Shutdown
The ECM initiates a normal APU shutdown when the AC line is within normal limits,
the DC bus alarm is not active, the 12 minute cool-down period has elapsed, and the
Engine Run command is not active. If started due to low DC Bus voltage, the ECM
continues to run the APU until specific conditions are met (see below) or a major
alarm occurs. The APU will run until the DC voltage of approximately 53V is obtained
and then the 12 minute cool-down period has elapsed.
4.1.4 Abnormal APU Shutdown
The ECM immediately shuts down the APU under the following conditions:
• Major alarm
• Activation of manual engine stop switch
• Receipt of software engine stop command
• General generator failure
4.2 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 immediately shuts down the unit if certain alarm conditions are detected. The ECM
reports status information via a parallel data interface and/or an Alphabus serial data (RS-
485) interface.
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 Low DC bus voltage (default, 49V).
3. Manual run switch is activated.
4. Software run command is received.
5. A self-test is initiated manually.
6. 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 49Vdc (if the unit is started due to low DC bus voltage, DC
bus voltage must reach >53V).
3. Cool-down period has expired.
4. Engine Run command is not active.