Alpha Technologies AlphaGen PN-6x-T 7.5kW 48VDC - Installation and Operation Manual - Manual (Page 40)

40 745-020-B0-003, Rev. C
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. The ECM continues to run the APU until the
above conditions are met or a major alarm occurs. The APU will run a minimum of 30
minutes if started due to low DC Bus voltage.
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 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 qualifi ed.
2. DC bus voltage is greater than 2V/cell +2 V (i.e., 50V for a 48V system).
3. Cool-down period has expired.
4. Engine Run command is not active.
5. If the unit is started due to low DC bus voltage, DC bus voltage must reach >53V.