🔍 Key Concepts

• Trace the power path on the one-line diagram from the ship’s service generators and shore power to the main switchboard 450 VAC section, then from the emergency generator to the emergency switchboard 450 VAC section. • Look carefully at how the Automatic Bus Transfer device (ABT) is connected: which side is the normal source (main bus) and which side is the emergency source (emergency generator/emergency switchboard)? • Recall SOLAS/USCG practice: the emergency diesel-generator normally starts automatically on loss of power to the main switchboard and is intended to feed the emergency switchboard, not the main bus.

💭 Think About

• When the 450 VAC main switchboard loses power at sea, which component first "notices" the loss and triggers the emergency generator start signal according to the diagram? • Once the emergency generator is running, which bus does it actually energize according to the drawing symbols and labels: the main switchboard or the emergency switchboard? • Does the ABT in this diagram appear to require a manual shift, or is it drawn as an automatic transfer between normal and emergency sources for the emergency bus? What does that imply about how the loads are restored?.

✅ Before You Answer

• Verify which bus is labeled "Emergency Swbd. 450 VAC Section" and follow its connection back through the ABT to see from where it can receive power. • Confirm whether any line in the diagram shows the emergency generator feeding directly into the main switchboard 450 VAC section (it usually should not). • Check whether the ABT symbol is between the main 450 VAC bus and the emergency 450 VAC bus, indicating that it will automatically transfer the emergency bus from normal (main) power to emergency generator power on loss of main power.