UNIT 9 p.95

Solution A: The emergency generator will automatically come on line.

Solution B: The wind milling effect drives the emergency generator below normal performance levels.

Solution C: The left main ac power contactor de-energizes. The right generator now powers the left main ac bus through contacts three and two of the de-energized external ac power contactor.

All other buses receive power except for the 115-volt ac and 28-volt dc monitor buses. Both generators must be operating for the monitor buses to receive power because of the action of the monitor bus relays.

Solution D: If the right generator or associated equipment should fail, the left generator supplies power to both main ac buses. Power goes to the right main ac bus through de-energized contacts three and two of the right main ac power contactor. Power for the other ac buses and the TR units is as previously described.

Solution E: When the left TR unit fails, the left main dc power contactor de-energizes. Power then goes across de-energized contacts A3 to A2, powering the left main dc bus. The right TR unit also continues to power the right main dc bus. Power distribution to the remaining dc buses is normal operation, except for the dc monitor bus. To power the monitor bus, both TR units must be operating. This is because of the action of the dc monitor bus relay.

Solution F: When the right TR unit fails, the right main dc contactor de-energizes. Power from the left TR unit runs across de-energized contacts A3 to A2 of the right dc contactor. From here power goes to the right main dc bus, thus maintaining operation of the entire dc distribution system except for the loss of the monitor dc bus.

Solution G: The emergency generator system automatically activates. The emergency generator solenoid de-energizes, activating the hydraulic motor that drives the emergency generator.

Solution H: The emergency generator provides ac and dc power to the essential bus circuits. The emergency system is completely self-sufficient and independent of the primary and secondary power sources.