A short in the Main DC Bus would cause which components to deenergize and illuminate which lights?

A short in the Main DC Bus would cause which components to deenergize and illuminate which lights?

• A. Line Contactor and Battery Relay; Battery Relay OPEN light and Generator FAIL light
• B. Battery Bus and Battery Relay; Battery Relay OPEN light and Hydraulic light
• C. Main DC Bus and Battery Relay; Generator FAIL light only
• D. Line Contactor and Battery Bus; Battery Relay OPEN light and Engine Fail light

Answer: (A)

When the Main DC Bus develops a short, protective actions switch in to isolate the fault. The line contactor and the battery relay lose power and drop out, cutting the generator from the bus and isolating the battery. That sequence causes the Battery Relay OPEN light to come on and the Generator FAIL light to illuminate, signaling both that the battery relay has opened and that the generator is not supplying the bus. Lights tied to the hydraulic system or engine status aren’t triggered by a DC bus fault, so they stay dark in this scenario.

When the Main DC Bus develops a short, protective actions switch in to isolate the fault. The line contactor and the battery relay lose power and drop out, cutting the generator from the bus and isolating the battery. That sequence causes the Battery Relay OPEN light to come on and the Generator FAIL light to illuminate, signaling both that the battery relay has opened and that the generator is not supplying the bus. Lights tied to the hydraulic system or engine status aren’t triggered by a DC bus fault, so they stay dark in this scenario.