If an AC BUS fails, the remaining DC Bus will power the DC Bus on the depowered side after about how many seconds?

If an AC BUS fails, the remaining DC Bus will power the DC Bus on the depowered side after about how many seconds?

• A. Immediately
• B. 1 second
• C. About 5 seconds
• D. 10 seconds

Answer: (C)

When one AC bus loses power, the DC distribution uses a controlled cross-feed between the two DC busses. The transfer isn’t instant; there’s a built-in delay of about five seconds. This delay ensures the AC loss is real and helps prevent transients, after which the remaining DC bus energizes the depowered DC bus so essential systems continue to be powered. If AC power returns, the cross-feed will release and normal power distribution resumes. So the timing is about five seconds.

When one AC bus loses power, the DC distribution uses a controlled cross-feed between the two DC busses. The transfer isn’t instant; there’s a built-in delay of about five seconds. This delay ensures the AC loss is real and helps prevent transients, after which the remaining DC bus energizes the depowered DC bus so essential systems continue to be powered. If AC power returns, the cross-feed will release and normal power distribution resumes. So the timing is about five seconds.