Why is it important to wait approximately 10 seconds after removing MMR power before removing MMR AC power?

• A. To allow 28 VDC to be completely removed from the system before removing 115 VAC
• B. To allow the system to cool
• C. To prevent data loss
• D. To ensure safety interlock resets

Answer: (A)

The main idea is safe, staged power-down of a system that has both DC and AC supplies. When you remove the DC power, energy can remain stored on the 28 V DC rails and in power-converter capacitors. Those stores don’t disappear instantly, so if you disconnect the AC power too soon, there can be residual energy that may backfeed or cause arcing at the AC disconnect or damage components. Waiting about 10 seconds gives that DC energy time to bleed off through proper paths, ensuring the 28 VDC is effectively removed before you remove the 115 VAC. This makes isolation safer for personnel and protects the equipment.