How many seconds should elapse after removing MMR power before removing MMR AC power?

• A. 5 seconds
• B. 10 seconds
• C. 15 seconds
• D. 20 seconds

Answer: (B)

Safe power-down sequencing is being tested here. After you remove MMR power, you need a brief pause to let any stored energy in capacitors and inductive components dissipate and for internal circuits to reset. Only then should you disconnect the AC power to avoid backfeeding, arcing, or voltage transients on the AC side during shutdown. Ten seconds is the balance that gives enough time for the DC bus to de-energize safely while keeping downtime reasonable. If you cut AC power too soon, residual energy can cause unwanted transients; waiting longer than needed just prolongs the downtime without added safety benefit.