Can a cabinet/rack based power distribution unit with a higher Ampere rating be used with a lower ampere rated power feed?
For example, can I connect a 50A rated cabinet power distribution unit to a 30A whip:
Using a 50A CDU on a 30A circuit is acceptable. The circuit itself MUST be limited to 30A maximum by the primary upstream Over-Current Protective Device (OCPD). Usage of the CDU in this manner would require an adapter with the appropriate connector for the 50A rated CDU to connect with the 30A rated power feed (30A male plug on one end and a 50A female receptacle on the other).
With the selection of any vendor’s cabinet/rack CDU/PDU you should be sure the CDU/PDU provides compliant branch circuit protection, and the source itself MUST always be limited by the primary upstream OCPD to the lowest common denominator with respect to ampacity throughout the entire chain.