We have a cabinet of servers and other hardware (switches, firewalls, etc) that all are currently running on 120v. I've confirmed that the power supply for all of our devices support both 120v and 240v and I understand we'll need to get a 240v PDU. My question is, if we switch from 120 to 240, what power cables do I need to purchase that will plug in to the PDU on one end, and into the server power supplies on the other? For reference, we're using mostly Dell Poweredge servers.
For 208 or 240v in the US and Canada the standard configuration:
From wall to PDU - L6-30R or L6-50R
If you have a UPS, it should use the same connectors both in and out.
The PDU may branch to smaller "extension" units using C19/C20 (Female Plug/Male Receptacle).
Whatever connects to the servers and equipment would use standard C13/C14 (Female Plug/ Male Receptacle) at both ends, which is the same connector as the power supply on those devices. You'd use cords like this one to plug in the servers:
As a UK user who only uses 220/240v I'm not aware of what plugs are used in the US but am very familar with the C13/C14 and C19/C20 and I would just like to add:
It is important that you are aware of the limitations of the C13/C14 connectors and when not to use them.
I have seen PDUs that only use C13 lead and high capacity PSUs that care connected to a C13 downstream.
C13 leads are only required to be fitted with wires of 6Amp capacity, and the physical plug is not designed to be used with more than 10Amps no matter what cables and fuses are used. Many C14 connectors will display a maximum current (ampacity) lower than 10 Amps. The C13 specification also only requires it to be able to handle 70 Degrees Celsius. So the 6 amp wires in some cases melt the socket if misused.
C19 on the other hand are designed with 16A in mind however check your cables for their capacity, it is marked if lower than 15A. Also pay attention to C20 sockets at most I see are only rated to 15A or 13A
Your equipment is using C13/5-15P power cords plugging into NEMA 5-15R receptacles on your existing 120v PDU. The 240v PDU is going to have IEC C14 receptacles, so you'll need IEC C13 to C14 power cables.