If you have a Catalyst 6500 switch with different input voltages connected, for example, power supplies (3000W) with 110V/20A inputs, and want to migrate to 220V/20A inputs, then one power supply can be connected to 220 Volts and the other to 110 Volts.
In order to migrate, complete these steps:
With power configured as redundant, unplug one of the 110 input voltages.
Plug in the 220 input voltage to that power supply.
The power supply should not come up, as they are configured in redundant mode. Change to combined power mode and verify that both power supplies are up and running.
Once you have verified that the 220 side produces voltage, unplug the other 110 input, and plug in the 220 input there. Change back to redundant power mode.
When power supply (PS) with higher voltage (220V) is turned on, it takes over all the power distribution for the system. The other PS (still with 110V) no longer provides power for the system. At this point, you can upgrade the voltage on this PS as well. Once the second PS is upgraded as well, both PS should begin sharing the load again since they are in redundant mode.
In other words, power supplies can have different line inputs while the transition takes place, but they cannot operate in redundant mode.