We have a 460v Inverter (Mitsubishi) that is driving a 460v motor (variable speed fan). We would like to use this on a 400v motor. Is this possible? We appreciate that the inverter will need re-programming with the details of the new motor (voltage & current etc) but does anybody see a problem doing this?
No problem. The inverter is the same, only the nameplate changes. Inverters, especially from Japanese companies, come in 3 "Classes": 200V Class, which covers 200-240V input; 400V Class, which covers 380-480V input, and 600V Class, which covers 550-690V input. There is often an overlap on the 600V Class that goes down to 480V, but in general most VFDs are OK with getting down to 50% of their rated voltage without problems.
Now, with a 400V source you will not be able to run your 460V motor at full speed, but you could still run it at around 87% speed. But if you are changing to a 380-400V rated motor when you have a 400V input, no problem at all.