Thanks for your feedback Marvo and Phoenix, it's very much appreciated.
What you've both said makes perfect sense, unlike my original post, which should have said 400V AC not 400A.
The VFD isn't installed yet. I think the requirement is to give the customer a general idea of what to expect. I had initially thought it might just be a straightforward 11kW divided by 3, i.e. 3.67kW per phase, but then started to have doubts.