The Siemens 4EU2722-0AB00-1BA0 is a commutating choke for converter applications — a 3-phase AC line reactor rated at 400V operating voltage and 900A continuous current, with a maximum of 1000A.
That means it can carry 900A indefinitely in a 40°C environment without exceeding the insulation temperature limit. The DC rated value of 1225.4A is higher because DC current produces less core saturation than AC at 50 Hz — useful if you're feeding a DC link directly. The IP00 enclosure means no protection against dust or water ingress; this choke is intended for installation inside a ventilated cabinet, not in a washdown or outdoor location.