This read-only integer reports the current, in amperes, drawn on a specific phase within a specific ATS input feed, or -1 if unsupported by that source. Admins use this to check whether load is balanced across the three phases of an input, since an unbalanced load can stress one phase's wiring or breaker more than the others. A phase drawing noticeably more current than the other two on the same input flags an imbalance the admin may want to address by redistributing downstream load.