That matters for pump, fan, and conveyor drives where the acceleration profile is moderate. That protects three-phase motors from single-phasing, which would otherwise overheat the remaining windings. No separate phase-loss relay needed. Rated motor power is 4 kW at 230 V, so it's sized for a 4 kW motor on a 230 V line. On a 400 V supply the motor current is lower, so the same breaker can cover a higher power motor — check the current setting range against the motor FLA.
Mounting and connections
Any mounting position. Main circuit terminals accept 2 × (0.5 to 1.5 mm²) solid or stranded, or 2 × (0.75 to 2.5 mm²). M3 screws for the main contacts. Clearance: 50 mm upwards and downwards, 30 mm to the side, zero forwards and backwards.