It also includes phase failure detection, which catches a lost phase on the primary side before the transformer draws single-phase current and overheats.
Clearance: 50 mm upwards and downwards, 30 mm at the side; zero forwards or backwards. Main circuit terminals accept solid or stranded up to 2× 2.5 mm² or a single 4 mm², with M3 screws and a Pozidriv size 2 tip.
Back-up fuse coordination
The breaker requires back-up fuses for fault levels above its own interrupting rating. At 400 V the maximum back-up fuse is gG 50 A; at 500 V it drops to gG 40 A; at 690 V it is gG 35 A. The interrupting capacity at 690 V AC is 6 kA — substantially lower than the 100 kA at 400 V — so on a 690 V line the back-up fuse must clear any fault above 6 kA. For transformer protection, this coordination ensures the breaker clears low-level overloads while the upstream fuse handles rare high-energy faults.