The 2-pole configuration (2P) switches both line and neutral, giving full isolation on single-phase AC branches.
Rated current is 3 A at 35 °C ambient, but the 5SY4203-7KK11 derates linearly as panel temperature rises: 2.82 A at 40 °C, 2.72 A at 45 °C, 2.62 A at 50 °C, 2.52 A at 55 °C, and 2.41 A at 60 °C (–). The operating range spans -40 to 75 °C, which covers outdoor cabinet installations in cold climates and poorly ventilated machine compartments.
Breaking capacity — what the two ratings mean
The 10 kA rating per EN 60898 is the service breaking capacity for domestic and light commercial installations — it certifies the breaker can clear a fault up to 10 kA and remain usable afterward. The 35 kA rating per IEC 60947-2 is the ultimate breaking capacity for industrial applications, where the breaker may need to interrupt a much higher prospective fault current once and then be replaced. In a panel fed by a transformer with a high short-circuit capacity (say 25 kA at the bus), the 35 kA IEC rating gives headroom that a standard domestic MCB would not.
Railway design and physical integration
The 5SY4203-7KK11 is explicitly designed for railway applications, which typically means it meets shock, vibration, and temperature cycling requirements beyond standard industrial MCBs. The housing is 36 mm wide (2 modular width units), 90 mm tall, and 76 mm deep with an installation depth of 70 mm.