Breaking Capacity — What the Ratings Mean
The 3VM1125-4EE32-0AA0: This MCCB delivers 121 kA interrupting capacity at 240 V AC, dropping to 76 kA at 415 V, 53 kA at 440 V, and 12 kA at 500 V. These figures govern its ability to safely clear a bolted fault without welding contacts or rupturing the case — critical for coordinating with upstream protective devices. At 240 V it handles the highest fault currents typical of North American 120/240 V split-phase service; at 415 V and 440 V it covers European and Asian 400 V-class industrial grids. The 12 kA at 500 V is still adequate for most motor branch circuits on 480 V systems.
Thermal Derating — Not a Fixed 25 A Across Temperature
The 25 A rating holds from 40 °C through 50 °C ambient. At 55 °C it derates to 24 A, at 65 °C to 23 A, and at 70 °C to 23 A. If this breaker sits in a crowded panel with elevated internal temperature, size the load at 23 A continuous, not 25 A. The rated insulation voltage is 800 V, and the maximum power loss is 9 W — negligible for panel ventilation but worth noting if the breaker is enclosed in a small junction box.
Panel Fit and Protection Class
Dimensions are 130 mm height, 76.2 mm width, 70 mm depth — a standard 3-pole MCCB footprint for DIN-rail or panel-mount installation. Front face carries IP40 protection (tools and wires over 1 mm kept out), suitable for enclosed distribution boards. No trip indicator, no undervoltage release, no communication function — this is a basic thermal-magnetic breaker for straightforward line protection.