The Siemens SENTRON 3VM1112-5GD42-0AA0 is a 4-pole molded case circuit breaker (MCCB) rated for 125 A continuous current (Iu) with a TM210 thermal-magnetic overcurrent release. Its interrupting capacity hits 187 kA at 240 VAC and 121 kA at 415 VAC, which means it can safely clear very high fault currents on the secondary side of a large distribution transformer without needing an upstream current-limiting fuse.
Sizing and thermal derating
The 125 A rating holds flat from 40 °C up to 50 °C ambient, then derates gradually to 114 A at 70 °C. That flat plateau through 50 °C is useful for panels in hot machine rooms or near furnace lines where ambient drift is common — you don't lose headroom until you cross 55 °C. Insulation voltage (Ui) is rated 690 V, and the maximum DC operational voltage is 500 V.
Panel fit and integration
The 3VM frame measures 101.6 mm wide by 130 mm tall by 70 mm deep. That 70 mm depth is shallower than many equivalent 125 A MCCBs, which helps when the backpanel clearance is tight against a gland plate or rear-mounted busbars. Front IP40 protection is standard for panel-mount indoor use.