Motor protection circuit breaker for high-fault-current panels
The Siemens 3RV2021-1CA20 is a SIRIUS motor protection circuit breaker designed for motor circuits where short-circuit currents can reach 100 kA at 400 V AC or 240 V AC. Class 10 trip characteristic means it clears overloads within 10 seconds at 7.2× the thermal setting — fast enough to protect standard IEC induction motors during a stalled-rotor event. Phase failure detection is built in, so a lost phase on the line side trips the breaker before single-phasing cooks the winding. Rated insulation voltage spans 20…690 V, and the breaking capacity holds at 100 kA up through 500 V AC, then steps to 10 kA at 690 V AC. That covers most 400 V and 480 V distribution systems found in industrial plants; the 690 V rating handles mining or marine installations where 690 V is the standard motor voltage. Mounts on 35 mm DIN rail per DIN EN 60715 via screw and snap-on — no tools needed for the snap action, but the screw clamp secures it against vibration in high-shock environments like a rolling mill drive cabinet. Spring-loaded terminals on the main circuit accept 2× (1…10 mm²) solid or stranded, which covers the typical motor feeder up to about 7.5 kW (10 hp) at 400 V.
Trip class and ambient derating in mill environments
Class 10 trip is the standard for standard-efficiency induction motors; if the motor manufacturer specifies Class 10, this breaker is a direct fit. Operating ambient range is -20…+60 °C, which takes the radiant heat near a furnace line or motor control center without derating the thermal trip curve — a common concern when the MCC sits close to the process. Storage and transport range extends to -50…+80 °C, so the part survives warehouse extremes and unheated shipping containers. The 45 mm width (3 module spaces on a DIN rail) leaves room for a contactor and overload relay in the same enclosure — tight for a 100 kA rated device.