Motor-protective circuit-breaker complete device (basic device and electronic control unit) according to IEC60947-4-1, electronic wide-range overload protection (4:1), phase-failure and unbalance protection, adjustable tripping class, high short-circuit breaking capacity. Flexible adaptation of the motor-protective circuit's current range through interchangeable electronic release units. Expandable with auxiliary contacts, voltage releases, current limiters, door coupling handles