The Siemens 3VU2911-4B is an auxiliary contact block that adds two changeover contacts (one normally-open, one normally-closed per changeover) to 3VU2.1, 3VU2.2, and 3VU2.3 motor-protective circuit breakers. It mounts directly onto the breaker side, extending the signal-feedback capability for remote status indication or interlocking circuits in a motor control centre.
Each changeover contact provides one NO and one NC pole, giving the control circuit two independent signal paths from a single breaker position. Typical use is feeding a PLC input for trip indication while simultaneously dropping out a holding contactor — all from the same auxiliary block.