The 3RT1044-3BM40: The AC-3 rating of 37 kW at 500 V is the headline motor-switching capacity — it tells you the contactor can handle a 3-phase induction motor of that power under normal starting conditions (6–8x inrush, switching off at rated current). The AC-4 rating of 55 A at 400 V is the more demanding duty class: it applies when the contactor makes and breaks stalled-rotor current, so if your application involves frequent reversing or inching, this 55 A figure is the one to size against, not the AC-3 kW number. The AC-1 maximum operating frequency of 1 000 switching cycles per hour and AC-4 maximum of 300 cycles per hour set the thermal limits for repetitive operation — useful for high-cycle conveyor or press applications. The auxiliary contact ratings span from 10 A at 24 V up to 6 A at 230 V and 3 A at 400 V, covering a range of PLC and relay interface voltages.
Environmental and Installation Conditions
The enclosure protection is IP20 on the front with the cover or box terminal fitted; the terminal itself is IP00, meaning the wiring compartment requires the panel's own IP rating. Wire sizes: solid conductors accept 2x (0.25... 2.5 mm²) for control wiring, while the main power terminals accept stranded 2x (10... 50 mm²) or solid/stranded 2x (2.5... 16 mm²).