What the 40 A and 440 V rating mean for your panel
The 5TT5841-2 is a Siemens SENTRON Insta contactor rated for 40 A operational current at 440 V AC. That 40 A figure is the continuous current the main contacts can carry in AC-1 duty — resistive loads like heaters or lighting banks. For motor loads, you'll need to derate per the motor's locked-rotor current; the 40 A frame typically handles a 7.5 kW motor at 400 V, but confirm the inrush against the contactor's making capacity. The coil is 24 V AC. That's a standard control voltage in many industrial panels, but note it's AC, not DC — if your control transformer or PLC output is 24 V DC, this contactor won't pull in reliably. The 24 V AC coil draws about 4-6 VA inrush; size your control transformer accordingly.
Contact arrangement and switching capacity
Three normally-open (NO) main contacts and one normally-closed (NC) auxiliary contact. The NO contacts carry the load; the NC contact is typically used for status feedback or interlocking. The switching capacity for incandescent lamp loads is 4000 W — that's about 9 A at 440 V, so it's fine for lighting contactor duty. The contactor occupies 3 modular width units on a DIN rail, which is 54 mm wide. That's a standard footprint for a 40 A frame — it fits alongside MCBs and other DIN-rail components in a distribution board.
Lifecycle and sourcing reality
The IP20 rating means it's protected against solid objects larger than 12 mm (fingers) but not against moisture — install it inside a panel with at least IP54 enclosure if the environment is wet or dusty.