The Siemens 3RT1023-1BB40-1AA0 is a SIRIUS power contactor in the Size S0 frame, built for switching motor loads in control panels. It carries a 24 VDC coil and snaps onto a 35 mm DIN rail per DIN EN 50022 — the standard mounting for panel builders. The 45 mm width and 85 mm height fit a compact footprint; depth is 101 mm including the terminals. The coil draws 5.4 W during both closing and holding, so the thermal load on the control transformer stays constant. Rated operating range is 0.8 to 1.1 times the rated voltage — at 24 VDC that means pickup is guaranteed down to about 19.2 V and the coil can ride through up to 26.4 V without damage. Ambient temperature range is -25 to +60 °C during operation, covering most indoor panel environments. The front face carries an IP20 rating — protected against finger contact — while the terminal area is IP00, so the contactor expects enclosure protection for the wiring zone. Degree of pollution 3 means it's rated for conductive pollution environments typical of industrial control panels.
Motor Switching Ratings and Coordination
For motor duty, this contactor is rated at AC-2 at 400 V for 4 kW and AC-4 at 400 V for 8.5 A. AC-2 covers slip-ring motor starting; AC-4 covers inching and plugging duty where the contactor makes and breaks stalled rotor current. The AC-12 maximum operational current is 10 A for resistive loads in the control circuit. Type 1 coordination requires a 63 A gL/gG fuse upstream; Type 2 coordination requires a 25 A gL/gG fuse. The difference matters for panel design: Type 2 coordination limits contactor damage under short circuit so the contactor remains usable after a fault, while Type 1 allows replacement. Mechanical endurance is rated at 10 million cycles typical.
Termination and Wiring
Main current circuit uses screw-type terminals accepting 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), or max 2x (0.75 to 4 mm²) solid or stranded wire. Auxiliary and control circuit terminals accept 2x (1 to 2.5 mm²), 2x (2.5 to 6 mm²), or max 2x 10 mm². AWG equivalents for main contacts are 2x (16 to 12), 2x (14 to 10), or 1x 8; for auxiliary contacts 2x (20 to 16), 2x (18 to 14), or 1x 12. Side-by-side mounting is permitted without derating.