The Siemens 3RT2028-1BB44-ZX95 is a SIRIUS S0-frame power contactor, built for switching motor loads in control panels. It carries a 24 VDC coil with an operating range of 0.8 to 1.1 times rated value, so the coil holds in at about 19.2 V and picks reliably at 26.4 V. The screw-type coil terminals match standard panel wiring practice.
Duty ratings and switching frequency
This contactor is rated for AC-3 motor duty at 750 operations per hour, and AC-4 inching/jogging at 250 ops/h. AC-1 resistive loads can run at 1000 ops/h. The mechanical endurance is 10 million operations, so the contactor outlasts the coil or arc chamber in most cycling applications. For DC switching, the contactor is rated at 6 A at 24 V, 2 A at 48 V, and 0.3 A at 220 V — these are resistive-load figures; inductive DC loads require derating or arc suppression.
Mounting and clearances
The S0 frame measures 85 mm high, 45 mm wide, and 151 mm deep. It mounts via screw or snap-on onto 35 mm DIN rail per EN 60715. Clearance requirements: 10 mm upward, 10 mm downward, 10 mm forward, and 6 mm to the side. The mounting position allows +/-180° rotation on a vertical surface and +/-22.5° tilt forward/backward, which gives flexibility in tight enclosures.
Termination and wiring
Main contacts accept solid or stranded wire from 1 to 10 mm². The coil terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) solid or stranded. Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C. Operating time at DC is 15 to 18 ms closing, with an arcing time of 10 ms.