The Siemens 3RT2028-1AU00 is a SIRIUS S0-frame power contactor rated 34 A in AC-3 duty at 480 V — that's the motor-switching current, not the resistive-heater current. The AC-3 rating governs inductive motor loads: starting current, breaking under full load. For a 480 V three-phase motor, this contactor handles up to about 34 A locked-rotor and 34 A full-load break.
Built-in auxiliary contacts: at 24 V rated value 10 A, at 48 V rated value 2 A, at 110 V rated value 1 A, at 230 V rated value 5 hp, at 400 V rated value 3 A. The 24 V 10 A rating covers PLC or relay coil loads; the 5 hp at 230 V covers small motor contactor coils. Arcing time 10 ms at 50 Hz.
Operating conditions
Mechanical life typical 10 million operations. Switching frequency: up to 1000 cycles/h at AC-1, 750 cycles/h at AC-3, 250 cycles/h at AC-4.