The Siemens 3RU1126-1HB0-ZW98 is a SIRIUS overload relay rated for 5.5...8 A motor protection, with one normally-open and one normally-closed auxiliary contact. It's a Size S0 unit, Class 10 trip curve, designed to mount directly onto a contactor — no separate enclosure needed for the motor starter assembly. The reusable packing ships in a pack of 88 units.
What the ratings mean for the buyer
The 5.5...8 A setting range covers small three-phase motors in the 2.2 to 4 kW ballpark at 400 V. Class 10 means the relay trips within 10 seconds at 7.2× the set current — fast enough to protect a standard induction motor during a locked-rotor condition without nuisance tripping on normal starts. The 1NO+1NC auxiliary gives you a feedback signal for the PLC and a hard-wired shutdown path; the NO side reports the relay state, the NC side breaks the contactor coil circuit on a trip.
Deployment context
Snaps onto the matching S0 contactor (3RT2 series) on a DIN rail inside the motor control center. The Class 10 curve is the standard choice for general-purpose pump, fan, and conveyor motors — not for high-inertia loads that need a longer trip delay like Class 20.