The Siemens 3RB1246-1EM20 is a solid state overload relay rated for full motor protection in the 25-100 A range, sized for S2/S3 contactor frames. It covers Class 5 through Class 30 trip curves and includes integrated ground-fault detection with monostable outputs and ground-fault signaling. The auxiliary circuit uses screw terminals; reset is selectable between manual, automatic, or remote. Control supply is AC 220-240 V, 50/60 Hz.
The 25-100 A range covers a wide band of motor full-load currents, from a small 7.5 kW motor up to roughly 45 kW at 400 V. The Class 5-30 adjustment lets you match the trip curve to the motor's thermal time constant — Class 10 for standard motors, Class 20 for high-inertia loads like fans or crushers, Class 30 for very long acceleration times. The integrated ground-fault detection means it can sense leakage to earth without a separate module, which simplifies the panel wiring for a motor control center. The AC 220-240 V control supply is common for European-style panels; if your panel runs 110 V or 24 VDC, this relay will not power up without a control transformer.
Integration Notes
This relay mounts individually (not on a contactor base) and fits the S2/S3 frame footprint. The main circuit uses a current transformer internally, so no separate CT is needed. Screw terminals on the auxiliary side are standard for panel wiring — no special tools. The manual-automatic-remote reset selector gives flexibility: manual for commissioning, automatic for unattended stations, remote for PLC-driven reset. If you are retrofitting into an existing panel, verify the control voltage matches your existing 220-240 V AC supply; the relay will not operate on 24 VDC.