What it is and what it does
The Siemens 3RB1246-1QM31 is a solid-state overload relay from the SIRIUS series, designed for motor protection in control panels. It covers a current range of 6.3 to 25 A on a 220 to 240 VAC supply at 50/60 Hz. This unit integrates thermistor (PTC) motor protection and internal earth-fault detection into a single device, reducing wiring and panel space compared to separate protection modules. The bistable outputs — 1NO/1NC for overload/thermistor/earth-fault and 1NO/1NC for overload warning — latch their state after a trip, so the relay holds the fault indication even if control power is lost.
Sourcing and lifecycle
For a BOM line or a line-down replacement, this part can be quoted to order. The current lifecycle status removes the urgency of last-time-buy planning for this order code.
What the ratings mean for fit
The 6.3 to 25 A setting range covers standard IEC frame-size motor ratings from about 3 kW to 11 kW at 400 V. The 220-240 VAC control supply is the relay's own operating voltage, not the motor circuit — it powers the internal electronics and the bistable output coils. Integrated earth-fault detection means this relay monitors for leakage to ground without a separate core-balance CT, which simplifies the panel wiring. The thermistor input allows direct connection of PTC sensors embedded in the motor windings, providing overtemperature protection beyond what a bimetallic overload curve can sense.