Motor protection relay, 20–25 A adjustable, Class 10
Its adjustable current response range of 20–25 A lets you dial in the full-load current of the motor without swapping the relay body — a practical fit for a 7.5 kW motor at 400 V or a 10 hp motor at 480 V, depending on service factor. The relay mounts directly onto a S0-size contactor — the Siemens 3RT102 or 3RT103 series — using the contactor mounting fastening method. No separate base or DIN-rail adapter needed; the assembly clips together as a single unit that occupies the same panel footprint as the contactor alone. Screw-type terminals on both the main current circuit and the auxiliary/control circuit accept 2× (0.5–1.5 mm²) solid/stranded or 2× (0.75–2.5 mm²) with ferrules, with AWG equivalents of 2× (16–12) for mains and 2× (20–16) for auxiliaries. Tightening torque for the main contacts is 2–2.5 N·m.
The relay occupies a 45 mm width × 85 mm height × 85 mm depth envelope — the standard S0 block size. Required spacing to grounded parts at the side is 6 mm. Relative humidity during operation is 0–90 %. Installation altitude is limited to 2,000 m above sea level.
Electrical ratings and power dissipation
Rated operational current is 25 A at an operating voltage of 690 V and frequency of 50–60 Hz. The relay has 3 poles for the main current circuit. Per-pole dissipation is 2.7 W. Control circuit consumption at 24 V is 2 A, at 110 V is 0.22 A, and at 230 V is 2 A. Insulation voltage with pollution degree 3 at AC is 690 V.