The Siemens 5TT5751-2 is a SENTRON Insta contactor with a 3 NO + 1 NC contact arrangement, rated at 63 A on AC supply. The coil accepts 24 V AC/DC, so it drops into either a 24 VDC control bus or a 24 VAC transformer circuit without a separate rectifier. Rated operating voltage is 230 V AC, with a maximum of 440 V AC — covers standard single-phase and three-phase line voltages up to 440 V phase-to-phase.
What the ratings mean for fit
The 63 A AC-1 (resistive) rating is the headline number — it tells you the contactor can switch resistive loads like heaters or lighting banks up to that current. For motor loads (AC-3 duty), the rating will be lower; the 63 A figure is the thermal current, not the motor-switching current. The 5 000 W switching capacity with filament lamp load means it handles incandescent lighting banks without contact welding — a common spec for building-automation panels. The 3 NO + 1 NC contact set provides three normally-open power poles and one normally-closed auxiliary contact. Dimensions are 71 mm deep, 54 mm wide, 90 mm tall, with an installation depth of 64 mm. It occupies 3 width units on a DIN rail.