Siemens 5TT5740-2 SENTRON Insta Contactor — 40 A, 4 NO, 24 V DC Coil
The Siemens 5TT5740-2 is a SENTRON Insta contactor with four normally-open (NO) main contacts, rated for 40 A continuous at 230 V AC and also rated for 400 V AC line voltage. The coil is 24 V DC, making it compatible with standard 24 V DC control systems common in industrial panels. The 40 A rating means it can switch resistive and moderate inductive loads up to that current — sized for lighting banks, small heating elements, or as a slave contactor for larger motor starters.
Ratings and What They Mean for Fit
Rated operating current of 40 A at both 230 V and 400 V AC — this is the thermal current (Ith) for the contactor, meaning it can carry 40 A continuously through the main poles in open air. The 3 000 W filament lamp switching capacity tells you it handles incandescent lighting loads with high inrush; for LED or fluorescent ballasts, derate per the manufacturer's guidelines. The coil draws from a 24 V DC supply; verify your control transformer or power supply can deliver the inrush without dropping below the pickup voltage. IP20 protection means it's suitable for installation inside a locked electrical enclosure — not for washdown or outdoor exposure. The 3 width units (each 18 mm) give a 54 mm wide footprint on the DIN rail, so it occupies three standard modular positions in a distribution board.
Panel Integration and Mounting
Snap-on mounting to 35 mm DIN rail per EN 60715. Overall dimensions: 90 mm high, 54 mm wide, 71 mm deep, with an installation depth of 64 mm behind the panel face. The 71 mm depth means it clears most standard 80 mm deep enclosures, but check your gland plate clearance if using a shallow box. Four NO contacts give you four independent switching poles — useful for splitting a load across phases or for multi-circuit control.