SIEMENS
SIEMENS 3RT20281BB40 IEC Magnetic Contactor 24V DC 3P
IEC magnetic contactor with 24 V DC coil, three poles, 38 A inductive and 50 A resistive ratings, 1NO/1NC auxiliary contacts, screw terminals and DIN-rail or surface mounting
- Reliable 24 V DC coil control for 3-pole circuits
- Handles 38 A inductive and 50 A resistive full-load currents
- Compact 3.6 in height and 1.7 in width fits tight panels
- Dual 1 NO/1 NC auxiliary contacts simplify control wiring
- DIN-rail or surface mounting with screw terminals for fast installation
IEC 3-pole 24 V DC motor starter
The SIEMENS 3RT20281BB40 is a three-pole IEC magnetic contactor designed for switching inductive loads up to 38 A and resistive loads up to 50 A. It operates from a 24 V DC coil and includes one normally open and one normally closed auxiliary contact. The unit suits panel builders and maintenance engineers who need a compact, rail-mountable starter for motor control circuits.
Coil consumption and thermal behaviour
The 24 V DC coil draws limited power during pick-up and hold, keeping panel heat rise low in continuous duty. With no integral fan, the contactor runs silently, relying on natural convection through the open-frame design. Rated currents of 38 A inductive and 50 A resistive are achieved without forced cooling, simplifying thermal planning inside the enclosure.
Screw terminals, DIN rail mounting, open frame
Screw terminals accept solid or stranded conductors for secure power and control wiring. The housing clips onto standard DIN rail or can be surface-mounted with screws, fitting a 3.6 in by 1.7 in footprint. The open-frame construction has no NEMA-rated enclosure, so the installer must provide a suitable cabinet for finger-safe and environmental protection.
Highlights
- Reliable 24 V DC coil control for 3-pole circuits
- Handles 38 A inductive and 50 A resistive full-load currents
- Compact 3.6 in height and 1.7 in width fits tight panels
- Dual 1 NO/1 NC auxiliary contacts simplify control wiring
- DIN-rail or surface mounting with screw terminals for fast installation
Specifications
| Brand | SIEMENS |
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Questions about this item
How do I mount the S0 frame and wire the screw terminals for the 24 V DC coil?
Clip the contactor onto a standard DIN rail or fasten it with the surface-mount holes, then secure each power and control wire under the screw terminals.
Which parts will need checking or replacement after extended operation?
The main power contacts and the 1 NO / 1 NC auxiliary contacts wear with each switching cycle; inspect them periodically and replace the contactor when contact resistance rises.
At what current level does the contactor reach its inductive-load limit during continuous use?
The inductive full-load rating is 38 A; sustained operation above that value will cause overheating and premature contact wear.
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