Siemens 3RT2045-1KB40-1AA0 Thermal Overload Relay

Siemens 3RT2045-1KB40-1AA0 is a three-pole Siemens Sirius 3RT2 motor starter/contactor with a 24 V DC coil, designed for reliable control of three-phase motors in industrial equipment. It is rated for up to 80 A and supports motor loads up to 37 kW at 400 V AC (AC-3 duty), making it suitable for mid-size motor control applications in production lines and machinery enclosures. The device includes a 1 normally open and 1 normally closed auxiliary contact (1 NO + 1 NC) for signaling or interlocking requirements, and it carries a rated insulation voltage of 1 kV, which supports standard industrial control circuits. This compact 3RT2 family unit is designed for straightforward integration with common Siemens accessories and control schemes, with the coil specified as 24 V DC to enable easy interfacing with PLCs and other low-voltage control equipment. When selecting a replacement or upgrade, verify the coil voltage, pole count, auxiliary contact configuration, and the 400 V AC-3 motor rating to ensure compatibility with your motor, protection devices, and control logic.