Siemens 3RT2645-1NB33 Capacitor Contactor, 75 kVAr, 20-33V AC/DC, Screw Terminal, Size S3 Original Brand New

Overview

The Siemens 3RT2645-1NB33 is a high-performance capacitor contactor specifically engineered for the reliable switching of capacitive loads. Designed according to the AC-6b utilization category, this contactor is the ideal solution for applications such as reactive current compensation systems and switching converters. Its robust design, integrated precharging resistors, and built-in overvoltage protection ensure a long service life and stable operation, minimizing disruptions to your power supply network.

Key Features & Benefit

• Optimized for Capacitive Loads: The 3RT2645-1NB33 is a specialized version of the SIRIUS 3RT2 series, designed specifically for AC-6b applications up to 75 kVAr at 400 V. It effectively handles the high inrush currents associated with switching capacitors.
• Integrated Precharging Resistors: Leading auxiliary contacts bring precharging resistors into the circuit before the main contacts close. This critical feature limits the peak charging current, protecting both the contactor and the electrical network from damaging current spikes.
• Integrated Varistor: The built-in varistor provides essential overvoltage protection for the control coil, extending the life of the contactor and improving system reliability.
• Versatile Control: The contactor is controlled by a wide-range 20-33 V AC/DC coil, making it flexible for integration into various control circuits.
• Reliable Auxiliary Contacts: Equipped with 1 NO + 1 NC auxiliary contacts, the device provides reliable feedback and control signaling for your system.
• Secure Connections: The screw terminals ensure a secure and durable electrical connection, simplifying installation and maintenance.
• Compact & Robust Design: With a size S3 frame, the 3RT2645-1NB33 offers a balance of high performance and a space-saving design, suitable for a variety of panel configurations.

Technical Specification

• Product Number: 3RT2645-1NB33
• Product Type: Capacitor Contactor
• Utilization Category: AC-6b
• Rated Power (Capacitive): 75 kVAr at 400 V
• Poles: 3-pole
• Control Supply Voltage: 20-33 V AC/DC (50/60 Hz)
• Auxiliary Contacts: 1 NO + 1 NC
• Terminal Type: Screw Terminal
• Size: S3
• Integrated Features: Varistor for overvoltage protection
• Standards: IEC 60947-1, IEC 60947-4-1, IEC 60947-5-1, IEC 60831-1, IEC 61921

Function

The Siemens 3RT2645-1NB33 capacitor contactor operates by utilizing a unique two-stage switching process. When the control coil is energized, the leading auxiliary contacts close first, engaging precharging resistors. These resistors limit the initial high-peak inrush current that occurs when a capacitor begins to charge. Following this brief precharging phase, the main contacts close, bypassing the resistors and allowing the full current to flow. This mechanism significantly reduces electrical stress on the contactor and the power supply network, extending the lifespan of all components.

Protection & Safety

Proper protection is crucial for the safe and reliable operation of the contactor.

• Main Connections: All main connections must be protected against short circuits and overloads using appropriate circuit breakers or fuses, as specified in the technical product data sheet.
• Control Connections: The control supply voltage connections require suitable protection to handle the contactor’s load characteristics. The integrated varistor provides overvoltage protection for the coil, but additional short-circuit protection for the control circuit is recommended.

Installation & Expansion

• Auxiliary Switches: The 3RT2645-1NB33 comes with an integrated 1 NO + 1 NC auxiliary switch.
• Expansion: The contactor can be expanded with additional lateral auxiliary switches, ensuring flexibility for complex control and monitoring requirements.

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