Microprocessor based overload relay - 3RB (Class 5 to 30E – Settable) - 3RB3123-4SB0

Product Description

Siemens 3RB3123-4SB0 Electronic Overload Relay – Intelligent Motor Protection with Adjustable Class 5E to 30E

The Siemens 3RB3123-4SB0 Electronic Overload Relay is an advanced microprocessor-based motor protection device designed to provide highly accurate and dependable protection for industrial motors. As part of the renowned Siemens SIRIUS 3RB3 Series, this electronic overload relay offers superior protection against overload conditions, phase failure, phase imbalance, and ground faults while ensuring reliable motor operation and extended equipment life. Designed for motors with a 3A to 12A adjustable current range, the 3RB3123-4SB0 combines intelligent electronic monitoring with flexible protection settings to meet the demands of modern industrial automation systems.

Unlike conventional thermal overload relays that rely on bimetal elements, the Siemens 3RB3123-4SB0 uses sophisticated electronic sensing technology and microprocessor-controlled evaluation. This enables highly accurate current monitoring and faster response to abnormal operating conditions. By continuously analyzing motor current, the relay can detect overload situations before they cause overheating, winding damage, insulation failure, or unexpected motor breakdowns. The result is improved equipment reliability, lower maintenance costs, and increased operational efficiency.

A key advantage of the 3RB3123-4SB0 Electronic Overload Relay is its adjustable trip class functionality. The relay allows users to select between Class 5E, 10E, 20E, and 30E protection characteristics depending on motor starting requirements. Fast-starting motors can utilize lower trip classes for rapid protection, while applications with heavy starting loads and longer acceleration times can operate with higher trip classes without nuisance tripping. This flexibility makes the relay suitable for pumps, fans, compressors, conveyors, mixers, HVAC equipment, packaging machinery, and various industrial process applications.

The Siemens 3RB3123-4SB0 provides an adjustable motor protection range of 3A to 12A, making it ideal for protecting small to medium-sized three-phase motors. At 400V AC, the relay supports motors from approximately 1.5 kW to 5.5 kW, while at 690V AC it can protect motors up to 7.5 kW. This wide adjustment range allows OEMs, panel builders, and maintenance teams to standardize motor protection solutions while reducing inventory complexity.

One of the most important features of the 3RB3123-4SB0 Motor Protection Relay is its integrated ground fault detection capability. The relay continuously monitors motor current and can identify insulation failures, moisture-related faults, and high-resistance ground faults before severe damage occurs. This additional protection layer improves system safety, minimizes downtime, and helps protect expensive motors and equipment from unexpected failures.

Designed in the compact S0 frame size, the relay is intended for direct mounting onto Siemens SIRIUS contactors, creating a space-saving and efficient motor starter combination. The main circuit and auxiliary circuit both feature reliable screw terminal connections, ensuring secure wiring, excellent vibration resistance, and long-term electrical reliability. This compact design simplifies installation while maximizing control panel space utilization.

For seamless integration into control systems, the Siemens 3RB3123-4SB0 includes 1 Normally Open (1NO) and 1 Normally Closed (1NC) auxiliary contacts. The NC contact is generally used for contactor disconnection during fault conditions, while the NO contact provides trip indication and status feedback for PLCs, alarm systems, and monitoring platforms. This integrated arrangement simplifies wiring and improves diagnostic capabilities.

The relay supports manual reset, automatic reset, and remote reset functionality, allowing flexibility across different industrial applications. Maintenance personnel can quickly restore operation after fault conditions are cleared, while automated systems can utilize remote reset capabilities for improved productivity and reduced downtime. Recovery time after overload trips is optimized to maintain both motor safety and operational continuity.

Built according to Siemens' stringent industrial standards, the 3RB3123-4SB0 Electronic Overload Relay features a 690V rated insulation voltage, 6kV surge withstand capability, IP20 protection, and reliable operation within ambient temperatures ranging from -25°C to +60°C. Integrated temperature compensation ensures consistent protection performance regardless of environmental fluctuations.

The Siemens 3RB3123-4SB0 is widely used in manufacturing plants, water treatment systems, HVAC installations, packaging machines, material handling equipment, process industries, and industrial automation projects. Its combination of intelligent protection features, compact design, adjustable trip classes, and Siemens reliability makes it a preferred choice for critical motor protection applications.

At SBsmart.in, we supply genuine Siemens industrial automation and motor protection products trusted by OEMs, panel builders, electrical contractors, and industrial maintenance professionals across India. When you purchase the Siemens 3RB3123-4SB0, you receive an authentic Siemens SIRIUS motor protection solution engineered for long-term reliability, superior performance, and maximum equipment safety.