Product Description

Siemens 3RB3123-4VB0 Electronic Overload Relay – 10–40 A, Class 5E–30E

The Siemens 3RB3123-4VB0 is a microprocessor-based electronic overload relay from the Siemens SIRIUS 3RB3 series, designed for reliable protection of three-phase motors in industrial automation and motor-control systems. It provides an adjustable current setting range of 10 to 40 A and selectable trip classes 5E, 10E, 20E and 30E. Siemens specifies this model for contactor mounting, with a compact S0 size, making it suitable for integration into SIRIUS motor-starter assemblies.

The relay provides electronic overload protection together with phase-failure and phase-asymmetry protection. The 3RB31 family also supports activatable internal ground-fault detection, manual and automatic reset, integrated electrical remote reset, TEST functionality and self-monitoring.

Siemens SIRIUS 3RB3 Electronic Overload Relay

The 3RB3123-4VB0 belongs to the Siemens SIRIUS 3RB electronic overload relay family, designed to monitor motor current electronically and protect motors against overload and other abnormal operating conditions.

Compared with conventional thermal overload relays, microprocessor-based electronic overload relays provide configurable trip characteristics and additional monitoring functions.

Typical applications include:

• Industrial motor control

• Pumps

• Fans and blowers

• Compressors

• Conveyors

• Machine tools

• Production machinery

• Process equipment

• Industrial automation

• OEM control panels

Adjustable 10–40 A Current Range

The 3RB3123-4VB0 provides an adjustable current-response setting of 10 to 40 A. Siemens' official datasheet confirms the 10–40 A range for this exact article.

This allows the relay to be set according to the rated current of the motor being protected.

The current setting should be selected using the motor nameplate data and the requirements of the complete motor-protection system.

Selectable Class 5E–30E

A major advantage of the 3RB3123-4VB0 is its adjustable trip-class selection.

The relay supports:

• Class 5E

• Class 10E

• Class 20E

• Class 30E

Siemens identifies these four trip classes as selectable in the 3RB31 electronic overload relay range.

This allows the protection characteristic to be matched to different motor starting times and load requirements.

Electronic Overload Protection

The primary function of the 3RB3123-4VB0 is electronic motor-overload protection.

The relay continuously monitors the motor current and trips when the measured condition exceeds the configured overload characteristics.

This can help protect motors against:

• Prolonged overcurrent

• Excessive mechanical loading

• Motor overheating caused by overload

• Abnormal operating conditions

• Improperly selected motor starting characteristics

Correct adjustment of the current setting and trip class is important for reliable motor protection.

Phase-Failure and Asymmetry Protection

The Siemens 3RB31 family provides phase-failure and phase-asymmetry protection in addition to overload protection.

Phase-related abnormalities can produce unbalanced current and additional motor heating. Electronic monitoring helps provide broader protection for three-phase motors.

This makes the relay suitable for motor-control applications where protection against phase-related operating conditions is required.

Internal Ground-Fault Detection

The 3RB31 family supports activatable internal ground-fault detection. Siemens identifies internal ground-fault detection among the available protection functions.

This can provide an additional monitoring function in suitable motor-protection applications without necessarily requiring a separate external detection device.

The overall protection scheme should still be designed according to the electrical requirements of the specific installation.

Manual, Automatic and Remote Reset

The 3RB3123-4VB0 benefits from the flexible reset functions available in the 3RB31 family.

Available reset functions include:

• Manual RESET

• Automatic RESET

• Integrated electrical remote RESET

These options allow the overload relay to be adapted to different machine-control strategies.

Manual reset is useful where operator intervention is required after a trip, while automatic or remote reset can be used in appropriately designed automated control systems.

TEST Function and Self-Monitoring

The 3RB3 electronic overload relay family includes a TEST function and self-monitoring capability.

These functions can assist during:

• Commissioning

• Troubleshooting

• Preventive maintenance

• Functional testing

• Control-panel servicing

The switch-position indication also provides a convenient visual reference for the relay's operating condition.

1 NO + 1 NC Auxiliary Contacts

The 3RB31 series provides 1 normally open (NO) and 1 normally closed (NC) auxiliary contact for control and signalling applications.

These auxiliary contacts can be incorporated into:

• Contactor control

• Trip indication

• PLC feedback

• Alarm signalling

• Motor fault monitoring

• Control-system interlocking

This provides a convenient way to communicate the overload relay's operating or trip state to the surrounding control system.

Contactor Mounting

The 3RB3123-4VB0 is designed for contactor mounting and belongs to the S0 size range. Siemens lists the mounting method as contactor mounting for this exact model.

This enables integration with compatible SIRIUS contactors to create a compact motor-starter assembly.

Contactor mounting can be useful for:

• Motor starters

• Machine-control panels

• OEM control cabinets

• Industrial automation panels

• Pump and fan control systems

The exact contactor compatibility should always be checked before assembly.

690 V Main-Circuit Rating

The official Siemens datasheet specifies a 690 V rated operational voltage for the main circuit and a 50–60 Hz operating frequency. It also specifies a maximum operational current of 40 A for the model.

These ratings should be considered together with the motor application, protection coordination, conductor sizing and installation conditions.

Industrial Motor-Control Applications

The 3RB3123-4VB0 can be used in many industrial motor-protection applications.

Pumps

It can protect compatible pump motors against overload, phase failure and asymmetry conditions.

Fans and Blowers

Selectable trip classes allow the protection characteristics to be matched to the motor's starting behaviour.

Compressors

Electronic overload monitoring can help protect compressor motors against excessive operating current.

Conveyors

The relay can protect conveyor motors from excessive mechanical loading and phase abnormalities.

Machine Tools

It can be integrated into motor-control systems used in production and machine-tool applications.

Process Automation

Its electronic protection, reset functions and auxiliary signalling make it suitable for automated process equipment.

Suitable for OEMs and Panel Builders

The 3RB3123-4VB0 is suitable for OEM machine manufacturers, electrical panel builders, automation integrators and industrial maintenance professionals.

Its combination of 10–40 A adjustable current, Class 5E–30E selection, electronic overload protection, phase-failure and asymmetry protection, optional ground-fault detection and contactor mounting makes it a flexible solution for industrial motor protection.

Key Features

• Siemens SIRIUS 3RB3 electronic overload relay

• Article number 3RB3123-4VB0

• Microprocessor-based electronic overload protection

• 10–40 A adjustable current range

• Class 5E, 10E, 20E and 30E adjustable

• Contactor mounting

• Size S0

• 690 V rated operational voltage

• 50–60 Hz operating frequency

• Overload protection

• Phase-failure protection

• Phase-asymmetry protection

• Activatable internal ground-fault detection

• 1 NO + 1 NC auxiliary contacts

• Manual and automatic RESET

• Integrated electrical remote RESET

• TEST function

• Self-monitoring

• Switch-position indication

Benefits

• Microprocessor-based protection: Provides configurable electronic motor protection.

• 10–40 A adjustable range: Covers a broad range of compatible motor currents.

• Class 5E–30E selection: Allows the trip characteristic to be matched to motor starting requirements.

• Phase protection: Helps protect against phase failure and asymmetry.

• Ground-fault detection: Adds an additional protection function when activated.

• Flexible reset: Supports manual, automatic and remote reset strategies.

• Diagnostic functions: TEST and self-monitoring assist commissioning and maintenance.

• Auxiliary signalling: 1 NO + 1 NC contacts provide useful control and trip-feedback signals.

• Contactor mounting: Allows integration with compatible SIRIUS motor starters.

• Compact S0 design: Helps optimize motor-control-panel space.

Why Choose Siemens 3RB3123-4VB0?

The Siemens 3RB3123-4VB0 is a versatile electronic overload relay for motors requiring adjustable protection in the 10–40 A range.

Its Class 5E, 10E, 20E and 30E selectable trip characteristics allow the relay to be configured for different motor starting conditions, while phase-failure and asymmetry protection provide additional monitoring. The 3RB31 family also supports internal ground-fault detection, flexible reset options, TEST functionality and self-monitoring.

With contactor mounting and S0 construction, it is well suited to integrated Siemens SIRIUS motor-starter assemblies used by OEMs, panel builders and industrial automation integrators.

Delivery Across India

SB Smart supplies Siemens industrial electrical and automation products across Faridabad, Gurgaon/Gurugram, Delhi NCR, Haryana, Noida, Punjab, Mumbai and major cities across India.

Major delivery locations include:

• Faridabad

• Gurgaon/Gurugram

• Delhi

• Delhi NCR

• Noida

• Greater Noida

• Haryana

• Punjab

• Mumbai

• Pune

• Ahmedabad

• Bengaluru

• Hyderabad

• Chennai

• Kolkata

• Jaipur

• Chandigarh

• Lucknow

• Indore

• Surat

• Vadodara

• Nagpur

• Coimbatore

• And other major cities across India

Frequently Asked Questions

1. What is Siemens 3RB3123-4VB0?

It is a Siemens SIRIUS 3RB3 microprocessor-based electronic overload relay with a 10–40 A adjustable current range and Class 5E–30E selectable trip classes.

2. What is the current setting range?

The current-response setting range is 10–40 A.

3. Which trip classes are available?

The relay supports Class 5E, 10E, 20E and 30E.

4. Does it provide phase-failure protection?

Yes. The 3RB31 family provides phase-failure and phase-asymmetry protection in addition to overload protection.

5. Does it provide ground-fault detection?

Yes. Internal ground-fault detection is available as an activatable function in the 3RB31 family.

6. How many auxiliary contacts does it have?

The 3RB31 family provides 1 NO + 1 NC auxiliary contacts.

7. What reset options are available?

The 3RB31 family supports manual, automatic and integrated electrical remote RESET.

8. Is it contactor-mounted?

Yes. The 3RB3123-4VB0 is specified for contactor mounting and is a Size S0 relay.

9. What is its rated operating voltage?

The main circuit has a rated operational voltage of 690 V and the device operates at 50–60 Hz.

10. Where can I buy Siemens 3RB3123-4VB0 in India?

You can explore the Siemens industrial electrical and automation product range at SB Smart for electronic overload relays, motor-protection devices, contactors and related control components.