SR3D Safety Control Unit – Flexible Safety Solution for Machines and Systems

The SR3D safety control unit provides a reliable means to safely and quickly stop machines and systems in the event of a hazard. With three safe relay outputs and an auxiliary contact (monitoring contact), the device meets the highest safety standards up to PL e / SIL 3. The SR3D is versatile, from emergency stop circuits to safety guard monitoring.

Application Areas of the SR3D
The SR3D safety control unit is used in the following areas:

• Emergency stop circuits (single or dual-channel)
• Safety guard monitoring on machines and systems
• Continuous operation combustion plants according to EN 50156-1 and EN 746-2
• Maritime applications (certified by TÜV Rheinland and Germanischer Lloyd)

Key Features and Benefits

• 2 possible start behaviors:
- Monitored manual start
- Automatic start

• Operation up to: PL e, SILCL 3, Category 4
• Cross-fault and ground-fault monitoring to ensure line integrity
• 3 safe, redundant, diverse relay outputs for maximum safety
• 1 auxiliary contact (monitoring contact) for status monitoring
• Connection options:
- Emergency stop buttons
- Safety switches
- Contactless safety switches
- Safety components with OSSD outputs

Functionality and Safety Concept
The SR3D ensures safe separation of safety circuits according to EN 60204-1 and fulfills the stop function requirements up to PL e / SIL 3 according to EN ISO 13849-1 and IEC 61508. If the emergency stop circuit is activated (e.g., by pressing an emergency stop button or opening a safety door), the SR3D immediately interrupts the enabling current paths and stops the machine.

Additional Safety Functions

• Force-guided relay contacts ensure that the safety function is maintained even if a fault occurs in the device.
• Cyclic monitoring of relay outputs to detect contact welding or failures.
• Feedback loop to monitor downstream contactors or expansion modules.
• LED display of switch status for quick diagnosis and maintenance.

Technical Specifications

• Protection class: IP54 (installation in control cabinets required)
• Operating voltage: AC 115 V / 230 V – Maintain a minimum distance of 10 mm to adjacent devices
• Mounting: On a 35 mm DIN rail according to EN 60715 TH35
• Climatic conditions: Ensure proper heat dissipation in the control cabinet to prevent overheating
• Distance to adjacent devices: Minimum of 10 mm for AC 115 V / 230 V version

Standards and Certifications
The SR3D meets the following safety standards and requirements:

• EN ISO 13849-1 (PL e)
• IEC 61508 (SIL 3)
• EN 60204-1 (safe separation of safety circuits)
• EN 50156-1 / EN 746-2 (for use in combustion plants)
• Certified by TÜV Rheinland and Germanischer Lloyd

Conclusion
The SR3D safety control unit is a reliable solution for the monitoring and shutdown of machines and systems in emergency stop and safety guard monitoring systems. Its redundancy, diversity, and force-guided relay contacts ensure maximum operational safety.