Siemens 6ES5935-3LA12 Power Supply Unit

Reliable Power Distribution for S5 Racks

The Siemens 6ES5935-3LA12 power supply unit provides regulated DC power to S5-135U and S5-155U backplane systems. This unit converts AC mains into multiple DC voltage rails for all connected modules. Large control cabinets require stable power sources, and this model delivers consistent performance across varying loads.

Input and Output Electrical Specifications

This power supply accepts an input voltage range of 185 V to 264 V AC or 93 V to 132 V AC via a selector switch. The unit delivers three isolated DC outputs: 5 V at 20 A, 24 V at 1 A, and 15 V at 0.5 A. Total output power reaches 140 watts, supporting heavily populated racks with numerous I/O modules. Furthermore, the integrated active inrush current limiting prevents circuit breaker tripping during startup.

Parameter	Specification
Model	Siemens 6ES5935-3LA12
Input Voltage (selectable)	93–132 V AC or 185–264 V AC
Input Frequency	47–63 Hz
Output 1	5 V DC at 20 A
Output 2	24 V DC at 1 A
Output 3	15 V DC at 0.5 A
Total Output Power	140 W
Efficiency	> 88% (at full load)
Inrush Current Limiting	Active, < 30 A peak
Hold-up Time	25 ms (at 230 V AC)
Dimensions (W x H x D)	70 mm x 125 mm x 120 mm
Weight	1.1 kg

Protection Features and Safety Mechanisms

This power supply incorporates comprehensive protection circuits for safe system operation. Overvoltage protection on each output clamps the voltage to safe levels. Short-circuit protection limits output currents and automatically recovers after fault removal. Additionally, the unit features overtemperature shutdown at 85°C to prevent component damage. A built-in input fuse provides primary-side fault protection.

Thermal Management and Cooling Design

The Siemens 6ES5935-3LA12 utilizes natural convection cooling through an extruded aluminum heatsink. This design eliminates the need for a fan, reducing noise and maintenance requirements. The unit maintains full output capacity from 0°C to 50°C without derating. Above 50°C, the output current derates linearly by 2.5% per degree Celsius. The ventilation slots require at least 40 mm clearance for adequate airflow.

Diagnostic Indicators and Monitoring

Three front-panel LEDs indicate power status for each DC output rail. A DC OK relay contact provides remote monitoring of the 5 V output health. The unit also features a collective fault signal that activates upon any protection event. These diagnostic tools simplify troubleshooting and preventive maintenance planning.

Installation and System Integration

You can install this power supply in the dedicated power slot of S5-135U and S5-155U racks. The unit connects to the backplane via a 32-pin connector for automatic voltage distribution. Always connect the protective earth terminal before energizing the unit. For redundant configurations, you can parallel two power supplies with isolation diodes. The operating temperature range spans from 0°C to 60°C with non-condensing humidity up to 95%.