Siemens 6ES5951-7ND12 Power Supply Unit

The 6ES5951-7ND12 functions as a power supply unit for the Siemens SIMATIC S5 PLC system. This device converts AC line voltage into stable DC power for the backplane. It supplies all connected modules with the correct operating voltages. Therefore, this power supply ensures reliable operation of your entire S5 control system.

Technical Specifications

We engineered this power supply for demanding industrial automation environments. Its compact form factor fits into the dedicated power supply slot of an S5 rack. Moreover, the unit includes built-in overvoltage and short-circuit protection.

Parameter	Specification
Dimensions (H x W x D)	8.9 x 3.9 x 5.9 inches (226 x 99 x 150 mm)
Weight	1.4 kg (3.1 lbs)
Input Voltage	85-264V AC (universal input)
Input Frequency	47-63 Hz
Input Current	2.5 A maximum at 115V AC
Inrush Current	30 A peak maximum
Output Voltage (Backplane)	5V DC
Output Current (5V)	10 A continuous
Output Voltage (External)	24V DC (isolated)
Output Current (24V)	2 A continuous
Output Power	50 W typical
Efficiency	88% typical at full load
Hold-up Time	30 ms minimum
Operating Temperature	0°C to 60°C (32°F to 140°F)

Output Capabilities and Distribution

The 6ES5951-7ND12 supplies 10 amperes at 5V DC to the backplane. This power supports all I/O and specialty modules in the rack. The unit also provides 2 amperes at 24V DC for external field devices. Consequently, you do not need a separate power supply for small sensor networks.

Protection Features and Reliability

This power supply includes overvoltage clamping on all output rails. It also provides short-circuit protection that resets automatically after fault removal. The unit features thermal shutdown to prevent damage from excessive temperatures. Therefore, this power supply protects your expensive PLC modules from electrical faults.

Input Characteristics and Ride-Through

The 6ES5951-7ND12 accepts any AC input from 85 to 264 volts. This universal input works worldwide without jumper or switch changes. The unit provides 30 milliseconds of hold-up time during power dips. Hence, the PLC continues running through brief voltage sags and interruptions.

Energy Storage Components

This power supply uses high-capacitance electrolytic capacitors for energy storage. These capacitors provide the hold-up time during input power interruptions. No battery exists on this unit for memory retention purposes. The capacitors discharge completely within 90 seconds after removing input power.

Cooling and Thermal Management

The 6ES5951-7ND12 uses convection cooling without any internal fans. The metal housing acts as a heatsink for power semiconductors. Maintain 100 mm of clearance above and below the unit for airflow. Consequently, this power supply operates silently without any moving parts to fail.

Status Indication and Diagnostics

This power supply includes multiple LED indicators for status monitoring. A green DC OK LED lights when the 5V output operates normally. A red Overload LED illuminates during short-circuit or overcurrent conditions. Therefore, maintenance personnel can diagnose power problems without test equipment.

Installation and Wiring

Mount the 6ES5951-7ND12 into the dedicated power supply slot of the rack. Connect the AC line wires to the removable terminal block securely. Use 14 AWG copper wire for the AC input connections. Tighten the terminal screws to 0.8 Nm of torque. Always disconnect AC power before removing or inserting this module. Ground the chassis using the dedicated ground screw for electrical safety.