Siemens 6ES5951-7ND32 Power Supply

The Siemens 6ES5951-7ND32 provides regulated DC power to S5 controller backplanes and I/O modules. This power supply unit measures 250 mm in depth and 25 mm in width. It fits standard SIMATIC S5 rack slots without any modifications. The unit weighs 0.65 kg, making installation straightforward.

Input Specifications and Energy Storage

You must supply 230V AC single-phase power to the input terminals. The Siemens 6ES5951-7ND32 accepts a voltage tolerance of ±15 percent from this nominal value. It also accepts 120V AC input with simple jumper reconfiguration. The unit stores 1200 µF of primary capacitance for hold-up during dips. This storage maintains output for up to 20 milliseconds after input loss.

Output Ratings and Protection Features

The Siemens 6ES5951-7ND32 delivers 5V DC at 8 amps for logic circuits. It also provides 24V DC at 1.5 amps for I/O and sensor power. A separate 24V DC output at 0.5 amps powers auxiliary devices. The unit includes overvoltage protection set at 5.7V and 28V respectively. Short-circuit protection automatically limits current and recovers after fault removal.

Internal Architecture and Component Layout

The power supply contains three separate circuit boards inside its metal housing. One board handles AC input rectification, while another manages DC output regulation. The third board provides filtering and protection circuits. The Siemens 6ES5951-7ND32 includes a 48-pin edge connector for backplane power distribution. A front terminal block provides access to auxiliary 24V outputs.

Status Indicators and Environmental Tolerance

You will find LED indicators for input present, output healthy, and overload status. The Siemens 6ES5951-7ND32 provides a relay contact signal for remote monitoring. The unit operates reliably from 0°C to 60°C ambient temperature. It tolerates humidity levels up to 95 percent without any condensation issues. The power supply uses natural convection cooling without any internal fan.

Below is a complete summary of its technical specifications.

Parameter	Value
Dimensions (D x W)	250 mm x 25 mm
Weight	0.65 kg
Input Voltage	230V AC or 120V AC ±15%
Primary Capacitance	1200 µF
Hold-up Time	20 ms
Output 5V DC	8 A
Output 24V DC (main)	1.5 A
Output 24V DC (aux)	0.5 A
Overvoltage Protection (5V)	5.7V
Overvoltage Protection (24V)	28V
Number of PC Boards	3
Backplane Connector	48-pin edge
Output Terminal Block	Front access
Status LEDs	Input, output, overload
Monitoring Output	Relay contact
Cooling Method	Natural convection
Operating Temperature	0°C to 60°C
Humidity Tolerance	95% non-condensing

The Siemens 6ES5951-7ND32 replaces older power supplies in S5-115U and S5-135U racks. You do not need any adapters or additional mounting hardware. This unit also accepts wide input frequency from 47 to 63 Hz. Consequently, it suits global installations without any configuration changes.