Siemens 6ES5951-7LB21 SIMATIC S5 PS 951 Power Supply

Overview

SIMATIC S5 • PS 951 POWER SUPPLY

6ES5951-7LB21 SIMATIC S5 PS 951 Power Supply

120/230 V AC power supply for S5-115U/H with a 5 V DC, 3 A main output.

At a Glance

Brand	Siemens
Model	6ES5951-7LB21
Product Type	PS 951 power supply module
Core Function	Converts 120/230 V AC to 5 V DC, 3 A
Compatible Series	SIMATIC S5-115U/H

Input Selection

Select the 120 V or 230 V AC input setting to suit the installed mains circuit.

Control Supply

The main 5 V output powers the controller circuits; auxiliary outputs serve PG/OP and 24 V circuits.

Replacement Check

Match the complete PS 951 article and calculate the installed rack current demand.

Product Overview

6ES5951-7LB21 is a PS 951 power supply module for the SIMATIC S5-115U/H controller. Its selectable 120/230 V AC input provides a 5 V DC, 3 A main control supply.

The unit also provides a 5.2 V PG/OP output and a 24 V auxiliary output. Siemens identifies this spare-part article as supplied without a backup battery.

Ordering focus: Compare the installed PS 951 input selection, 3 A rack demand and battery arrangement with the full order code.

Key Functions

S5 controller power

The 5 V main output feeds the controller circuits at a rated 3 A.

Separate auxiliary outputs

The unit provides a 5.2 V connection for PG/OP equipment and a 24 V auxiliary output.

Input monitoring and protection

The power supply provides at least 20 ms mains buffering and electronic short-circuit protection.

Official Specifications

Permissible input range at 120 V setting	94 to 132 V AC
Permissible input range at 230 V setting	187 to 264 V AC
Rated line frequency	50 Hz
Permissible line frequency	47 to 63 Hz
Rated input current at 120 V AC	0.55 A
Rated input current at 230 V AC	0.33 A
Maximum inrush current	15 times rated input current
Input I²t value	0.135 A²s
Active power consumption	44.8 W
Main 5 V output tolerance	±1.5%
Permissible main output current	0.3 to 3 A
PG/OP output voltage and tolerance	5.2 V DC ±1.5%
Maximum PG/OP output current	1 A
Auxiliary output voltage and tolerance	24 V DC ±5%
Maximum auxiliary output current	0.2 A
Minimum mains buffering	20 ms at minimum input voltage
Protection class	Class 1
Isolation type-test voltage	2700 V DC
Typical module power loss	19.8 W
Approximate module weight	1.6 kg

Official source:Siemens S5-115U programmable controller manual.

Frequently Asked Questions

Can 6ES5951-7LB21 run from either 120 V or 230 V AC?

Yes, its input selector supports either mains setting when set to the supply actually connected.

How much 5 V rack current can 6ES5951-7LB21 deliver?

The main control output is rated at 3 A, so the installed module load must stay within that limit.

Which PG or operator supply is available from 6ES5951-7LB21?

The dedicated PG/OP output provides 5.2 V DC at up to 1 A.

Does 6ES5951-7LB21 provide an auxiliary 24 V supply?

Yes, it has a 24 V DC auxiliary output rated up to 0.2 A.

What should I check before connecting mains to 6ES5951-7LB21?

Set the input voltage selector appropriately and connect the supply conductors to the specified L1, N and protective-earth terminals.

How long does 6ES5951-7LB21 bridge a mains interruption?

The specified minimum mains buffering time is 20 ms at the minimum input voltage.

Is a backup battery included with 6ES5951-7LB21?

Siemens identifies this spare-part listing as supplied without a backup battery.

Compatibility & Ordering Notes

Before ordering 6ES5951-7LB21: Match the complete -7LB21 article, the installed 120/230 V AC connection and the 3 A controller load; this article is identified as supplied without a backup battery.

S5-115U/H replacement checklist

• Set the voltage selector for the actual 120 V or 230 V AC mains supply.
• Add the 5 V consumption of the CPU and connected modules before selecting the 3 A supply.
• Check the rack, PS 951 connector arrangement and any backup battery requirement.
• Do not treat the higher-current -7LD21 variant as an automatic drop-in substitute.

Hot Selling Models