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Entry type: FAQ Entry ID: 109757358, Entry date: 06/07/2018

How do you provide the power supply for the SIMATIC Compact Field Unit PA (CFU PA)?

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The SIMATIC CFU PA requires a 24 V power supply that can be connected redundantly as an option. This entry gives you the essential requirements and various options for providing the 24 V power supply of the SIMATIC CFU PA.


The SIMATIC CFU PA is designed for operation with a directly connected safety extra low voltage (SELV) from a limited power source (LPS).

This is why you must only connect safety extra low voltages (SELV/PELV) from a limited power source (LPS) to the power supply connections.

The following requirements result for the power supply:

  • Rated voltage: DC 24 V (tolerance range 19.2 V to 28.8 V)
  • Power limitation: maximum 100 VA

To meet these specifications with little effort you can use power supplies that comply with the requirements for NEC Class 2 according to the National Electrical Code (r) (ANSI / NFPA 70).

Refer also to the information in the manual for the SIMATIC CFU PA 109748741.

Similar power supply requirements also apply for the following devices:

  • SCALANCE XF204-2BA und XF204-2BA DNA

In the following we present different ways of providing the power supply of the CFU PA.
As an option you can also provide redundant power supplies in all the examples.

Power supplies with NEC Class 2 certification

One power supply for one CFU PA.

Fig. 01

The following table gives an overview of NEC Class 2 certified power supplies.

 DesignationArticle numberProduct support
LOGO!POWER 24 V / 2.5 A6EP3332-6SB00-0AY06EP3332-6SB00-0AY0 
SITOP PSU100C 24 V/2.5 A6EP1332-5BA006EP1332-5BA00 
SITOP PSU100C 24 V/3.7 A

Table 01

Redundancy module SITOP PSE202U with NEC Class 2 certification

SITOP power supply 24 V DC with up to 40 A and the redundancy module SITOP PSE202U with NEC Class 2 certification for power limitation to maximum 100 VA. One redundancy module supplies one CFU PA.

Fig. 02

One SITOP power supply can supply multiple redundancy modules and therefore multiple CFU PAs. As on option, the power supply of the redundancy module can also be redundant. In order for the outputs of the redundancy module comply with NEC class 2, the feeding SITOP power supplies must be certified according to UL 60950.

It is not permissible to operate the redundancy module without a connected GND line. The maximum permissible length of the GND line to the load power supplies is 50 cm.

DesignationArticle numberProduct support 
SITOP PSE202U NEC CLASS 26EP1962-2BA006EP1962-2BA00 

Table 02

SITOP PSE200U selectivity module with NEC Class 2 certification

Any SITOP power supply 24 V DC and the SITOP PSE200U selectivity module for power limitation at each output to a maximum of 100 VA. The selectivity module has 4 outputs and as such permits you to connect up to 4 CFU PAs per selectivity module.

Fig. 03

One SITOP power supply can supply multiple selectivity modules.

DesignationArticle number Product support 

Table 03

Power supply system SITOP PSU8600 with expansion module CNX8600 8 x 2.5 A

Compact power supply SITOP PSU8600 with up to 4 expansion modules CNX8600 8 x 2.5 A. It is possible to connect up to 8 CFU PAs per expansion module CNX8600 8 x 2.5 A.

Fig. 04

 DesignationArticle number  Product support
SITOP PSU8600 20A PN6EP3436-8SB00-2AY06EP3436-8SB00-2AY0 
SITOP PSU8600 40A PN6EP3437-8SB00-2AY06EP3437-8SB00-2AY0 
SITOP PSU8600 20A/4X5A PN6EP3436-8MB00-2CY06EP3436-8MB00-2CY0 
SITOP PSU8600 40A/4X10A PN6EP3437-8MB00-2CY06EP3437-8MB00-2CY0 
SITOP CNX8600 8X2.5A6EP4436-8XB00-0DY06EP4436-8XB00-0DY0 

Table 04

Further Information

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