The following are recommended as overcurrent protective devices:
• On the primary side: Circuit breakers
• On the secondary side: Miniature circuit breakers or SITOP select (article number
6EP1961-2BA00)
Additional data can be obtained in the "Siemens Industry Mall (
mall.industry.siemens.com/goos/WelcomePage.aspx?regionUrl=/de&language=en
)".
When selecting the miniature circuit breaker, take into consideration local installation
guidelines.
Table 8-8
MCBs by conductor cross-section and temperature
Conductor cross-section
Max. current up to 40 °C
Max. current up to 55 °C
1.5 mm
2
10 A
6 A
2.5 mm
2
16 A
10 A
4 mm
2
25 A
16 A
6 mm
2
32 A
20 A
24 V busbar
20 A
20 A
Select the tripping characteristic of the miniature circuit breakers to match the loads to be
protected and the max. current provided by the power supply unit in the event of a short-circuit.
8.8.4
Overvoltage protection
Overvoltage protection devices are required for cable lengths > 30 m.
The following Dehn overvoltage protection elements (surge arresters) are recommended for
protecting the 24 V power supply of the components and the 24 V signal cables against
overvoltage:
Table 8-9
Recommendations for overvoltage protection
24 V power supply
24 V signal cables
Manufacturer: Dehn
Article: BVT AVD 24
Article number: 918422
For digital inputs and outputs up to 0.1 A
Manufacturer: Dehn
Article: BXT ML4 BE C 24 and BSP BAS 4
Article numbers: 920364 and 926304
For digital inputs and outputs up to 0.5 A
Manufacturer: Dehn
Article: DCO SD2 ME 24 and DCO SD2 MD 24
Article numbers: 917921 and 917941
Always place the overvoltage protection elements at the boundary of the area to be protected,
e.g. at the entry point to the control cabinet. All 24 V conductors which exit the protected area
must be routed through an overvoltage protection element.
The diagram below uses a CU320-2 DP as an example to show how the overvoltage protection
elements are connected.
Control cabinet design and EMC booksize
8.8 24 V DC supply voltage
Booksize power units
128
Equipment Manual, 01/2022, 6SL3097-6AC30-0BP0