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Dimensions
Section 12
11
Circuit breakers for direct
current applications (cont.)
24 V - 48 V direct current applications
Technical advice
Personal protection
Personal protection (earth-leakage protection) is not mandatory for this voltage
range (24-48 V DC).
In fact, according to the standards currently in force, the minimum ventricular
fibrillation current
If
for human beings is in the order of 25 mA for alternating current
(50 Hz), whereas for direct current, it is more than 50 mA.
The table below shows the data according to the standards and conditions:
Environment
Voltage specifications
AC
DC
Dry environment
Zman = 2000 Ohm
Uf = Z x If 50 V
100 V
Wet environment
Zman = 1000 Ohm
Uf = Z x If 25 V
50 V
With
Z
corresponding to the impedance of the human body in the different types of
environment,
If
being the current passing through the body and
Uf
the minimum contact voltage
required to reach the danger current.
Under normal operating conditions, this voltage range (< 50 V) is therefore not
dangerous to human beings.
DB124238
DB124239
DB124237
U
f
I
f
Z
man
Standards: IEC 60479-2, NF C 15100, IEC 60755.