P Series
DC-DC Converters >100Watt
Industrial Environment
Safety of operator accessible output circuit
If the output circuit of an DC-DC converter is operator ac-
cessible, it shall be an SELV circuit according to IEC/EN
60950 related safety standards
nominal voltages if in series or +/– configuration) of 35 V.
However, it is the sole responsibility of the installer to as-
sure the compliance with the relevant and applicable safety
regulations. More information about this subject and about
output circuits at hazardous voltages are given in: Techni-
cal Information: Safety.
The following table shows some possible installation con-
figurations, compliance with which causes the output circuit
of the DC-DC converter to be an SELV circuit according to
IEC/EN 60950 up to a configured output voltage (sum of
Table 4: Safety concept leading to an SELV output circuit
Conditions Front end
DC-DC converter
Result
Nominal
supply
Minimum required grade
of insolation, to be pro-
Maximum DC Minimum required safety
output voltage status of the front end output specified safety status of the of the DC-DC
Measures to achieve the
Safety status
voltage
vided by the AC-DC front from the front circuit
end, including mains
output circuit
converter
output circuit
end 1
supplied battery charger
Mains
Operational (i.e. there is
≤168 V
Primary circuit (The nominal Double or reinforced insula-
SELV circuit
≤250 V AC no need for electrical iso-
lation between the mains
supply circuit and the
DC-DC converter input
circuit)
voltage between any input
pin and earth can be up to
250 V AC or 240 V DC.)
tion, based on 250 V AC and
240 V DC (provided by the
DC-DC converter) and
earthed case 3
Basic
Earth related hazardous
voltage secondary circuit 2
(The nominal voltage
Double or reinforced insula-
tion, based on the maximum
nominal output voltage from
the front end (both provided
between any input pin and
earth can be up to 250 V AC by the DC-DC converter) and
or 240 V DC.)
earthed 2 case
Unearded hazardous voltage Supplementary insulation,
secondary circuit
based on 250 V AC and DC
and double or reinforced
insulation, based on the
maximum nominal output
voltage from the front end
(both providedby the DC-DC
converter) andearthed 3 case
Supplementary
Unearded hazardous voltage Basic insulation, based on
secondary circuit 3
250 V AC and DC (provided
by theDC-DC converter)
1 The front end output voltage should match the specified input voltage range of the DC-DC converter.
2 The maximum rated input voltage of the EQ units according to IEC/EN 60950/UL 1950 is 150 V.
3 Has to be insulated from earth by at least supplementary insulation (by the installer) according to the relevant safety standards, e.g.
IEC/EN 60950, based on the maximum nominal output voltage from the front end. If the converter case is accessible, it has to be
earthed or the front end output circuit has to be insulated from the converter case by at least basic insulation, based on the maximum
nominal mains supply voltage.
Max. 250 V AC or 240 V DC
10052
Fuse
+
~
Mains
AC-DC
front
end
DC-DC
con-
verter
Battery
SELV
Fuse
–
~
Max. 250 V AC or 240 V DC
Earth
connection
Fig. 11
Schematic safety concept
Use fuse, suppressor diode and earth connections as per
table: Safety concept leading to an SELV output circuit.
Use fuse(s) also if required by the application. See: Instal-
lation Instructions.
Edition 4/6.99
8/8
MELCHER
The Power Partners.
BEL [ BEL FUSE INC. ]
