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Table 14: Electric strength test voltages
Characteristic
Input - Output
24/48 IMS 6
Unit
Electric strength
test voltage 1 s
1.2
kV
rms
1.5
kV DC
Coupling
capacitance
1.2
nF
Insulation resist.
at 500 V DC
>100
M
Partial discharge
extinction voltage
Consult factory
kV
AC-DC
front
end
DC-DC
con-
verter
Mains
~
Fuse
Battery
Earth
connection
Suppressor
diode
SELV
Earth
connection
+
–
~
10004
Fig. 23
Schematic safety concept. Use fuse, suppressor diode
and earth connection as per table:
Safety concept leading
to an SELV output circuit
.
Table 15: Insulation concept leading to an SELV output circuit
Conditions Front end
DC-DC converter
Result
Supply
voltage
Minimum required grade
of isolation, to be provided DC output
by the AC-DC front end,
including mains supplied
battery charger
Maximum
Minimum required safety
status of the front end
output circuit
Measures to achieve the
specified safety status of the
output circuit
Safety status of
the DC-DC
converter output
circuit
voltage
from the
front end
1
Mains
250 V AC
Basic
60 V
Earthed SELV circuit
2
Operational insulation, pro-
vided by the DC-DC converter
SELV circuit
ELV circuit
Input fuse
3
output suppressor
diodes
4
, and earthed
output circuit
2
Earthed SELV
circuit
>60 V
Hazardous voltage
secondary circuit
Double or reinforced
60 V
SELV circuit
Operational insulation, pro-
vided by the DC-DC converter
SELV circuit
1
The front end output voltage should match the specified input voltage range of the DC-DC converter.
2
The earth connection has to be provided by the installer according to the relevant safety standard, e.g. IEC/EN 60950.
3
The installer shall provide an approved fuse (type with the lowest rating suitable for the application) in a non-earthed input line directly
at the input of the DC-DC converter (see fig.: Schematic safety concept). For UL’s purpose, the fuse needs to be UL-listed. See also:
Input Fuse
4
Each suppressor diode should be dimensioned in such a way, that in the case of an insulation fault the diode is able to limit the output
voltage to SELV (<60 V) until the input fuse blows (see fig.: Schematic safety concept).
5
Has to be insulated from earth by double or reinforced insulation according to the relevant safety standard, based on the maximum
output voltage from the front end.
Cleaning Agents
In order to avoid possible damage, any penetration of
cleaning fluids has to be prevented, since the power sup-
plies are not hermetically sealed.
Protection Degree
The protection degree of the DC-DC converters is IP 30.
Isolation
The electric strength test is performed as factory test in ac-
cordance with IEC/EN 60950 and UL 1950 and should not
be repeated in the field. Melcher will not honour any guar-
antee claims resulting from electric strength field tests.
Edition 1 06.00
Industrial Environment DC/DC Converters < 40W IMS6 Series