Industrial Environment
Cleaning Agents
DC/DC Converters < 40W
Table 14: Electric strength test voltages
Characteristic
Electric strength
test voltage 1 s
Coupling
capacitance
Insulation resist.
at 500 V DC
Partial discharge
extinction voltage
Input - Output
24/48 IMS 6
1.2
1.5
1.2
>100
Consult factory
IMS6 Series
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.
Unit
kV
rms
kV DC
nF
M
kV
Table 15: Insulation concept leading to an SELV output circuit
Conditions Front end
Supply
voltage
Minimum required grade
of isolation, to be provided
by the AC-DC front end,
including mains supplied
battery charger
Maximum
DC output
voltage
from the
front end
1
60 V
Minimum required safety
status of the front end
output circuit
DC-DC converter
Measures to achieve the
specified safety status of the
output circuit
Result
Safety status of
the DC-DC
converter output
circuit
SELV circuit
Earthed SELV
circuit
Mains
Basic
250 V AC
Earthed SELV circuit
2
ELV circuit
Operational insulation, pro-
vided by the DC-DC converter
Input fuse
3
output suppressor
diodes
4
, and earthed
output circuit
2
Operational insulation, pro-
vided by the DC-DC converter
>60 V
Double or reinforced
60 V
Hazardous voltage
secondary circuit
SELV circuit
SELV circuit
1
2
3
4
5
The front end output voltage should match the specified input voltage range of the DC-DC converter.
The earth connection has to be provided by the installer according to the relevant safety standard, e.g. IEC/EN 60950.
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.
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).
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.
~
Mains
Fuse
AC-DC
front
end
Battery
DC-DC
con-
verter
10004
Suppressor
diode
SELV
+
~
–
Earth
connection
Earth
connection
Fig. 23
Schematic safety concept. Use fuse, suppressor diode
and earth connection as per table:
Safety concept leading
to an SELV output circuit.
Edition 1 06.00
POWER-ONE [ POWER-ONE ]
