
Cassette Style
AC-DC Converters
S Series PFC
Edition 5/5.2000
21/28
Leakage Currents in AC-DC operation
Leakage currents flow due to internal leakage capacitance
and RFI suppression Y-capacitors. The current values are
proportional to the mains voltage and nearly proportional to
the mains frequency and are specified at an input voltage of
254 V (50 Hz) where phase, neutral and protective earth
are correctly connected as required for class I equipment.
V
MI
500
1500
10 k
220 nF
22 nF
10061
Under test conditions the leakage current flows through a
measuring instrument (MI) as described in fig.:
Measuring
instrument for earth leakage current tests, which takes into
account impedance and sensitivity of a person touching
unearthed accessible parts. The current value is calculated
by dividing the measured voltage by 500
. If inputs of K-
units are connected in parallel, their individual leakage cur-
rents are added.
Fig. 28
Measuring instrument (MI) for earth leaking current tests
according to IEC/EN 60950.
Vo+
Vo–
N
P
10062
N
P
MI for
earth
leakage
current
Fig. 29
Test set-up
Table 14: Leakage currents
Characteristic
Class I
Unit
LK 4000, LK 5000
Maximum earth
3.5
mA
leakage current
Specified value at 254 V, 50 Hz
0.82
Safety of operator accessible output circuit
If the output circuit of an AC-DC converter is operator ac-
cessible, it shall be an SELV circuit according to the IEC/EN
60950 related safety standards.
The following table shows a possible installation configura-
tion, compliance with which causes the output circuit of an
K series AC-DC converter to be an SELV circuit according
to IEC/EN 60950 up to a configured output voltage (sum of
nominal voltages if in series or +/– configuration) of 36 V.
However, it is the sole responsibility of the installer to as-
sure the compliance with the relevant and applicable safety
regulations. More information is given in:
Technical Infor-
mation: Safety.
Table 15: Safety concept leading to an SELV output circuit
Conditions
AC-DC converter
Installation
Result
Nominal voltage
Grade of insulation
Measures to achieve the resulting
Safety status of the AC-DC
between input and output
safety status of the output circuit
converter output circuit
provided by the AC-DC converter
Mains
Double or reinforced
Earthed case 1 and installation
SELV circuit
≤250 V AC
according to the applicable standards
1 The earth connection has to be provided by the installer according to the relevant safety standards, e.g. IEC/EN 60950.
AC-DC
con-
verter
Mains
SELV
Earth connection
+
–
~
10021
Fuse
Fig. 30
Schematic safety concept. Use fuses and earth connec-
tion as per: Installation Instructions and table: Safety con-
cept leading to an SELV output circuit
.