Basic standard Burst
IEC 61000-4-4
Surge
IEC 61000-4-5
ESD
IEC
61000-4-2
Radiated electromagnetic
field
IEC 61000-4-3
RF common
mode voltage
IEC 61000-4-6
Acceptance criterion B B B A A
Voltage range: 200-240 V, 380-500 V, 525-600 V, 525-690 V
Line
4 kV CM
2 kV/2 Ω DM
4 kV/12 Ω CM
— —
10 V
RMS
Motor
4 kV CM
4 kV/2 Ω
1)
— —
10 V
RMS
Brake 4 kV CM
4 kV/2 Ω
1)
— —
10 V
RMS
Load sharing 4 kV CM
4 kV/2 Ω
1)
— —
10 V
RMS
Control wires
2 kV CM
2 kV/2 Ω
1)
— —
10 V
RMS
Standard bus 2 kV CM
2 kV/2 Ω
1)
— —
10 V
RMS
Relay wires 2 kV CM
2 kV/2 Ω
1)
— —
10 V
RMS
Application and Fieldbus
options
2 kV CM
2 kV/2 Ω
1)
— —
10 V
RMS
LCP cable
2 kV CM
2 kV/2 Ω
1)
— —
10 V
RMS
External 24 V DC
2 V CM
0.5 kV/2 Ω DM
1 kV/12 Ω CM
— —
10 V
RMS
Enclosure
— —
8 kV AD
6 kV CD
10V/m —
Table 3.14 EMC Immunity Form
1) Injection on cable shield
AD: Air Discharge
CD: Contact Discharge
CM: Common mode
DM: Differential mode
3.6 Mains Supply Interference/Harmonics
A frequency converter takes up a non-sinusoidal current
from mains, which increases the input current I
RMS
. A non-
sinusoidal current is transformed by means of a Fourier
analysis and split up into sine-wave currents with different
frequencies, i.e. different harmonic currents I
N
with 50 Hz
as the basic frequency.
Harmonic currents I
1
I
5
I
7
Hz 50 Hz 250 Hz 350 Hz
Table 3.15 Transformed Non-sinusoidal Current
The harmonics do not affect the power consumption
directly but increase the heat losses in the installation
(transformer, cables). Consequently, in plants with a high
percentage of rectifier load, maintain harmonic currents at
a low level to avoid overload of the transformer and high
temperature in the cables.
Illustration 3.24 Intermediate Circuit Coils
NOTE
Some of the harmonic currents might disturb communi-
cation equipment connected to the same transformer or
cause resonance in connection with power-factor
correction batteries.
Input current
I
RMS
1.0
I
1
0.9
I
5
0.4
I
7
0.2
I
11-49
< 0.1
Table 3.16 Harmonic currents compared to the RMS input current
To ensure low harmonic currents, the frequency converter
is equipped with intermediate circuit coils as standard. DC-
coils reduce the total harmonic distortion (THD) to 40%.
3.6.1
The Effect of Harmonics in a Power
Distribution System
In Illustration 3.25 a transformer is connected on the
primary side to a point of common coupling PCC1, on the
medium voltage supply. The transformer has an
impedance Z
xfr
and feeds a number of loads. The point of
Introduction
VLT
®
AutomationDrive FC 300 Design Guide, 0.25-75 kW
MG33BE02 - VLT
®
is a registered Danfoss trademark 41
3
3
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