Specifications
2.9.4 General Aspects of Harmonics
Emission
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 with 50 Hz as the basic frequency:
Harmonic currents I
1
I
5
I
7
Hz 50 250 350
Table 2.14 Harmonic Currents
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.
175HA034.10
Illustration 2.27 Harmonics Diagram
NOTICE
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.
To ensure low harmonic currents, the frequency converter
is equipped with intermediate circuit coils as standard. This
normally reduces the input current I
RMS
by 40%.
The voltage distortion on the mains supply voltage
depends on the size of the harmonic currents multiplied
by the mains impedance for the frequency in question.
The total voltage distortion THD is calculated on the basis
of the individual voltage harmonics using this formula:
THD
%=
U
2
5
+
U
2
7
+ ... +
U
2
N
(U
N
% of U)
2.9.5 Harmonics Emission Requirements
Options: Definition:
1 IEC/EN 61000-3-2 Class A for 3-phase balanced
equipment (for professional equipment only up to 1
kW total power).
2 IEC/EN 61000-3-12 Equipment 16 A-75 A and profes-
sional equipment as from 1 kW up to 16 A phase
current.
Table 2.15 Equipment Connected to the Public Supply Network
2.9.6 Harmonics Test Results (Emission)
Power sizes up to PK75 in T2 and T4 complies with IEC/EN
61000-3-2 Class A. Power sizes from P1K1 and up to P18K
in T2 and up to P90K in T4 complies with IEC/EN
61000-3-12, Table 4. Power sizes P110 - P450 in T4 also
complies with IEC/EN 61000-3-12 even though not
required because currents are above 75 A.
Individual Harmonic Current I
n
/I
1
(%)
I
5
I
7
I
11
I
13
Actual
(typical)
40 20 10 8
Limit for
R
sce
≥120
40 25 15 10
Harmonic current distortion factor (%)
THD PWHD
Actual
(typical)
46 45
Limit for
R
sce
≥120
48 46
Table 2.16 Harmonics Test Results (Emission)
Provided that the short-circuit power of the supply S
sc
is
greater than or equal to:
S
SC
= 3 ×
R
SCE
×
U
mains
×
I
equ
= 3 × 120 × 400 ×
I
equ
at the interface point between the user’s supply and the
public system (R
sce
).
It is the responsibility of the installer or user of the
equipment to ensure, by consultation with the distribution
network operator if necessary, that the equipment is
connected only to a supply with a short-circuit power S
sc
greater than or equal to that specified in the equation.
Other power sizes can be connected to the public supply
network by consultation with the distribution network
operator.
Compliance with various system level guidelines:
The harmonic current data in the table are given in
accordance with IEC/EN61000-3-12 with reference to the
power drive systems product standard. They may be used
Introduction VLT® HVAC Drive FC 102 Design Guide
42 MG16C102 - Rev. 2013-08-20
2
2