Danfoss VLT HVAC Drive FC 100 Series, Руководство по конструкции

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2.9.4 General Aspects of Harmonics
Emission
A Adjustable frequency drive takes up a non-sinusoidal
current from line power, 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 50 250 350
Table 2.13
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 prevent an overload of the transformer and
high temperature in the cables.
175HA034.10
Figure 2.31
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.
To ensure low harmonic currents, the Adjustable frequency
drive is equipped with intermediate circuit coils as
standard. This normally reduces the input current I
RMS
by
40%.
The voltage distortion on the line power supply voltage
depends on the size of the harmonic currents multiplied
by the line power 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 25 + U
2
7 + ... + U
2
N
(U
N
% of U)
2.9.5 Harmonics Emission Requirements
Equipment connected to the public supply network
Options: Definition:
1 IEC/EN 61000-3-2 Class A for 3-phase balanced
equipment (for professional equipment only up to
1.5 hp [1 kW] total power).
2 IEC/EN 61000-3-12 Equipment 16 A-75 A and profes-
sional equipment as from 1.5 hp [1 kW] up to 16 A
phase current.
Table 2.14
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 75A.
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 2.15 Harmonics Test Results (Emission)
Provided that the short-circuit power of the supply S
sc
is
greater than or equal to:
SSC = 3 × RSCE × Uline power × Iequ = 3 × 120 × 400 × Iequ
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 specified above.
Other power sizes can be connected to the public supply
network by consultation with the distribution network
operator.
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HVAC Drive Design Guide
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