![background image](http://html1.mh-extra.com/html/danfoss/vlt/vlt_design-manual_3509564030.webp)
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 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 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
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 2.13
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.
Provided that the short-circuit power of the supply S
sc
is
greater than or equal to:
SSC = 3 × RSCE
×
Umains × 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.
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
as the basis for calculation of the harmonic currents'
influence on the power supply system and for the
documentation of compliance with relevant regional
guidelines: IEEE 519 -1992; G5/4.
2.9.7 Immunity Requirements
The immunity requirements for frequency converters
depend on the environment where they are installed. The
requirements for the industrial environment are higher
than the requirements for the home and office
environment. All Danfoss frequency converters comply
with the requirements for the industrial environment and
consequently comply also with the lower requirements for
home and office environment with a large safety margin.
In order to document immunity against electrical
interference from electrical phenomena, the following
immunity tests have been made on a system consisting of
a frequency converter (with options if relevant), a screened
control cable and a control box with potentiometer, motor
cable and motor.
The tests were performed in accordance with the following
basic standards:
•
EN 61000-4-2 (IEC 61000-4-2): Electrostatic
discharges (ESD): Simulation of electrostatic
discharges from human beings.
•
EN 61000-4-3 (IEC 61000-4-3): Incoming electro-
magnetic field radiation, amplitude modulated
simulation of the effects of radar and radio
communication equipment as well as mobile
communications equipment.
•
EN 61000-4-4 (IEC 61000-4-4): Burst transients:
Simulation of interference brought about by
switching a contactor, relay or similar devices.
•
EN 61000-4-5 (IEC 61000-4-5): Surge transients:
Simulation of transients brought about e.g. by
lightning that strikes near installations.
•
EN 61000-4-6 (IEC 61000-4-6): RF Common mode:
Simulation of the effect from radio-transmission
equipment joined by connection cables.
See
Introduction
VLT
®
Refrigeration Drive Design Guide
MG16G102 - VLT
®
is a registered Danfoss trademark
29
2
2