Analysing Mains Interference; Options For Reducing Mains Interference; Radio Frequency Interference; Classification Of The Operating Site - Danfoss VLT AQUA Drive FC 202 Design Manual

System Integration
Higher losses
•
Harmonics reduce the active power, apparent
power, and reactive power.
•
Distort electrical loads resulting in audible
interference in other devices, or, in worst case,
3 3
even destruction.
•
Shorten the lifetime of devices as a result of
heating.
NOTICE
Excessive harmonic content puts a load on power factor
correction equipment and may even cause its
destruction. For this reason, provide chokes for power
factor correction equipment when excessive harmonic
content is present.

3.3.3 Analysing Mains Interference

To avoid impairment of mains power quality, a variety of
methods are available for analysing systems or devices that
generate harmonic currents. Mains analysis programs, such
as harmonic calculation software (HCS), analyse system
designs for harmonics. Specific countermeasures can be
tested beforehand and ensure subsequent system compati-
bility.
For analysing mains systems, go tohttp://www.danfoss-
hcs.com/Default.asp?LEVEL=START for software download.
NOTICE
Danfoss has a very high level of EMC expertise and
provides EMC analyses with detailed evaluation or mains
calculations to customers in addition to training courses,
seminars, and workshops.
3.3.4 Options for Reducing Mains
Interference
Generally speaking, mains interference from converters is
reduced by limiting the amplitude of pulsed currents. This
improves the power factor λ (lambda).
Several methods are recommended to avoid mains
harmonics:
•
Input chokes or DC-link chokes in the frequency
converters.
•
Passive filters.
•
Active filters.
•
Slim DC links.
•
Active front end and low harmonic drives.
•
Rectifiers with 12, 18 or 24 pulses per cycle.
52
Design Guide

3.3.5 Radio Frequency Interference

Frequency converters generate radio frequency
interference (RFI) due to their variable-width current
pulses. Converters and motor cables radiate these
components and conduct them into the mains system.
RFI filters are used to reduce this interference on the
mains. They provide noise immunity to protect devices
against high-frequency conducted interference. They also
reduce interference emitted to the mains cable or radiation
from the mains cable. The filters are intended to limit
interference to a specified level. Built-in filters are often
standard equipment rated for specific immunity.
NOTICE
All VLT
with integrated mains interference chokes as standard.

3.3.6 Classification of the Operating Site

Knowing the requirements for the environment the
frequency converter is intended to operate in is the most
important factor regarding EMC compliance.
3.3.6.1 Environment 1/Class B: Residential
Operating sites connected to the public low-voltage power
grid, including light industrial areas, are classified as
Environment 1/Class B. They do not have their own high-
voltage or medium-voltage distribution transformers for a
separate mains system. The environment classifications
apply both inside and outside buildings. Some general
examples are business areas, residential buildings,
restaurants, car parks, and entertainment facilities.
3.3.6.2 Environment 2/Class A: Industrial
Industrial environments are not connected to the public
power grid. Instead, they have their own high-voltage or
medium-voltage distribution transformers. The
environment classifications apply both inside and outside
the buildings.
They are defined as industrial and are characterised by
specific electromagnetic conditions:
•
•
•
Danfoss A/S © 09/2014 All rights reserved.
®
AQUA Drive frequency converters are equipped
The presence of scientific, medical or industrial
devices.
Switching of large inductive and capacitive loads.
The occurrence of strong magnetic fields (for
example, due to high currents).
MG20N602