Capacitive Currents; Energy Efficiency; Introduction To Energy Efficiency - Danfoss VLT AHF 005 Design Manual

Basic Operating Principle o...

3.1.2 Capacitive Currents

If the specific application requires a higher power factor at
no-load and a reduction of the capacitive current in
standby, use a capacitor disconnect. A contactor
3 3
disconnects the capacitor at loads below 20%.
NOTICE
It is important to note that the capacitors must not be
connected at full load or disconnected at no load.
It is important to consider the capacitive current in the
design of applications where the harmonic filter is supplied
by a generator. The capacitive current can cause
overvoltage of the generator in no-load and low-load
conditions. The overvoltage causes an increase of the
voltage, which then may exceed the allowed voltage for
the filter and the frequency converter. Therefore, always
use a capacitor disconnect in generator applications and
consider the design carefully. For more information about
capacitive currents, refer to chapter 4.2.1.1 Terminals for
Capacitor Disconnect.
Mains
and
mains
cable
Illustration 3.9 Power Drive System (PDS) and Complete Drive Module (CDM)
Auxiliaries:
•
®
VLT
•
®
VLT
•
®
VLT
•
®
VLT
•
®
VLT
16
Complete drive module (CDM)
Infeed
Auxiliaries
section
Motor starter
contactors, soft starters, ...
Motor control system = CDM or starter
Advanced Harmonic Filter AHF 005
Advanced Harmonic Filter AHF 010
Line Reactor MCC 103
Sine-wave Filter MCC 101
dU/dt Filter MCC 102
Danfoss A/S © 10/2016 All rights reserved.
®
VLT Advanced Harmonic Filter AHF 005/AHF 010
Compared to multi-pulse rectifiers, passive harmonic filters
(such as VLT
are more robust against background distortion and supply
imbalance. However, the performance of passive filters is
inferior to the performance of active filters when it comes
to part load performance and power factor. For details
about the performance positioning of the various
harmonic mitigation solutions offered by Danfoss, consult
the relevant harmonic mitigation manuals.

3.2 Energy Efficiency

3.2.1 Introduction to Energy Efficiency

The standard EN 50598 Ecodesign for power drive systems,
motor starters, power electronics, and their driven
applications provides guidelines for assessing the energy
efficiency of frequency converters.
The standard provides a neutral method for determining
efficiency classes and power losses at full load and at part
load. The standard allows combination of any motor with
any frequency converter.
Extended product
Motor system
Drive system (PDS)
Basic
drive
Auxiliaries
module
(BDM)
®
Advanced Harmonic Filter AHF 005/AHF 010)
Driven equipment
Trans-
Motor
mission
Load
machine
MG80C502