WEG CFW-09 - Load Reactor; RFI Filter

267
CHAPTER 8 - CFW-09 OPTIONS AND ACCESSORIES
The installation of frequencyinvertersrequires certain care in order to prevent
electromagneticinterference(EMI). This interference maydisturbtheoperation
of the inverter itself or other devices, such as, electronic sensors, PLCs,
transducers, radio equipment, etc.
To avoid these problems, follow the installation instructions contained in this
Manual. Never install electromagnetic noise generating circuits such as input
power and motor cables near analog signal or control cables.
Care should also be taken with the radiated interference, by shielding the
cables and circuits that tend to emit electromagnetic waves and cause
interference.
The electromagnetic interference can also be transmitted through the power
supply line. This type of interference is minimized in the most cases by
capacitiveRadio Frequency Filters (commonand differential mode) which are
alreadyinstalled inside the CFW-09. However, when inverters are installed in
residentialareas,the installationof anexternaladditionalfilter mayberequired.
In this case contact WEG to select the most suitable filter type.
8.
9
RFIFIL
TER
The use of a three-phase load reactor, with an approximate 2 % voltage drop
decreasesthedv/dt(voltagerisingrate)ofthePWMpulsescommonlygenerated
at the inverter output of anyAC frequency converter.
This practice reduces the voltagespikes on the motor windings and leakage
currents that may be generated when long distance cables between inverter
and motor are used.
There are many factors that influence the peak level (Vp) and rise time (tr) of
voltage spikes: Cable type, cable length, motor size, switching frequencyand
other variables all affect Vp and dv/dt.
WEG, asspecialists inbothVSDs andmotors are able to provide anintegrated
solution. The load reactor value is calculated in the same way as the line
reactor (refer to item 8.7.1).
If the cables between inverter and motor are longer than 100 m (300 ft), the
cablecapacitance to groundmaycause nuisanceovercurrent(E00) orground
fault (E11) trips. In this case it is also recommended to use a load reactor.
8.8
LOAD REACTOR
U
V
W
PE
Figure 8.20
– Load reactor connection
AC
Input
P
E
R
S
T
Load reactor near
the inverter