Load Reactor; Rfi Filter - WEG CFW-09 User Manual

8.8 LOAD REACTOR

8.9 RFI FILTER

CHAPTER 8 - CFW-09 OPTIONS AND ACCESSORIES
The use of a three-phase load reactor, with an approximate 2 % voltage drop
decreases the dv/dt (voltage rising rate) of the PWM pulses commonly generated
at the inverter output of any AC frequency converter.
This practice reduces the voltage spikes 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 frequency and
other variables all affect Vp and dv/dt.
WEG, as specialists in both VSDs and motors are able to provide an integrated
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
cable capacitance to ground may cause nuisance overcurrent (E00) or ground
fault (E11) trips. In this case it is also recommended to use a load reactor.
PE R S T
AC
Input
Figure 8.20 – Load reactor connection
The installation of frequency inverters requires certain care in order to prevent
electromagnetic interference (EMI). This interference may disturb the operation
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
capacitive Radio Frequency Filters (common and differential mode) which are
already installed inside the CFW-09. However, when inverters are installed in
residential areas, the installation of an external additional filter may be required.
In this case contact WEG to select the most suitable filter type.
U V W PE
Load reactor near
the inverter
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