Options And Accessories; Line Reactor; Application Criteria - WEG CFW-10 EASYDRIVE User Manual

CHAPTER 8 - OPTIONS AND ACCESSORIES
8.2

LINE REACTOR

8.2.1 Application Criteria

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Filter
Power
Supply
PE
Ground
Figure 8.21 - Connection of the external RFI filter
Due to the input circuit characteristic, common to the most
inverters available on the market, consisting of a diode rectifier
and a capacitor bank, the input current (drained from the power
supply line) of inverters is a non sinusoidal waveform and
contains harmonics of the fundamental frequency (frequency
of the power supply: 60Hz or 50Hz).
These harmonic currents circulate through the power supply
line and cause harmonic voltage drops which distort the power
supply voltage of the inverter and other loads connected to
this line. These harmonic currents and voltage distortions may
increase the electrical losses in the installation, overheating
the components (cables, transformers, capacitor banks,
motors, etc.), as well as lowering the power factor.
The harmonic input currents depend on the impedance values
that are present in the rectifier input/output circuit.
The installation of a line reactor reduces the harmonic content
of the input current, providing the following advantages:
increasing the input power factor;
reduction of the RMS input current;
reduction of the power supply voltage distortion;
increasing the life of the DC link capacitors.
In a general manner, the CFW-10 series inverters can be
connected directly to the power supply line without line
reactors. But in this case, ensure the following:
To ensure the inverter expected life, a minimum line
impedance that introduces a voltage drop as shown in table
8.1, as a function of the motor load, is recommended. If the
line impedance (transformers + wirings) is lower than these
values, it is recommended to use line reactor(s).
When it is necessary to add a line reactor to the system, it
is recommended to size it considering a 2% to 4% voltage
drop (for nominal output current). This pratice is results in a
compromise between motor voltage drop, power factor
improvement and harmonic current distortion reduction.
Driving Panel
CFW-10
Conduit or
Shielded Cable Motor
PE
Motor
Ground
(frame)