User`s guide

167
CHAPTER 8 - CFW-08 OPTIONS AND ACCESSORIES
Power
Supply
Ground
Filter
CFW-08
Driving Panel
Conduit or
Shielded
Cable
Motor
Motor Ground
(frame)
PE
PE
Figure 8.28
- Connection of the external RFI filter - Category C1
8.21
LINE REACTOR
Due to the input circuit characteristic, common to the most
inverters available on themarket, consisting of a dioderectifier
and a capacitorbank,the input current(drainedfrom the power
supply line) of inverters is a non sinusoidal waveform and
contains harmonics of the fundamental frequency(frequency
of the power supply - 60 Hz or 50 Hz).
These harmonic currents circulate through the power supply
lineandcause harmonic voltage dropswhich distortthe power
supply voltage of the inverter and other loads connected to
this line.These harmoniccurrentsand 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 input current harmonics are determined by the value of
the impedances present at the input circuit.
Theinstallation of a line reactor reduces theharmonic 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.
Install it as close as
possible to the inverter
8.21.1
Application Criteria
In a general manner, the CFW-08 series inverters can be
connecteddirectlyto thepowersupplyline without linereactors.
But in this case, ensure the following:
To ensure the inverter expected life, a minimum line
impedance that introduces a voltagedrop as shownin table
8.3, as a function of the motor load,is recommended. If the
line impedance (transformers and wirings) is lower than
these values, it is recommended to use line reactor(s).
When it is necessaryto 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 results in a
compromise between motor voltage drop, power factor
improvement and harmonic current distortion reduction.
This practice results in a compromise between motor
voltage drop, power factor improvement and harmonic
currentdistortion reduction.