Engineering
09/01 AWB8230-1412GB
16
Mains contactor
The mains contactor is connected to the mains side input cables
L1, L2, L3 (type dependant). It allows the operational switch on
and off of the DF5 series frequency inverters from the mains supply
as well as shutdown during a fault.
Mains contactors and the assignment with the DF5 series
frequency inverters are listed in Section ”Mains contactors”,
Page 113 in the Appendix.
Current peaks
In the following cases, a relatively high peak current can occur on
the primary side of the frequency inverter (i.e. on the supply
voltage side), which under certain conditions, can destroy the
input rectifier of the frequency inverter:
• Imbalance of the voltage supply greater than 3 %.
• The maximum power output of the supply point must be at least
10 times greater than the maximum frequency inverter rating
(approx 500 kVA).
• If sudden voltage dips in the supply voltage are to be expected,
e.g. :
– a number of frequency inverters are operated on a common
supply voltage.
– a Thyristor system and a frequency inverter or operated on a
common supply voltage.
– power factor correction devices are switched on or off.
In the cases mentioned, a mains choke with approx. 3 % voltage
drop at rated operation should be installed.
Mains choke
The mains choke (also referred to as a commutating choke or line
reactor) is connected to the mains side input cables L1, L2, L3 (type
dependent). It reduces the harmonics and leads to a reduction of
the apparent mains current by up to 30 %.
A mains choke also limits current peaks which occur, caused by
potential dips (e.g. caused by p.f. correction equipment or earth
faults) or switching operations on the mains.
The mains choke increases the lifespan of the DC link capacitors
and consequently the lifespan of the frequency inverter. Its use is
also recommended:
• with a single-phase supply (DF5-322),
• with derating (temperatures above +40 °C, sites of installation
which are more than 1000 m above sea level),
• with parallel operation of multiple frequency inverters on a
single mains supply point,
• with DC link coupling of multiple frequency inverters
(interconnected operation).
Mains chokes and the assignment to DF5 series frequency inver-
ters are listed in Section ”Mains choke”, Page 116 in the
Appendix.
Line filter, Radio interference filter
Line filters are a combination of mains chokes and radio interfe-
rence filters in a single enclosure. They reduce the current harmo-
nics and dampen high frequency radio interference levels.
Radio interference filters only dampen high frequency radio inter-
ference levels.
Caution!
When line filters or radio interference filters are used, the
leakage current to earth increases. Observe this point
when residual-current circuit-breakers are used.
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