5Xxe With Or Without Integrated Mains Filter; Operation Of An Sk 5Xxe - nord NORDAC PRO SK 500E Series User Manual

SK 54xE – Users Manual for Frequency Inverters
1.2 SK 5xxE with or without integrated mains filter
NORD supplies the inverter series (SK 500E ... SK 545E) in two different versions, which differ in that
in contrast to the type Typ SK 5xxE-...-A, the inverter type SK 5xxE-...-O is equipped with an EMC
mains filter at the factory.
The EMC mains filter which is integrated into the SK 5xx-...-A types is fitted to the mains input and is
used to fulfil the requirements of the EMC Directive 2004/108/EC (issue of the CE mark).
1.2.1 Operation of an SK 5xxE-...-A frequency inverter
If an input choke is connected upstream of the frequency inverter, a resonance circuit results from
the mains impedance, the input choke and the X2-capacitors of the internal EMC filter.
This resonance circuit is excited by harmonics in the mains voltage as well as by switching actions in
the mains, however, due to the typically high damping level, this does not result in permanent
oscillations of increasing amplitude.
If devices are connected to the supply network in parallel, e.g. compensation systems, wind energy
plant, etc., which permanently or temporarily generate harmonics in the frequency range stated above,
stronger excitation of the resonance circuit may occur, as a result of which there is an increase of the
harmonic voltage, which is superimposed on the mains voltage.
Result:
– Overload up to total failure of the X2 capacitors
– Impermissible charging of the link circuit with error messages, up to exceeding of the
permissible link circuit voltage with total failure.
In both cases, permanent damage to the frequency inverter is possible
Information
For inverters of Size 8 to 11 link circuit chokes are available, which are used in place of the input choke. In the
resonance circuit described above, there is no inductance due to the input choke, so that the resulting resonant
frequency is in a non-critical high frequency range.
1.2.2 Operation of an SK 5xxE-...-O frequency inverter
The SK 5xxE-xxx-340-O is not equipped with an EMC mains filter and only has reduced X2-capacitors
for the basic reduction of interference at the mains input. In "O" frequency inverters, the mains-side
filtration is reduced to an absolute minimum, so that with the use of an input / mains choke, resonant
frequencies in excess of the maximum permissible pulse frequency (16 kHz) of the frequency inverter
result.
In this considerably higher frequency range, adequate damping can be assumed, as a result of which
the resonance phenomena with the consequences described above is not to be expected.
A suitable bottom-mounted filter is available in order to comply with the EMC requirements for these
inverters (please see chapter 8.3 "Electromagnetic compatibility (EMC)"), (please see chapter 2.8
"Line filter").
12
Devices above 45 kW (Size 8 – 11)
BU 0505 EN-3021