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Harmonic currents
The line-side converter takes a current from the power supply, whereby the amplitude of this
current is dependent on the load state of the machine and the curve of this current over time
is approximately block-shaped. This current can be broken down into a fundamental-
frequency current and harmonic currents with 5, 7, 11, 13 etc. times the frequency of the
fundamental frequency.
The percentage magnitude of the harmonic currents referred to the fundamental-frequency
current is virtually independent of the load and is specified in the device-specific technical
data.
In the case of 12-pulse input circuits, the 5th and 7th harmonics are almost completely
eliminated, and for 24-pulse circuits, the 11th and 13th harmonics are also eliminated.
As the line-side and machine-side converters cannot be ideally decoupled using the DC link,
there are also harmonic-current components in the line-side current, where the frequency of
the harmonic currents depends on the converter output frequency (interharmonic harmonic
currents).
NOTICE
Harmonic currents
Due to these harmonic currents, the devices are not suitable for direct connection to public
grids.
Observe the requirements of the electric utility company (e.g. VDEW guidelines).
NOTICE
Harmonic currents
Reactive power compensation systems reduce harmonics to a limited extent.
Filter circuit systems are optionally available. These filter out most of the harmonic currents
and also help to compensate for displacement reactive power.
Take the power system data into account in the design of filter circuit systems.
High-frequency emitted interference
High-frequency emitted interference generally cannot be defined for the converter as
component.
The converters are suitable for use in industrial environments. If your equipment
configuration is EMC-compliant, you will not be working with additional filtering measures to
ensure that no other electrical equipment is affected by interference. This means that the
important protection objectives of the EMC Directive have been fulfilled.
In accordance with EN 61800-3, devices with a rated current greater than 400 A and devices
that are connected to an IT supply system, are assigned Category C4. For C4, no limit values
are specified for the interference emission. In cases such as these, draw-up an EMC plan.
The following applies to the other devices: The devices are assigned Category C3.
Installation and Operating Instructions for LOHER DYNAVERT I Series 7
Operating Instructions, 10/2022, 4BS0745-002
Preparations for use
4.3 EMC
51
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