Depending on the line supply, the main solutions for reducing current harmonics are
1)DC chokes (1) (see below)
2)Line chokes (1) (see page 74)
3)16% and 10% passive fi lters (1) (see page 84)
4)Use of passive fi lters with a DC choke (see pages 80 to 83)
These fi ve solutions can be used on the same installation (1).
It is always easier and less expensive to deal with current harmonics at installation
level as a whole rather than at the level of each individual unit, particularly when
using passive filters.
To illustrate further,
A passive filter is used to reduce current harmonics with total harmonic distortion
factors of less than 16% or 10%.
These performance levels can be improved still further and the harmonic distortion
reduced to less than 10% or 5% if the fi lter is used with a DC choke
Also,The Active Front End allows the Altivar 61 drive to be used in applications requiring a
particularly low harmonic level (THDI < 4%).
The Active Front End consists of a set of three modules installed upstream of the
drive between the line supply and the motor.
It is made up of the following elements:
A line fi lter module (LFM) 1, used at the input, incorporating:
A charging circuit
A line contactor
An EMC fi lter
A line filter choke (LFC) 2, consisting of three single-phase chokes, connected
between the line fi lter module (LFM) and the active infeed converter (AIC)
An active infeed converter (AIC) 3