A line reactor is needed for high system fault levels, partly to protect the actual converter against excessive harmonic currents, and thus against overload, and partly to limit harmonics to the permitted values. The harmonic currents are limited by the complete inductance comprising the line reactor and mains supply cable inductance. Line reactors can be omitted if the mains supply cable inductance is increased sufficiently, i.e., the value of RSC must be sufficiently small.

RSC = Relative Short-Circuit power: Ratio of short-circuit power Sk line at the line connection point to fundamental apparent output Sconv of the connected converters (in accordance with EN 61800-5-1/VDE 0160).

For SINAMICS G130 drive converter chassis units:

Power

Line reactor not required

Line reactor required

kW

for RSC

for RSC

< 200

≤ 43

> 43

200 ... 500

≤ 33

> 33

> 500

≤ 20

> 20

As, in practice, it is not known on which supply configuration individual converters are to be operated, i. e. which supply shortcircuit power is present at the converter connection point, it is recommended that a line reactor is connected on the line side of the converter.

A line reactor can only be dispensed with when the value for RSC is less than that in the above table. This is the case when, as shown in the following figure, the converter is connected to the line through a transformer with the appropriate rating.

Attention: A line reactor is always needed, however, if a line filter is used.

In this case, the supply short-circuit power Sk1 at the converter connection point is approximately:
Sk1 = Stransf / (Vk transf + Stransf / Sk2 line)

Formula symbol

Meaning

S Trafo

Transformer power rating

S k Trafo

Relative short-circuit power of transformer

S k2 Netz

Short-circuit power of the higher-level voltage level