Fundamentals Of Line-Commuted Converters; Requirements Of The Supply System; Three-Phase System - Siemens SINAMICS DCM 6RA80 Faq

Fundamentals of line-commuted converters

Requirements of the supply system

The line voltage must be sinusoidal, supply of a line-commuted converter via a DC voltage
source is not possible.
U = Û * sin ( *t), Û: Peak voltage of the supply network
Netz
= 2 * * f: Angular frequency, f: Frequency of the line voltage, 1 / f = T: Period
At 50 Hz line, T = 1 / 50 = 0.02 = 20 ms
At 60 Hz line, T = 1 / 60 = 0.0167 = 16.7 ms
The rms value U of the line voltage is measured with the voltmeter.
RMS
Û = U * root(2) = U
RMS
Line voltage at 50 Hz and V
Netzspannung bei 50 Hz und U
600,00
L
400,00
i
n
e
200,00
V
0,00
o
0
l
-200,00
t
a
One line period:
g
-400,00
360 degrees electrical
e
= 2
-600,00

Three-phase system:

A three-phase system comprises three individual phases (U, V, W) of the same voltage and
a phase shift by 120 degrees.
Phase voltage, e.g. U
single voltage measured against the neutral point of the transformer.
Phase-to-phase voltage, e.g. U
The phase-to-phase voltage is the phase voltage times the root (3).
e.g.: U = 230 V
U
The phase-to-phase voltage is always specified on the technical data and on the rating plate
of the SINAMICS DCM.
Neutral point
transformer
* 1.41421, at 400 V
RMS
5 10
Time in [ms]
: The voltage of an individual phase is the line-to-neutral voltage,
U
: This is the voltage measured between two phases.
UV
U = U * root (3) = 230 * 1.732 = 400 V
UV U
U
U
UV
V
W
U
W
Transformer secondary winding
= 400 *1.41421 = 566 V
RMS
= 400 V
= 400 V
RMS
eff
15 20
Zeit in [ms]
Phases U, V, W with the line-to-
neutral voltage and the
line-to-line voltage
31
25 30