Siemens SINAMICS S150 - Page 182

Fundamental Principles and System Description
Engineering Information
SINAMICS Engineering Manual – November 2015
Ó Siemens AG
182/528
Example calculation:
A pump drive is to be supplied by a SINAMICS G150 converter. The drive is supplied by a line voltage of 500 V and
operated at a maximum ambient temperature of 30°C. The speed setting range is relatively small, which means that
the drive utilizes only the output frequency range from 30 Hz to 50 Hz in operation. A SINAMICS G150 with an output
power of 200 KW at 500 V is required to meet the relevant load requirements. This device has a rated output current
of 330 A at the factory-set pulse frequency of 1.25 kHz.
The motor needs to run as quietly as possible which means that a pulse frequency of at least 2.5 kHz is required.
It is necessary to determine whether or by how much the converter needs to be overdimensioned if it is to be
operated with the factory-set overload reaction p0290 = 2 at a pulse frequency of 2.5 kHz under the conditions stated
above.
The current derating factor k
Pulse-2x
to be applied practically is calculated according to the formula
÷
ø
ö
ç
è
æ
-
×+×
÷
ø
ö
ç
è
æ
°
-°
×+×
÷
÷
ø
ö
ç
ç
è
æ
-
×+×=
-
-
-
-
Hz
Hzf
C
TC
V
VV
kk
OutA
Line
LineLine
PulsexPulse
50
10
05.01
40
40
2.015.01
min
max
max
2
.
With the given values
· k
Pulse
= 82 %
(according to the derating table in chapter "Converter Cabinet Units SINAMICS G150“),
· V
Line-max
= 690 V for SINAMICS G150 with the line supply voltage range 500 V – 600 V 3AC,
(according to key to calculation formula on the previous page),
· V
Line
= 500 V,
· T
A
= 30°C
and
· f
Out-min
= 30 Hz
the result is
÷
÷
ø
ö
ç
ç
è
æ
-
×+×
÷
÷
ø
ö
ç
ç
è
æ
°
°-°
×+×
÷
÷
ø
ö
ç
ç
è
æ
-
×+×=
-
Hz
HzHz
C
CC
V
VV
k
xPulse
50
1030
0501
40
3040
201
690
500690
50182
2
...%
(
)
(
)
(
)
021051138182
2
...% ×××=
- xPulse
k
219182
2
.%×=
- xPulse
k
%.9699
2
=
- xPulse
k
Where the current derating factor to be practically applied is k
Pulse-2x
= 99.96 % (or almost 100 %), no current derating
is effectively required in operation at a pulse frequency of 2.5 kHz. This means that the converter can operate
continuously at its rated output current of 330 A, making overdimensioning unnecessary.
Even if once briefly in operation the ambient temperature of 30 C were to be exceeded or the frequency were to drop
below the minimum operational output frequency of 30 Hz, the system would only react to the overload by reducing
the pulse frequency to the factory setting of 1.25 kHz. The drive could therefore continue to function normally. The
only negative, but nevertheless generally acceptable effect, would be an increase in motor noise during the period of
pulse frequency reduction.