Siemens SINAMICS S150 - Page 168

Fundamental Principles and System Description
Engineering Information
SINAMICS Engineering Manual – November 2015
Ó Siemens AG
168/528
The I
2
t value, averaged over a load duty cycle duration T of max. 300 s, must not exceed the 100 % value. The
exeptions are stated in the table.
For the following SINAMICS converters or Motor Modules the permissible I
2
t value is limited to values of less than
100 % with load duty cycles:
Converter
or
Motor Module
Line
volt-
age
Output
rat-
ing
Output
current
Permissible
I
2
t value
with load
duty cycles
Converter
or
Motor Module
Line
volt-
age
Output
rat-
ing
Output
current
Permissible
I
2
t value
with load
duty cycles
SINAMICS G and S 400 V 110 kW 210 A 90 % SINAMICS G 400 V 630 kW 1120 A 72 %
SINAMICS G and S 400 V 315 kW 605 A 72 % SINAMICS G 400 V 710 kW 1380 A 73 %
SINAMICS G and S 400 V 400 kW 745 A 73 % SINAMICS G 400 V 900 kW 1560 A 86 %
SINAMICS G and S 400 V 450 kW 840 A 87 % SINAMICS G + S 500 V 200 kW 330 A 90 %
SINAMICS G and S 400 V 560 kW 985 A 95 % SINAMICS G + S 690 V 315 kW 330 A 90 %
SINAMICS S 4AS3 400 V 800 kW 1330 A 93 % SINAMICS S LC 690 V 1500kW 1560 A 85 %
The I
2
t value is the criterion for losses and temperature rise in the power unit during the load duty cycle and is defined
as follows:
dt
kI
tI
T
valuetI
T
DRated
2
0
2
)(1
ò
÷
÷
ø
ö
ç
ç
è
æ
×
×=
• 100 %
Key to equation:
· I(t) RMS value of the output current of the converter or inverter as a function of time
(In the case of parallel connections of S120 Motor Modules, I(t) is the RMS value of the output
current of a partial inverter resp. one Motor Module.)
· I
Rated
Rated output current of the converter or inverter
(In the case of parallel connections of S120 Motor Modules, I
Rated
is the rated output current of a
partial inverter resp. one Motor Module, not taking into account the derating factor for parallel
operation.)
· k
D
Current derating factor (total derating factor; see above for definition)
· T Load duty cycle duration which must not exceed the 300 s value for the standard load duty cycle
For the practical calculation of the I
2
t value, it is generally helpful to apply a finite number m of phases of constant
current in each case as an approximate substitute to the output current time characteristic required by the application.
This simplifies the calculation as the integration is replaced by a simple summation.
ú
ú
û
ù
ê
ê
ë
é
×
÷
÷
ø
ö
ç
ç
è
æ
×
++×
÷
÷
ø
ö
ç
ç
è
æ
×
+×
÷
÷
ø
ö
ç
ç
è
æ
×
×=
m
DRated
n
DRatedDRated
T
kI
I
T
kI
I
T
kI
I
T
valuetI
2
2
2
2
1
2
1
2
......
1
• 100 %
where TT
m
m
=
å
1
,
i.e. the sum of all phases T
1
to T
m
equals the load duty cycle duration T, where T must be ≤ 300 s. The diagram
below illustrates the correlations.
Approximation of the current characteristic over time using time phases with constant current