Siemens SINAMICS S120 - Page 493

SINAMICS S150
Engineering Information
SINAMICS Engineering Manual – November 2015
Ó Siemens AG
493/528
Calculation example 1:
A SINAMICS S150 / 400 V / 400 kW / 745 A converter is to supply a high-speed motor with a rated current of 535 A
and a rated frequency of 200 Hz. The drive has been configured with a pulse frequency of 2.5 kHz for this
application. This is twice the factory-set pulse frequency.
We now need to determine whether option L04 can be selected on this drive.
The increase in pulse frequency to 2.5 kHz means that the converter output current must be reduced. The current
derating factor is 72 %, which means that the output current and output power must be reduced to 72 % of their
nominal values. As a result, the drive now requires only 72 % of nominal input power or nominal input current. With a
nominal input current of 745 A in the standard version, the converter now needs only 536 A. As this value is below
the 605 A stated in the last column of the table above, a converter with option L04 can be used.
Calculation example 2:
A SINAMICS S150 / 400 V / 560 kW / 985 A converter is to supply an 8-pole SIMOTICS TN series N-compact 1LA8
motor (400 V/500 kW/920 A) with an efficiency η = 96.4 % (P
L-Mot
= 18.67 kW) and a power factor of cosφ
Mot
= 0.81.
We now need to determine whether option L04 can be installed on this drive.
The calculation formulae below are taken from section "Active Infeed" in chapter "Fundamental Principles and
System Description" and converted appropriately for the SINAMICS S150 calculation.
Starting with the mechanical power P
mech
of 500 kW on the motor shaft, we obtain the electrical active power P
Line
to
be drawn from the mains supply by adding the power losses of the motor P
L Mot
and the power losses of the
SINAMICS S150 P
L S150
to the mechanical power P
mech
:
P
Line
= P
mech
+ P
L Mot
+ P
L S150
= 500 kW + 18.67 kW + 27.25 kW
= 545.92 kW.
The line current I
Line
required by the SINAMICS S150 with a line-side power factor of cosφ
Line
= 1 (corresponds to the
SINAMICS S150 factory setting) is calculated as follows:
I
Line
= P
Line
/ ( √3 • V
Line
• cosφ
Line
)
= 545.92 kW / ( √3 • 400 V • 1.0 )
= 788 A
Because this value is lower than the 840 A stated in the last column in the table above, a converter with option L04
can be used.