Fundamental Principles and System Description
Engineering Information
SINAMICS Engineering Manual – November 2015
Ó Siemens AG
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1.14.2.5 Partial load efficiency of S120 Motor Modules
The charts below show the partial-load efficiency of air-cooled SINAMICS S120 Motor Modules for constant-torque
drives. The calculations are based on a typical efficiency at full load of 98.5 %. The efficiency is represented in two
different ways. In one chart, the efficiency is shown as a function of the output frequency with the output current as a
parameter, and in the second chart, as a function of the output current with the output frequency as a parameter.
Figure 1a) shows the characteristic curve of the efficiency for constant-torque drives as a function of the output
frequency ratio f
Out
/f
Out-rated
which is proportional to the motor speed ratio n/n
rated
. The parameter for the family of
curves is the output current ratio I
Out
/I
Out-rated
which is proportional to the motor torque ratio M/M
rated
.
MoMo efficiency in %
Figure 1a)
Efficiency of air-cooled SINAMICS S120 Motor Modules in constant-torque drives
as a function of the output frequency ratio in %
Figure 1b) shows the characteristic curve of the efficiency for constant-torque drives as a function of the output
current ratio I
Out
/I
Out-rated
which is proportional to the motor torque ratio M/M
rated
. The parameter for the family of
curves is the output frequency ratio f
Out
/f
Out-rated
which is proportional to the motor speed ratio n/n
rated
.
MoMo efficiency in %
Figure 1b)
Efficiency of air-cooled SINAMICS S120 Motor Modules in constant-torque drives
as a function of the output current ratio in %
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