Fundamental Principles and System Description
Engineering Information
SINAMICS Engineering Manual – November 2015
Ó Siemens AG
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speed encoder as independent single drives for applications with simple control requirements. At a low output
frequency and low depth of modulation (output voltage < 92 % of input voltage), these converters utilize space vector
modulation SVM and switch over to pulse-edge modulation PEM automatically if the depth of modulation required at
higher output frequencies is so high that it can no longer be provided by space vector modulation SVM (output
voltage > 92 % of input voltage). The minor irregularities in the torque characteristic caused by transient phenomena
during transition between different modulation systems are virtually irrelevant for applications with simple control
requirements of the kind mentioned above.
VLine
fMot
fMot-rated
0
0,5 1,0
VMot
0
60%
40%
20%
90%
100%
SVM
PEM1 PEM2
Constant-flux range Field-weakening range
V ~ f
V = const
SVM
SVM + PEM
V = const
V ~ f
Maximum attainable motor voltage with space vector modulation SVM and pulse-edge modulation PEM
For SINAMICS S120 Motor Modules and SINAMICS S150 converters, the modulator mode (parameter p1802) is
automatically preset to the value 4 (space vector modulation without overmodulation) in vector control mode because
the default technological application is "Standard drive vector" (parameter p0500 = 0). In this case, these units utilize
only space vector modulation SVM because, and this applies particularly to SINAMICS S120 Motor Modules, they
are predominantly used in coordinated multi-motor drive systems with sophisticated control technology which
demand very high control quality (e.g. strip finishing lines, paper-making machines and foil-drawing machines). These
types of application can rarely tolerate the minor irregularities in the torque characteristic caused by transient
phenomena during transition between different modulation systems. If SINAMICS S120 Motor Modules and
SINAMICS S150 converters are required to operate with pulse-edge modulation PEM, the modulator mode
(parameter p1802) must be set to 9 (pulse-edge modulation) during commissioning.
Basically, it would also be possible to achieve depths of modulation or output voltages in excess of 92 % through
overmodulation of the space vector modulation SVM (by setting parameter p1802 to values 0, 1, 2, 5, 6). While it is
possible by this method to prevent the slight irregularities in the torque characteristic on transition between
modulation systems, it also causes the harmonics spectrum in the motor current to increase, resulting in higher
torque ripples and higher motor losses. With a very high level of overmodulation (maximum modulation depth setting
in parameter p1803 > approx. 103 %), the control quality decreases significantly. Pulse-edge modulation PEM with its
optimized pulse patterns therefore offers obvious advantages in this case, as it enables a high depth of modulation
(high output voltage) combined with good drive behavior (in terms of torque accuracy and motor losses) to be
achieved.
*
)
Exceptions regarding the use of pulse-edge modulation:
Converters with output-side sine-wave filter. Pulse-edge modulation cannot be selected under these conditions.
If either a Basic or Smart Infeed is used to supply the inverter, the following formulae apply for the DC link voltage at
full load: V
DCLink
≈ 1.32 • V
Line
resp. V
DCLink
= 1.30 • V
Line
. In this case, the maximum output voltage is limited to 85 %
of the line input voltage for units with a supply voltage of 380 V to 480 V 3AC and to 83 % for units with a supply
voltage of 500 V to 600 V 3AC.
If an Active Infeed is used to supply the inverter, the following formula applies to the DC link voltage because the
Active Infeed utilizes a step-up converter function: V
DCLink
> 1.42 • V
Line
(factory setting: V
DCLink
= 1.5 • V
Line
). This
means that the maximum output voltage even without pulse-edge modulation can correspond to 100 % of the line
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