Siemens SIMODRIVE 611 Planning Manual page 122

5 Control Modules
5.5 Induction motor control with analog setpoint interface 6SN1122–0BA1_–0AA_
5
5-122
S
The voltage rate–of–rise (gradient) of the drive converter manifests typical
values of between
5 – 7 kV / µs.
For third–party motors, where the insulation has not been designed to
handle these voltage gradients, a series reactor must be used, independent
of the selected pulse frequency.
S
For the IM operating type, motors with a maximum rated torque of
Pn
Mn =
2π
60 s/min
may be used.
If the motor data are known, a series reactor or the drive converter pulse
frequency can be defined using the following formula, whereby it must be
observed, that when increasing the inverter clock frequency, the module current
must be reduced; or, a module with a higher current rating must be selected:
L + L + L
s1 s2
L Stator leakage inductance of the motor in H
s1
L Rotor leakage inductance of the motor in H
s2
L Inductance of the series reactor in H (=0, if a series reactor
vor
is not used)
V DC link voltage
DC link
(=600 V or 625 V for a controlled infeed,
= rectified line supply voltage for an uncontrolled infeed
e.g. 570 V at 400 V
f Inverter clock frequency of the drive converter in Hz,
T
refer to Section 4.2.2
n Max. motor speed
max
n Speed at the start of field weakening
FS
An approximate value
can be calculated with n
I No–load motor current in A
0
V Rated motor voltage in V
Nmot
n Rated motor speed
N
If the motor data is not known, the converter current should be dimensioned for
4950 Hz pulse frequency for higher current motors, (rated current
results in a converter current reduction factor of approx. 83 %.
Please note that this formula is less accurate than the one specified above. If
possible, please use the more accurate formula. This could possibly mean that
the series reactor costs could be reduced.
S
for motors, which have a higher motor frequency than 500 Hz, the converter
pulse frequency must be increased. The following formula is valid:
w 6 f
f
T max mot
f Inverter clock frequency of the drive converter in Hz,
T
refer to Section 4.2.2
f Max. motor stator frequency
max mot
 650 Nm
n
N
U
n
ZK max
vor 
10 2 fT
n
FS
line supply voltage)
RMS
V n
DC link N
FS [
V
1.6
Nmot
rms
rms
 Siemens AG 2001 All rights reserved
SIMODRIVE 611 Planning Guide (PJU) – 05.01 Edition
05.01
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