Siemens SIMOVERT MASTERDRIVES Manual page 877

Engineering Information
11-20
In order to determine the arithmetic mean value of the DC link current,
the mean values of the individual inverters are added together. For one
inverter, the calculation is as follows:
P
=
I
Link Inv mean
η
Mot
P
Mot A
∑
=
P
Mot mean
+
P P
Mot A Mot E
2
T Cycle time
Only positive motor outputs are evaluated. When calculating the mean
motor output, one must make sure that the initial value and the final
value of the motor speed do not have different signs. An interpolation
point must therefore exist for every zero passage.
n
Mot
∆
t
i
P
Mot
P
Mot A
∆
t
i
Fig. 11-11 Example of motor speed and motor output in a time segment
Adding the mean values for the individual inverters gives the mean
value for the rectifiers as follows:
∑
=
I I
Link Re ct mean Link Inv mean
Mot mean
⋅ η ⋅
U
Inv Link
+
P
Mot E
⋅ ∆
t
i
2
T
Mean motor output in time segment ∆ t
(A: initial value, E: final value)
P
Mot E
Motorized (positive)
Regenerative (negative)
6SE7087-6QX70 (Version AE)
Compendium Motion Control
06.2005
[W]
i
t
t
∆
t i
Siemens AG
SIMOVERT MASTERDRIVES