Siemens SINAMICS S120 Function Manual page 294

Vector control
5.23 Asynchronous pulse frequency
Application example
Situation:
A large (> 250 kW) Motor Module in the chassis format and a small (< 250 kW) Motor
Module, e.g. in the booksize format, are to be connected to one DRIVE-CLiQ line.
The factory setting of the current controller cycle of the small Motor Module is 250 µs,
corresponding to a pulse frequency of 2 kHz. The factory setting of the current controller
cycle of the large Motor Module is 400 µs, corresponding to a pulse frequency of 1.25 kHz.
Problem:
For standard applications, the current controller cycle of the large Motor Module is increased
up to 500 µs, an integer multiple of the current controller cycle of 250 µs. As a consequence,
the pulse frequency of the large Motor Module is 1 kHz. As a consequence, the Motor
Module in the chassis format is no longer optimally utilized.
Solution:
Activate separation of pulse frequency and current controller cycle for the large Motor
Module.
The Motor Module Booksize is still operated in synchronism with the current control cycle of
250 µs at a pulse frequency of 2 kHz.
For Motor Modules in the chassis format, set the pulse frequency to asynchronous operation
with p1800.10 = 12. Then increase the pulse frequency of the Motor Module Chassis to 1.25
KHz using p1800, while the current controller cycle remains at 500 µs. The Motor Module
chassis is better utilized as a result of the increased pulse frequency.
Boundary conditions for asynchronous pulse frequency
● A higher system utilization as a result of the activated gating unit for the asynchronous
pulse frequency (p1810.12 = 1) and the required current actual value correction (p1840 =
1) causes
– Halving of the maximum number of axes that can be used
– A reduction in the current controller dynamic response
● The maximum pulse frequency that can be set is limited to double the frequency of the
current controller cycle.
● The pulse procedure, where the pulse frequency can be freely adjusted, is not suitable for
a permanent-magnet synchronous motor without an encoder.
● If output reactors or filters are connected to a Motor Module in the chassis format, when
dimensioning the reactors, the maximum pulse frequency must be taken into account and
for sine-wave filters, the minimum pulse frequency.
● The motor data identification must be performed with current controller cycles of 250 µs
or 500 µs with 2 kHz.
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Function Manual, 11/2017, 6SL3097-4AB00-0BP5
Drive functions