Descriptions of functions
10.23 Dynamic overload capability of the power unit
SINAMICS DCM DC Converter
592 Operating Instructions, 12/2018, A5E34763375A
Configuring for dynamic overload capability
The following information is available on request from your Siemens office for each
SINAMICS DCM converter unit:
● The
maximum overload duration t
on
when starting up with a cold power unit and specified
constant overload with overload factor X (i.e. load with X times the device rated DC
current * p50077) (see the small table at the top right)
● The
maximum zero current interval t
starting from
(maximum cooling time) until the power unit
reaches the thermal state "cold" (see below the small table at the top right)
●
Limiting characteristic fields for determining overload capability
during thermally
stabilized, intermittent operation with overload (periodic duty cycles)
– Tabular representation: Top left
– Representation as curve with logarithmic y axis: Curve at bottom left
– Representation as curve with linear y axis: Curve at bottom right
The power unit is "cold" when the calculated thyristor temperature rise is less than 5% of its
maximum permissible value. This state can be queried using a binary assignable output.
Note
If you start duty cycles with a cold power unit at least partially within the specified duty cycle
limits, then the thermally stabilized state is reached without I
2
t monitoring responding.
2
t monitoring is parameterized for a shutdown function (p50075 = 2), you should not come
too close to the limiting characteristic when configuring periodic duty cycles that are longer
than, slightly shorter than, or equal to 300
s.
r cases, however - and particularly when parameterizing I
2
t monitoring for a
reduction in the armature current setpoint (p50075 = 1)
- you can utilize the maximum
overload capability determined by the limiting characteristic to its full extent.
Structure of limiting characteristic fields for intermittent operation with overload:
Each of the limiting characteristic fields relates to a duty cycle during intermittent overload
operation with an
(time period) of 300 s.
A duty cycle of this type consists of two time intervals:
● The
(actual armature current value ≤ p50077 * rated unit DC current)
● and the
(actual armature current value ≥ p50077 * rated unit DC
current).
Each limiting characteristic represents the maximum permissible
in
excess of the
maximum base-load current Ig
for a specific
and a specific
device.
For the
of the duty cycle, the
determined using the
overload factor must not be exceeded.
If no limiting characteristic has been specified for the required overload factor, then it will be
subject to the limiting characteristic for the next largest overload factor.
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