Siemens SINAMICS DCM Manual page 552

10.22.2 Configuring for dynamic overload capability
The DVD documentation for the SINAMICS DCM provides the following information for each
converter unit:
● The maximum overload duration t
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
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
Note:
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
If I t monitoring is parameterized for a shutdown function (p50075 = 2), you should not come
2
too close to the limiting characteristic when configuring periodic duty cycles that are longer
than, slightly shorter than, or equal to 300 s.
In all other cases, however - and particularly when parameterizing I2t 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 overall duration (time period) of 300 s.
A duty cycle of this type consists of two time intervals:
The base load duration (actual armature current value ≤ p50077 * rated unit DC current) and
The overload duration (actual armature current value ≥ p50077 * rated unit DC current)
Each limiting characteristic represents the maximum permissible overload duration Tp in
excess of the maximum base-load current Ig for a specific overload factor X and a specific
device.
For the remaining duration of the duty cycle, the base-load current 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.
The limiting characteristic fields apply for a duty cycle duration of 300 s.
For cycle durations < 300 s, the overload duration must be reduced proportionally (cycle
duration/300 s).
SINAMICS DCM DC Converter
Operating Instructions, 02.2015, A5E34763375/RS-AA/001
10.22 Dynamic overload capability of the power unit
when starting up with a cold power unit and specified
on
(maximum cooling time) until the power unit
starting from
ac.maher.co.ir
Descriptions of functions
t monitoring responding.
2
553