Siemens SINAMICS Series Operating Instructions Manual page 595

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).
For cycle durations > 300 s, only the same overload duration as with a cycle duration of
300 s is permitted; the base-load duration is correspondingly longer.
The limiting characteristic fields apply for p50077 = 1.00. When setting p50077 to ≤ 1.00,
i.e. reducing the thermal load, the currents that are actually flowing must be evaluated with
the factor 1/p50077:
Overload factor for characteristic X:
X =
Actual maximum base-load current Ig:
Ig = p50077 × maximum base-load current acc. to characteristic
Basic tasks for configuring periodic operation with overload
Designations:
Base load duration
Overload duration
Basic task 1
Known:
Device types, cycle duration, overload factor, overload duration
To be found:
Minimum base load duration and maximum base-load current
To reach solution:
Select the limiting characteristic for the known unit and overload factor
Cycle duration <300 s:
Overload duration
Cycle duration ≥300 s:
Overload duration
If:
Then:
Otherwise: Read the maximum base-load current for overload duration
SINAMICS DCM DC Converter
Operating Instructions, 12/2018, A5E34763375A
Actual overload current / (p50077×rated unit DC current)
as a % of the rated unit DC current
= Minimum base load duration for 300 s cycle duration
300
= Maximum overload duration for 300 s cycle duration
300
= (300 s/cycle duration) × overload duration
300
= overload duration
300
Overload duration
Required duty cycle cannot be configured
characteristic
10.23 Dynamic overload capability of the power unit
> overload duration
300 300
Descriptions of functions
for base-load current = 0
from the limiting
300
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