Siemens SINAMICS DCM Manual page 553

Descriptions of functions
10.22 Dynamic overload capability of the power unit
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 overload current / (p50077×rated unit DC current)
Actual maximum base-load current Ig:
Ig = p50077 × maximum base-load current acc. to characteristic
as a % of the rated unit DC current
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:
Other-
wise:
Example 1:
Known:
30 A/4Q unit; cycle duration 113.2 s; overload factor = 1.45; overload duration = 20 s
To be found:
Minimum base load duration and maximum base-load current
Solution:
Limiting characteristic for 30 A/4Q unit, overload factor 1.5
Overload duration
Base load duration
Maximum base-load current = approx. 45% of I
554
= 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 > overload duration
300
Required duty cycle cannot be configured
Read the maximum base-load current for overload duration
characteristic
= (300 s./113.2 s.)×20 s. = 53 s.
300
= 300 s. – 53 s. = 247 s. →
300
ac.maher.co.ir
for base-load current = 0
300
300
= 13.5 A
N
SINAMICS DCM DC Converter
Operating Instructions, 02.2015, A5E34763375/RS-AA/001
from the limiting