Descriptions of functions
10.23 Dynamic overload capability of the power unit
SINAMICS DCM DC Converter
594
Operating Instructions, 12/2018, A5E34763375A
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
300
= (300 s/113.2 s) × 20 s = 53 s
base-load duration
300
= 300 s – 53 s = 247 s
→
maximum base-load current = approx. 45% of I
N
= 13.5 A
Basic task 2
Known:
Device types, cycle duration, overload factor, base-load current
To be found:
Minimum base load duration and maximum overload duration
To find solution:
Select the limiting characteristic for the known unit and the known overload factor.
Read the overload duration
300
for the base-load current from the limiting characteristic.
Cycle duration <300 s:
Max. overload duration = (Cycle duration/300 s) * Overload duration
300
Min. base-load duration = Cycle duration – Max. overload duration
Cycle duration
≥
300 s:
Max. overload duration = Overload duration
300
Min. base-load duration = Cycle duration – Max. overload duration
Example 2:
Known:
30 A/4Q device; cycle duration 140 s; current overload factor = 1.15;
base-load current = 0.6*IN = 18 A
To be found:
Minimum base load duration and maximum overload duration
Solution:
Limiting characteristic for 30 A/4Q unit, overload factor 1.2
Base-load current = 60% of I
N
→
Overload duration
300
= 126.35 s
Max. overload duration = (140 s/300 s) × 126.35 s = approx. 58 s
Min. base-load duration = 140 s - 58 s = 82 s
