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Breaker / Fuse Sizing Calculator
Load Parameters
Load Current (I
b
)
A
Max Fault Current (I
sc
)
kA
Breaker Selection
Device Type
MCB / MCCB (Circuit Breaker)
Fuse (HRC)
Rated Current (I
n
)
6 A
10 A
16 A
20 A
25 A
32 A
40 A
50 A
63 A
80 A
100 A
125 A
160 A
200 A
250 A
400 A
630 A
Thermal Setting (I
r
/ I
n
)
x I
n
(Adjustable for MCCB, fixed 1.0 for Fuse)
Breaking Capacity (I
cu
)
6 kA
10 kA
15 kA
25 kA
36 kA
50 kA
70 kA
100 kA
kA
Compliance Checks
1. Rating Check (I
n
≥ I
b
)
CHECK
2. Setting Check (I
r
≥ I
b
)
CHECK
3. Fault Capacity (I
cu
≥ I
sc
)
CHECK
Selected Device
Effective Trip (I
r
)
- A
📄 Export Report
🔄 Reset
Technical Notes & Engineering Logic
Variable Definitions
I
b
(Load Current):
Design current of circuit.
I
n
(Rated Current):
Device nominal rating.
I
r
(Trip Current):
Actual thermal trip point (I
n
× Setting).
I
cu
:
Ultimate breaking capacity.
Selection Logic
Rule 1 (I
n
≥ I
b
):
Device must handle load.
Rule 2 (I
r
≥ I
b
):
Trip setting must not be below load.
Rule 3 (I
cu
≥ I
sc
):
Must interrupt max fault current.
Notes
Fuses:
Setting locked to 1.0 (Fixed).
Cable Sizing:
Ensure Cable I
z
≥ I
n
separately.
Standard:
Logic follows IEC 60947-2 screening.