MCB / MCCB / ACB sizing
Find a nominal current candidate using your design load, cable capacity and manufacturer correction factor.
Enable JavaScript for live calculations. Read the method and default example below.
Method and assumptions
- Candidate current only. For an adjustable breaker use the relevant protective setting and manufacturer coordination data.
- Trip curve, poles, frame, Icu/Ics, overload characteristic and selectivity are not selected automatically.
- Also verify the device conventional operating current condition (I2 ≤ 1.45 Iz), starting conditions and disconnection time.
Before using the result
- Do not choose an MCB, MCCB or ACB solely by current. Confirm fault level and ratings at the actual operating voltage.
Worked example
Illustrative default inputs. Enter your project values above.
- Design load value
- 160
- Load unit
- Amps
- Supply arrangement
- Three phase — balanced
- Supply voltage
- 415 V
- Power factor for kW conversion
- 0.85
- Corrected cable capacity (Iz)
- 250 A
- Manufacturer current-rating factor
- 1
- Prospective fault level
- 25 kA
Default results
- Design current (Ib)
- 160 A
- Nominal current candidate
- 160 A
- Cable capacity check
- Ib ≤ In ≤ Iz
Choose a reference or send your BOQ
Compare relevant product families, then confirm the exact rating, control supply and duty. Price and availability are confirmed with your enquiry.
Technical references
These references support planning. The exact model documentation and a project-specific engineering review govern the final specification.