Formula and Method
Current is calculated from kW and voltage, then multiplied by the sizing factor and rounded up to the next common breaker rating.
Assumptions
- Standard rating list is used for preliminary selection
- Trip curve, breaking capacity, coordination, and local code are not selected automatically
Important Warnings
- Do not select a breaker from current alone. Verify cable ampacity, short-circuit current, trip curve, and equipment standard.
- Continuous-load rules differ by market and application.
FAQ
Why does the calculator round up?
Protective devices are sold in standard current ratings. The tool rounds the calculated minimum to the next common rating.
Does this choose MCB or MCCB?
No. It estimates current rating only. The product family depends on breaking capacity, setting range, application, and standard.