Supplied-value arithmetic only
Circuit-Breaker Preliminary Input Checks
Check three basic inequalities for an already selected overcurrent protective device. This page does not choose a rating, MCB/MCCB type, B/C/D curve, trip settings, breaking category or selectivity.
Three preliminary comparisons
Arithmetic evaluated
The public Schneider Electrical Installation Guide explains these IEC-based overload and breaking-capacity comparisons and also notes the special tested backup/cascading case. This page requires every quantity explicitly and only reports whether the numerical inequalities hold.
Current IEC product and installation scopes
IEC 60364-4-43:2023 is the current fourth edition for protection against overcurrent and coordination of overcurrent-protection measures. IEC 60898-1:2015 with Amendment 1:2019 and Corrigendum 1:2020 applies to specified a.c. circuit-breakers for household and similar installations up to 440 V, 125 A and 25 kA. IEC 60947-2:2024, sixth edition, applies to low-voltage circuit-breakers intended for instructed or skilled persons within its voltage scope. These standards use different product contexts and short-circuit ratings; a current threshold alone cannot choose between them.
What is not checked
Passing all three boxes is not approval. Still verify system voltage/frequency and AC/DC duty, poles and neutral, maximum and minimum fault currents, automatic-disconnection time and earth-fault loop, conductor short-circuit thermal withstand and energy limitation, protective conductor and RCD/additional protection, inrush/start and nuisance tripping, adjustable settings, ambient/installation derating, isolation, coordination/selectivity/backup using tested manufacturer data, upstream/downstream equipment, local law and inspection/testing.
B/C/D letters are not selected from a load name. The exact starting-current envelope and required fault/disconnection performance must be checked against the selected device time-current bands. Likewise, selectivity cannot be established by a universal current ratio; use verified manufacturer tables/curves or a validated coordination study.
Checked example
IB=28 A, In=32 A, Iz=41 A, I₂=46.4 A, Ik,max=10 kA and applicable breaking capacity=15 kA pass all three numerical comparisons; the missing checks above still remain.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
