{"id":4244,"date":"2026-09-25T00:00:00","date_gmt":"2026-09-25T00:00:00","guid":{"rendered":"https:\/\/chac-electric.com\/?p=4244"},"modified":"2026-10-19T03:37:15","modified_gmt":"2026-10-19T03:37:15","slug":"%d1%87%d1%82%d0%be-%d0%bf%d1%80%d0%b5%d0%b4%d1%81%d1%82%d0%b0%d0%b2%d0%bb%d1%8f%d0%b5%d1%82-%d1%81%d0%be%d0%b1%d0%be%d0%b9-%d0%ba%d1%80%d0%b8%d0%b2%d0%b0%d1%8f-%d1%81%d1%80%d0%b0%d1%89%d0%b8%d0%b2","status":"publish","type":"post","link":"https:\/\/chac-electric.com\/ru\/blog\/what-is-type-b-mcb-tripping-curve-applications-and-selection\/","title":{"rendered":"\u0427\u0442\u043e \u0442\u0430\u043a\u043e\u0435 \u0442\u0438\u043f B MCB? \u041a\u0440\u0438\u0432\u0430\u044f \u0441\u0440\u0430\u0431\u0430\u0442\u044b\u0432\u0430\u043d\u0438\u044f, \u043f\u0440\u0438\u043c\u0435\u043d\u0435\u043d\u0438\u044f \u0438 \u0432\u044b\u0431\u043e\u0440"},"content":{"rendered":"

A \u0421\u0418\u041f-\u0430\u0432\u0442\u043e\u043c\u0430\u0442\u0438\u0447\u0435\u0441\u043a\u0438\u0439 \u0432\u044b\u043a\u043b\u044e\u0447\u0430\u0442\u0435\u043b\u044c \u0442\u0438\u043f\u0430 B<\/strong> is a miniature circuit breaker with a B time-current characteristic. Its instantaneous magnetic operating band is commonly 3\u20135 times rated current in the IEC-based product families covered by the manufacturer\u2019s curve. That band is not the normal load allowance, and \u201cType B\u201d here does not mean a Type B residual-current device. Select the breaker from the load\u2019s starting behavior and the circuit\u2019s fault-clearing requirements together.<\/p>\n

\"\u0427\u0442\u043e<\/p>\n

Understand the magnetic band and the thermal curve<\/h2>\n

A thermal-magnetic MCB responds to sustained overload through its thermal mechanism and to sufficiently high current through its magnetic mechanism. Schneider Electric\u2019s Acti9 FAQ gives a B-curve band of 3\u20135 times rated current. For a hypothetical B20 device using that characteristic, the band corresponds to 60\u2013100 A. This is an illustration of the multiplier, not a guaranteed trip point at every temperature or duration.<\/p>\n

Below the magnetic region, the thermal curve still matters. A breaker carrying somewhat more than its rating does not necessarily open instantly. Read the complete manufacturer time-current curve, including tolerances and test conditions, when checking overloads and disconnection time.<\/p>\n

Check the actual inrush before calling a load low-inrush<\/h2>\n

B-curve devices are often considered for resistive loads and circuits with modest starting currents. \u201cLighting,\u201d however, is not a complete electrical description: a bank of LED drivers can draw a short charging pulse at switch-on. Obtain the driver\u2019s inrush information and any manufacturer limit on the number of drivers per protective device.<\/p>\n

The useful design question is whether the combined startup stays within the breaker\u2019s acceptable operating envelope. A low running wattage does not prove low inrush. Group switching, simultaneous restart after a power failure and replacement driver types can all change that envelope without changing the circuit\u2019s everyday current.<\/p>\n

Compare B and C curves against the fault conditions<\/h2>\n

The B-curve tripping characteristic<\/strong> has a lower magnetic threshold than the C characteristic in the cited Acti9 guidance, which gives C as 5\u201310 times rated current. Moving to C can tolerate a larger startup pulse, but it also changes the current needed for rapid magnetic operation. Check the fault path and required disconnection time before accepting that change.<\/p>\n

For a long cable run, inspect the minimum fault-current condition as well as the maximum fault level at the board. A device must interrupt the largest credible fault within its rating and operate quickly enough at the fault conditions relevant to the installation. Raising the threshold solely to stop a nuisance trip can leave that second check unresolved.<\/p>\n

\"CHAC<\/p>\n

Keep the curve letter separate from other ratings<\/h2>\n

A B marking does not establish breaking capacity, AC\/DC suitability, residual-current sensitivity or arc-fault detection. Those are separate characteristics. In particular, a Type B RCD classification concerns residual-current waveforms, whereas a B-curve MCB characteristic concerns overcurrent operation. Similar wording is not evidence of equivalent protection.<\/p>\n

Review the available curves in CHAC\u2019s miniature circuit breaker range<\/a> and the exact variant on the CQB2-63 MCB page<\/a>. Confirm the model curve and rating instead of transferring a competitor\u2019s threshold or application approval to a CHAC catalogue number.<\/p>\n

Diagnose unwanted trips before changing the breaker<\/h2>\n

Record when the trip occurs, which loads switch together and whether the event follows maintenance or a change of equipment. Immediate startup trips and delayed overload trips call for different investigations. Check the circuit and connections before assuming the selected curve is the only problem.<\/p>\n

A replacement MCB curve selection<\/strong> should document the load inrush, cable protection and disconnection-time review. The 20 A MCB selection guide<\/a> shows how the current rating and curve remain separate decisions. Keep that record so a later technician understands why the replacement was chosen.<\/p>\n

Which part of the specification answers each question?<\/h2>\n\n\n\n\n\n\n\n\n
Question<\/th>\nRelevant characteristic<\/th>\nDo not confuse it with<\/th>\n<\/tr>\n<\/thead>\n
Will it tolerate startup?<\/td>\nFull time-current curve and load inrush<\/td>\nRunning current alone<\/td>\n<\/tr>\n
Can it clear the fault?<\/td>\nBreaking capacity at the declared voltage<\/td>\nThe B curve letter<\/td>\n<\/tr>\n
Does it detect leakage?<\/td>\nA separate residual-current function<\/td>\nA Type B MCB marking<\/td>\n<\/tr>\n
Can it operate on DC?<\/td>\nExplicit DC rating and wiring instructions<\/td>\nIts AC trip curve<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n

\u0427\u0430\u0441\u0442\u043e \u0437\u0430\u0434\u0430\u0432\u0430\u0435\u043c\u044b\u0435 \u0432\u043e\u043f\u0440\u043e\u0441\u044b<\/h2>\n

\u041a\u0430\u043a\u043e\u0432 \u0434\u0438\u0430\u043f\u0430\u0437\u043e\u043d \u0445\u043e\u0434\u0430 \u0434\u0432\u0438\u0436\u0435\u043d\u0438\u044f \u043f\u0440\u0438\u0431\u043e\u0440\u043d\u043e\u0439 \u0432\u044b\u043a\u043b\u044e\u0447\u0430\u0442\u0435\u043b\u0438 \u0442\u0438\u043f\u0430 B?<\/h3>\n

\u0421\u043e\u0433\u043b\u0430\u0441\u043d\u043e \u0441\u0442\u0430\u043d\u0434\u0430\u0440\u0442\u0443 IEC 60898-1, \u043c\u0433\u043d\u043e\u0432\u0435\u043d\u043d\u044b\u0439 \u0440\u0430\u0431\u043e\u0447\u0438\u0439 \u0440\u0435\u0436\u0438\u043c \u043e\u0431\u044b\u0447\u043d\u043e \u0443\u043a\u0430\u0437\u044b\u0432\u0430\u0435\u0442\u0441\u044f \u0432 \u043f\u0440\u0435\u0434\u0435\u043b\u0430\u0445 \u043e\u0442 3 \u0434\u043e 5 \u0440\u0430\u0437 \u043e\u0442 \u043d\u043e\u043c\u0438\u043d\u0430\u043b\u044c\u043d\u043e\u0433\u043e \u0442\u043e\u043a\u0430, \u043d\u043e \u0442\u043e\u0447\u043d\u044b\u0435 \u0438\u0441\u043f\u044b\u0442\u0430\u0442\u0435\u043b\u044c\u043d\u044b\u0435 \u043f\u0440\u0435\u0434\u0435\u043b\u044b \u0438 \u0434\u0430\u043d\u043d\u044b\u0435 \u043e \u043f\u0440\u043e\u0434\u0443\u043a\u0442\u0435 \u043e\u043f\u0440\u0435\u0434\u0435\u043b\u044f\u044e\u0442\u0441\u044f \u043f\u043e \u0441\u043e\u043e\u0442\u0432\u0435\u0442\u0441\u0442\u0432\u0443\u044e\u0449\u0435\u0439 \u043c\u043e\u0434\u0435\u043b\u0438. \u0412\u0441\u0435\u0433\u0434\u0430 \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u0443\u0439\u0442\u0435 \u043a\u0440\u0438\u0432\u0443\u044e \u0441\u043e\u043e\u0442\u0432\u0435\u0442\u0441\u0442\u0432\u0443\u044e\u0449\u0435\u0439 \u043c\u043e\u0434\u0435\u043b\u0438.<\/p>\n

When should I use a B-curve MCB?<\/h3>\n

Consider it where the load\u2019s inrush is compatible with the B characteristic and the circuit meets the required disconnection conditions. Resistive and some lighting circuits may fit, but LED drivers, transformers and other electronic loads need an actual inrush check.<\/p>\n

\u041c\u043e\u0436\u043d\u043e \u043b\u0438 \u0437\u0430\u043c\u0435\u043d\u0438\u0442\u044c C-\u043a\u043e\u043d\u0443\u0441 \u043d\u0430 B-\u043a\u043e\u043d\u0443\u0441?<\/h3>\n

\u0422\u043e\u043b\u044c\u043a\u043e \u043f\u043e\u0441\u043b\u0435 \u043f\u0440\u043e\u0432\u0435\u0440\u043a\u0438 \u0438\u0441\u0442\u043e\u0440\u0438\u0438 \u043d\u0435\u0436\u0435\u043b\u0430\u0442\u0435\u043b\u044c\u043d\u044b\u0445 \u0438\u043c\u043f\u0443\u043b\u044c\u0441\u043e\u0432, \u043f\u0435\u0440\u0435\u0433\u0440\u0443\u0437\u043e\u043a \u0438 \u0443\u0441\u043b\u043e\u0432\u0438\u0439 \u043d\u0435\u0438\u0441\u043f\u0440\u0430\u0432\u043d\u043e\u0433\u043e \u0442\u043e\u043a\u0430. \u0411\u043e\u043b\u0435\u0435 \u043d\u0438\u0437\u043a\u0438\u0439 \u043f\u043e\u0440\u043e\u0433 \u043c\u0430\u0433\u043d\u0438\u0442\u043d\u043e\u0433\u043e \u043d\u0430\u043f\u0440\u044f\u0436\u0435\u043d\u0438\u044f \u043c\u043e\u0436\u0435\u0442 \u0443\u043b\u0443\u0447\u0448\u0438\u0442\u044c \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0438\u0435 \u043d\u0435\u0438\u0441\u043f\u0440\u0430\u0432\u043d\u043e\u0441\u0442\u0435\u0439, \u043d\u043e \u043f\u0440\u0438 \u044d\u0442\u043e\u043c \u043c\u043e\u0436\u0435\u0442 \u043f\u0440\u0438\u0432\u0435\u0441\u0442\u0438 \u043a \u0441\u0440\u0430\u0431\u0430\u0442\u044b\u0432\u0430\u043d\u0438\u044e \u0432\u043e \u0432\u0440\u0435\u043c\u044f \u0437\u0430\u043f\u0443\u0441\u043a\u0430.<\/p>\n

\u0417\u043d\u0430\u0447\u0438\u0442 \u043b\u0438 \u0442\u0438\u043f B, \u0447\u0442\u043e \u0430\u0434\u0430\u043f\u0442\u0435\u0440 DC \u0441\u043e\u0432\u043c\u0435\u0441\u0442\u0438\u043c?<\/h3>\n

\u041d\u0435\u0442. \u201cB\u201d \u2014 \u044d\u0442\u043e \u043e\u0431\u043e\u0437\u043d\u0430\u0447\u0435\u043d\u0438\u0435 \u0434\u043b\u044f \u0441\u0435\u043c\u0435\u0439\u0441\u0442\u0432\u0430 \u0432\u044b\u043a\u043b\u044e\u0447\u0430\u0442\u0435\u043b\u0435\u0439, \u043d\u0435 \u043e\u0442\u043d\u043e\u0441\u044f\u0449\u0435\u0435\u0441\u044f \u043a \u043d\u043e\u043c\u0438\u043d\u0430\u043b\u044c\u043d\u043e\u043c\u0443 \u0442\u043e\u043a\u0443. \u0423\u0431\u0435\u0434\u0438\u0442\u0435\u0441\u044c \u0432 \u0442\u043e\u043c, \u0447\u0442\u043e \u043d\u0430\u043f\u0440\u044f\u0436\u0435\u043d\u0438\u0435, \u043e\u0431\u0440\u0430\u0442\u043d\u0430\u044f \u0441\u0432\u044f\u0437\u044c \u0438 \u0434\u0430\u043d\u043d\u044b\u0435 \u0438\u0441\u043f\u044b\u0442\u0430\u043d\u0438\u0439 \u043d\u0430 \u043f\u043e\u0441\u0442\u043e\u044f\u043d\u043d\u044b\u0439 \u0442\u043e\u043a \u0441\u043e\u043e\u0442\u0432\u0435\u0442\u0441\u0442\u0432\u0443\u044e\u0442 \u0434\u0440\u0443\u0433 \u0434\u0440\u0443\u0433\u0443.<\/p>\n

What is the difference between B and C curve circuit breakers?<\/h3>\n

In the cited Acti9 guidance, B has a 3\u20135 times rated-current magnetic band and C has a 5\u201310 times band. Both also have thermal overload behavior. Choose using the exact model curve, load inrush and fault-clearing requirements rather than an application label alone.<\/p>\n<\/section>\n

\u0421\u0441\u044b\u043b\u043a\u0438<\/h2>\n