{"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":"%d9%85%d8%a7-%d9%87%d9%8a-%d8%aa%d8%b7%d8%a8%d9%8a%d9%82%d8%a7%d8%aa-%d9%85%d9%86%d8%ad%d9%86%d9%8a%d8%a7%d8%aa-%d8%a7%d9%86%d9%82%d8%b7%d8%a7%d8%b9-%d8%a7%d9%84%d9%85%d9%83%d9%88%d9%86%d8%a7%d8%aa","status":"publish","type":"post","link":"https:\/\/chac-electric.com\/ar\/blog\/what-is-type-b-mcb-tripping-curve-applications-and-selection\/","title":{"rendered":"\u0645\u0627 \u0647\u0648 \u0646\u0648\u0639 \u0627\u0644\u0645\u0643\u0648\u0646\u0627\u062a \u0627\u0644\u0645\u064a\u0643\u0627\u0646\u064a\u0643\u064a\u0629 \u0627\u0644\u0645\u062a\u0639\u062f\u062f\u0629 (MCB) \u0645\u0646 \u0627\u0644\u0646\u0648\u0639 B\u061f \u0645\u0646\u062d\u0646\u0649 \u0627\u0644\u0627\u0646\u0642\u0637\u0627\u0639 \u0648\u0627\u0644\u062a\u0637\u0628\u064a\u0642\u0627\u062a \u0648\u0627\u062e\u062a\u064a\u0627\u0631\u0647\u0627"},"content":{"rendered":"

A \u0642\u0641\u0644 \u0627\u0644\u062a\u064a\u0627\u0631 \u0627\u0644\u0645\u062a\u0631\u062f\u062f \u0645\u0646 \u0627\u0644\u0646\u0648\u0639 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

\"\u0645\u0627<\/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

\u0627\u0644 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 \u0635\u0641\u062d\u0629 CQB2-63 MCB<\/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

\u0627\u0644\u0623\u0633\u0626\u0644\u0629 \u0627\u0644\u0634\u0627\u0626\u0639\u0629<\/h2>\n

\u0645\u0627 \u0647\u0648 \u0646\u0637\u0627\u0642 \u0627\u0644\u0633\u0641\u0631 \u0644\u0628\u0637\u0627\u0642\u0629 MCB \u0645\u0646 \u0627\u0644\u0646\u0648\u0639 B\u061f<\/h3>\n

\u0648\u0641\u0642\u064b\u0627 \u0644\u0644\u0645\u0648\u0627\u0635\u0641\u0629 IEC 60898-1\u060c \u064a\u062a\u0645 \u062a\u062d\u062f\u064a\u062f \u0645\u0646\u0637\u0642\u0629 \u0627\u0644\u062a\u0634\u063a\u064a\u0644 \u0627\u0644\u0641\u0648\u0631\u064a\u0629 \u0639\u0627\u062f\u0629\u064b \u062d\u0648\u0644 3-5 \u0623\u0636\u0639\u0627\u0641 \u0627\u0644\u062a\u064a\u0627\u0631 \u0627\u0644\u0645\u0642\u062f\u0631\u060c \u0648\u0644\u0643\u0646 \u0627\u0644\u062d\u062f \u0627\u0644\u0623\u0642\u0635\u0649 \u0627\u0644\u0645\u062d\u062f\u062f \u0644\u0627\u062e\u062a\u0628\u0627\u0631\u0627\u062a \u0647\u0630\u0647 \u0627\u0644\u0645\u0646\u0637\u0642\u0629 \u0648\u0627\u0644\u0628\u064a\u0627\u0646\u0627\u062a \u0627\u0644\u062e\u0627\u0635\u0629 \u0628\u0627\u0644\u0645\u0646\u062a\u062c \u064a\u062a\u0645 \u062a\u062d\u062f\u064a\u062f\u0647\u0645\u0627 \u0648\u0641\u0642\u064b\u0627 \u0644\u0644\u0646\u0645\u0648\u0630\u062c \u0627\u0644\u0645\u0642\u062f\u0645.<\/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

\u0647\u0644 \u064a\u0645\u0643\u0646\u0646\u064a \u0627\u0633\u062a\u0628\u062f\u0627\u0644 \u0645\u0646\u062d\u0646\u0649 C \u0628\u0646\u0645\u0648\u0630\u062c B\u061f<\/h3>\n

\u0648\u0644\u0627 \u064a\u064f\u0633\u062a\u062e\u062f\u064e\u0645 \u0625\u0644\u0627 \u0628\u0639\u062f \u0627\u0644\u062a\u062d\u0642\u0642 \u0645\u0646 \u062a\u0627\u0631\u064a\u062e \u0627\u0644\u062d\u0648\u0627\u062f\u062b\u060c \u0648\u0638\u0631\u0648\u0641 \u0627\u0644\u0625\u0631\u0633\u0627\u0644 \u0627\u0644\u0639\u0631\u0636\u064a \u0648\u062a\u064a\u0627\u0631 \u0627\u0644\u062e\u0637\u0623. \u0642\u062f \u064a\u062d\u0633\u0646 \u0639\u062a\u0628\u0629 \u0645\u063a\u0646\u0627\u0637\u064a\u0633\u064a\u0629 \u0623\u062f\u0646\u0649 \u0645\u0646 \u0639\u0645\u0644\u064a\u0629 \u0625\u0632\u0627\u0644\u0629 \u0627\u0644\u062e\u0637\u0623\u060c \u0644\u0643\u0646\u0647\u0627 \u0642\u062f \u062a\u0633\u0628\u0628 \u0627\u0646\u0642\u0637\u0627\u0639 \u0627\u0644\u062a\u064a\u0627\u0631 \u0623\u062b\u0646\u0627\u0621 \u0628\u062f\u0621 \u0627\u0644\u062a\u0634\u063a\u064a\u0644.<\/p>\n

\u0647\u0644 \u064a\u0639\u0646\u064a \u0627\u0644\u0646\u0648\u0639 B \u0623\u0646\u0651\u0647 \u0645\u062a\u0648\u0627\u0641\u0642 \u0645\u0639 DC\u061f<\/h3>\n

\u0644\u0627. \u201cB\u201d \u0647\u0648 \u062a\u0635\u0646\u064a\u0641 \u062f\u0627\u0626\u0645\u064a \u0627\u0644\u062a\u064a\u0627\u0631 \u0644\u0623\u0633\u0631\u0629 \u0645\u0642\u0627\u0648\u0645\u0627\u062a \u0627\u0644\u062a\u0628\u0627\u0637\u0624\u060c \u0648\u0644\u064a\u0633 \u062a\u0635\u0646\u064a\u0641\u064b\u0627 \u0644\u0644\u062c\u0647\u062f \u0627\u0644\u062f\u0627\u0626\u0631\u064a. \u064a\u064f\u0631\u062c\u0649 \u0627\u0644\u062a\u062d\u0642\u0642 \u0645\u0646 \u0627\u0644\u062c\u0647\u062f \u0648\u0627\u0644\u0642\u0637\u0628\u064a\u0629 \u0648\u0628\u064a\u0627\u0646\u0627\u062a \u0627\u0644\u0627\u062e\u062a\u0628\u0627\u0631 \u0627\u0644\u062f\u0627\u0626\u0631\u064a \u0628\u0634\u0643\u0644 \u0645\u0646\u0641\u0635\u0644.<\/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

\u0627\u0644\u0645\u0631\u0627\u062c\u0639<\/h2>\n