MCBs

MCBs, or miniature circuit breakers, are a type of switch used to automatically turn off electrical circuits during abnormal conditions. MCBs often replace fuses in low voltage electrical circuits as they can be more reliable, much more sensitive and are resettable.


How an MCB Works


When continuous overcurrent flows through an MCB, a bimetallic strip is heated and causes it to bend. This bending of the bimetallic strip releases a mechanical latch opening the contacts and turning off the MCB, thereby stopping the current to flow in the circuit. To restart the flow of current the MCB must be manually turned on. This mechanism protects the MCB from faults arising due to overcurrent or overload and is intended to prevent the accidental overloading of the cable in a no-fault situation. The speed of the MCB tripping will vary with the degree of the overload. This is usually achieved by the use of a thermal device in the MCB. The second characteristic is the magnetic fault protection, which is intended to operate when the fault reaches a predetermined level and to trip the MCB within one-tenth of a second. The level of this magnetic trip gives the MCB its type characteristic.


MCBs are used to perform many functions such as local control switches, isolating switches against faults and overload protection devices for installation or specific equipment or appliances.


MCB Types


MCBs have three common types for circuit protection in residential, commercial and industrial applications. The use is classified by a type, which determines the tripping characteristics of the MCB:


Type B - trips between 3 and 5 times the load current


This type will trip instantly at a rate of three to five times its rated current. These are normally used for resistive or small inductive loads where switching surges are very small. Therefore, these are suitable for residential or light commercial installations.


Type C - trips between 5 and 10 times the full load current


This type will trip instantly at a rate of five to ten times its rated current. These are normally used for high inductive loads where switching surges are high such as small motors and fluorescent lighting. In such cases, type C MCBs are preferred to handle higher value of short circuit currents. Therefore, these are suitable for highly inductive commercial and industrial installations.


Type D - trips between 10 and 20 times the full load current


This type will trip instantly at a rate of ten to twenty-five times its rated current. These are normally used for very high inductive loads where high inrush current is very frequent. These are suitable for specific industrial and commercial applications. The common examples of such applications include x-ray machines, UPS systems, industrial welding equipment, large winding motors, etc.


How to select a suitable MCB for the application?


Focus on 3 main points to choose the right MCB for the electrical circuit


  1. Ampere rating

  2. Short circuit breaking capacity

  3. Application type

...
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Description Price Number of Poles Current Rating Model Number Range Series Tripping Characteristics Rated AC Voltage Rated DC Voltage Breaking Capacity Mounting Style Length Width Depth Application
RS Stock No. 922-6964
Mfr. Part No.FAZ-B4/1
BrandEaton
€18.21
Each
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1 4 A - XEffect FAZ Type B 240 V 48V 10 kA - 17.8mm 65.5mm 80mm Appliances, Business Equipment, Control Circuit, Lighting, Supplementary Protection
RS Stock No. 791-3164
Mfr. Part No.A9F53116
€16.14
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1 16 A - Acti 9 iC60H Type B 12 → 60 V, 100 → 133 V, 220 → 240 V 12 → 48 V, 72 V 10 kA DIN Rail 85mm 18mm 78.5mm -
RS Stock No. 791-3391
Mfr. Part No.A9F54320
€70.37
Each
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3 20 A - Acti 9 iC60H Type C 12 → 133 V, 220 → 240 V, 380 → 415 V, 440 V 100 → 133V 10 kA DIN Rail 85mm 54mm 78.5mm -
RS Stock No. 798-2205
Mfr. Part No.EUB16B
BrandEuropa
€3.32
Each
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- - - - - - - - - - - - - -
RS Stock No. 199-2972
Mfr. Part No.RS/B32
BrandWylex
€18.13
Each
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- - - - - - - - - - - - - -
RS Stock No. 772-1280
Mfr. Part No.5SY4204-7
BrandSiemens
€61.49
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2 4 A - Sentron 5SY4 Type C 400 V - 10 kA - 90mm 36mm 76mm -
RS Stock No. 791-3518
Mfr. Part No.A9F55206
€54.43
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2 6 A - Acti 9 iC60H Type D 12 → 133 V, 220 → 240 V, 380 → 415 V, 440 V 100 → 133V 10 kA DIN Rail 85mm 36mm 78.5mm -
RS Stock No. 746-7649
Mfr. Part No.S201-C2
BrandABB
€15.57
Each
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1 2 A - System M Pro S200 Type C 230 V 72V 6 kA - 88mm 17.5mm 69mm -
RS Stock No. 847-3469
Mfr. Part No.FAZ-D1/2
BrandEaton
€60.68
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2 1 A - XEffect FAZ Type D 240 → 415 V - 10 kA - 36mm 84.7mm 72.6mm -
RS Stock No. 825-6172
Mfr. Part No.P2MB3PC125
BrandLovato
€166.60
Each
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3 125 A - ModuLo P2MB Type C 230 V, 400 V 60V 10 kA - 85mm 81mm 80mm -
RS Stock No. 862-1034
Mfr. Part No.S202UDC-K2
BrandABB
€113.92
Each
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2 2 A - System M Pro S200 Type K - 125V 10 kA - 35mm 92mm 77.8mm -
RS Stock No. 734-9462
Mfr. Part No.A9N21377
€72.79
Each
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1 + N 20 A - Acti 9 DT40 Type D 400 V - 6 kA - - - - -
RS Stock No. 624-0440
Mfr. Part No.FAZ-C20/3
BrandEaton
€71.47
Each
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3 20 A - XEffect FAZ Type C 400 V - 10 kA - 80mm 52.5mm 73.5mm -
RS Stock No. 790-8787
Mfr. Part No.A9F43201
€52.76
Each
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2 1 A - Acti 9 iC60N Type B 12 → 133 V, 220 → 240 V, 380 → 415 V, 440 V 100 → 133V 6 kA - - - 78.5mm -
RS Stock No. 510-6765
Mfr. Part No.18639
€421.58
Each
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3P 65 A - - NG125 Type C - - 8 kA DIN Rail Mount 103mm 81mm 87mm -
RS Stock No. 922-7080
Mfr. Part No.FAZ-C4/1N
BrandEaton
€46.72
Each
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1 + N 4 A - XEffect FAZ Type C 240 V 48V 10 kA - 17.8mm 65.5mm 80mm Appliances, Business Equipment, Control Circuit, Lighting, Supplementary Protection
RS Stock No. 521-4989
Mfr. Part No.5SY6105-7
BrandSiemens
€18.93
Each
units
1 500 mA - Sentron 5SY6 Type C 230 V, 400 V - 6 kA - 89.8mm 17.6mm 76.4mm -
RS Stock No. 847-3298
Mfr. Part No.FAZ-C2/2
BrandEaton
€43.08
Each
units
2 2 A - XEffect FAZ Type C 240 → 415 V - 10 kA - 36mm 84.7mm 72.6mm -
RS Stock No. 892-9426
Mfr. Part No.NHXB50
BrandWylex
€6.47
Each
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1 50 A - NSB Series 1 Type B 230 V - 6 kA - 18mm 90mm 76mm Residential
RS Stock No. 132-015
Mfr. Part No.2CDS272001R0064
BrandABB
€46.88
Each
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2 6 A - System M Pro S200 Type C 440 V 125V 10 kA - 88mm 35mm 75.8mm -
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