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. 490-012
Mfr. Part No.PXL-D2/3
BrandEaton
€90.13
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3 2 A - xPole PXL, S200 Type D 400 V 48V 10 kA - 52.5mm 80mm 60mm -
RS Stock No. 731-9487
Mfr. Part No.4 077 84
BrandLegrand
€61.37
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2 16 A - DX Range DX3 Type C 230 V, 400 V - 10 kA - - - - -
RS Stock No. 825-5615
Mfr. Part No.P1MB1PC63
BrandLovato
€14.66
Each
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1 63 A - ModuLo P1MB Type C 230 V 60V 10 kA - 86.5mm 18mm 79.52mm -
RS Stock No. 622-0367
Mfr. Part No.5SY7314-7
BrandSiemens
€108.81
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3 300 mA - Sentron 5SY7 Type C 400 V - 15 kA - 89.8mm 52.8mm 76mm -
RS Stock No. 222-5683
Mfr. Part No.AHC062
BrandEaton
€33.29
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2 6 A - Memera AHC Type C - - 10 kA - - - - -
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Mfr. Part No.A9P22740
€179.72
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3P+N 40 A A9P22740 Acti 9 Acti9iDT40T Type C 230 V ac - 6 kA DIN Rail 18mm 78mm 81mm -
RS Stock No. 847-3330
Mfr. Part No.FAZ-C3/3
BrandEaton
€69.99
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3 3 A - xEffect FAZ Type C 240 → 415 V - 10 kA - 54mm 84.7mm 72.6mm -
RS Stock No. 131-955
Mfr. Part No.2CDS272001R0324 - S202MC32
BrandABB
€47.87
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2 32 A - System M Pro S200 Type C 440 V 125V 10 kA - 88mm 35mm 75.8mm -
RS Stock No. 825-5902
Mfr. Part No.P1MB4PB02
BrandLovato
€95.97
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4 2 A - ModuLo P1MB Type B 230 V, 400 V - 10 kA - 86.5mm 72mm 79.52mm -
RS Stock No. 823-4670
Mfr. Part No.4 067 86
BrandLegrand
€29.65
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1 25 A - DX Range DNX3 Type C 250 V 12V 4.5 kA - 77.7mm 17.8mm 94.8mm -
RS Stock No. 191-6086
Mfr. Part No.A9P22604
€39.73
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1P+N 4 A A9P22604 Acti 9 Acti9iDT40T Type C 230 V ac - 6 kA DIN Rail 18mm 78mm 81mm -
RS Stock No. 490-129
Mfr. Part No.PXL-D8/3
BrandEaton
€90.13
Each
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3 8 A - xPole PXL, S200 Type D 400 V 48V 10 kA - 52.5mm 80mm 60mm -
RS Stock No. 488-6202
Mfr. Part No.2CDS254001R0405 - S204B40
BrandABB
€142.11
Each
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4 40 A - System M Pro S200 Type B 440 V 125V 6 kA - 88mm 70mm 75.8mm -
RS Stock No. 124-3189
Mfr. Part No.5SY4404-8
BrandSiemens
€145.31
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4 4 A - Sentron 5SY4 Type D 400 V - 10 kA - 70.4mm 76mm 89.8mm Industrial, Plant Engineering
New
RS Stock No. 842-0843
Mfr. Part No.NC1V-2100-20AA
BrandIdec
€37.05
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Mfr. Part No.470238
BrandABB
€21.09
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1 + N 16 A SN201 L C16-L - SN201 Type C 230 V - 4.5 kA DIN Rail 18mm 69mm 85mm Final Distribution and Protection of Long Cable Lenghts in TN and IT Systems
RS Stock No. 769-4611
Mfr. Part No.FAZ6-C25/1
BrandEaton
€14.46
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1 25 A - xEffect FAZ6 Type C 230 → 400 V - 6 kA - 80mm 17.5mm 61.5mm -
New
RS Stock No. 842-0758
Mfr. Part No.NC1V-1100-15AA
BrandIdec
€11.23
Each
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Mfr. Part No.236289
BrandEaton
€50.06
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2 16 A - xPole PXL, S200 Type C 400 V 48V 10 kA - 35mm 80mm 60mm -
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Mfr. Part No.2CCS551001R0065 - S401EB6
BrandABB
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1 6 A - Smissline S400 Type B 230 V, 400 V - 6 kA - - 18mm - -
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