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. You can learn more about MCBs in our complete MCB guide.


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 Model Number Range Series Number of Poles Current Rating Tripping Characteristics Rated AC Voltage Mounting Style Rated DC Voltage Breaking Capacity at Maximum Voltage Rating Length Width Depth Application
RS Stock No. 132-122
Mfr. Part No.2CDS272001R0164 S202M-C16
BrandABB
£44.43
Each
Units
- System M Pro S200 2 16A Type C 440V - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 488-7457
Mfr. Part No.2CDS251001R0065 - S201B6
BrandABB
£10.85
Each
Units
- System M Pro S200 1 6A Type B 253V - 72V 6 kA 88mm 17.5mm 75.8mm -
RS Stock No. 132-015
Mfr. Part No.2CDS272001R0064 S202M-C6
BrandABB
£48.34
Each
Units
- System M Pro S200 2 6A Type C 440V - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 535-4138
Mfr. Part No.2CDS271001R0064 S201M-C6
BrandABB
£16.77
Each
Units
- System M Pro S200 1 6A Type C 253V - 72V 10 kA 88mm 17.5mm 75.8mm -
RS Stock No. 132-071
Mfr. Part No.2CDS272001R0104 S202M-C10
BrandABB
£44.43
Each
Units
- System M Pro S200 2 10A Type C 440V - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 535-4144
Mfr. Part No.2CDS271001R0104 S201M-C10
BrandABB
£15.38
Each
Units
- System M Pro S200 1 10A Type C 253V - 72V 10 kA 88mm 17.5mm 75.8mm -
RS Stock No. 539-8201
Mfr. Part No.2CDS211001R0064 SH201-C6
BrandABB
£11.79
Each
Units
- System M Pro S200 1 6A Type C 440V - 60V 6 kA 85mm 17.5mm 69mm -
RS Stock No. 535-4100
Mfr. Part No.2CDS271001R0024 S201M-C2
BrandABB
£17.73
Each
Units
- System M Pro S200 1 2A Type C 253V - 72V 10 kA 88mm 17.5mm 75.8mm -
RS Stock No. 535-4150
Mfr. Part No.2CDS271001R0164 S201M-C16
BrandABB
£15.38
Each
Units
- System M Pro S200 1 16A Type C 253V - 72V 10 kA 88mm 17.5mm 75.8mm -
RS Stock No. 539-8223
Mfr. Part No.2CDS211001R0164 SH201-C16
BrandABB
£11.34
Each
Units
- System M Pro S200 1 16A Type C 440V - 60V 6 kA 85mm 17.5mm 69mm -
RS Stock No. 746-7699
Mfr. Part No.2CDS252001R0024 S202-C2
BrandABB
£38.64
Each
Units
- System M Pro S200 2 2A Type C 400V - - 6 kA - 35mm 69mm -
RS Stock No. 535-4352
Mfr. Part No.2CDS273001R0634 S203M-C63
BrandABB
£75.72
Each
Units
- System M Pro S200 3 63A Type C 440V - - 10 kA 88mm - 75.8mm -
RS Stock No. 746-7649
Mfr. Part No.2CDS251001R0024 S201-C2
BrandABB
£14.46
Each
Units
- System M Pro S200 1 2A Type C 230V - 72V 6 kA 88mm 17.5mm 69mm -
RS Stock No. 527-9633
Mfr. Part No.2CDS253001R0321 S203-D32
BrandABB
£54.86
Each
Units
- System M Pro S200 3 32A Type D 440V - - 6 kA - - 75.8mm -
RS Stock No. 535-4122
Mfr. Part No.2CDS271001R0044 S201M-C4
BrandABB
£17.36
Each
Units
- System M Pro S200 1 4A Type C 253V - 72V 10 kA 88mm 17.5mm 75.8mm -
RS Stock No. 535-4318
Mfr. Part No.2CDS273001R0324 S203M-C32
BrandABB
£66.97
Each
Units
- System M Pro S200 3 32A Type C 440V - - 10 kA - - 75.8mm -
RS Stock No. 132-009
Mfr. Part No.2CDS272001R0024 S202M-C2
BrandABB
£50.79
Each
Units
- System M Pro S200 2 2A Type C 440V - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 539-8217
Mfr. Part No.2CDS211001R0104 SH201-C10
BrandABB
£11.34
Each
Units
- System M Pro S200 1 10A Type C 440V - 60V 6 kA 85mm 17.5mm 69mm -
RS Stock No. 746-7703
Mfr. Part No.2CDS252001R0044 S202-C4
BrandABB
£38.64
Each
Units
- System M Pro S200 2 4A Type C 400V - - 6 kA - 35mm 69mm -
RS Stock No. 132-116
Mfr. Part No.2CDS272001R0204 S202M-C20
BrandABB
£44.43
Each
Units
- System M Pro S200 2 20A Type C 440V - 125V 10 kA 88mm 35mm 75.8mm -