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 Rated AC Voltage Tripping Characteristics Breaking Capacity Mounting Style Rated DC Voltage Length Width Depth Application
RS Stock No. 184-9034
Mfr. Part No.CPB1016D3
BrandContactum
MYR66.60
Each
units
3 16 A - - - 415 V Type D 10 kA DIN Rail - - - - Domestic Household Premise
RS Stock No. 184-9023
Mfr. Part No.CPB1006B
BrandContactum
MYR22.70
Each
units
1 6 A - - - 415 V Type B 10 kA DIN Rail - - - - Domestic Household Premise
RS Stock No. 184-9059
Mfr. Part No.CPB25
BrandContactum
MYR15.50
Each
units
1 25 A - - - - Type B 6 kA - - - - - Domestic Household Premise
RS Stock No. 184-9035
Mfr. Part No.CPB1020B3
BrandContactum
MYR66.60
Each
units
3 20 A - - - 415 V Type B 10 kA DIN Rail - - - - Domestic Household Premise
RS Stock No. 184-9055
Mfr. Part No.CPB1063D3
BrandContactum
MYR79.90
Each
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3 63 A - - - 415 V Type D 10 kA DIN Rail - - - - Domestic Household Premise
RS Stock No. 184-9056
Mfr. Part No.CPB16
BrandContactum
MYR15.50
Each
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1 16 A - - - 250 V Type B 6 kA - - - - - Domestic Household Premise
RS Stock No. 184-9039
Mfr. Part No.CPB1032B
BrandContactum
MYR22.70
Each
units
1 32 A - - - 415 V Type B 10 kA DIN Rail - - - - Domestic Household Premise
RS Stock No. 184-9094
Mfr. Part No.CPMCBBM2
BrandContactum
MYR8.80
Each
units
- - - - - - - - - - - - - -
RS Stock No. 184-9047
Mfr. Part No.CPB1040C
BrandContactum
MYR22.70
Each
units
1 40 A - - - 415 V Type C 10 kA DIN Rail - - - - Domestic Household Premise
RS Stock No. 184-9043
Mfr. Part No.CPB1032C3
BrandContactum
MYR66.60
Each
units
3 32 A - - - 415 V Type C 10 kA DIN Rail - - - - Domestic Household Premise
RS Stock No. 184-9041
Mfr. Part No.CPB1032C
BrandContactum
MYR22.70
Each
units
1 32 A - - - 415 V Type C 10 kA DIN Rail - - - - Domestic Household Premise
RS Stock No. 184-9052
Mfr. Part No.CPB1063B
BrandContactum
MYR25.30
Each
units
1 63 A - - - 415 V Type B 10 kA DIN Rail - - - - Domestic Household Premise
RS Stock No. 184-9053
Mfr. Part No.CPB1063C
BrandContactum
MYR25.30
Each
units
1 63 A - - - 415 V Type C 10 kA DIN Rail - - - - Domestic Household Premise
RS Stock No. 188-1753
Mfr. Part No.CPBM1
BrandContactum
MYR8.80
Each
units
- - - - - - - - - - - - - -
RS Stock No. 184-9049
Mfr. Part No.CPB1050B
BrandContactum
MYR25.30
Each
units
1 50 A - - - 415 V Type B 10 kA DIN Rail - - - - Domestic Household Premise
RS Stock No. 184-9021
Mfr. Part No.CPB06
BrandContactum
MYR15.50
Each
units
1 6 A - - - 250 V Type B 6 kA - - - - - Domestic Household Premise
RS Stock No. 184-9064
Mfr. Part No.CPBBL
BrandContactum
MYR4.70
Each
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- - - - - - - - DIN Rail - - - - -
RS Stock No. 184-9046
Mfr. Part No.CPB1040B
BrandContactum
MYR22.70
Each
units
1 40 A - - - 415 V Type B 10 kA DIN Rail - - - - Domestic Household Premise
RS Stock No. 184-9024
Mfr. Part No.CPB1006B3
BrandContactum
MYR66.60
Each
units
3 6 A - - - 415 V Type B 10 kA DIN Rail - - - - Domestic Household Premise
RS Stock No. 184-9025
Mfr. Part No.CPB1006C
BrandContactum
MYR22.70
Each
units
1 6 A - - - 415 V Type C 10 kA DIN Rail - - - - Domestic Household Premise