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 Mounting Style Rated DC Voltage Breaking Capacity at Maximum Voltage Rating Length Width Depth Break Time
RS Stock No. 746-7652
Mfr. Part No.2CDS251001R0044 S201-C4
BrandABB
$46.94
Each
units
1 4 A - System M Pro S200 230V Type C - - 6 kA 88mm 17.5mm 69mm -
RS Stock No. 435-516
Mfr. Part No.2CCS862001R0824 S802S-C100
BrandABB
$377.39
Each
units
2 100 A - High Performance S800 400 V, 690V Type C - 250V 50 kA 95mm - 88.5mm -
RS Stock No. 539-8166
Mfr. Part No.2CDS211001R0205 SH201-B20
BrandABB
$25.58
Each
units
1 20 A - System M Pro S200 440V Type B - 60V 6 kA 85mm 17.5mm 69mm -
RS Stock No. 535-4251
Mfr. Part No.2CDS273001R0064 S203M-C6
BrandABB
$160.64
Each
units
3 6 A - System M Pro S200 440V Type C - - 10 kA - - 75.8mm -
RS Stock No. 746-7722
Mfr. Part No.2CDS252001R0324 S202-C32
BrandABB
$75.17
Each
units
2 32 A - System M Pro S200 400V Type C - - 6 kA 88mm - 69mm -
RS Stock No. 435-453
Mfr. Part No.2CCS862001R0801 S802S-D80
BrandABB
$374.15
Each
units
2 80 A - High Performance S800 400 V, 690V Type D - 250V 50 kA 95mm 53mm 88.5mm -
RS Stock No. 435-370
Mfr. Part No.2CCS893001R0825 S803N-B100
BrandABB
$456.77
Each
units
3 100 A - High Performance S800 400 V, 690V Type B - - 36 kA - 79.5mm 88.5mm -
RS Stock No. 131-911
Mfr. Part No.2CDS272001R0105 S202M-B10
BrandABB
$90.02
Each
units
2 10 A - System M Pro S200 440V Type B - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 746-7700
Mfr. Part No.2CDS252001R0084 S202-C8
BrandABB
$85.35
Each
units
2 8 A - System M Pro S200 400V Type C - - 6 kA 88mm 35mm 69mm -
RS Stock No. 132-116
Mfr. Part No.2CDS272001R0204 S202M-C20
BrandABB
$100.26
Each
units
2 20 A - System M Pro S200 440V Type C - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 535-4122
Mfr. Part No.2CDS271001R0044 S201M-C4
BrandABB
$32.51
Each
units
1 4 A - System M Pro S200 253V Type C - 72V 10 kA 88mm 17.5mm 75.8mm -
RS Stock No. 539-8330
Mfr. Part No.2CDS213001R0064 SH203-C6
BrandABB
$88.86
Each
units
3 6 A - System M Pro S200 440V Type C - - 6 kA 85mm 52.5mm 69mm -
RS Stock No. 535-6156
Mfr. Part No.2CDS273001R0505 S203M-B50
BrandABB
$160.58
Each
units
3 50 A - System M Pro S200 440V Type B - - 10 kA 88mm 52.5mm 75.8mm -
RS Stock No. 746-7659
Mfr. Part No.2CDS251001R0084 S201-C8
BrandABB
$31.18
Each
units
1 8 A - System M Pro S200 230V Type C - - 6 kA 88mm 17.5mm 69mm -
RS Stock No. 455-6327
Mfr. Part No.S202-C16
BrandABB
$121.64
Each
units
3 - - System M Pro S200 - - - - - 57.5mm 96.5mm 46.5mm -
RS Stock No. 535-4100
Mfr. Part No.2CDS271001R0024 S201M-C2
BrandABB
$49.01
Each
units
1 2 A - System M Pro S200 253V Type C - 72V 10 kA 88mm 17.5mm 75.8mm -
RS Stock No. 132-087
Mfr. Part No.2CDS272001R0634 S202M-C63
BrandABB
$109.04
Each
units
2 63 A - System M Pro S200 440V Type C - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 131-905
Mfr. Part No.2CDS272001R0404 S202M-C40
BrandABB
$109.67
Each
units
2 40 A - System M Pro S200 440V Type C - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 488-6886
Mfr. Part No.2CDS252001R0205 - S202B20
BrandABB
$76.04
Each
units
2 20 A - System M Pro S200 440V Type B - 125V 6 kA 88mm 35mm 75.8mm -
RS Stock No. 535-4217
Mfr. Part No.2CDS271001R0634 S201M-C63
BrandABB
$40.53
Each
units
1 63 A - System M Pro S200 253V Type C - 72V 10 kA 88mm 17.5mm 75.8mm -