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 Breaking Capacity at Maximum Voltage Rating Length Width Depth
RS Stock No. 125-1426
Mfr. Part No.1492-SPM1B250
kr 142,56
Each
Units
1 25 A - 1492 1492SPM Type B 277V 48V - - 10 kA 17.5mm 74mm 88mm
RS Stock No. 125-1478
Mfr. Part No.1492-SPM2C630
kr 899,22
Each
Units
2 63 A - 1492 1492SPM Type C 277 V, 480V 96V - - 10 kA 35mm 75mm 88mm
RS Stock No. 125-1468
Mfr. Part No.1492-SPM2C020
kr 441,63
Each
Units
2 2 A - 1492 1492SPM Type C 277 V, 480V 96V - - 10 kA 35mm 75mm 88mm
RS Stock No. 125-1472
Mfr. Part No.1492-SPM2C100
kr 275,15
Each
Units
2 10 A - 1492 1492SPM Type C 277 V, 480V 96V - - 10 kA 35mm 75mm 88mm
RS Stock No. 125-1512
Mfr. Part No.1492-SPM2D160
kr 346,92
Each
Units
2 16 A - 1492 1492SPM Type D 277 V, 480V 96V - - 10 kA 35mm 75mm 88mm
RS Stock No. 125-1429
Mfr. Part No.1492-SPM2B020
kr 431,66
Each
Units
2 2 A - 1492 1492SPM Type B 277 V, 480V 96V - - 10 kA 35mm 75mm 88mm
RS Stock No. 125-1488
Mfr. Part No.1492-SPM3C250
kr 539,33
Each
Units
3 25 A - 1492 1492SPM Type C 277 V, 480V - - - 10 kA 53mm 75mm 88mm
RS Stock No. 125-1443
Mfr. Part No.1492-SPM3B130
kr 424,68
Each
Units
3 13 A - 1492 1492SPM Type B 277 V, 480V - - - 10 kA 53mm 75mm 88mm
RS Stock No. 125-1428
Mfr. Part No.1492-SPM2B010
kr 431,66
Each
Units
2 1 A - 1492 1492SPM Type B 277 V, 480V 96V - - 10 kA 35mm 75mm 88mm
RS Stock No. 125-1438
Mfr. Part No.1492-SPM3B010
kr 687,87
Each
Units
3 1 A - 1492 1492SPM Type B 277 V, 480V - - - 10 kA 53mm 75mm 88mm
RS Stock No. 125-1430
Mfr. Part No.1492-SPM2B040
kr 431,66
Each
Units
2 4 A - 1492 1492SPM Type B 277 V, 480V 96V - - 10 kA 35mm 75mm 88mm
RS Stock No. 125-1439
Mfr. Part No.1492-SPM3B020
kr 684,88
Each
Units
3 2 A - 1492 1492SPM Type B 277 V, 480V - - - 10 kA 53mm 75mm 88mm
RS Stock No. 125-1450
Mfr. Part No.1492-SPM3B630
kr 1 435,56
Each
Units
3 63 A - 1492 1492SPM Type B 277 V, 480V - - - 10 kA 53mm 75mm 88mm
RS Stock No. 125-1431
Mfr. Part No.1492-SPM2B050
kr 431,66
Each
Units
2 5 A - 1492 1492SPM Type B 277 V, 480V 96V - - 10 kA 35mm 75mm 88mm
RS Stock No. 125-1440
Mfr. Part No.1492-SPM3B040
kr 684,88
Each
Units
3 4 A - 1492 1492SPM Type B 277 V, 480V - - - 10 kA 53mm 75mm 88mm
RS Stock No. 125-1454
Mfr. Part No.1492-SPM1C040
kr 193,40
Each
Units
1 4 A - 1492 1492SPM Type C 277V 48V - - 10 kA 17.5mm 74mm 88mm
RS Stock No. 125-1496
Mfr. Part No.1492-SPM1D040
kr 245,24
Each
Units
1 4 A - 1492 1492SPM Type D 277V 48V - - 10 kA 17.5mm 74mm 88mm
RS Stock No. 125-1466
Mfr. Part No.1492-SPM1C630
kr 390,79
Each
Units
1 63 A - 1492 1492SPM Type C 277V 48V - - 10 kA 17.5mm 74mm 88mm
RS Stock No. 125-1510
Mfr. Part No.1492-SPM2D060
kr 344,93
Each
Units
2 6 A - 1492 1492SPM Type D 277 V, 480V 96V - - 10 kA 35mm 75mm 88mm
RS Stock No. 125-1451
Mfr. Part No.1492-SPM1C010
kr 193,40
Each
Units
1 1 A - 1492 1492SPM Type C 277V 48V - - 10 kA 17.5mm 74mm 88mm