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 Breaking Capacity at Maximum Voltage Rating Length Width Depth
RS Stock No. 825-6166
Mfr. Part No.P2MB2PC125
BrandLovato
SGD164.38
Each
units
2 125A - ModuLo P2MB 230 V, 400V Type C - - 60V 10 kA 85mm 54mm 80mm
RS Stock No. 825-5661
Mfr. Part No.P1MB2PB02
BrandLovato
SGD59.58
Each
units
2 2A - ModuLo P1MB 230 V, 400V Type B - - 80V 10 kA 86.5mm 36mm 79.52mm
RS Stock No. 825-5734
Mfr. Part No.P1MB2PC40
BrandLovato
SGD51.56
Each
units
2 40A - ModuLo P1MB 230 V, 400V Type C - - 80V 10 kA 86.5mm 36mm 79.52mm
RS Stock No. 825-5839
Mfr. Part No.P1MB3PC10
BrandLovato
SGD82.00
Each
units
3 10A - ModuLo P1MB 230 V, 400V Type C - - - 10 kA 86.5mm 54mm 79.52mm
RS Stock No. 825-5851
Mfr. Part No.P1MB3PC50
BrandLovato
SGD93.48
Each
units
3 50A - ModuLo P1MB 230 V, 400V Type C - - - 10 kA 86.5mm 54mm 79.52mm
RS Stock No. 825-5860
Mfr. Part No.P1MB3PC63
BrandLovato
SGD93.48
Each
units
3 63A - ModuLo P1MB 230 V, 400V Type C - - - 10 kA 86.5mm 54mm 79.52mm
RS Stock No. 825-5539
Mfr. Part No.P1MB1NC40
BrandLovato
SGD52.38
Each
units
- 40A - ModuLo P1MB 230V Type C - - 60V 6 kA 86.5mm 36mm 79.52mm
RS Stock No. 825-5731
Mfr. Part No.P1MB2PC32
BrandLovato
SGD51.56
Each
units
2 32A - ModuLo P1MB 230 V, 400V Type C - - 80V 10 kA 86.5mm 36mm 79.52mm
RS Stock No. 825-6163
Mfr. Part No.P2MB3PC100
BrandLovato
SGD170.51
Each
units
3 100A - ModuLo P2MB 230 V, 400V Type C - - 60V 10 kA 85mm 81mm 80mm
RS Stock No. 825-5582
Mfr. Part No.P1MB1PC02
BrandLovato
SGD20.94
Each
units
1 2A - ModuLo P1MB 230V Type C - - 60V 10 kA 86.5mm 18mm 79.52mm
RS Stock No. 825-5841
Mfr. Part No.P1MB3PC20
BrandLovato
SGD82.00
Each
units
3 20A - ModuLo P1MB 230 V, 400V Type C - - - 10 kA 86.5mm 54mm 79.52mm
RS Stock No. 825-5700
Mfr. Part No.P1MB2PC02
BrandLovato
SGD59.58
Each
units
2 2A - ModuLo P1MB 230 V, 400V Type C - - 80V 10 kA 86.5mm 36mm 79.52mm
RS Stock No. 825-6012
Mfr. Part No.P1MB4PD63
BrandLovato
SGD150.79
Each
units
4 63A - ModuLo P1MB 230 V, 400V Type D - - - 10 kA 86.5mm 72mm 79.52mm
RS Stock No. 825-5911
Mfr. Part No.P1MB4PB04
BrandLovato
SGD118.35
Each
units
4 4A - ModuLo P1MB 230 V, 400V Type B - - - 10 kA 86.5mm 72mm 79.52mm
RS Stock No. 825-5974
Mfr. Part No.P1MB4PC63
BrandLovato
SGD150.79
Each
units
4 63A - ModuLo P1MB 230 V, 400V Type C - - - 10 kA 86.5mm 72mm 79.52mm
RS Stock No. 825-6153
Mfr. Part No.P2MB2PC080
BrandLovato
SGD143.84
Each
units
2 80A - ModuLo P2MB 230 V, 400V Type C - - 60V 10 kA 85mm 54mm 80mm
RS Stock No. 825-5927
Mfr. Part No.P1MB4PB16
BrandLovato
SGD132.02
Each
units
4 16A - ModuLo P1MB 230 V, 400V Type B - - - 10 kA 86.5mm 72mm 79.52mm
RS Stock No. 825-5804
Mfr. Part No.P1MB3PB16
BrandLovato
SGD82.00
Each
units
3 16A - ModuLo P1MB 230 V, 400V Type B - - - 10 kA 86.5mm 54mm 79.52mm
RS Stock No. 825-5611
Mfr. Part No.P1MB1PC50
BrandLovato
SGD22.60
Each
units
1 50A - ModuLo P1MB 230V Type C - - 60V 10 kA 86.5mm 18mm 79.52mm
RS Stock No. 825-6015
Mfr. Part No.P1MB4PD40
BrandLovato
SGD132.02
Each
units
4 40A - ModuLo P1MB 230 V, 400V Type D - - - 10 kA 86.5mm 72mm 79.52mm