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. 776-6864
Mfr. Part No.A9F04104
kr 236,65
Each
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1 4A - Acti 9 iC60N Type C 230 V, 400V 72V - - 6 kA 18mm - 91mm
RS Stock No. 776-6974
Mfr. Part No.A9F04316
kr 811,17
Each
Units
3 16A - Acti 9 iC60N Type C 440V 133V - - 6 kA 54mm 78.5mm 91mm
RS Stock No. 776-6915
Mfr. Part No.A9F04204
kr 674,57
Each
Units
2 4A - Acti 9 iC60N Type C 440V 133V - - 6 kA - - 91mm
RS Stock No. 776-6912
Mfr. Part No.A9F04210
kr 597,33
Each
Units
2 10A - Acti 9 iC60N Type C 440V 133V - - 6 kA - 78.5mm 91mm
RS Stock No. 776-6918
Mfr. Part No.A9F04206
kr 558,19
Each
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2 6A - Acti 9 iC60N Type C 440V 133V - - 6 kA - 78.5mm 91mm
RS Stock No. 776-2682
Mfr. Part No.A9N21552
kr 531,36
Each
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- 1A - Acti 9 iDPN Type C 230V - - - 10 kA 18mm - 80mm
RS Stock No. 776-6851
Mfr. Part No.A9F04102
kr 298,08
Each
Units
1 2A - Acti 9 iC60N Type C 230 V, 400V 72V - - 6 kA - - 91mm
RS Stock No. 776-6867
Mfr. Part No.A9F04106
kr 242,09
Each
Units
1 6A - Acti 9 iC60N Type C 230 V, 400V 72V - - 6 kA - 78.5mm 91mm
RS Stock No. 776-6924
Mfr. Part No.A9F04216
kr 550,54
Each
Units
2 16A - Acti 9 iC60N Type C 440V 133V - - 6 kA - - 91mm
RS Stock No. 776-2698
Mfr. Part No.A9N21555
kr 466,56
Each
Units
- 6A - Acti 9 iDPN Type C 230V - - - 10 kA 18mm - 80mm
RS Stock No. 776-6760
Mfr. Part No.A9F03104
kr 138,28
Each
Units
1 4A - Acti 9 iC60N Type B 230 V, 400V 72V - - 6 kA - - 91mm
RS Stock No. 776-6707
Mfr. Part No.A9N21557
kr 466,56
Each
Units
- 16A - Acti 9 iDPN Type C 230V - - - 10 kA - 70mm 80mm
RS Stock No. 776-2317
Mfr. Part No.A9F07210
kr 665,88
Each
Units
2 10A - Acti 9 iC60H Type C 440V 133V - - 10 kA - 78.5mm 91mm
RS Stock No. 776-6726
Mfr. Part No.A9N21597
kr 1 159,27
Each
Units
- 16A - Acti 9 iDPN Type C 400V - - - 10 kA - 70mm 80mm
RS Stock No. 776-2291
Mfr. Part No.A9F07202
kr 733,41
Each
Units
2 2A - Acti 9 iC60H Type C 440V 133V - - 10 kA 36mm - 91mm
RS Stock No. 776-2310
Mfr. Part No.A9F07216
kr 645,15
Each
Units
2 16A - Acti 9 iC60H Type C 440V 133V - - 10 kA - 78.5mm 91mm
RS Stock No. 776-6996
Mfr. Part No.A9F04363
kr 2 022,67
Each
Units
3 63A - Acti 9 iC60N Type C 440V 133V - - 6 kA - 78.5mm 91mm
RS Stock No. 776-2415
Mfr. Part No.A9F07432
kr 1 394,50
Each
Units
4 32A - Acti 9 iC60H Type C 440V 250V - - 10 kA - - 91mm
RS Stock No. 776-2112
Mfr. Part No.A9F06216
kr 366,64
Each
Units
2 16A - Acti 9 iC60H Type B 440V 133V - - 10 kA 36mm 78.5mm 91mm
RS Stock No. 776-6811
Mfr. Part No.A9F03220
kr 438,44
Each
Units
2 20A - Acti 9 iC60N Type B 440V 133V - - 6 kA - 78.5mm 91mm