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. 776-3219
Mfr. Part No.A9N61530
MYR612.13
Each
units
2 15 A - Acti 9 C60H-DC - Type C 20 kA - 500V 36mm 73mm 81mm -
RS Stock No. 791-3332
Mfr. Part No.A9F54206
MYR299.36
Each
units
2 6 A - Acti 9 iC60H 440 V, 12 → 133 V, 220 → 240 V, 380 → 415 V Type C 10 kA DIN Rail 100 → 133V 85mm 36mm 78.5mm -
RS Stock No. 791-3556
Mfr. Part No.A9F55306
MYR544.67
Each
units
3 6 A - Acti 9 iC60H 440 V, 12 → 133 V, 220 → 240 V, 380 → 415 V Type D 10 kA DIN Rail 100 → 133V 85mm 54mm 78.5mm -
RS Stock No. 535-4138
Mfr. Part No.2CDS271001R0064
BrandABB
MYR97.58
Each
units
1 6 A - System M Pro S200 253 V Type C 10 kA - 72V 88mm 17.5mm 75.8mm -
RS Stock No. 489-6603
Mfr. Part No.5SY6110-7
BrandSiemens
MYR81.96
Each
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1 10 A - Sentron 5SY6 230 V, 400 V Type C 6 kA - - 89.8mm 17.6mm 76.4mm -
RS Stock No. 734-9068
Mfr. Part No.A9F77210
MYR350.84
Each
units
2 10 A - Acti 9 iC60N 400 V, 440 V, 100 → 130 V, 12 → 60 V, 220 → 240 V, 380 → 415 V Type C 6 kA - 12 → 144V - 36mm - -
RS Stock No. 734-9589
Mfr. Part No.A9N21020
MYR191.17
Each
units
1 + N 2 A - Acti 9 DT40 400 V Type C 4.5 kA - - - - - -
RS Stock No. 791-3158
Mfr. Part No.A9F53104
MYR113.46
Each
units
1 4 A - Acti 9 iC60H 100 → 133 V, 12 → 60 V, 220 → 240 V Type B 10 kA DIN Rail 72 V, 12 → 48 V 85mm 18mm 78.5mm -
RS Stock No. 707-6091
Mfr. Part No.2CCP844001R1829
BrandABB
MYR2,297.78
Each
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4 100 A - High Performance S800 - - 5 kA - 1200V 95mm 106mm 88.5mm -
RS Stock No. 864-4320
Mfr. Part No.PLSM-C20-MW
MYR89.59
Each
units
1 20 A - xPole PLSM 230 V ac Type C 10 kA - 48V 17.5mm 80mm 75mm -
RS Stock No. 622-0008
Mfr. Part No.5SY4101-7
BrandSiemens
MYR113.57
Each
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1 1 A - Sentron 5SY4 230 V, 400 V Type C 10 kA - - 89.8mm 17.6mm 76.4mm -
RS Stock No. 381-5811
Mfr. Part No.8720S
MYR32.17
Each
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- - - - - - - - - - - - - -
RS Stock No. 791-3382
Mfr. Part No.A9F54316
MYR398.92
Each
units
3 16 A - Acti 9 iC60H 440 V, 12 → 133 V, 220 → 240 V, 380 → 415 V Type C 10 kA DIN Rail 100 → 133V 85mm 54mm 78.5mm -
RS Stock No. 776-8823
Mfr. Part No.A9F84320
MYR174.40
Each
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3 20 A - Acti 9 iC60H 440 V Type C 10 kA - 144V - 54mm - -
RS Stock No. 746-7652
Mfr. Part No.S201-C4
BrandABB
MYR88.30
Each
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1 4 A - System M Pro S200 230 V Type C 6 kA - - 88mm 17.5mm 69mm -
RS Stock No. 539-8245
Mfr. Part No.2CDS211001R0204
BrandABB
MYR69.57
Each
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1 20 A - System M Pro S200 440 V Type C 6 kA - 60V 85mm 17.5mm 69mm -
RS Stock No. 776-3060
Mfr. Part No.A9N18364
MYR1,672.68
Each
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3 63 A - Acti 9 C120N 440 V Type C 10 kA, 20 kA - ≤375V - 73mm 81mm -
RS Stock No. 535-4201
Mfr. Part No.2CDS271001R0504
BrandABB
MYR110.00
Each
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1 50 A - System M Pro S200 253 V Type C 10 kA - 72V 88mm 17.5mm 75.8mm -
RS Stock No. 734-9315
Mfr. Part No.A9F94425
MYR1,827.66
Each
units
4 25 A - Acti 9 iC60L 100 → 130 V, 12 → 60 V, 220 → 240 V, 380 → 415 V, 400 V, 440 V Type C 10 kA - 12 → 250V - 72mm - -
RS Stock No. 791-3146
Mfr. Part No.A9F53102
MYR163.13
Each
units
1 2 A - Acti 9 iC60H 100 → 133 V, 12 → 60 V, 220 → 240 V Type B 10 kA DIN Rail 72 V, 12 → 48 V 85mm 18mm 78.5mm -