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. 776-3398
Mfr. Part No.A9F76216
MYR512.15
Each
units
2 16 A - Acti 9 iC60N 440 V Type B 6 kA - 125V 36mm - 85mm -
RS Stock No. 825-5835
Mfr. Part No.P1MB3PC06
BrandLovato
MYR292.36
Each
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3 6 A - ModuLo P1MB 230 V, 400 V Type C 10 kA - - 86.5mm 54mm 79.52mm -
RS Stock No. 776-8781
Mfr. Part No.A9F84110
MYR32.14
Each
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1 10 A - Acti 9 iC60H 230 V, 400 V Type C 10 kA - 72V - 18mm - -
RS Stock No. 489-6451
Mfr. Part No.5SY6320-7
BrandSiemens
MYR349.92
Each
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3 20 A - Sentron 5SY6 400 V Type C 6 kA - - 89.8mm 52.8mm 76mm -
RS Stock No. 825-6163
Mfr. Part No.P2MB3PC100
BrandLovato
MYR567.58
Each
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3 100 A - ModuLo P2MB 230 V, 400 V Type C 10 kA - 60V 85mm 81mm 80mm -
RS Stock No. 776-8955
Mfr. Part No.A9F73325
MYR168.39
Each
units
3 25 A - Acti 9 iC60N 440 V Type B 6 kA - 144V - 54mm - -
RS Stock No. 847-3245
Mfr. Part No.102167 & FAZ-C10/2-NA
BrandEaton
MYR503.34
Each
units
2 10 A - xEffect FAZ 240 → 415 V Type C 10 kA - - 35.4mm 105mm 75.5mm -
RS Stock No. 746-7980
Mfr. Part No.S202-K8
BrandABB
MYR352.66
Each
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2 8 A - System M Pro S200 400 V Type K 6 kA - - - - 69mm -
RS Stock No. 922-7204
Mfr. Part No.279138 | FAZ-C10/2-DC
BrandEaton
MYR572.73
Each
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2 10 A - xEffect FAZ - Type C 10 kA - 125V 35.4mm 65.5mm 80mm Computers, Control Instrumentation, External Load Circuit, HACR Internal/External Equipment, Internal/External Convenience Receptacle Circuit, Motor Control Circuit, PLC I/O Point, Power Conditioner, Power Supplies, Relay, Uninterruptable Power Supplies
RS Stock No. 791-3562
Mfr. Part No.A9F55320
MYR502.28
Each
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3 20 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. 769-4719
Mfr. Part No.239100 & FAZ6-C6/2
BrandEaton
MYR230.59
Each
units
2 6 A - xEffect FAZ6 230 → 400 V Type C 6 kA - - 80mm 17.5mm 61.5mm -
RS Stock No. 847-3572
Mfr. Part No.278886 & FAZ-D3/3
BrandEaton
MYR401.59
Each
units
3 3 A - xEffect FAZ 240 → 415 V Type D 10 kA - - 54mm 84.7mm 72.6mm -
RS Stock No. 488-7110
Mfr. Part No.2CDS251001R0105 - S201B10
BrandABB
MYR79.83
Each
units
1 10 A - System M Pro S200 253 V Type B 6 kA - 72V 88mm 17.5mm 75.8mm -
RS Stock No. 489-6625
Mfr. Part No.5SY6106-7
BrandSiemens
MYR89.64
Each
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1 6 A - Sentron 5SY6 230 V, 400 V Type C 6 kA - - 89.8mm 17.6mm 76.4mm -
RS Stock No. 847-3291
Mfr. Part No.102160 & FAZ-C2/2-NA
BrandEaton
MYR516.05
Each
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2 2 A - xEffect FAZ 240 → 415 V Type C 10 kA - - 35.4mm 105mm 75.5mm -
RS Stock No. 734-9605
Mfr. Part No.A9N21024
MYR152.95
Each
units
1 + N 10 A - Acti 9 DT40 400 V Type C 4.5 kA - - - - - -
RS Stock No. 776-9034
Mfr. Part No.A9F74320
MYR168.39
Each
units
3 20 A - Acti 9 iC60N 440 V Type C 6 kA - 144V - 54mm - -
RS Stock No. 489-6467
Mfr. Part No.5SY6325-7
BrandSiemens
MYR349.92
Each
units
3 25 A - Sentron 5SY6 400 V Type C 6 kA - - 89.8mm 52.8mm 76mm -
RS Stock No. 535-4352
Mfr. Part No.2CDS273001R0634
BrandABB
MYR466.99
Each
units
3 63 A - System M Pro S200 440 V Type C 10 kA - - 88mm - 75.8mm -
RS Stock No. 776-8980
Mfr. Part No.A9F74140
MYR24.06
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1 40 A - Acti 9 iC60N 230 V, 400 V Type C 6 kA - 72V - 18mm - -
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