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. 791-3405
Mfr. Part No.A9F54363
MYR616.50
Each
units
3 63 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. 514-0248
Mfr. Part No.S203-K32
BrandABB
MYR470.82
Each
units
3 32 A - System M Pro S200 440 V Type K 6 kA - - 88mm - 75.8mm -
RS Stock No. 776-8784
Mfr. Part No.A9F84116
MYR32.14
Each
units
1 16 A - Acti 9 iC60H 230 V, 400 V Type C 10 kA - 72V - 18mm - -
RS Stock No. 124-3156
Mfr. Part No.5SY4150-7
BrandSiemens
MYR201.77
Each
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1 50 A - Sentron 5SY4 230 V, 400 V Type C 10 kA - - 17.6mm 76.4mm 89.8mm Industrial, Plant Engineering
RS Stock No. 776-3070
Mfr. Part No.A9N18371
MYR2,288.44
Each
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4 63 A - Acti 9 C120N 440 V Type C 10 kA, 20 kA - ≤500V 108mm 73mm 81mm -
RS Stock No. 776-3026
Mfr. Part No.A9N18469
MYR2,862.94
Each
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3 100 A - Acti 9 C120H 440 V Type C 15 kA, 30 kA - ≤375V - 73mm 81mm -
RS Stock No. 776-8924
Mfr. Part No.A9F73216
MYR108.25
Each
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2 16 A - Acti 9 iC60N 440 V Type B 6 kA - 144V - 36mm - -
RS Stock No. 776-9056
Mfr. Part No.A9F74406
MYR399.92
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4 6 A - Acti 9 iC60N 440 V Type C 6 kA - 250V - 72mm - -
RS Stock No. 776-3089
Mfr. Part No.A9N18386
MYR1,878.78
Each
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3 63 A - Acti 9 C120N 440 V Type D 10 kA, 20 kA - ≤375V 81mm 73mm 81mm -
RS Stock No. 776-3174
Mfr. Part No.A9N61510
MYR327.32
Each
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1 15 A - Acti 9 C60H-DC - Type C 20 kA - 250V - 73mm 81mm -
RS Stock No. 776-3206
Mfr. Part No.A9N61525
MYR726.91
Each
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2 5 A - Acti 9 C60H-DC - Type C 20 kA - 500V - - 81mm -
RS Stock No. 624-0327
Mfr. Part No.FAZ-C4/1
BrandEaton
MYR102.91
Each
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1 4 A - xEffect FAZ 230 V Type C 10 kA - - 80mm 17.5mm 73.5mm -
RS Stock No. 791-3344
Mfr. Part No.A9F54216
MYR314.43
Each
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2 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 36mm 78.5mm -
RS Stock No. 769-4545
Mfr. Part No.FAZ6-C10/1N
BrandEaton
MYR188.38
Each
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1 + N 10 A - xEffect FAZ6 230 → 400 V Type C 6 kA - - 80mm 17.5mm 61.5mm -
RS Stock No. 791-3290
Mfr. Part No.A9F54106
MYR101.94
Each
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1 6 A - Acti 9 iC60H 100 → 133 V, 12 → 60 V, 220 → 240 V Type C 10 kA DIN Rail 72 V, 12 → 48 V 85mm 18mm 78.5mm -
RS Stock No. 772-1303
Mfr. Part No.5SY4210-7
BrandSiemens
MYR404.30
Each
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2 10 A - Sentron 5SY4 400 V Type C 10 kA - - 90mm 36mm 76mm -
RS Stock No. 791-3152
Mfr. Part No.A9F53106
MYR91.82
Each
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1 6 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. 772-1524
Mfr. Part No.A9N61522
MYR667.88
Each
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2 2 A - Acti 9 C60H-DC - Type C - - 500V 81mm 36mm 73mm -
RS Stock No. 734-9239
Mfr. Part No.A9F77206
MYR384.49
Each
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2 6 A - Acti 9 iC60N 100 → 130 V, 12 → 60 V, 220 → 240 V, 380 → 415 V, 400 V, 440 V Type C 6 kA - 12 → 144V - - - -
RS Stock No. 791-3284
Mfr. Part No.A9F54102
MYR145.25
Each
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1 2 A - Acti 9 iC60H 100 → 133 V, 12 → 60 V, 220 → 240 V Type C 10 kA DIN Rail 72 V, 12 → 48 V 85mm 18mm 78.5mm -
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