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 Mounting Style Rated DC Voltage Breaking Capacity at Maximum Voltage Rating Length Width Depth Break Time
RS Stock No. 535-4352
Mfr. Part No.2CDS273001R0634
BrandABB
SGD142.39
Each
units
3 63 A - System M Pro S200 440V Type C - - 10 kA 88mm - 75.8mm -
RS Stock No. 527-9633
Mfr. Part No.S203-D32
BrandABB
SGD87.08
Each
units
3 32 A - System M Pro S200 440V Type D - - 6 kA - - 75.8mm -
RS Stock No. 746-7722
Mfr. Part No.S202-C32
BrandABB
SGD84.60
Each
units
2 32 A - System M Pro S200 400V Type C - - 6 kA 88mm - 69mm -
RS Stock No. 132-071
Mfr. Part No.2CDS272001R0104
BrandABB
SGD84.23
Each
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2 10 A - System M Pro S200 440V Type C - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 132-122
Mfr. Part No.2CDS272001R0164
BrandABB
SGD89.18
Each
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2 16 A - System M Pro S200 440V Type C - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 131-905
Mfr. Part No.2CDS272001R0404
BrandABB
SGD90.63
Each
units
2 40 A - System M Pro S200 440V Type C - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 746-7706
Mfr. Part No.S202-C6
BrandABB
SGD71.85
Each
units
2 6 A - System M Pro S200 400V Type C - - 6 kA 88mm 35mm 69mm -
RS Stock No. 514-0080
Mfr. Part No.S201-K1
BrandABB
SGD44.14
Each
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1 1 A - System M Pro S200 253V Type K - 72V 6 kA - 17.5mm 75.8mm -
RS Stock No. 746-7728
Mfr. Part No.S202-C25
BrandABB
SGD66.17
Each
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2 25 A - System M Pro S200 400V Type C - - 6 kA 88mm 35mm 69mm -
RS Stock No. 176-273
Mfr. Part No.S401MC32
BrandABB
SGD78.72
Each
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1 32 A - Smissline S400 230 V, 400V Type C - 60V 10 kA 91mm 18mm 97mm -
RS Stock No. 514-0125
Mfr. Part No.S201-K6
BrandABB
SGD38.77
Each
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1 6 A - System M Pro S200 253V Type K - 72V 6 kA 88mm 17.5mm 75.8mm -
RS Stock No. 132-009
Mfr. Part No.2CDS272001R0024
BrandABB
SGD97.89
Each
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2 2 A - System M Pro S200 440V Type C - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 435-263
Mfr. Part No.2CCS892001R0821
BrandABB
SGD287.78
Each
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2 100 A - High Performance S800 400 V, 690V Type D - - 36 kA - 53mm 88.5mm -
RS Stock No. 539-8217
Mfr. Part No.2CDS211001R0104
BrandABB
SGD23.48
Each
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1 10 A - System M Pro S200 440V Type C - 60V 6 kA 85mm 17.5mm 69mm -
RS Stock No. 131-961
Mfr. Part No.2CDS272001R0254
BrandABB
SGD85.64
Each
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2 25 A - System M Pro S200 440V Type C - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 527-9649
Mfr. Part No.S203-D40
BrandABB
SGD81.18
Each
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3 40 A - System M Pro S200 440V Type D - - 6 kA - 52.5mm 75.8mm -
RS Stock No. 535-4318
Mfr. Part No.2CDS273001R0324
BrandABB
SGD123.15
Each
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3 32 A - System M Pro S200 440V Type C - - 10 kA - - 75.8mm -
RS Stock No. 746-7781
Mfr. Part No.S203-C40
BrandABB
SGD99.75
Each
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3 40 A - System M Pro S200 400V Type C - - 6 kA - - 69mm -
RS Stock No. 131-983
Mfr. Part No.2CDS272001R0044
BrandABB
SGD96.23
Each
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2 4 A - System M Pro S200 440V Type C - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 746-7605
Mfr. Part No.S203-B32
BrandABB
SGD80.49
Each
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3 32 A - System M Pro S200 400V Type B - - 6 kA 88mm 52.5mm 69mm -