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. 131-955
Mfr. Part No.2CDS272001R0324 - S202MC32
BrandABB
TWD1,813.00
Each
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2 32 A - System M Pro S200 440V Type C - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 746-7986
Mfr. Part No.S202-K6
BrandABB
TWD2,345.00
Each
units
2 6 A - System M Pro S200 400V Type K - - 6 kA 88mm 35mm 69mm -
RS Stock No. 539-8144
Mfr. Part No.2CDS211001R0105
BrandABB
TWD463.00
Each
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1 10 A - System M Pro S200 440V Type B - 60V 6 kA 85mm 17.5mm 69mm -
RS Stock No. 746-7659
Mfr. Part No.S201-C8
BrandABB
TWD564.00
Each
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1 8 A - System M Pro S200 230V Type C - - 6 kA 88mm 17.5mm 69mm -
RS Stock No. 746-7762
Mfr. Part No.S203-C13
BrandABB
TWD2,133.00
Each
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3 13 A - System M Pro S200 400V Type C - - 6 kA 88mm 52.5mm 69mm -
RS Stock No. 746-7573
Mfr. Part No.S202-B25
BrandABB
TWD1,362.00
Each
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2 25 A - System M Pro S200 400V Type B - - 6 kA 88mm 35mm 69mm -
RS Stock No. 132-059
Mfr. Part No.2CDS272001R0325
BrandABB
TWD1,462.00
Each
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2 32 A - System M Pro S200 440V Type B - 125V 10 kA 88mm 35mm 75.8mm -
RS Stock No. 746-8078
Mfr. Part No.S204-K63
BrandABB
TWD7,702.00
Each
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4 63 A - System M Pro S200 400V Type K - - 6 kA - - 69mm -
RS Stock No. 514-0080
Mfr. Part No.S201-K1
BrandABB
TWD962.00
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1 1 A - System M Pro S200 253V Type K - 72V 6 kA - 17.5mm 75.8mm -
RS Stock No. 539-8188
Mfr. Part No.2CDS211001R0325
BrandABB
TWD463.00
Each
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1 32 A - System M Pro S200 440V Type B - 60V 6 kA 85mm 17.5mm 69mm -
RS Stock No. 488-7457
Mfr. Part No.2CDS251001R0065 - S201B6
BrandABB
TWD577.00
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1 6 A - System M Pro S200 253V Type B - 72V 6 kA 88mm 17.5mm 75.8mm -
RS Stock No. 192-0841
Mfr. Part No.67011
BrandABB
TWD26,571.00
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- - - - - - - - - - - - - -
RS Stock No. 189-5641
Mfr. Part No.350236
BrandABB
TWD1,684.00
Each
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2 10 A S202L-C10 - - 400V Type C DIN Rail - 6 kA 69mm 35mm 88mm -
RS Stock No. 746-7712
Mfr. Part No.S202-C13
BrandABB
TWD1,459.00
Each
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2 13 A - System M Pro S200 400V Type C - - 6 kA 88mm 35mm 69mm -
RS Stock No. 746-7968
Mfr. Part No.S201-K63
BrandABB
TWD1,099.00
Each
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1 63 A - System M Pro S200 230V Type K - - 6 kA 88mm 17.5mm 69mm -
RS Stock No. 192-0833
Mfr. Part No.68070
BrandABB
TWD54,531.00
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4 250 A XT3N - - 690V - - 500V 27 kA 140mm 70mm 150mm -
RS Stock No. 189-5642
Mfr. Part No.442051
BrandABB
TWD5,643.00
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4 40 A F204 - - 230 / 400V - - - - 60mm 70mm 80mm Instantaneous
RS Stock No. 192-0890
Mfr. Part No.66805
BrandABB
TWD11,366.00
Each
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- - - - - - - - - - - - - -
RS Stock No. 746-7898
Mfr. Part No.S203-D8
BrandABB
TWD2,239.00
Each
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3 8 A - System M Pro S200 400V Type D - - 6 kA 88mm 52.5mm 69mm -
RS Stock No. 435-289
Mfr. Part No.2CCS861001R0634
BrandABB
TWD2,568.00
Each
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1 63 A - High Performance S800 400 V, 690V Type C - 250V 50 kA 95mm 26.5mm 88.5mm -