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. 132-009
Mfr. Part No.2CDS272001R0024
BrandABB
HK$454.10
Each
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2 2 A - System M Pro S200 440 V Type C 10 kA - 125V 88mm 35mm 75.8mm -
RS Stock No. 535-4150
Mfr. Part No.2CDS271001R0164
BrandABB
HK$138.17
Each
units
1 16 A - System M Pro S200 253 V Type C 10 kA - 72V 88mm 17.5mm 75.8mm -
RS Stock No. 535-4188
Mfr. Part No.2CDS271001R0324
BrandABB
HK$138.17
Each
units
1 32 A - System M Pro S200 253 V Type C 10 kA - 72V 88mm 17.5mm 75.8mm -
RS Stock No. 131-983
Mfr. Part No.2CDS272001R0044
BrandABB
HK$445.92
Each
units
2 4 A - System M Pro S200 440 V Type C 10 kA - 125V 88mm 35mm 75.8mm -
RS Stock No. 132-122
Mfr. Part No.2CDS272001R0164
BrandABB
HK$356.27
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2 16 A - System M Pro S200 440 V Type C 10 kA - 125V 88mm 35mm 75.8mm -
RS Stock No. 535-5995
Mfr. Part No.2CDS271001R0165
BrandABB
HK$112.82
Each
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1 16 A - System M Pro S200 253 V Type B 10 kA - 72V 88mm 17.5mm 75.8mm -
RS Stock No. 746-7699
Mfr. Part No.S202-C2
BrandABB
HK$292.61
Each
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2 2 A - System M Pro S200 400 V Type C 6 kA - - - 35mm 69mm -
RS Stock No. 535-4251
Mfr. Part No.2CDS273001R0064
BrandABB
HK$644.71
Each
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3 6 A - System M Pro S200 440 V Type C 10 kA - - - - 75.8mm -
RS Stock No. 488-7457
Mfr. Part No.2CDS251001R0065 - S201B6
BrandABB
HK$101.65
Each
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1 6 A - System M Pro S200 253 V Type B 6 kA - 72V 88mm 17.5mm 75.8mm -
RS Stock No. 539-8267
Mfr. Part No.2CDS211001R0404
BrandABB
HK$84.58
Each
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1 40 A - System M Pro S200 440 V Type C 6 kA - 60V 85mm 17.5mm 69mm -
RS Stock No. 132-071
Mfr. Part No.2CDS272001R0104
BrandABB
HK$373.55
Each
units
2 10 A - System M Pro S200 440 V Type C 10 kA - 125V 88mm 35mm 75.8mm -
RS Stock No. 539-8223
Mfr. Part No.2CDS211001R0164
BrandABB
HK$89.12
Each
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1 16 A - System M Pro S200 440 V Type C 6 kA - 60V 85mm 17.5mm 69mm -
RS Stock No. 746-7637
Mfr. Part No.S204-B63
BrandABB
HK$1,000.00
Each
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4 63 A - System M Pro S200 400 V Type B 6 kA - - - 70mm 69mm -
RS Stock No. 746-8107
Mfr. Part No.2CDS274001R0635
BrandABB
HK$1,060.00
Each
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4 63 A - System M Pro S200 400 V Type B 10 kA - - 83mm 70mm 74.8mm -
RS Stock No. 707-6079
Mfr. Part No.2CCP844001R1259
BrandABB
HK$2,294.75
Each
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4 25 A - High Performance S800 - - 5 kA - 1200V 95mm 106mm 88.5mm -
RS Stock No. 539-8273
Mfr. Part No.2CDS213001R0065
BrandABB
HK$286.20
Each
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3 6 A - System M Pro S200 440 V Type B 6 kA - - 85mm 52.5mm 69mm -
RS Stock No. 488-6943
Mfr. Part No.2CDS251001R0325 - S201B32
BrandABB
HK$92.79
Each
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1 32 A - System M Pro S200 253 V Type B 6 kA - 72V 88mm 17.5mm 75.8mm -
RS Stock No. 131-927
Mfr. Part No.2CDS272001R0255
BrandABB
HK$397.25
Each
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2 25 A - System M Pro S200 440 V Type B 10 kA - 125V 88mm 35mm 75.8mm -
RS Stock No. 455-6327
Mfr. Part No.S202-C16
BrandABB
HK$566.55
Each
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3 - - System M Pro S200 - - - - - 57.5mm 96.5mm 46.5mm -
RS Stock No. 535-4122
Mfr. Part No.2CDS271001R0044
BrandABB
HK$155.22
Each
units
1 4 A - System M Pro S200 253 V Type C 10 kA - 72V 88mm 17.5mm 75.8mm -