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庫存編號 825-5762
製造零件編號P1MB2PD20
BrandLovato
HK$311.71
單位
2 20 A - ModuLo P1MB 230 V, 400V Type D - 80V 10 kA 86.5mm 36mm 79.52mm -
RS庫存編號 825-5949
製造零件編號P1MB4PB63
BrandLovato
HK$911.64
單位
4 63 A - ModuLo P1MB 230 V, 400V Type B - - 10 kA 86.5mm 72mm 79.52mm -
RS庫存編號 825-5712
製造零件編號P1MB2PC06
BrandLovato
HK$341.64
單位
2 6 A - ModuLo P1MB 230 V, 400V Type C - 80V 10 kA 86.5mm 36mm 79.52mm -
RS庫存編號 825-5835
製造零件編號P1MB3PC06
BrandLovato
HK$530.99
單位
3 6 A - ModuLo P1MB 230 V, 400V Type C - - 10 kA 86.5mm 54mm 79.52mm -
RS庫存編號 825-5545
製造零件編號P1MB1PB01
BrandLovato
HK$203.65
單位
1 1 A - ModuLo P1MB 230V Type B - 60V 10 kA 86.5mm 18mm 79.52mm -
RS庫存編號 825-5974
製造零件編號P1MB4PC63
BrandLovato
HK$911.64
單位
4 63 A - ModuLo P1MB 230 V, 400V Type C - - 10 kA 86.5mm 72mm 79.52mm -
RS庫存編號 825-5609
製造零件編號P1MB1PC32
BrandLovato
HK$118.00
單位
1 32 A - ModuLo P1MB 230V Type C - 60V 10 kA 86.5mm 18mm 79.52mm -
RS庫存編號 825-5661
製造零件編號P1MB2PB02
BrandLovato
HK$360.17
單位
2 2 A - ModuLo P1MB 230 V, 400V Type B - 80V 10 kA 86.5mm 36mm 79.52mm -
RS庫存編號 825-5598
製造零件編號P1MB1PC10
BrandLovato
HK$118.00
單位
1 10 A - ModuLo P1MB 230V Type C - 60V 10 kA 86.5mm 18mm 79.52mm -
RS庫存編號 825-5747
製造零件編號P1MB2PC63
BrandLovato
HK$341.64
單位
2 63 A - ModuLo P1MB 230 V, 400V Type C - 80V 10 kA 86.5mm 36mm 79.52mm -
RS庫存編號 188-1644
製造零件編號P1MBUH2PC03
BrandLovato
HK$810.72
單位
2 - - - - - - DIN Rail Mount - - 36mm 75.52mm 116mm -
RS庫存編號 188-1645
製造零件編號P1MBUH2PC04
BrandLovato
HK$776.43
單位
2 - - - - - - DIN Rail Mount - - 36mm 75.52mm 116mm -
RS庫存編號 188-1654
製造零件編號P1MBUH3PC03
BrandLovato
HK$1,063.58
單位
3 - - - - - - DIN Rail Mount - - 54mm 75.52mm 116mm -
RS庫存編號 188-1646
製造零件編號P1MBUH2PC06
BrandLovato
HK$690.18
單位
2 - - - - - - DIN Rail Mount - - 36mm 75.52mm 116mm -
RS庫存編號 825-5797
製造零件編號P1MB3PB04
BrandLovato
HK$565.15
單位
3 4 A - ModuLo P1MB 230 V, 400V Type B - - 10 kA 86.5mm 54mm 79.52mm -
RS庫存編號 825-5542
製造零件編號P1MB1PB04
BrandLovato
HK$183.90
單位
1 4 A - ModuLo P1MB 230V Type B - 60V 10 kA 86.5mm 18mm 79.52mm -
RS庫存編號 188-1676
製造零件編號ULC256A18A
BrandLovato
HK$1,562.93
單位
2 - - - - - - - - - 1000mm - - -
RS庫存編號 825-5942
製造零件編號P1MB4PC01
BrandLovato
HK$894.31
單位
4 1 A - ModuLo P1MB 230 V, 400V Type C - - 10 kA 86.5mm 72mm 79.52mm -
RS庫存編號 188-1655
製造零件編號P1MBUH3PC04
BrandLovato
HK$1,078.45
單位
3 - - - - - - DIN Rail Mount - - 54mm 75.52mm 116mm -
RS庫存編號 825-5952
製造零件編號P1MB4PC10
BrandLovato
HK$798.12
單位
4 10 A - ModuLo P1MB 230 V, 400V Type C - - 10 kA 86.5mm 72mm 79.52mm -