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 Tripping Characteristics Rated AC Voltage Rated DC Voltage Breaking Capacity Mounting Style Length Width Depth Application
RS stock no. 772-1515
Mfr. Part No.A9N61526
R 1,542.74
Each
units
2 6 A - Acti 9 C60H-DC Type C - 500V - - - 36mm 73mm -
RS stock no. 772-1524
Mfr. Part No.A9N61522
R 1,528.21
Each
units
2 2 A - Acti 9 C60H-DC Type C - 500V - - 81mm 36mm 73mm -
RS stock no. 772-1511
Mfr. Part No.A9N61521
R 1,528.21
Each
units
2 1 A - Acti 9 C60H-DC Type C - 500V - - - 36mm 73mm -
RS stock no. 772-1518
Mfr. Part No.A9N61511
R 681.27
Each
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1 16 A - Acti 9 C60H-DC Type C - 250V - - 81mm - 73mm -
RS stock no. 772-1502
Mfr. Part No.A9N61506
R 625.66
Each
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1 6 A - Acti 9 C60H-DC Type C - 250V - - 81mm 18mm 73mm -
RS stock no. 772-1509
Mfr. Part No.A9N61508
R 668.91
Each
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1 10 A - Acti 9 C60H-DC Type C - 250V - - - 18mm 73mm -
RS stock no. 734-9068
Mfr. Part No.A9F77210
R 777.65
Each
units
2 10 A - Acti 9 iC60N Type C 12 → 60 V, 100 → 130 V, 220 → 240 V, 380 → 415 V, 400 V, 440 V 12 → 144V 6 kA - - 36mm - -
RS stock no. 772-1505
Mfr. Part No.A9N61502
R 650.29
Each
units
1 2 A - Acti 9 C60H-DC Type C - 250V - - 81mm - 73mm -
RS stock no. 772-1530
Mfr. Part No.A9N61531
R 1,697.04
Each
units
2 16 A - Acti 9 C60H-DC Type C - 500V - - - 36mm 73mm -
RS stock no. 772-1533
Mfr. Part No.A9N61533
R 1,688.29
Each
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2 25 A - Acti 9 C60H-DC Type C - 500V - - - 36mm 73mm -
RS stock no. 734-9239
Mfr. Part No.A9F77206
R 777.65
Each
units
2 6 A - Acti 9 iC60N Type C 12 → 60 V, 100 → 130 V, 220 → 240 V, 380 → 415 V, 400 V, 440 V 12 → 144V 6 kA - - - - -
RS stock no. 624-0327
Mfr. Part No.FAZ-C4/1
BrandEaton
R 412.06
Each
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1 4 A - XEffect FAZ Type C 230 V - 10 kA - 80mm 17.5mm 73.5mm -
RS stock no. 734-9598
Mfr. Part No.A9N21021
R 535.45
Each
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1 + N 3 A - Acti 9 DT40 Type C 400 V - 4.5 kA - - - - -
RS stock no. 860-8463
Mfr. Part No.3TX4422-2A
BrandSiemens
R 309.90
Each
units
- - - - - - - - - - - - - -
RS stock no. 791-3293
Mfr. Part No.A9F54110
R 380.61
Each
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1 10 A - Acti 9 iC60H Type C 12 → 60 V, 100 → 133 V, 220 → 240 V 12 → 48 V, 72 V 10 kA DIN Rail 85mm 18mm 78.5mm -
RS stock no. 772-1521
Mfr. Part No.A9N61528
R 1,571.88
Each
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2 10 A - Acti 9 C60H-DC Type C - 500V - - - 36mm 73mm -
RS stock no. 734-9141
Mfr. Part No.A9F77310
R 1,164.44
Each
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3 10 A - Acti 9 iC60N Type C 12 → 60 V, 100 → 130 V, 220 → 240 V, 380 → 415 V, 400 V, 440 V 12 → 144V 6 kA - - - - -
RS stock no. 790-8853
Mfr. Part No.A9F44110
R 429.55
Each
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1 10 A - Acti 9 iC60N Type C 12 → 60 V, 100 → 133 V, 220 → 240 V 12 → 48 V, 72 V 6 kA - - - 78.5mm -
RS stock no. 734-9273
Mfr. Part No.A9F77250
R 946.90
Each
units
2 50 A - Acti 9 iC60N Type C 12 → 60 V, 100 → 130 V, 220 → 240 V, 380 → 415 V, 400 V, 440 V 12 → 144V 6 kA - - 36mm - -
RS stock no. 734-9150
Mfr. Part No.A9F77316
R 1,164.44
Each
units
3 16 A - Acti 9 iC60N Type C 12 → 60 V, 100 → 130 V, 220 → 240 V, 380 → 415 V, 400 V, 440 V 12 → 144V 6 kA - - 54mm - -