What is a Miniature Circuit Breaker (MCB)? 

Miniature Circuit Breaker (MCB) Rating 

Overload Current Rating- Amperes

Overload occurs as a result of putting too many appliances on one circuit. This will make the circuit draw more current than it or the cable can actually take. This could happen anywhere in the home, but especially in the kitchen. Take for instance, when the microwave, kettle, electric bob, blender, and dishwasher are all being used simultaneously. The MCB on the circuit cuts power, thereby preventing a case of overheating and possibly, fire in the cable and terminals.

Short Circuit Rating – Kilo Amperes

Short circuit occurs as a result of a fault somewhere in the circuit or electrical appliance. Short circuit is potentially more dangerous than overload as the speed and scale of the current is in a different order of magnitude. Short circuit happens when there is a direct connection between the neutral and live conductors. Without the resistance given by the usual circuit integrity, electrical current rushes through the circuit in a loop and increases the amperage by up to three thousand times in mere milliseconds.

The MCBs used in domestic installations are usually rated at 6000 amps or 6kA. SO the relationship between a typical domestic appliance rating and normal voltage (240v) allows that the over-current occurring as a result of short circuit should not exceed 6kA. However, in industrial and or commercial settings where 415v and large machinery are being used, it will be advised that a 10kA rated MCB is used. The ratings signify the max prospective fault current (PFC) that the MCB can take and still function properly by switching the circuit. Should the PFC be exceeded, this may cause failure in the MCB, which may result in contact welding shut.

Miniature Circuit Breaker (MCB)  Products 

ElectGo offers a wide range of MCBs from well-known brands - Schneider Electric , ABB

Miniature Circuit Breaker (MCB) Working Principle & Its Classification

Usually, and under normal working conditions, the MCB works as a switch (a manual switch) used to put the circuit ON or OFF. In short-circuit or overload situations, the device automatically trips. This will cause a current interruption in the load circuit and rectify the problem. The visual indication of the trip can be seen as the operating knob automatically moves to the OFF position.

The automatic operation/ tripping MCB can be gotten in two ways; magnetic tripping and thermal tripping.

During overload, the current coursing through the bimetal causes the temperature of the bimetal to rise. The heat that accompanies the rise in temperature within the bimetal then causes a deflection in the bimetal. This is due to the expansion of metals. The deflection releases the trip latch, and the contacts get separated. In other MCBs, the magnetic field created by the coil causes a pull on the bimetal such it causes a deflection which will activate the tripping mechanism.

In short circuit or heavy overload situations, magnetic tripping is used more. Under normal working conditions, the slug is held in place by the light spring. This is because the magnetic field created by the coil is not strong enough to attract the latch. When there is a problem in the circuit, and current flows through it, the magnetic field created by the coil is strong enough to pull the spring holding the slug in position thereby moving the slug and activating the tripping mechanism.

Most MCBs make use of a combination of both thermal and magnetic tripping mechanisms. In both operations, an arc is formed when the contacts start separating. Then through an arc runner, the arc is forced into arc splitter. The arc splitter plates are also referred to as arc chutes.  In which an arc is formed into a series of arcs and at the time, energy is extracted and cooled. Therefore the arrangement removes arcs.

MCB is used for protecting the circuit ( wiring, connected Load, equipment, appliances, etc.)  in cases of:

• Overload
• Short Circuit
• Over-current

All installations must be done by a fully qualified electrician on site. DO well to contact an electrician at sg.electgo.com they will get the job done. And note that there are certain standards to which most domestic wiring schemes adhere.

• 6 Amp- for standard lighting circuits
• 10 Amps- large lighting circuits- These are becoming rare in domestic settings as a result of  changes in technological trends tending towards lower lighting sources such as LED
• 16 Amps and 20 Amps- usually these two ratings are used in boilers and heaters depending on the power rating.
• 32 Amp – Ring Final. The technical term for a power circuit or sockets. A two-bedroom apartment, for example, can have 2 x 32A power circuits to separate downstairs and upstairs sockets. Larger apartments can have any number of 32 A circuits.
• 40 Amp – Cookers / electric hobs / small showers
• 50 Amp – 10kw Electric showers / Hot tubs.

Types of Miniature Circuit Breaker (MCB)

MCBs are installed in spaces depending on the need of the appliance. Hence, you will find multiple MCB types that can be used for a range of purposes. The most popular MCB types are A, B, C, D, K and Z. Of these, the most commonly used are B, C and D. These categories are often based on their trip curve or tripping capacities.

Uses of Miniature Circuit Breaker (MCB)

Free eBook - An Introduction Guide To Circuit Breaker

Reference: 

Schneider Electric: https://eshop.se.com/in/blog/post/mcb-miniature-circuit-breakers-guide-types-sizes-and-uses.html#:~:text=Types%20of%20MCB&text=The%20most%20popular%20MCB%20types,with%20small%20scale%20of%20operations.