How MCB Work

How MCB Work ?

In this post, we will find out a unique way to Understand – How MCB Work ? So let’s Start, An MCB is a little, intriguing gadget that protects you and your home from electrical problems. This breaker protects you from two eventualities.

How MCB Work
How MCB Work
  • First, there’s a short circuit,
  • and then there’s an overload.

In the event of a short circuit, the MCB trips in under three milliseconds, isolating the internal connections.

 

How this smart device detects current chaos so quickly and precisely?

How MCB Work
How MCB Work
 
The current spikes under both of the previously mentioned fault state, causing overheating and fusing or destroying the circuit. However, until you could do that, you had to physically replace the fuse every time it blew. Good luck with the outage, which happens all the time.
The circuit breaker is an automatic on-off mechanism that keeps one side of the wire moving and the other fixed during an electric fault. If the circuit opens wide, we’re done with the MCB design; once the fault has passed, simply manually turn it on. Before we go any further with the MCB design, a quick note about the current direction: an MCB activates in less than three milliseconds, which is significantly less than the time it takes for a human to blink.

How does this system recognize the occurrence of an electric fault?

The answer is that it has sensing elements that activate a triggering mechanism
How MCB Work
How MCB Work
 

Let’s start by looking at how we can construct a super-fast triggering mechanism that opens wide; a creative technique to accomplish this goal is shown here. As depicted, this device has a lever to which a rectangular ring is attached. In this arrangement, two springs and a central lever join the rectangular ring.

When the lever is moved up, the bottom spring compresses and the top spring expands. The forces of both of these springs are eventually transferred to the liver via the rectangular ring, and this force is in the upward direction.

How MCB Work
How MCB Work

As you can see, the rectangular ring is originally displaced from the center of the lever, therefore the torque created by the force acting on the rectangular ring is clockwise. If you release the lever in this position, the clockwise torque will return the lever to its original position.

However, if you push the lever higher, you’ll notice that the offset distance suddenly becomes positive, indicating that after a critical limit, the torque will act on it in a counterclockwise direction, and when the MCB is turned on, the structure of the MCB will prevent the lever from rotating any further counterclockwise.

How MCB Work
How MCB Work

Now, if an external trigger twists the lever slightly clockwise, the torque on the lever changes and the circuit opens wide quickly without the need for an external force.

As the operator lowers the lever, you can see how the mechanism works in super slow motion. After a little angle, the lever generates its own torque, and there is no need to add external power. Now the only question is whether the mechanism works in practice.

How can we generate this small input trigger or input motion when a fault occurs?

How MCB Work
How MCB Work

The best solution is to use an electromagnet; this coil produces magnetic fields that are proportional to the current passing through it; as the current increases, the magnetic field becomes stronger throughout the Post; note that in the case of a short circuit, the current can rise by a thousand times in magnitude in milliseconds.

An iron cylinder and pin are put inside this electromagnet on a spring slightly offset from its center, generating an extremely strong magnetic field. The powerful magnetic field pushes the cylinder downward, pushing the pin. This slight movement of the pin is the mechanism’s input trigger, and it causes the circuit to open, as we mentioned earlier.

How MCB Work
How MCB Work
If you’re wondering why this cylinder isn’t attracted down in regular current flow, it’s because the force in normal current flow isn’t strong enough to overcome spring tension, however short circuit current can reach up to 10 to 100 times the typical current force, causing the circuit to trip. Folks, the risk of a fault isn’t finished yet; once the contacts are opened, the current doesn’t just stop flowing; the fault current is of significant value, and it will cause an air discharge or current to flow through the air.

Arc Chute

How MCB Work
How MCB Work
To extinguish the arc, a component known as an arc runner or arc chute is used. An arc chute is an arrangement of parallel plates arranged at small intervals as the contacts separate the heavy fault current flowing as an arc triggers a massive temperature rise that can cause damage, so this arc should be killed. The resistance of current passing through the air increases with length and decreases with the area. In this case, we require a higher resistance to the current passing through the air.
Because the air is heated, the arc will be pushed up later, the arc will be fragmented into little chunks, diminishing its area with increased resistance, and the arc will fade away at current zero. Now let’s look at how the MCB protects the second sort of fault and overload scenario.

Overload Condition

How MCB Work
How MCB Work
An overload occurs when you use multiple appliances at the same time. Because all of the appliances in our homes are connected in parallel, such a scenario will result in an increase in current. This is another dangerous scenario that we must avoid. The current flow in a short circuit rises by 10 to 100 times the rated current, but it only rises two to five times in an overload. You could believe that using a different magnetic with a lower operating rating will fix the problem, but it won’t.

let’s see why

How MCB Work
How MCB Work
The problem with this new overload coil is that it will activate even if you simply turn on another electrical appliance. Fluorescent tubes, for example, have an in-rush current during startup that lasts about 10 milliseconds before returning to normal, so using a lower rated electromagnet will cause the breaker to trip unnecessarily when you turn on another electrical appliance. A bi-metallic strip is an excellent solution for solving the overload condition. This sensor is a little slower and offsets inrush currents because it only lasts 10 milliseconds, but it trips the MCB when the overload current persists for two seconds or more in a bi-metallic strip.

Heat causes the strip to bend slowly as the current rises, which pulls a c-shaped lever and therefore the main lever down, opening the contacts. The current value at which the bi-metallic strip should work can be modified with this screw, which is only set by manufacturers. Apart from the MCB, we offer additional breaker types built for different types of failures. We hope you now have a thorough grasp of a micro breaker. With this properly engineered device, you are secure from electrical calamities.

How MCB Work
How MCB Work
  1. RCD
  2. ELCB
  3. MCCB
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