L&T Switchgear Exora 20A MCB ‘C’ Curve 15kA 3 Pole TP BB30200C
All you need to know about MCB (What is an MCB and What is it used for?)
Nowadays, electrical devices are in abundance and sometimes we have to pay through the nose for some of them. I even know a few people who think of one or more of their appliances as their most prized possessions (Yes, I’m talking about you and your double door refrigerator!). But we sometimes forget about the safety measures that are essential to protect our electrical appliances.
A MCB or Miniature Circuit Breaker is a device that protects your appliances and your home in situations where voltage fluctuations may occur because of power surges. A MCB shuts off the power supply in case of an overload or short circuit. A MCB is like a fuse but better. A fuse usually has a wire which snaps in case of voltage fluctuations and must be replaced every time that happens, unlike MCB which can be reset using a button or a lever depending on the product. However, it is not wise to simply reset the MCB without finding out why the trip occurred in the first place.
This image shows how an MCB looks from the inside. It basically has an incoming terminal, an on/off switch, a magnetic coil, a bimetallic strip, and an outgoing terminal all arranged in a series. The switch is kept at the on position and power flows normally through the circuit. When there is an overload, the bimetallic strip gets overheated and causes it to switch off automatically.
There are 6 types of MCB – Type A, Type B, Type C, Type D, Type K, and Type Z. Each of these types has a different trip current curve, that is, the maximum amount of current it can handle before it trips. It can get quite confusing to pick the correct MCB and so here is a guide to help you out.
|Type of MCB||Trip Curve||Ideal Usage|
|A||2 to 3 times (instant)||Protection of highly sensitive devices|
|B||3 to 5 times||Lights; Low power domestic appliances|
|C||5 to 10 times||Motors, Transformers; Commercial, Domestic and Industrial Use (Most Common)|
|D||10 to 20 times||High power industrial use|
|K||8 to 12 times||Where inrush currents are high|
|Z||2 to 3 times (requires less than 0.1 seconds)||Semiconductor and control circuits|
When I say a trip curve is a certain number of times, I mean that the MCB will trip when the current reaches that many times the rated current. So if the rated current is 10A and you are using a type A MCB, the MCB will not trip till the current is at 20A, it might trip between 20A to 30A and it will definitely trip after the 30A mark is reached. Many places even mention the range required and you may use the appropriate device as the case may be.
Now you know how to keep your house safe from power fluctuations. (plug your product)
Big Brands in MCB – Siemens, L&T Switchgear, Legrand, Schneider Electric, ABB, Havells, etc.