Molded case circuit breaker, application and accessories!

Do you know what a molded case circuit breaker is? Do you know where this type of circuit breaker is used? In this article the World of Electrical shows a molded case circuit breaker, explaining in detail its features, applications and mainly, what is the difference between the molded case circuit breaker and the mini circuit breakers, so come on guys!

Molded case circuit breaker
For those unfamiliar, molded case circuit breakers were developed to protect distribution circuits, generators and motors. They are generally found in different rated current values.

In this article, we will use for example a molded case circuit breaker from Tramontina that supports a current of up to 250A, but you can find circuit breakers from this same manufacturer that support currents between 50A and 800A.

Molded case circuit breaker accessories
Discover the functions and accessories of a molded case circuit breaker!

Molded case circuit breaker: Structure
In case you don’t know, this type of circuit breaker is a protection device that shuts down the circuit when there is an overload, short circuit or other electrical failures. The manufacture of this circuit breaker has the main objective of supporting high short-circuit currents, and its shielded box prevents access to the interior of the circuit breaker.

They are assembled in pre-molded thermoplastic boxes, forming the outer housing of the circuit breaker. That is why the name molded case circuit breaker, precisely because of the type of armored assembly of the circuit breaker! The manufacture and development of these molded case circuit breakers meet the NBR 60947 standard, which is the standard response for low voltage control and switching devices.

The difference for mini circuit breaker
In addition to the housing structure that we mentioned earlier, the other components and internal contacts of the molded case circuit breakers are much more robust, and the arc-extinguishing chambers are capable of interrupting the circuit with currents 20 to 30 times greater than those common circuit breakers.

Many professionals in the Electrical Industry may claim that there are mini circuit breakers and molded case circuit breakers capable of interrupting the same amount of electrical current, and that is true! However, even so there are some important differences such as:

A molded case circuit breaker is more robust
Molded case circuit breaker withstands much greater short-circuit current
A molded case circuit breaker can have accessories
Molded case circuit breaker:
Molded case circuit breakers are mainly applied in industrial environments, where interruptions with high short-circuit current occur, but we can also see this type of circuit breaker in compact switchboards. So we can find these circuit breakers in the general low voltage picture in commercial establishments and condominiums for example.

They can also be used for the protection of electric motors, protection of distribution circuits and protection of generators. As the molded case circuit breaker is also developed to perform electrical maneuvers, in some specific situations it can be used to act as a circuit breaker or disconnector.

Molded case circuit breaker: Accessories
We said earlier that one of the main differences of this type of circuit breaker is the possibility of having accessories, right? Now you will know the installation and application of three accessories for this molded case circuit breaker.

The first two accessories are the trip coil and the auxiliary contact, which are inside the circuit breaker as shown in the image below! Each accessory has a right fitting position, that is, on the right side of the circuit breaker is the trip coil, and the one on the left side is the auxiliary contact.

How to choose the best circuit breaker?
The trip coil and auxiliary contact are accessories of a molded case circuit breaker!

The coil is responsible for disconnecting the circuit breaker remotely! An example of use is through a button on the control panel that is located in a room far from this circuit breaker.

The auxiliary contact is a type of micro switch with reversible contact, used to indicate the status of the circuit breaker, showing whether it is in the “ON” position or in the “OFF” position. One way of signaling this is by using two traffic lights of different colors.

The third accessory is the manual rotary drive and it is an external drive mechanism. Its function is to turn the molded case circuit breaker on or off without having to open the panel door, and installation is very simple! Simply attach the bracket and screw the screws into the circuit breaker housing.

How to choose the best circuit breaker?
See how to install the manual rotary drive on the molded case circuit breaker

Then just plug the stem into the slot and tighten it, lastly just attach the key to the stem and the accessory is ready to use. It has a safety lock that prevents the electrical panel from opening while the drive is in the ON position.