Molded Case Vs. TM Breakers

What Ron said notwithstanding, there is a problem with your question as worded. You are asking for a comparison between what you perceive to be two options, but in fact you have mixed up three related, but not comparable things, because they are three ASPECTS of circuit breakers that could potentially exist in the SAME breaker.

Molded case relates to the CONSTRUCTION of the breaker, officially a Molded Case Circuit Breaker or MCCB as opposed to Insulated Case Circuit Breaker (ICCB) or Power Circuit Breaker (PCB) or Miniature Circuit Breaker (MCB).

Thermal Magnetic has to do with the TRIP SYSTEM of the breaker, as opposed to Magnetic Only or Electronic Trip or Hydraulic Trip.

100% has to do with the USE RATING of an MCCB, as opposed to a normal rating. Ron describes that well except there is no such thing as an 80% rated MCCB. There are normal MCCBs and there are 100% rated MCCBs. All MCCBs that are in a panel next to other breakers are normal breakers and all breakers are tested and listed at 100% of their rated value. But you cannot USE them that way. Breakers protect the conductors. Conductors are to be sized for 125% of their continuous load. The inverse of 125% is 80%, meaning that since the conductors are rated for 125% of the load, the maximum load is 80% of the rating of the conductors and since the breakers are sized to protect the conductors, you would never see more that 80% of the load on those breakers; continuously, which is where the 80% rated concept comes from. Then BECAUSE of that, panel mfrs take advantage of that fact in how the panel and MCCBs are designed with regard to heat dissipation, which is why MCCBs in a panel can be mounted next to each other, touching.

But it if you need to use an MCCB at 100% of its rating continuously, it CANNOT be used in a panel like that, it must have free air around it to dissipate the added heat. So because of THAT, breakers intended to be used at 100% continuously must be specifically LABELED as such, which will mean it cannot be used in a panel, except as a main. If it is not a Main, it must be separately enclosed by itself.

Then when you start discussing POWER Circuit Breakers (PCBs), where each PCB has its own totally separate cubicle in switchgear, those are ALL rated 100%, so its unnecessary to mention it.

SO back to your original question; you CAN have a Molded Case Thermal Magnetic 100% rated breaker. So thats why asking for a comparison is technically spurious.

If you want to learn more, please visit our website.

3

A circuit breaker is an automatically operated electrical switch used to protect electrical circuits from damage caused by overcurrent/overload. Overcurrent is an excessive current or current beyond the rating of protected equipment. Overload is a running overcurrent that causes overheating of protected equipment.

While there are numerous types of circuit breakers, this article will focus on the molded case circuit breaker or MCCB.

Sager contains other products and information you need, so please check it out.

MCCBs are used to provide circuit protection in applications requiring adjustable tripping, high current, and manual tripping of the circuit. They are often used in industrial applications such as panelboards, switchboards, motor control centers, and control panels.

MCCBs have two working principles: an electromagnetic element, protecting against overcurrent (short circuit), and a thermal element, protecting from overload.

The electromagnetic element is a solenoid coil that generates a weak electromagnetic field during normal operation. If a short circuit occurs, large current flows through the solenoid creating a strong electromagnetic field that instantly pulls the contacts open, interrupting the circuit.

The thermal element is a bimetallic contact that expands and contracts with temperature changes. This allows current flow during normal operation but as current increases beyond the preset value, the contact expands until it opens, interrupting current flow from the main supply and protecting the equipment. This also helps prevent overheating of electrical equipment and wiring due to excessive current flow.

MCCBs, like all circuit breakers, have five main parts:

1. Frame: protects internal parts of the circuit breaker
2. Operating mechanism: opens and closes the circuit breaker, typically a handle or lever to manually operate the circuit breaker
3. Trip unit: detects and interrupts an overload or short circuit
4. Contacts: allows current flow when closed and prevents current flow when open
5. Arc extinguisher: extinguishes the arc formed when the contacts open thus preventing damage to the device and surrounding equipment

Specifications of MCCBs

1. Current rating: MCCBs are designed for higher currents, typically 10A-A. This is generally the most important factor to consider when choosing an MCCB for the application.
2. Breaking capacity: This is the ability of an MCCB to interrupt a circuit during a fault, specified in kA. This is the maximum amount of current the device can safely interrupt before damage occurs internally to the device.
3. Tripping characteristics: MCCBs feature adjustable tripping characteristics allowing for customization of the devices response to overload conditions.

Advantages of MCCBs

• Higher current ratings
• Adjustable tripping characteristics
• High performance in a compact size
• Wide range of accessories for operating and automation requirements
• No possibility of phase failure all poles trip simultaneously

Disadvantages of MCCBs

• Higher cost than miniature circuit breakers and fuses
• Susceptible to dust and corrosion
• Not suitable for high voltages

To explore the full selection of circuit breakers from MISUMI, visit our page here. You can also check out the selection of fuses at this link.