Thermal vs. Electromagnetic MCCB for Industrial Power Systems: Which Is Superior?

Have you ever dug deeper when your Circuit Breaker Trips for no reason? Have proper power protections failed to activate at the right time, or have you found that your circuit breakers are failing prematurely? If you have experienced either of these scenarios, you should be asking yourself if your MCCB type suits your specific operating environment.

The vast majority of MCCBs (Moulded Case Circuit Breakers)on the market today are thermal-magnetic mccbs that provide adequate protection from tripping for residential and commercial applications; however, in the following industrial environments, factories, motor control circuits, high temperature workshops, and renewable energy applications, thermal-magnetic mccb limits become clear. This is where the use of pure electromagnetic styled mccbs (such as the ELM1 electromagnetic) becomes very effective; Pure electromagnetic mccbs offer solutions to many of the problems in the industrial power system.

This article will provide you with a brief overview of the differences between Thermal-Magnetic mccb and Pure Electromagnetic MCCB, the applications of each, and why it's critical to select the right mccb in today's modern industrial environment.

What Is a Thermal-Magnetic MCCB?

The Thermal-Magnetic mccb is a widely used MCB and features two forms of protection: overload protection and short-circuit protection.

• Overload Protection:This is achieved via a bimetallic strip. When the bimetallic strip heats up from too much current flowing through it, it bends away from the circuit, resulting in a tripped finger; this is known as overload protection.
• Short-Circuit Protection: The short-circuit protection circuit is provided by an electromagnetic coil. The electromagnetic coil becomes energized when a large amount of current flows through the circuit (short). The magnetic field generated by the coil causes the breaker to trip immediately; this protection is called short-circuit protection.

The operation of the thermal-magnetic MCCB is simple - when the bimetallic strip is heated by too much current flowing through the bimetallic strip, the bimetallic strip will warp and open to trip the breaker during overload conditions; the electromagnetic coil opens the breaker within a very short period of time during heavy short-circuit current conditions.

One major disadvantage of the thermal protection system is that it relies on thermal deformation in order to protect from overload conditions—i.e., the thermal protection system is temperature dependent.

What Is a Pure Electromagnetic MCCB?

A pure electromagnetic MCCB does not use a bimetal thermal strip to protect against overload and short-circuit conditions like a TC-MCCB. Instead, MCCB trip settings depend exclusively on electromagnetic induction and do not rely on thermal influence for either overload or short-circuit protection. Pure electromagnetically based MCCBs provide more reliable trip operation than TC-MCCBs, offering higher voltage and/or current, lower risk of nuisance tripping in harsh conditions, and fewer maintenance requirements.

Core Differences: Electromagnetic MCCB vs Thermal-Magnetic MCCB

1. Temperature Stability

Industrial environments typically have an unpredictable temperature profile within their MCCB (indoor and outdoor); therefore, temperature stability is crucial to maintain consistent performance over time.

Thermal-Magnetic MCCBs: Typically, TC-MCCBs are subject to "thermal drift" from the time their enclosure has accumulated heat from the environment. For example, if the TC-MCCB has an ambient temperature of 51 degrees Celsius and the bimetal thermal member has "remembered" that temperature for too long, then when it comes to needing to trip, it will not be able to because of this drift, causing excess delay in operation. Excessive heating, either from inside or outside the enclosure, can lead to false trip operation, adding to unplanned downtime due to nuisance tripping, as well as inefficient operation.

Pure Electromagnetic MCCBs: Pure electromagnetic MCCB trip settings remain absolutely stable even when thermal conditions may vary greatly. They can perform predictably well in very high-temperature environments and carry heavy, continuous loads without adding risk due to failure because of overheating.

2. Motor Load Adaptability

Most operational motors in industrial applications develop inrush currents (up to 3-5 times higher than the rated current) that are higher than normal while starting up. An MCCB that is not functioning properly must tell the difference between these temporary increases and true faults in current.

Thermal-Magnetic Breakers: These breakers tend to be too responsive to changes in current, as many mistakenly classify motor inrush changes with overload. This leads to the breaker being tripped too often, which can interrupt operational functions and therefore reduce efficiency.

Pure Electromagnetic Breakers: These breakers have been specifically designed for motor application and therefore have advanced technology for sensing current to distinguish a motor inrush from a true overload. This allows them to perform equally in applications that regularly involve starting a motor.

3. Fault Response and Protection Accuracy

To minimize damage to critical electrical equipment, the ability to quickly sense and trip a fault is very important.

Thermal-Magnetic Circuit Breakers: They place a time delay on tripping a fault, as their thermal overload protection is produced by heating a bimetallic strip and deforming the strip. Therefore, the ability to immediately sense a surge of current is limited with this type of breaker, which results in more damage to equipment.

Pure Electromagnetic Circuit Breakers: Based on the principles of electromagnetic induction, pure electromagnetic circuit breakers have instantaneously tripping circuits that are capable of responding to short-circuit and overload conditions within microseconds. Consequently, this type of circuit breaker isolates the fault more quickly, thus reducing the risk of damage to the motor, cable, and other sensitive equipment.

4. Long-Term Operational Reliability

Circuit breakers used in an industrial setting need to perform reliably over time and provide continued performance despite the wear that occurs through everyday use.

Thermal-Magnetic Circuit Breakers: Due to the extremes of heat and cold, bimetallic strips are subject to material fatigue, which impacts the trip accuracy over time. Outdated circuit breakers can sometimes cause both unwanted trips and also fail to trip correctly.

Pure Electromagnetic MCCBs: An ELM1 electromagnetic type MCCB (molded case circuit breaker) will not suffer from high-temperature damage due to thermal degradation. There are no thermal degradation components to limit their accuracy; therefore, they will maintain accurate tripping characteristics throughout their life, which is designed to provide for a minimum of 125,000 mechanical cycles before parts need to be repaired or replaced.

When Should You Choose an Electromagnetic MCCB?

Pure electromagnetic MCCBs are not the best choice in lower-demand environments such as residential applications or stationary loads; however, electromagnetic MCCBs are extremely valuable in the following industrial applications:

• Heavily heated production shops and heat-centered distribution cabinets
• Motors that cycle on and off frequently for motor control applications
• Renewable energy generation is affected by constantly changing load conditions in renewable energy
• Unattended electrical distribution systems where no false tripping is acceptable
• Marine and industrial applications requiring high reliability over an extended period of time

Can Thermal-Magnetic MCCBs Still Be Used?

Absolutely, thermal-magnetic MCCBs provide an economical choice in residential power applications, or in smaller commercial buildings when either power requirements or temperature fluctuations are stable.

The key in these applications is determining the type of MCCB required based on the conditions expected in that application. In low- or stable-demand applications, thermal-magnetic MCCBs generally meet performance and durability requirements. However, in industrial applications where precise performance and reliability at high-demand levels are paramount, a pure electromagnetic MCCB such as an ELM1 is a far superior choice.

Final Thoughts

The key differences between a thermal-magnetic MCCB and a pure electromagnetic MCCB are adaptability to their operating conditions and reliability over time. Thermal-magnetic MCCBs are subject to thermal drift, can experience mis-tripping if exposed to high temperatures, and can exhibit reduced accuracy as the thermal-magnetic MCCB ages. Because of this, thermal-magnetic MCCBs are not the best choice in industrial operations where precision is necessary for operation 24/7.

Conversely, ELM1 electromagnetic MCCBs directly address these issues by being temperature-independent, very rapid in operation, and extremely reliable under various operating conditions. By eliminating the problems associated with thermal-magnetic MCCBs, ELM1 electromagnetic MCCBs protect industrial equipment from overloads, short-circuits, and other electrical problems that may disrupt operations.

If you are experiencing intermittent or unreliable MCCB performance, you might want to consider upgrading to an ELM1 electromagnetic MCCB. Please contact us for a personalized consultation, and we will work with you to put together an appropriate solution for your industrial application.