The short answer is no, thermal-magnetic circuit breakers (TMCBs) are not being entirely replaced by electronic/adjustable trip circuit breakers (ETCBs), but they are being increasingly superseded in certain applications.

Here's a breakdown of the reasons why

Thermal-Magnetic Circuit Breakers (TMCBs):
Pros



Simple and Reliable

Well-established technology with a long history.

Cost-Effective

Generally less expensive than ETCBs.

Good for Basic Protection

Provides adequate overcurrent and short-circuit protection for many common applications.

No External Power Required

Operates using the thermal and magnetic effects of the current itself.

Easy to Understand and Maintain

Familiar technology for most electricians.

Cons



Fixed Trip Curves

The trip characteristics are predetermined and cannot be adjusted after manufacturing.

Less Accurate

Trip times can vary depending on ambient temperature and previous loading.

Limited Features

Typically only provide basic overcurrent and short-circuit protection.

Slower Response to Overloads

Thermal element can be slow to respond to moderate overloads.

Electronic/Adjustable Trip Circuit Breakers (ETCBs)



Pros



Adjustable Trip Curves

Offers flexibility to tailor protection to specific load requirements and system coordination. This is a HUGE advantage.

Greater Accuracy

More precise and consistent tripping characteristics.

Advanced Features

Can include features like ground fault protection, pre-alarms, metering, communication capabilities (e.g., Modbus), and data logging.

Improved System Coordination

Easier to coordinate with other protective devices in the system.

Faster Response to Overloads

Electronic sensing allows for faster tripping on overloads.

Remote Monitoring and Control

Some models can be monitored and controlled remotely.

Cons



Higher Cost

More expensive than TMCBs.

More Complex

Requires more knowledge and expertise to configure and maintain.

Requires Power

Needs an external power source (often the line being protected) to operate the electronic components. A loss of power can affect its operation (though often with fail-safe mechanisms).

Potentially More Susceptible to EMI/RFI

The electronic components can be susceptible to electromagnetic interference, requiring proper shielding and grounding.

Why TMCBs Still Have a Place



Residential Applications

Cost is a significant factor, and TMCBs provide adequate protection for most residential circuits.

Basic Industrial Applications

Where adjustable tripping is not critical and cost is a primary concern.

OEM Equipment

In some manufactured equipment, TMCBs may be sufficient and preferred due to their simplicity and cost.

Redundant systems or critical systems with specific power needs In some applications, a simpler system is more desirable to prevent single points of failure.

Why ETCBs are Gaining Popularity



Complex Industrial and Commercial Systems

Where precise protection, coordination, and monitoring are essential.

Critical Infrastructure

Data centers, hospitals, and other facilities where power reliability is paramount.

Renewable Energy Systems

Solar and wind power installations often require advanced protection and monitoring capabilities.

Applications Requiring Selective Coordination

Ensuring that only the closest breaker to a fault trips, minimizing downtime.

Energy Management

ETCBs with metering capabilities can provide valuable data for energy management and optimization.

In Summary

TMCBs are a mature and cost-effective technology that will continue to be used in many applications. However, ETCBs are increasingly becoming the preferred choice for applications that require advanced features, precise protection, system coordination, and remote monitoring capabilities.

Think of it like this



TMCBs

The workhorse; reliable and affordable for general-purpose applications.

ETCBs: The sophisticated tool; provides advanced capabilities for complex and critical applications.The choice between TMCBs and ETCBs ultimately depends on the specific requirements of the application, budget, and the level of protection and control desired. The trend is definitely towards more and more applications taking advantage of the precision and adjustability that ETCBs offer, especially as the price of ETCBs comes down. Flag for review