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Miniature Circuit Breaker (MCB)

Miniature Circuit Breakers (MCBs) are widely used protective devices in low-voltage electrical distribution systems. Their main function is to prevent damage to wires, cables, and electrical equipment caused by overloads or short circuits, ensuring a safe and reliable power supply.

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Why Choose

GEYA Miniature Circuit Breaker (MCB)

Have a self-developed appearance design patent.

The shell is made of flame-retardant, environmentally friendly, and safe materials. Flame retardant grade up to V1.

The product can not only be matched with accessory series products but also can be matched with reclosing module to realize automatic reclosing function

  • Rated current: 1~125A
  • Rated frequency: 50-60HZ
  • Rated voltage: 230/400VAC
  • Number of poles: 1-4 poles
  • Insulation voltage: up to 500V
  • Rated breaking capacity: up to 6000A
  • Rated impulse withstand voltage: 6KV
  • Mechanical life: 8000 times
circuit breaker catalog cover

Download GEYA MCB Catalog PDF

MCB Applications

MCBs find extensive use in various applications, ensuring the safety and reliability of electrical systems across different sectors

Residential and commercial buildings
Safeguarding final distribution circuits from overloads and short circuits.
Industrial control circuits and equipment
Protecting control circuits and equipment from excessive currents.
Power transmission and motor protection:
Preventing damage to electric motors and power transmission systems.
Renewable energy systems
Ensuring the safety and stability of solar, wind, and other clean energy installations.
Data centers and telecom base stations
Maintaining uninterrupted operation of critical IT and communication equipment.
Laboratories and medical equipment
Protecting sensitive electronic devices and medical equipment from electrical damage.

Miniature Circuit Breaker Types

GEYA Miniature Circuit Breakers have an extra wide and complete range of MCBs to cover most applications and markets. We have Type A MCB, Type B MCB, Type C MCB, Type D MCB, Type K MCB, and Type Z MCB.

Miniature Circuit Breaker Type A

Type A MCBs offer general-purpose protection for resistive and slightly inductive loads, tripping instantly at 2-3 times the rated current.

Miniature Circuit Breaker Type B

Type B MCBs provide protection for resistive and moderately inductive loads, tripping instantly at 3-5 times the rated current.

Miniature Circuit Breaker Type C

Type C MCBs are suitable for highly inductive loads, tripping instantly at 5-10 times the rated current.

Miniature Circuit Breaker Type D

Are designed for extremely inductive loads, such as transformers and motors, tripping instantly at 10-20 times the rated current.

Miniature Circuit Breaker Type H

Type H MCBs offer protection for highly inductive loads in harsh environments, tripping instantly at 7-10 times the rated current.

Miniature Circuit Breaker Type K

Type K MCBs provide protection for cables and insulated conductors, tripping instantly at 8-12 times the rated current.

Miniature Circuit Breaker Type G

Type G MCBs are used for general-purpose protection in domestic and similar applications, tripping instantly at 5-8 times the rated current.


Miniature Circuit Breaker Type Z

Type Z MCBs offer protection for semiconductor devices and sensitive electronic equipment, tripping instantly at 2-3 times the rated current.

SGS & ISO Audited

SGS & ISO Audited

GEYA is a professional industrial electrical supplier that has passed SGS certification and obtained ISO quality system certification and ISO environmental management system certification.

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0% Quality Complaint

GEYA has an advanced internal quality testing laboratory and a 48+QC testing team, which conducts 100% testing of industrial electrical equipment before shipment to ensure product quality and eliminate your doubts.

Manufacture Test Certificate

We will issue a test certificate for each order before shipment. Ensure that industrial electrical equipment complies with chemical composition standards and meets mechanical performance standards.

Leading Miniature Circuit Breaker Supplier in the Electrical Equipment Market

We produce our products with strict coordination with international standards. GEYA ensures to have detailed archives to make sure there are no errors in our product planning and development, production, and sales. To carry out all these parameters our devices like miniature circuit breakers are all passing in a series of tests.

Latest Manufacturing Process

We don't just hire the best professionals to handle our post-production, planning, and manufacturing processes. We also invest in cutting-edge technology to keep us at the forefront of innovation in our production process.

Competitive Price

We're dedicated to providing the best products and services to our valued customers without breaking the bank. GEYA offers top-quality products at the most competitive prices. Our goal is to ensure that every purchase from our customers is a great value.


1.What is the warranty period for GEYA's products?

Our products usually have a standard warranty period of 18 months, and the specific terms may vary depending on different products and customer agreements.

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MCB Miniature Circuit Breakers: A Complete Guide to Types, Selection, and Applications

Table of Contents

What is an MCB (Miniature Circuit Breaker)?

An MCB, or Miniature Circuit Breaker, is a small safety device you’ll find in most modern electrical panels. Its job is simple but crucial: protect electrical circuits from overloads and short circuits, which can cause overheating and even fires.

Think of it like a watchful guard for your wiring. If the current flowing through a circuit gets too high – either from too many appliances running at once (overload) or a fault in the wiring (short circuit) – the MCB automatically cuts off the power.

It does this using a clever combination of thermal and magnetic mechanisms. The thermal part responds to sustained overcurrents, while the magnetic part reacts instantly to the huge spike in current during a short circuit. This two-pronged approach ensures reliable and safe protection for your home or workplace.

What are the components of an MCB?

what is MCB
  1. Casing (Molded Case): A hard, insulated shell protecting the internal parts. Typically made of thermoplastic.
  2. Terminals (Line and Load): Connect the MCB to incoming and outgoing wires. Designed for specific wire sizes.
  3. Contact System (Moving and Fixed Contacts): Work like a switch, closing to allow current flow and separating to interrupt it. Made of conductive, often silver-plated, material.
  4. Arc Extinguishing System (Arc Chutes): Safely controls and extinguishes the electric arc generated when the contacts open under load.
  5. Tripping Mechanism: This is the heart of the MCB’s protection and has two key parts:
    1. Bi-metallic Strip (Thermal Trip): Bends when overheated by excessive current, triggering the MCB to trip. Protects against sustained overloads.
    2. Electromagnetic Coil (Instantaneous Trip): Activates instantly when a short circuit occurs, creating a magnetic field that trips the MCB.
  6. Operating Mechanism (Toggle Handle): The external lever for manually switching the MCB on, off, or resetting it after a trip.
  7. Trip-Free Mechanism: A safety feature that ensures the MCB will trip even if the handle is held in the “on” position during a fault.
  8. Adjustable Trip Settings (Optional): Some MCBs allow for fine-tuning the trip current for overload protection.
  9. Din Rail Mounting Clip: Allows for secure installation on a standard DIN rail within a panel.
  10. Phase Barriers (Multi-Pole MCBs): Insulate between phases in multi-pole MCBs to prevent arcing.
  11. Electrical Ratings Label: Provides essential information about the MCB’s capabilities and limitations, including rated current, voltage, and trip characteristics.

Definition and Working Principle of MCBs

A Miniature Circuit Breaker (MCB) is an electromechanical device designed to protect electrical circuits from damage caused by overcurrents, which can occur due to overloads or short circuits. Unlike traditional fuses that melt and need replacement, MCBs are reusable and can be reset after they trip.

Working Principle:

MCBs utilize two main mechanisms to detect and interrupt overcurrents:

  1. Thermal Tripping (Overload Protection): This mechanism protects against sustained overloads, where the current exceeds the rated value for an extended period. A bimetallic strip, made of two different metals with different thermal expansion coefficients, is heated by the current passing through it. When the current exceeds the rated value for a certain time, the heat causes the bimetallic strip to bend and release a latch, interrupting the circuit.
  2. Magnetic Tripping (Short Circuit Protection): This mechanism provides instantaneous protection against short circuits, where a very high current flows due to a fault in the circuit. A solenoid coil with a movable plunger is placed in series with the circuit. During a short circuit, the high current flowing through the coil creates a strong magnetic field that attracts the plunger. This action releases the latch mechanism, interrupting the circuit much faster than the thermal trip.

In essence, MCBs act as automatic switches that “trip” or break the circuit when an overcurrent is detected, preventing damage to wiring, and appliances, and reducing the risk of electrical fires.

Differences between MCB and other circuit breakers

MCBs are compact circuit breakers ideal for homes and small businesses. For larger electrical loads, you’d need Molded Case Circuit Breakers (MCCBs) which handle much higher currents. For protection against electrical shocks, Residual Current Devices (RCDs) are used alongside MCBs.


Not All MCBs are Created Equal: Understanding the Different Types

While all Miniature Circuit Breakers (MCBs) share the same basic job – protecting circuits from overcurrents – they come in different types to suit various applications. The right type of MCB ensures optimal protection and prevents nuisance tripping. Here’s a look at some common types:

Based on Tripping Characteristics:

  • Type B: The most common type found in homes, Type B MCBs are best suited for circuits with primarily resistive loads like lighting and heating appliances. They are designed to trip quickly on short circuits but tolerate minor, temporary surges in current.
  • Type C: These MCBs have a higher tolerance for inrush currents, making them suitable for circuits with inductive loads like motors, pumps, and some appliances like refrigerators and air conditioners. They trip faster than Type D but slower than Type B.
  • Type D: Designed for circuits with high inrush currents, Type D MCBs are typically found in industrial settings and are used to protect equipment like large motors, transformers, and welding machines. They have the highest tolerance for inrush currents to prevent unwanted tripping during startup.

Beyond Tripping Characteristics:

MCBs are also categorized based on factors like:

  • Number of Poles: Single-pole MCBs protect single-phase circuits, while double-pole and triple-pole MCBs are used for two-phase and three-phase circuits, respectively.

  • Current Rating: This indicates the maximum current an MCB can carry continuously without tripping. Common ratings range from 6A to 63A for household applications.

  • Voltage Rating: Specifies the maximum voltage the MCB can safely handle. Typically 230V or 400V for domestic use.

Choosing the right MCB involves considering the specific requirements of the circuit, including the type of load, expected current, and potential for inrush currents. Consulting a qualified electrician is always recommended to ensure proper selection and installation.

How Does A Miniature Circuit Breaker Work?

Miniature Circuit Breakers (MCBs) are your electrical system’s safety heroes. They prevent damage and fires by detecting dangerous overloads and short circuits. Inside an MCB, a thermal mechanism trips when current flow creates excess heat, while a magnetic mechanism instantly trips during the high current surge of a short circuit. This dual action ensures reliable protection for your home or business.

Want to see it in action? Check out this video: 

视频来源:  chrvoje engineering

 Choosing the Right MCB: A Guide to Safe and Reliable Protection

Selecting the correct Miniature Circuit Breaker (MCB) is crucial for a safe and efficient electrical system. An undersized MCB might lead to nuisance tripping, while an oversized one could fail to protect your circuits adequately. Here’s a step-by-step guide to help you choose the right MCB:

Determine Load Type and Rated Current:

  • Identify the type of load: Is it primarily resistive (lighting, heaters), inductive (motors, pumps), or a mix? Inductive loads draw higher inrush currents during startup, requiring an MCB with a suitable trip curve.
  • Calculate the total current: Add up the amperage ratings of all devices connected to the circuit. This determines the minimum current rating your MCB needs to handle continuously.

Consider Short Circuit Current and Breaking Capacity:

  • Short circuit current: This is the maximum current that can flow through a circuit during a fault. Your MCB must be able to interrupt this current safely without being damaged.
  • Breaking capacity: Measured in kA (kiloamperes), this rating indicates the maximum short circuit current an MCB can safely interrupt. Choose an MCB with a breaking capacity higher than the potential short circuit current at the installation point.

 Selecting the Right MCB Brand and Series:

While technical specifications are paramount, brand reputation and specific series features also matter. Here are a few reputable brands and their popular MCB series:

  • GEYA (GYM9H Series): 

    Known for their cost-effectiveness and reliability, GEYA’s GYM9H series offers a range of MCBs for various applications.

  • ABB (S200 Series): 

    ABB is a global leader in electrical equipment, and its S200 series is known for its quality and advanced features.

  • Schneider Electric (iC65 Series):

     Schneider Electric’s iC65 series offers high performance and reliability, with features like enhanced safety and communication capabilities.

  • Siemens (5SY4 Series): 

    Siemens is renowned for its quality and innovation, and the 5SY4 series provides robust and reliable circuit protection.

  • General Electric (HB1 Series):

    GE’s HB1 series is a popular choice for its durability and wide range of current ratings.

Note: This is not an exhaustive list, and other reputable brands and series are available.

GYM9H 01


Breaking capacity:10ka
Rated current:1-63A



Breaking capacity:10ka
Rated current:1-63A

GYM9H-125 01


Breaking capacity:10ka
Rated current:80-125A


Breaking capacity:6ka
Rated current:6-63A

Consider Installation Environment and Conditions:

  1. Ambient temperature: Extreme temperatures can affect MCB performance. Consult the manufacturer’s specifications for suitable operating temperature ranges.
  2. Humidity and dust: Choose MCBs with appropriate IP (Ingress Protection) ratings for environments with high humidity, dust, or corrosive elements.
  3. Space constraints: Consider the physical size of the MCB and ensure it fits comfortably within your distribution board or panel.

Consult a Qualified Electrician:

While this guide provides a general overview, it’s crucial to consult with a qualified electrician for proper MCB selection and installation. They can assess your specific requirements, local regulations, and ensure a safe and compliant electrical system.

MCB Installation and Maintenance: Ensuring Long-lasting Protection

Proper installation and regular maintenance are essential to ensure your MCBs provide reliable protection for years to come. Here’s a guide to keep your electrical system safe and efficient:

Correct Installation Steps and Wiring:

While it’s best to leave MCB installation to a qualified electrician, understanding the process is crucial:

  1. Turn off the main power supply: Safety first! Never work on a live electrical panel.
  2. Select the correct MCB: Ensure it matches the circuit’s requirements (current rating, tripping characteristics, etc.).
  3. Connect the wires: Follow the manufacturer’s instructions for proper wire stripping length and secure connections to the MCB terminals.
  4. Secure the MCB: Snap the MCB firmly into place on the DIN rail within the distribution board.
  5. Label the circuit: Clearly label the MCB with the circuit it protects for easy identification.
  6. Test the installation: Turn on the main power and test the MCB’s operation by switching it on and off.

Regular Inspection and Maintenance:

  • Visual inspection: Periodically check for any signs of damage, overheating (discoloration), or loose connections.
  • Toggle test: Switch the MCB on and off a few times to ensure smooth operation and a positive “click.”
  • Cleaning: Dust and debris can accumulate inside the panel, potentially affecting performance. Gently clean the MCB and panel using a soft brush or compressed air.
  • Professional inspection: Schedule a thorough inspection by a qualified electrician every few years or as recommended by local regulations.

Common Fault Diagnosis and Handling:

  • MCB keeps tripping: This indicates an overload or a possible short circuit in the protected circuit. Identify and address the root cause before resetting the MCB.
  • MCB won’t reset: The MCB might be damaged and need replacement. Consult a qualified electrician.
  • Burning smell or discoloration: This signifies overheating and requires immediate attention. Turn off the power and call an electrician.

MCB Safety Precautions:

  • Never bypass or tamper with an MCB: This compromises safety and could lead to fire hazards.
  • Don’t ignore repeated tripping: It’s a sign of an underlying issue that needs addressing.
  • Use the correct tools and techniques: Improper handling can damage the MCB or the panel.
  • When in doubt, call a professional: Electricity is dangerous. Don’t hesitate to seek help from a qualified electrician for any installation, troubleshooting, or maintenance needs.
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MCB FAQs: Your Questions Answered

Several signs indicate your MCB might need replacing:

  • Frequent Tripping: If an MCB trips often without an obvious overload, it could be nearing the end of its lifespan or have internal damage.
  • Failure to Reset: If the MCB won't reset after addressing a potential overload or short circuit, it's likely faulty.
  • Visible Damage: Any signs of burning, melting, or physical damage to the MCB warrant immediate replacement.
  • Age: While MCBs don't have a strict expiry date, consider replacement after 15-20 years as their performance can degrade over time.

The most common reasons for MCB tripping are:

  • Overload: Too many appliances running on a single circuit, exceeding its current rating.
  • Short Circuit: A fault in the wiring creating an unintended path for electricity, resulting in a rapid surge in current.
  • Ground Fault: (If protected by an RCD/RCBO) Current leaking to the ground, indicating a potential shock hazard.
  • Faulty MCB: Internal damage or wear can cause an MCB to trip even without an actual fault.

The MCB's current rating should match the circuit's capacity and the connected load:

  1. Determine Circuit Capacity: Check the cable size and its current-carrying capacity.
  2. Calculate Total Load: Add up the amperage of all devices on the circuit.
  3. Select MCB Rating: Choose an MCB with a rating slightly higher than the total load but lower than the circuit's capacity.

Important: Consult a qualified electrician for accurate load calculations and MCB selection.

While they all protect circuits, they do so in different ways:

  • MCB (Miniature Circuit Breaker): Protects against overloads and short circuits.
  • RCCB (Residual Current Circuit Breaker): Detects and protects against earth leakage currents to prevent electric shocks.
  • RCBO (Residual Current Circuit Breaker with Overload Protection): Combines the functions of an MCB and RCCB in a single device.

Contact us for more information

If you have any questions about our miniature circuit breaker products, or you are looking for professional technical support, please do not hesitate to contact our Cngeya team immediately. We are committed to providing customers with excellent service and personalized solutions.

Why choose our technical support?

Expertise: Our team has rich industry experience and technical knowledge.

Quick response: We promise to respond quickly to your consultation and technical support needs.

Personalized service: We understand that each customer’s needs are unique, so we provide customized services.

How to contact us?

Phone: +86 1356 777 0207 — Speak directly with our customer service representative.
Email: market@cngeya.com — Send a detailed inquiry and we will respond promptly.

Working hours: 24 hours on call, we are always ready to answer your questions.

Address: Wenzhou Bridge Industrial Zone Beibaixiang Town Yueqing City Zhejiang Province — Welcome to visit.

We look forward to establishing a long-term cooperative relationship with you to ensure that your electrical system is safe, reliable and efficient. Do not hesitate to contact us and let our professional team be your strong support on the road to success.

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