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KINO ELECTRICS CO. LTD：Your Professional Moulded Case Circuit Breaker Manufacturer !
 

KINO was established in 2005 and is a professional manufacturer of low voltage electrical device. We are specialized in manufacturing the mini circuit breakers, molded case circuit breakers, ac contactors, over load relays, photovoltaic series breakers and other related electrical baskets of products. Our mission is to be a professional manufacturer for worldwide customers with high quality and best service.

Rich Products

Our company can produce mini circuit breakers, isolating switches, leakage circuit breakers, single-phase leakage circuit breakers, three-phase leakage circuit breakers, lightning arresters, molded case circuit breakers, distribution boxes, etc.

Advanced Equipment

We have 1600M² of work space and 5 production lines, as well as various assembly, calibration, packaging and other equipment.

Versatile Products

Our mini circuit breaker is an overcurrent protection device used in residential, commercial and industrial electrical systems; and the isolating switch is an important switching device in the power system. The isolating switch can be used in conjunction with other control equipment to realize the control of the power system.

Leading Service

We have many years of industry experience and a complete production management, quality supervision, sales service operation system. Whether you want to buy a mini circuit breaker or a molded case circuit breaker, just send your requirements via email and we can customize the product for you.

What is Moulded Case Circuit Breaker？

 

 

A molded case circuit breaker, or MCCB, is a safety device used to protect an electrical circuit from overload or short circuits. It works by automatically cutting off the power supply when a fault or overcurrent situation arises, thus preventing any damage to the electrical system. MCCBs can be used in both low-voltage and high-voltage systems. In addition to providing protection against faults, they also provide isolation of the circuit for maintenance. MCCBs are typically installed in the distribution panel and provide a visible indication to let users know when the power is off.

 

Types of Moulded Case Circuit Breaker

As MCCB are advanced versions of MCB, they are also classified like them based on the tripping curves. MCCBs come in a range of trip types (B, C, D, K, and Z), each with unique time-current curve characteristics.

Type B

This type of molded case circuit breaker trips between 3-5 times the rated current. Tripping time is 0.04-13 seconds. These mostly have resistive, domestic applications and can handle low surge currents.

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Type C

These trip between 5-10 times their rated current. Tripping times fall within the range of 0.04-5 seconds. Applications involve relatively modest inductive loads, such as small motors, transformers, and electromagnets typically used in industrial settings. Suitable for higher surges.

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Type D

Type D MCCBs are known to trip between 10-20 times their rated current, and their tripping time ranges from 0.04 to 3 seconds. These MCCBs exhibit the highest surge tolerance and are thus selected for applications with extremely inductive loads like large electrical motors commonly found in industrial environments.

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Type K

These trip when the current reaches 10-12 times their rated current. Tripping time falls between 0.04 to 5 seconds. Applications involve inductive loads like motors.

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Type Z

Type Z MCCBs are the most sensitive among MCCBs, tripping when the current reaches only 2-3 times their rated current. They have the shortest tripping time and are employed for applications where extreme sensitivity is essential. This includes protecting semiconductor-based medical equipment and other costly devices that are susceptible to low current surges.

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Features of Moulded Case Circuit Breaker

MCCB (Molded Case Circuit Breaker) has several key features, including molded case, overload and short-circuit protection, etc., making MCCB a popular choice for electrical protection. Here are some of the key features of MCCB

Adjustable Moulded Case Circuit Breaker
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Plastic Shell
The MCCB is housed in a plastic case that provides insulation and protection to the internal components. The molded case is usually made of durable and flame-retardant materials, ensuring the safety and reliability of the circuit breaker.

 

Adjustable Current Rating
MCCBs are available in a wide range of current ratings, giving flexibility in selecting the right circuit breaker for different applications. The current rating determines the maximum current that the MCCB can withstand without tripping.

 

Overload and Short Circuit Protection
MCCB provides overload and short circuit protection. They are designed to detect and interrupt excessive currents caused by overloads or short circuits, preventing damage to circuits and equipment.

 

Trip Mechanism
MCCB uses a combination of thermal and magnetic trip mechanisms to detect abnormal conditions. Thermal trip mechanisms respond to sustained overcurrent, while magnetic trip mechanisms react quickly to short circuits or high fault currents.

 

Trip Indication
MCCBs often have a trip indication feature that provides visual or remote indication when the circuit breaker has tripped. This helps determine the cause of the trip and aids in troubleshooting.

 

Manual and Automatic Operation
Molded case circuit breakers can be manually operated via their operating handles or levers. They allow manual on/off control as well as reset after tripping. Some MCCBs also support automatic operation via electric mechanisms or remote control systems.

 

Selectivity and Coordination
MCCBs are designed for selectivity and coordination with other protective devices in the electrical system. This ensures that only the equipment closest to the fault is operational, minimizing downtime and disruption in the event of an electrical fault.

 

Accessories and Auxiliary Contacts
MCCBs usually have various accessories available such as auxiliary contacts, shunt releases, undervoltage releases, etc. These accessories provide additional functionality and integration with the control system.

 

Environmental Protection
MCCBs designed for specific applications (such as marine or hazardous environments) may have additional features to protect against corrosion, moisture, dust, or explosive environments.

 

Working Principle of Moulded Case Circuit Breaker
 

An MCCB protects a circuit from fault current. It uses thermal and magnetic mechanisms to break those fault currents. The thermal mechanism is used for overload protection while the magnetic mechanism is used for short circuit protection.

Overload Protection

Overload occurs when the current exceeds a limit for a prolonged duration. MCCB has a thermal mechanism that contains a bimetallic contact to protect from overload. A bimetallic strip is made from two different types of metal having different rates of thermal expansion. Upon temperature change, the strip bends or contracts. The main current passes through the bimetallic strip. If the current exceeds a certain limit, the contacts heat up and expand. Due to different expansion rates, the strip bends and trips the circuit. In electrical devices, the current can overload for short duration of time, it is normal and should not be considered as fault current. Therefore, MCCB has a time delay that allows the overload current for a short duration of time before tripping the circuit.

Short Circuit Protection

MCCB protects against a short circuits using a solenoid that produces electromagnetic force. The main current flows through the solenoid that attracts and repels a plunger responsible for tripping the breaker. If the current remains below the threshold, the solenoid produces a weak magnetic force that cannot attract the plunger. In short circuit conditions, a very high current flows through the solenoid that generates a very strong magnetic force. It attracts the plunger that trips the circuit.

 

 
 
Components of Moulded Case Circuit Breaker

MCCB is a combination of electrical and mechanical parts. Varies categories of molded case circuit breaker (MCCBS) are available like frame size, current and breaking capacity so many parts are used as per categories. The parts details are given below mentioned.

01.

Frame

The frame is also known as the molded case. It serves as the housing for all the circuit breaker components. Constructed from a thermoset composite resin or glass polyester, it offers high dielectric strength within a compact design. The designation of the frame depends on the size of the molded case and describes the breaker’s characteristics, including maximum voltage and current ratings.

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Operating Mechanism

The operating mechanism facilitates the opening and closing of contacts within the MCCB. The speed of contact movement is determined by the handle’s motion. A midway position indicates that the contacts have tripped. The MCCB is designed to be “trip-free,” preventing tripping when in the “on” position.

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Arc Extinguisher

It is a special kind of fire extinguisher, which is important to keep your space safe from electrical accidents. It puts out the spark that happens when a circuit breaker stops the flow of electricity. A reliable steel-strong box protects the chamber’s extinguisher inside the frame. Power current during current jumping in MCCBs generates a slight blow-apart effect which loads the MCCB contacts opening.

04.

Trip Unit

The trip unit is the core component for the control of the circuit breaker that is to serve as a control signal of the tripping mechanism during short circuits or overload current. Traditional MCCBs such as mechanical spring trip units are based on electromechanical trip units. It is an amalgamation of active thermomagnetic apparatus, which take current and pressure as their input functions to directly manage the mechanical activation of actuators.

 

Applications of Moulded Case Circuit Breaker

 

MCCB is superior to MCB and has more application due to its higher current handling and adjustable trip setting capabilities. On application, MCCBs are used for heavy-duty applications such as in industries.

 

Welding Machine Protection
MCCB protects the machine from electric arc and high voltage in the welding industry. The device is isolated from the supply side of the transformer by using an MCCB with grounding. It is also used to protect the machine from its supply line. An MCCB protects a transformer rated for 600 volts or higher and has a total rating of at least 200 amperes at 400 volts or less.

 

Generators
Generators produce high levels of amps and need costly gen-sets. To shield the linked circuits and generator from faults that may happen in the system, having an MCCB is essential as it can handle its high current ratings and protects your generators as needed.

 

Electric Feeders Protection
If you are using feeder circuits to distribute electric current, they can carry hundreds of amps. In some instances, you may also have additional circuits that will need trip settings. MCCBs come in handy in both the situations.

 

Capacitor Banks
These are used to correct power factors in industrial and commercial electrical systems. If the currents they draw are very high, MCCB protection becomes a necessity to reduce currents.

 

Protecting Motors
Electric motors also need to be adequately protected and MCCBs do this work very well. Inrush current may need to be adjusted, providing the necessary overload protection without tripping.

 

Adjustable Trip Settings for Applications with Low Currents
MCCBs, even though they are known to be used with high current applications can also be used with low current ones. They provide adjustable trip settings.

 

Factors to Consider When Choosing an Moulded Case Circuit Breaker

 

Choosing the right Molded Case Circuit Breaker is crucial for the safety of your workers and equipment and for ensuring optimum system efficiency. Here are some key factors to consider when selecting an MCCB.

The Frame Size
It is crucial to pick a unit with appropriate dimensions for the available space. Usually, the same frame size is available with various current ratings, so consider the availability of space and the line’s calculated load when picking the correct unit. The rated current classification is usually chosen based on the priority coefficient (1.25).

 

Operating voltage
There are three things pertaining to voltage that must be considered when choosing an MCCB. First is the system voltage. The next one is the rated operation voltage or the amount of voltage the MCCB is designed to function optimally. The last one is the insulation voltage which is the amount of voltage the MCCB can withstand without its parts breaking down.

 

Current Rating
The current rating specifics the highest current the MCCB can continuously carry while maintaining safety. MCCBs can actually carry a little over the current rating, but only for limited time. MCCBs’ current ratings range from 10A-2500A. Matching the current rating with your machinery’s current should be your first consideration when choosing an MCCB.

 

Ultimate Short-Circuit Breaking Capacity (Icu)
Many MCCBs have different Icu for the rated current of a frame level. When selecting the unit, it is crucial to ensure that the expected short circuit current is below the Icu to ensure that in case of a fault, the unit can handle the fault current without being damaged.

 

Shunt Trip for Protection Relays
When an MCCB trip due to an external signal from a protection relay, it is known as a shunt trip. If such protection relays (sensors) are part of the electrical system, you must choose an MCCB that accepts inputs from such sensors.

 

Maintenance Of Moulded Case Circuit Breaker

 

 

Molded-case circuit breakers (MCCB) are switching devices commonly found inside panelboards, switchboards, motor control centers, control panels, combination starters, individual enclosures, and bus duct plug-in units. Regular maintenance is key to ensuring the reliability and longevity of MCCBs. Not only that, it also prevents downtime, ensures efficient energy consumption, and detects problems early before they result in major equipment failure.

Safety First
Always begin by ensuring your safety. Disconnect the power supply to the MCCB and lock out the circuit to prevent accidental energization.

 

Visual Inspection
Inspect the MCCB for any signs of physical damage, overheating, or loose connections. Check for any foreign objects inside the MCCB.

 

Clean the MCCB
Use a soft brush or compressed air to clean dust and debris from the MCCB electrical components. Don’t use any abrasive materials that could damage the internal components.

 

Tighten Connections
Check for loose connections on the line and load terminals. Tighten any loose screws or bolts to ensure proper electrical contact.

 

Inspect Insulation
Inspect the insulation for signs of wear, cracks, or damage. Replace any damaged insulation right away to prevent electrical faults.

 

Check Mechanical Operation
Operate the MCCB manually to ensure smooth mechanical operation. Verify that the trip mechanism engages and disengages correctly.

 

Test the Trip Unit
If your MCCB has an adjustable trip unit, test its functionality. Use a calibrated test kit to verify that the MCCB trips at the specified current levels.

 

Inspect Arc Chutes
Arc chutes are critical for extinguishing the arc during a fault. Check for any damage or wear. Replace arc chutes if they show signs of deterioration.

 

Lubricate Moving Parts
Apply a small amount of appropriate lubricant to moving parts, such as hinges and levers, to ensure smooth operation.

 

Check Calibration
If your MCCB has a thermal-magnetic trip unit, verify that it operates within its specified calibration. Recalibrate if necessary using manufacturer-recommended procedures.

 

Verify Labeling
Ensure all labels, including ratings and operational instructions, are clear and legible. Replace any faded or damaged labels.

 

Record Maintenance Activities
Keep a detailed record of all maintenance activities, including dates, findings, and actions taken. This documentation is crucial for future reference and compliance.

 

Perform Infrared Thermography
Use infrared thermography to identify any hotspots, which may indicate loose connections or other potential issues.

 

Conduct Megger Testing
Periodically perform insulation resistance testing using a megger to identify insulation breakdown or degradation.

 

 
Frequently Asked Questions
 
 

Q: Do MCCBs have short time withstand rating?

A: MCCBs are downstream protective devices, and hence are expected to sense & clear circuit faults instantaneously without any delay. For this reason, MCCBs do not need to have any shortime withstand rating. However, MCCB's of ratings 1000A & above are also available with short time withstand rating.

Q: Are MCCBs suitable for DC applications?

A: Yes, MCCBs with thermal-magnetic releases are suitable for DC application. The thermal rating in these MCCBs remain unchanged.However MCCBs with static or microprocessor based release are not suitable for DC applications.

Q: What types of protection is offered by MCCBs in an installation?

A: Standard MCCBs offer overload and short circuit protection to an installation. However, accessories are available to enable an MCCB to offer earth fault, earth leakage and undervoltage protection as well.

Q: How does MCCB work?

A: The main function of MCCB is to protect the circuit against overload by manual switching. When a load is connected to the circuit, the current will increase between the source and load due to the thermal effect. This current will cause overcurrent protection or an open circuit if it exceeds a certain value.

Q: How can you tell the difference between MCB and MCCB?

A: An MCB contains a fixed tripping circuit, whereas an MCCB has a movable tripping circuit. The pole in circuit breakers refers to the number of switching and safety phases it contains to maximize protection. An MCB usually has 1, 2, or 3 poles, while the MCCB can have up to 4 poles.

Q: How do you choose the breaking capacity of MCCB?

A: The breaking capacity of an MCCB refers to its ability to interrupt the flow of current under fault conditions. It is imperative to select an MCCB with a breaking capacity that exceeds the potential fault current of your system. This guarantees the MCCB's effectiveness in isolating faults and preventing further damage.

Q: Where should we use MCCB?

A: MCCBs are used in high energy requirement applications such as high-power equipment in industries or for commercial purposes. MCBs have ratings under 100 amps. MCCBs goes as high as 2500 amps. It is a low-voltage circuit breaker.

Q: What are the inside parts of a MCCB?

A: Molded Case Circuit Breakers are composed of five main components. These are: Molded case/frame, operating mechanism, arc extinguishers, contacts and trip units.

Q: What are the characteristics of MCCB?

A: MCCB (Molded Case Circuit Breaker) has several key features, including molded case, overload and short-circuit protection, etc., making MCCB a popular choice for electrical protection. The MCCB is housed in a plastic case that provides insulation and protection to the internal components.

Q: How do you wire a MCCB?

A: First, we need to connect the MCCB with the power source, then connect the magnetic contactor, then connect the transformer, then connect the start switch and stop switch, then connect the overload and motor with the circuit breaker.

Q: What is the preventive maintenance of MCCB?

A: Molded case circuit breakers need very little maintenance. Low-voltage breakers should be inspected every one to three years, medium-voltage annually. High-voltage circuit breakers need the most frequent tests and inspections with a maximum of six months between checks.

Q: How do you check for MCCB tripping?

A: Thermal power testing involves passing a huge current through the MCCB. If the MCCB does not trip, it is faulty. Magnetic protection capacity is tested by passing a very strong current in short pulses. Magnetic protection should be instantly achieved if the MCCB is working properly.

Q: Can we use MCCB for motor starter?

A: No. While an MCCB can provide some level of motor protection, it is not designed to control the motor's operation, specifically the starting process.

Q: What are the MCCB specifications?

A: The MCCB has single, two, three, or four-pole versions. The rating current of an MCCB is 10 to 200 amps (the rating current is the maximum current that the circuit should draw) MCCB's are primarily used in heavy current circuits. They are commonly used in heavy-duty industrial applications.

Q: Can I use MCCB at home?

A: There are many different types of MCCB that you can use in your home or office. The most common type is the standard moulded case circuit breaker. It's a simple, inexpensive way to protect your home or office from electrical fires and appliance damage.

As one of the most professional moulded case circuit breaker manufacturers and suppliers in China, we're featured by quality products and competitive price. Please rest assured to buy moulded case circuit breaker in stock here and get quotation from our factory. Also, customized service is available.

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