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What is a Shunt Trip Breaker and How Does It Work?

Written by  Edwin Jones  / Fact checked by  Andrew Wright

What is a shunt trip breaker? Does it add protection to your electrical system?

The shunt trip breaker is a combination of the shunt trip accessory and the main circuit breaker. This installs on the main breaker to add protection to your electrical system. This adds security to your electrical system as it manually or automatically cuts the electric supply in your circuit.

This accessory can help prevent short circuits and avoid electrical damage should a disaster occur in your home.

Let me tell you more about the shunt trip breaker to help you decide if you need additional protection for your electrical system.

Table of Contents

What is Shunt Trip Breaker and How Does It Work

Where are shunt trip breakers most used, how to install a shunt trip accessory to the breaker.

You should know that shunt trip breakers are different from GFCI circuit breakers.

The GFCI circuit breaker contains one big white tail wire for neutral connections only. It cannot be connected to any control package because the GFCI circuit breaker is solely designed to detect a sudden electrical surge. It has no other purpose but to cut power in case of a short.

Meanwhile, the shunt trip breaker wiring comprises two wires. One connected to the ground, and another to a control system. The control system can be connected to a sensor or to a manual switch. When activated, the shunt trip accessory will cause the main breaker to trip.

For example, if you install a shunt trip with a smoke detector, it will activate and cut off the power should the smoke sensor trigger. It can also be installed with a remote switch , allowing you to trip your breaker manually.

It is crucial to know the difference between a regular circuit breaker and a circuit breaker installed with shunt trip accessories.

The shunt trip definition means that it is a way to cut off electrical power through other sensors, not just via thermal activation. Since this is an optional accessory for a circuit breaker, it is not required for a home electrical system.

However, it is recommended for added safety. This is especially true if you’re working with industrial machinery. Furthermore, you can use it as a manual emergency switch to shut down your main breaker.

Before installing a shunt trip, consider its cost and your existing system. You may need to change the breaker panel  and circuit breakers, especially if it is not compatible with shunt trips. You may also need a new line to connect the remote emergency switch to your breaker box.

Generally, most commercial kitchens, elevators, and offices have this shunt trip breaker because it is required. Commercial kitchens use this device in compliance with ANSI/ASME CSD-1, while elevators and escalators comply with ASME A17.1. These codes refer to the controls and safety standards provided by ASME’s.

This question is a topic of discussion among Reddit members as well. Join the conversation here:

Found at a dominos by u/Guilty_Sympathy_496 in electricians

Mostly, installing a shunt trip relay requires that the breaker and the shunt be from the same maker. Also, not all breaker models are compatible with this accessory.

Once you’re sure that your system can take a shunt trip accessory, installation is pretty much straightforward. You can watch this video by Aaron CBIONE for some tutorials.

Note: Every circuit breaker comes with different instructions. It would depend on the brand and model of the breaker .

However, the critical part of every installation is that you need to connect the shunt to your sensor. You may need a shunt trip breaker diagram as a reference to ensure correct installation.

Also, check the brand and model of your breaker before proceeding with the installation. Some makers only allow a factory install of the shunt trip and other accessories. DIY installation may void the warranty of your breakers. It’s best to read up on the manual or consult an electrical professional before making any changes.

What is a shunt trip breaker? The shunt trip is an optional accessory for a circuit breaker for added protection to your system. It is designed to connect to a secondary sensor. It will trip the breaker automatically if the sensor is triggered. It can also be activated via a remote switch that you can install.

Do you think that a circuit breaker is enough to protect your investment? Or do you want an additional layer of protection for your electrical circuit? If you’re not decided yet, reach out to me in the comments section below, and I will be happy to help you.

I am Andrew Wright. With 8 years of experience designing, installing, and maintaining electrical power systems. I love my job, and I have always wanted to offer others the necessary help so they can take care of their houses.

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What Is A Shunt Trip Breaker & How Does It Work? Detailed Guide

Hello readers welcome to the new post. In this post, we will learn What Is A Shunt Trip Breaker & How Does It Work. The shunt trip breaker is a combination of a shunt trip accessory and a main circuit breaker. it connects to the main breaker for the protection of the electrical system. it also added security to the system since it manually or automatically cut the supply in the circuit. In this post, we will discuss the all details shunt trip breaker and other parameters. So let’s get started What is a shunt trip

Table of Contents

What is a Shunt Trip Breaker?

If the circuit breaker trips it finds faults condition and automatically shuts off the current flow to prevent the circuit from overheating.  The shunt trip breaker is an optional device for a circuit breaker that helps to trip the breaker remotely in any instant or automatically in case of surge saving any damage and instrument damage.

There are 2 main types of shunt trip breakers first one is manual and the second one is automatic.

Manual witches help to off the breaker externally with the use of the remote button. Automatic switch off power when detecting surges from the external power supply.

 How Does a Shunt Trip Breaker Work?

Normally the current passes through the circuit breaker. But if these currents become high surges, the larger surge of power changes the electromagnet below the breaker switch, tripping the cutting power and switch.

The shunt trip breaker offers extra techniques to charge the electromagnet and trip switch, helping remote or automatic power shutoff. Some hunt trips are connected to an external power supply.  When power surges get that source, signal flow from shunt trip to the breaker, mechanical cutting power.

The shunt trip can make a connection with the remote switch outside the building. Pushing the button on the switch sends a surge through shunt trip wiring and off the power.

 Components of  Shunt Trip Breaker

Read more  Top Reasons Why Electric Outlet Stopped Working Breaker Not Tripped?

A shunt trip breaker comes with differnt components:

• The frame of the shunt trip circuit breaker works as an external protective housing and covers all inner components. it is made with the use of durable materials like metallic that help to avoid damage to sensitive inner circuits.
• Contacts are the main part of the circuit breaker that carries electric current. in a shunt trip circuit breaker, there are two types of contacts, main contacts, and auxiliary contacts. The main contact is used for normal power transmission, and auxiliary contacts are used for connecting the external control system

Operating Mechanism:

• The working phenomena in shunt trip circuit breakers help to open and close contacts. it comes with latch releases and trip units. The latch releases are used for maintaining contacts in the closed position until the trip mechanism works. The trip unit detects abnormal electrical conditions and starts the tripping process.

Electromagnet:

• At the core of the shunt trip circuit breaker electromagnet exists, which is important for working. If the external signal gets, the electromagnet activates and produces a magnetic field. This field work on latch releases resulted to open circuit breaker contacts.
• It is the main part of the shunt trip breaker that operates uniformly with an electromagnet. its working is to get an external signal and convert into electrical energy. this energy is used to producing the field needed for tripping breaker.

Why Are Shunt Trip Breakers Important?

irrespective optional nature of the shunt trip breaker, it can be an important safety instrument in a power system. As a result, many engineers use this breaker as a layer of security since they save damage during power surges.

This breaker is good for many fonts but it’s commonly used during fire. By turning off power if a fire breaks out, the electrical hazard is no main risk. Some connections shunt trip to smoke alarm in homes, for power automatically off when detector trigger alarm. It not be good option, since in some conditions smoke alarm gets off due to steam from the shower of smoke from the kitchen

 Applications of Shunt Trip Breakers

• In commercial buildings like offices, and shopping malls, shunt trip circuit breakers are connected to ensure sure safety of many components and protect them from electrical faults. It also connected with a building management system to help remote operations
• Industrial facilities mostly work with high-power machines, so electrical safety is needed. Shunt trip breakers are used in such facilities for protection from faults and to reduce the chances of electrical accidents.
• Laboratories and research facilities also use these breakers since they are equipped with sensitive devices.
• There is a need for a regular power supply for critical patient care. Shunt trip breakers help to make sure emergency power is constant without any interruption.
• Data centers come with computing devices and sensitive data. Shunt trip breakers are used to protect these facilities from electrical hazards.

 Advantages of Shunt Trip Breakers

• The main benefit of a shunt breaker is that it can remotely shut off in case of any fault. It quickly works and disconnects power in fire which helps to avoid damage in the home and protects people.
• These devices also increase safety levels and security by automating off power to the circuit if there is any fault. it helps to save electrical fires and any other damage.
• The shunt breaker is easily connected and confined with a power system, so it is easy to install the device in the building.
• The shunt breaker is a less cost solution for safety measures in buildings and industries. it is less costly to buy and connect and helps to save homes and buildings in the result of high fault.
• Shunt breakers support many electrical systems and devices so it is versatile devices that are used for the protection of circuits.

 Comparison with Other Circuit Protection Devices

Shunt trip breakers vs. standard circuit breakers.

The basic difference between shunt trip breakers and regular circuit breakers is their function. Regular breakers are manually operated and based on a user-to-flip switch if requried or on current overloading that triggers the unlatching process.

While shunt trip breaker provdies more layers of controls. it can be triggered remotely with the use of a switch or automated system. These features allow them to immediately off power in case of fault.

Shunt trip breakers vs. ground fault circuit interrupters (GFCIs)

GFCI monitors equality between L1 and L2, if there is more than predefined difference in trips. The shunt breaker is a combination type device that combines in regular breaker with its regular function trip it has a remote control to trip breaker.

Ground fault breakers monitor current on neutral wire flowing back to the neutral bar, the four to six-milliampere different trip breakers, and shunt trip breakers can tripled remotely from other switches or points. In industrial uses, it is used to shut off in emergency condtion, when access to an electrical panel is difficult.

Shunt trip breakers vs. arc fault circuit interrupters (AFCIs)

Shunt Trip Breaker

• It used for overloading and short protection
• its working principle is based on thermal magnetic trip
• Its detection range is 10 to 1000A
• its response time is 10 to 20 milliseconds
• It used for arc fault protections
• It works based on a microprocessor for detecting arcing
• The detection range is 5 to 6000 A
• Response time is 10 to 40 milliseconds

What Are 3 Types Of Shunt Trip Breakers?

• Standard breakers
• Arc fault circuit interrupter circuit breakers

Shunt trip breaker wiring

Follow these steps for shunt trip breaker wiring.

• First of all, see the diagram shown below.
• Arrange requried tools and materials like wire strippers, nuts, and voltage tester.
• Remove the power and wire that shunt the breaker according to instructions.
• Again connect power to the circuit and test breaker to check that working well

Diagram of Shunt Trip Breaker Wiring Diagram

WHICH TYPE OF SHUNT TRIP BREAKER TO USE?

The manual breaker is best to use for small buildings or conditions where any technical staff is available to reset the breaker,. The automatic breaker can be best for larger-size buildings or conditions where there is no option for staff for breaker resetting.

it is also preferred for trigger shunt trip breakers at a distance or remotely. These relays are connected to fire alarm systems and can send a signal to the breaker for tripping if there is any fault.

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How does a shunt trip breaker work?

The shunt trip is a device in the circuit breaker that mechanically trips the breaker when power is given to shunt trip terminals. Power for shunt trip does not come in breakers, so it provided from an external source

How is a shunt trip breaker wiring?

Make the connection of accurate voltage (120V to 240V for the -1021 suffix) with 2 terminals on the shunt trip. Land with a leg from source contact on one terminal and a neutral wire. (L2 , X2 ) to the other terminal

What is the purpose of a shunt with a relay?

Shunt relays are used to bypass normal controls like switches , dimmers, or panel-mounted relays when employed on an emergency circuit.

What is shunt trip and under voltage?

The shunt trip coil is connected to the breaker to offer a remote trip of the breaker but Undervoltage or no voltae coil is connected to offer automatic tripping when power losses occur or when there is a major voltage dip.

Where is shunt trip used?

The shunt trip helps to remotely and fastly turn off the breaker when needed especially in conditions where safety and speed is important, like during a fire or when there is needed to isolate certain areas of the electrical system without physically going to the breaker

What is the difference between shunt and resistance?

The shunt is an electrical device that produces a low resistance path for current. It helps current to flow to another point in cirucit. Shunts are also referred to as ammeter shunts or current shunt resistors.

What is the purpose of a shunt breaker?

its main purpose is to remotely and fastly turn off  circuit breaker when necessary

Is the shunt resistor AC or DC?

Shunt provdies DC mV signal for driving moving coil ammeter, overlading protection, and control units for high amper range.

Where are shunt trip breakers required?

These breakers are used in commercial  and industrial buildings, also for facilities where safety is a top priority

Why is it called a shunt resistor?

In older circuits, resistors connected in parallel to the ammeter as shunts for expanding the current measuring range called shunt resistors. but now resist used for detection circuit current  collectively referred to as shunt resistors

Why is low resistance called shunt?

When a resistor is connected with another resistor of low value, then the equivalent resistance is less the lowest resistor, that is shunt resistors.

What is another name for a shunt resistor?

Shunts also called ammeter shunts  or current shunt resistors.

What is a unit of shunt resistance?

The unit of shunt resistance is ohm (Ω).

What is shunt resistance formula?

The shunt resistance formula is:

• Rs is the shunt resistance
• V is the voltage of the shunt resistor
• I is the current passing through the shunt resistor

What is shunt release in a circuit breaker?

The shunt releases is opening coil plus release. Thermal trips and electromagnetic trips also use trip units. use a certain voltage to shunt trip the coil, and the breaker will trip and open.

What is the difference between a shunt trip and series trip?

What are the different types of shunt trip breakers, does a shunt trip breaker need a neutral, what is the difference between shunt trip and a shunt close.

When used as a shunt trip the coils trip breaker when a rated voltage is given. When used as shunt close, coils closes breaker when voltae is provided

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Home » circuit breaker » Shunt trip breaker

Shunt Trip Breaker: How It Works to Trip a Circuit Breaker.

While circuit breakers protect appliances from power surges , shunt trip breakers add more protection to our electrical system and equipment .

If you are looking to add additional protection to your home circuit, or even trip your breaker remotely from your comfort zone, why not shop for a shunt trip circuit breaker?

Table of Contents

What is a shunt trip breaker?

A shunt trip device is an optional accessory for breakers that allows you to trip a circuit breaker with a remote, or automatically trip the switch during electrical surge or short circuit .

Shunt trip breakers are mostly used in commercial and industrial applications to enhance safety and protection of electrical appliances.

Types of shunt trip breakers

There are two main types of shunt trip circuit breakers they include.

• Automatic shunt trip breakers: These breakers trip automatically when they detect an electrical fault such as an overcurrent or a fire alarm.
• Manual shunt trip breakers:  These breakers are tripped manually by pressing the remote button.

How the shunt trip circuit breakers work

A shunt trip breaker works like other circuit breakers . However, it comes with a solenoid coil which is connected to a separate control circuit. 

When the control circuit is energized due to electrical fault or overload, it creates a magnetic field around the solenoid coil, which pulls a plunger inward.

This plunger is connected to the tripping mechanism of the circuit breaker. So when it is pulled inward, it trips the breaker and cuts off the power source.

Alternatively, a shunt trip breaker can also work with a remote control so you can trip the breaker remotely when there are electrical hazards

Where are shunt trips required

Shunt trip circuit breakers are used in various applications such as

• Industrial machines to protect it from damages that may arise from electrical faults.
• Fire protection systems to automatically shut off electrical power in the event of a fire outbreak.
• in commercial buildings for additional protection against electrical damage.
• hospitals and healthcare facilities to protect hospital equipment from electrical damage.

Advantages of using a shunt trip breaker

There are several advantages to using a shunt trip devices, these include:

• Enhanced Safety: It provides an additional layer of safety by quickly tripping the main breaker in the event of a fault or overload, preventing potential damage to electrical equipment.
• Remote tripping capability: A shunt trip breaker usually comes with a remote control to enable you to turn off the breaker at any needed time.
• Protection of sensitive equipment: It can help protect sensitive electrical equipment from power surges caused by overload or faults, ensuring the durability of the equipment.

Shunt trip breaker wiring

Before you wire a shunt trip, there are some things you will need to know.

Shunt trip is an accessory and is not compatible with all breakers. Some breakers come with an in-built shunt trip, others require specific models, or to be installed in the factory. Therefore, it is necessary that you evaluate all these before the wiring .

If the breaker is compatible with the shunt trip device, you can then follow this wiring diagram to install it.

Based on the MCCB shunt trip breaker wiring diagram above, the 3-phase 4-wire system from supply is connected to the mccb breaker .

The neutral wire is connected to the shunt coil, and the control line wires to the EPO button. 

Difference between a shunt breaker and a GFCI 

A shunt trip and a ground fault circuit interrupters (GFCI ) are both electrical devices , however, they are designed to work in different ways and for different purposes.

Below are their major differences.

When to call an electrician

If you have any issues with your electrical system, or went us to help you with a quotation or any wiring advice, contact us as we are here for you.

About mariaelectricals

Hi, I am Emmanuel Nwankwo, a commercial electrician and the founder of mariaelectricals.com . I established this blog to share my decades of work experience in electrical installations and repairs.

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• What Is a Shunt Trip Breaker and How Does It Work

What Is a Shunt Trip Breaker and How Does It Work?

First things first: what is a shunt trip breaker? A shunt trip breaker is a specialized circuit breaker that is designed to remotely shut off power to a circuit in emergency situations, such as a fire or security breach. These breakers are commonly used in commercial and industrial buildings, as well as other facilities where safety is a top priority. In this article, we'll explore this type of breaker in detail and explain why hiring an  electrical services provider for a wiring shunt trip breaker is essential. 

The Many Benefits of a Shunt Breaker

Let’s recap: a shunt trip breaker is an electrical component connected to a circuit breaker and allows for remote operation through a schematic and AMP connection. Now that you know what a shunt trip circuit breaker is, it's time to move to the next part of this article: the benefits of using a shunt breaker.

• Remote Shut-Off: One of the main benefits of shunt breakers is that they can be remotely shut off in the event of an emergency. This allows them to quickly and easily disconnect power in a fire or other emergency, which can help prevent damage to the building and protect the occupants.
• Increased Safety: Besides remote shut-off, shunt trip circuit breakers provide an added level of safety and security by automatically shutting off power to a circuit in the event of an emergency. This helps prevent electrical fires and other hazards, protecting both people and property.
• Easy Installation: Shunt breakers are relatively easy to install and can be integrated into existing electrical systems, making it possible to retrofit older buildings with these devices.
• Cost-Effective: A shunt breaker is a cost-effective solution for increasing safety and security in commercial and industrial buildings. They are relatively inexpensive to purchase and install and can help prevent costly damage to the building and its contents in case of any emergency.
• Compatibility: Shunt breakers are compatible with a wide range of electrical systems and devices, making them a versatile and practical solution for increasing safety in various settings.

How Does a Shunt Trip Breaker Work?

A shunt trip breaker works by tripping the breaker when it receives a signal from an external device, such as a fire alarm or security system. This helps to prevent dangerous electrical fires or other hazards. When an emergency occurs, the external device sends a signal to the breaker, which causes the breaker to trip and open the circuit, interrupting the flow of electricity and preventing power from reaching the circuit, allowing for a quick and easy power disconnection.

Types of Shunt Trip Breakers

Now that you know the answer to "How does a shunt trip breaker work", it's time to discover about the two main types of shunt trip breakers.

• Manual Shunt Trip Breaker: This type of trip breaker requires manual intervention to reset the breaker after it has been tripped, meaning someone must physically go to the breaker and reset it after an emergency situation. This breaker is typically used in smaller residential buildings or situations where a dedicated staff member is available to reset the breaker.
• Automatic Shunt Trip Breaker: This type of breaker can automatically reset itself after being tripped and is typically used in larger buildings or in situations where there is not always someone available to reset the breaker. These breakers are often connected to fire alarm systems or other emergency management systems for auto-reset.

When is a Shunt Trip Breaker Required?

If you're wondering when is a shunt trip breaker required, know that it is required in any electrical system where there is a need to quickly and easily shut off power in the event of an emergency, such as a fire or security breach. Continue reading as we describe the importance of using shunt trip breakers and how to figure out which one you need to use for your building or facility.

The Importance of Using a Shunt Trip Breaker

• Shunt trip breakers automatically shut off power in emergencies.
• They prevent dangerous electrical fires and other hazards.
• They allow for quick and easy power disconnection in emergencies.
• They are easy to install and cost-effective solutions for increasing safety.
• They can be connected to fire alarm and emergency management systems.
• They ensure that the electrical system is in compliance with safety regulations.
• They are a versatile and practical solution for increasing safety in various settings.

Which Type of Shunt Trip Breaker to Use?

A manual breaker may be appropriate for a smaller building or in situations with a dedicated staff member available to reset the breaker, while an automatic breaker may be more appropriate for a larger building or in situations where someone is not always available to reset the breaker. Another option to consider is the use of a shunt trip relay, which can be used to trigger a shunt trip breaker remotely. These relays are typically connected to fire alarm systems or other emergency management systems and can send a signal to the breaker to trip it when an emergency occurs.

Shunt Trip Breaker Wiring Diagram

If you're wondering how to wire a shunt trip breaker, know that wiring can seem like a daunting task, but with the right knowledge and tools, it can be done relatively easily. Follow the steps below:

• Obtain a "How to wire a shunt trip breaker wiring diagram." (Check above).
• Gather necessary tools and materials such as wire strippers, nuts, and a voltage tester.
• Disconnect the power and wire the shunt breaker according to the instructions provided.
• Reconnect power to the circuit and test the breaker to ensure it works properly.

It is important to pay close attention to the diagram and follow the instructions carefully. This will ensure that the breaker is wired correctly and functions. Once the wiring is complete, you can reconnect the power to the circuit and test the breaker to ensure that it is working properly. It is always better to consult with a professional if you aren't confident about the wiring process. 

What Does a Shunt Trip Breaker Do?

We hope by now you know what does a shunt trip breaker do, but here's a recap: a shunt trip breaker is a specialized circuit breaker that protects your house electrical systems from damage or hazards in emergencies. It works by tripping the breaker when it receives a signal from an external device, such as a fire alarm or security system, preventing dangerous electrical fires or other regular hazards.

Nevertheless, it is important to understand what does shunt mean in electrical terms and the role of electrical shunt trip breakers in commercial and industrial settings. Finally, to determine the appropriate type of breaker for your specific needs, it is best to consult an electrical services provider. If you're based in Colorado or surrounding areas, McCarrick Electric has got you covered.

Superior Electrical Solutions in Colorado 

At McCarrick Electric, we have 25+ years of experience providing top-quality electrical services in Colorado. We value all of our customers, and that's why we offer a 15% discount for first-time residential clients and veterans. We take pride in our integrity, attention to detail, and cost-effectiveness. For more information, connect with us via our contact form or give us a call.

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Circuit Breaker Accessories Explained

The purpose of accessories on a power circuit breaker is to provide additional functions and protection beyond basic circuit interruption. For example, a motor can automatically charge the closing spring of the breaker, reducing the time required for the breaker to close.

Other accessories can offer additional functions, such as undervoltage or overvoltage protection, or enable remote operation of the breaker. These accessories enhance the safety, reliability, and functionality of the power distribution system.

Circuit breaker accessories are matched to the system control voltage and may be available as factory-installed options or in field-installable kit form. Some typical control voltages include: 250VDC, 240VAC, 120VAC, 125VDC, 48VDC, 24VDC.

Auxiliary Switch

Auxiliary Switches provide remote indication of the breaker main contact position, changing state when the minimum isolating distance between the main contacts is reached. They typically feature Form C contacts, with options for both NO (Normally Open) and NC (Normally Closed) states, sharing a common neutral.

A Contact – Open or closed same as the breaker.

B Contact – Opposite to the breaker contacts.

Connected/Closed Switches

Connected/closed switches combine information from the “connected device” and “closed device,” indicating that the “circuit is closed.”

Bell Alarm / Overcurrent Trip Switch

The overcurrent trip switch provides remote indication that the circuit breaker has opened due to an electrical fault. Typically equipped with one set of Form C contacts, offering options for both NO (Normally Open) and NC (Normally Closed) states with a common neutral. The switch is activated, and the outputs change state whenever the breaker is tripped by an overcurrent, ground fault, or protective relay function via the Trip Unit.

A trip caused by the manual OPEN button or by the Shunt Trip or Undervoltage Trip Device accessory does not activate the Bell Alarm. The accessory can be reset, returning the contacts to their normal configuration, by reclosing the breaker or by manually resetting the target on the breaker escutcheon.

Bell Alarm Lockout

The Bell Alarm with Lockout prevents closing of the breaker after a protection trip until the lockout is reset.

Electric Reset

The electric reset is used to reset the circuit breaker remotely after an electrical fault.

Ready-to-close Switch

The ready-to-close switch indicates that the following conditions are met and the circuit breaker can be closed:

• The circuit breaker is open
• The closing springs are charged
• The circuit breaker in not locked/interlocked in open position
• There is no standing closing order
• There is no standing opening order

Spring-Charging Motor

The spring-charging motor provides a means of electrically charging the closing springs automatically after the circuit breaker closes. When the springs are fully charged, a cutoff switch automatically de-energizes the motor. The closing springs will recharge automatically after the breaker closes unless an external switch contact is wired into the spring-charging circuit.

Spring-Charged Contact

The spring-charged contact indicates that the circuit breaker is charged. Usually a form C contact.

Shunt Trip / Shunt Close

The shunt trip coil opens the circuit breaker when energized. Shunt Close will close a circuit breaker when energized if the device is ready to close. Shunt trip and shunt close share the same coil; the action is determined by the location of the coil. The shunt close accessory features an anti-pump feature that prevents the breaker from repeatedly closing if the closing signal is maintained.

Undervoltage Trip

The undervoltage trip opens the circuit breaker when its supply voltage drops below the threshold voltage. Undervoltage trip coils require continuous power supply to keep the circuit breaker closed.

Time-Delay Module for Undervoltage Trip

The time-delay module for the undervoltage trip can be used to set an adjustable time delay before the undervoltage trip opens the circuit breaker, preventing nuisance tripping from a momentary voltage drop. The time-delay mechanism is connected in series with the undervoltage trip (MN) and is installed outside of the circuit breaker.

Electric Lockout

The electric lockout accessory uses a coil similar to an Undervoltage Trip Device to prevent the breaker from closing unless the coil is energized. Consequently, the breaker cannot be closed unless control voltage is applied; however, the loss of control voltage will not trip the breaker.

For instance, two breakers can be interlocked to ensure that they cannot both be closed simultaneously. The Electric Lockout coils on the two breakers to be interlocked can be wired in series with a normally closed Auxiliary Switch contact on the other breaker to provide the interlocking function. Mechanical bypass is utilized to permit cold startup when control power is not available.

Electrical Closing Push Button

The electrical closing push button closes the circuit breaker electrically via the shunt close. Requires installation of shunt close.

Operations Counter

The operations counter registers the total number of operating cycles for the circuit breaker.

Communications Module

The circuit breaker communications module provides communication between circuit breaker trip unit and the communication network. Dedicated switches can be used to read status of circuit breaker. Actuators can be used to control the circuit breaker.

Position Switch

The cell position switch indicates the circuit breaker position in the cradle/cell. This accessory is for drawout circuit breakers only and typically contains normally-open and normally-closed contacts. There can be one to three position switches for each type.

• Disconnected

Open-Fuse Lockout

The Open-Fuse lockout is provided on integrally fused breakers or when the breaker is used in combination with a Fuse Rollout Element. When any fuse blows, the Open-Fuse Lockout trips the breaker to prevent single-phasing.

An indicator shows which fuse has blown. The breaker is mechanically trip-free and cannot be reclosed until the blown fuse is replaced, and the Open-Fuse Lockout is reset.

Hidden-Close Button

The Hidden Close Button is an unmarked replacement for the normal CLOSE button. Pressing the Hidden Close Button in the usual manner will not close the breaker; instead, a rod inserted with light pressure is used to engage the hidden-close button.

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How does a shunt trip work to trip a circuit breaker?

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