Last Updated on October 22, 2023 by Kevin Chen
A shunt trip breaker is a device used to protect circuit breakers from nuisance tripping. In the event of a short circuit, for example, the shunt trip breaker senses the excess current and breaks (shuts off) the power supply by shunting it to ground, rather than allowing it to pass through the circuit breaker. A shunt trip breaker is always installed in conjunction with a circuit breaker.
It does not replace the need for a standard circuit breaker but rather works as an additional safety feature. Let’s take a closer look at what this protective device does and how it operates.
A shunt trip breaker is an auxiliary device that protects the main circuit breaker from nuisance tripping due to high voltage or high current levels caused by momentary overload conditions, such as arc flash protection response or switching events that may cause fault currents above allowable levels.
How Exactly Does a Shunt Trip Breaker Work?
Image source: Etechnog
A shunt trip breaker has a current transformer that senses the amount of current through the device. When the current exceeds the normal level, the shunt trip breaker shunts the current to ground, interrupting the flow of current.
Activation thresholds are set by the user and depend on the current rating of the shunt trip breaker, the size and type of circuit breakers being protected, and the load on the circuit. Shunt trip breakers are connected in series with the circuit breakers they’re protecting.
When a circuit breaker trips, the current flowing through the circuit drops to near zero. This drop in current is sensed by the shunt trip breaker and it resets. When the current through the circuit breaker is large, the shunt trip breaker activates before the circuit breaker trips.
If a shunt trip breaker activates, it does not reset until the cause of the high current is removed. A shunt trip breaker is therefore able to protect a circuit breaker from nuisance tripping due to momentary high current conditions.
Types of shunt trip breakers
Based on the modes of control, shunt trip breakers are divided into two main categories. These are manual and automatic.
Shunt trip breakers with manual switches allow you to turn them on and off remotely even when you are outside the building away from the circuit They are the most preferred type probably due to the convenience that they give users.
On the other hand, automatic shunt trip breakers operate based on the behavior of the current. This implies that they will shut off immediately after detecting a surge in current.
What are the benefits of a Shunt Trip Breaker?
-High energy cost savings: A shunt trip breaker is able to prevent or delay the tripping of circuit breakers in high current scenarios, reducing energy costs for businesses that rely on electricity for operation.
-Increased uptime: A shunt trip breaker reduces the number of times circuit breaker trips by sensing excessive current and quickly shutting it off. Circuit breakers are designed to trip when they experience an overload so that short circuits can be cleared before the circuit is damaged.
A shunt trip breaker ensures that the circuit breaker will not trip due to a momentary high current condition when the shunt trip breaker removes the current. This protects the circuit breaker so it remains operational and can handle the higher current load.
Limitations of a Shunt Trip Breaker
Shunt trip breakers do not offer complete protection against nuisance tripping. They are not designed to handle large overload events. For example, a shunt trip breaker typically can interrupt about 2.5 times the normal current on a circuit.
It is important to note that these devices are generally not suitable for use with motors rated above 5 horsepower (HP).
Shunt trip breakers are connected in series with the circuit breakers they’re protecting. If a shunt trip breaker fails, it will cause the circuit breakers to trip. A shunt trip breaker cannot be used on circuits that are supplying emergency power.
How to install a shunt trip breaker
When installing a shunt trip breaker, make sure it’s placed in the correct phase and circuit. Follow the manufacturer’s installation instructions and consult a circuit diagram to ensure you are connecting the shunt trip breaker to the correct circuit.
Connect the shunt trip breaker to the breaker that is upstream from the circuit breakers it will protect. Make sure the shunt trip breaker is properly installed and maintained according to manufacturer instructions, including periodic inspections and tests.
Where do you install a shunt trip breaker?
A shunt trip breaker should be installed in the main service panel. It should be installed in a section of the panel that is easily accessible. The shunt trip breaker should not be installed in between fuses so it can be easily checked for operation.
What controls a shunt trip breaker?
A shunt trip breaker is an electromechanical device that is controlled by the current through the device. It has no internal trip mechanism. It is therefore always connected across the circuit to be protected.
An SCR (silicon-controlled rectifier) or a transistor is used in the shunt trip circuit to control the current. The SCR is either a bidirectional device or a unidirectional device. If the SCR is a unidirectional device, it is turned on by the current flowing in one direction and off when the current stops.
Shunt trip breakers are also remote-controlled. This allows the switch operator to manually trip the shunt trip breaker in an emergency situation. The remote control can be controlled by a switch on the panel board or it can be a separate device.
Best Practices When Using Shunt Trip Breakers
Follow these best practices when using shunt trip breakers to maximize the protection they offer and help avoid unnecessary costs:
Install the shunt trip breaker on the same side of the panel where the breakers it protects are located to avoid travel distance issues that can affect the performance of the shunt trip breaker.
Install the shunt trip breaker as close as possible to the circuit breakers it protects, but with enough distance to avoid creating a series inductive load. Stagger the shunt trip breakers so they are not all in one line on the same side of the panel.
What is a shunt trip button?
A shunt trip button is a device that allows an inspector to trip a circuit breaker without physical contact. The inspector simply presses the button and it trips the breaker. it is useful in situations where the inspector is unable to physically reach a circuit breaker.
A shunt trip button can be used with a magnetic key fob or remote control. They are available in a variety of shapes and sizes to meet the needs of various applications.
How do you check a shunt trip breaker?
How can I tell that a shunt trip breaker is working? The only way to do so is by testing it.
How do you test a shunt trip breaker?
A simple method of testing a shunt trip breaker is to set up the circuit breaker in the open position and test it. If the breaker trips, then you know that it is working properly.
Another method is to use a load tester that can be connected to the circuit breaker. The load tester will apply a small amount of current that should trigger the circuit breaker.
How to Choose a Shunt Trip Breaker
When choosing a shunt trip breaker, there are a few factors you should keep in mind to ensure you select the right device for your application.
Make sure the shunt trip breaker is rated for the current and voltage of the circuit it will protect. Choose a shunt trip breaker that is rated for the maximum current for continuous operation and one that is rated for the maximum current for the “continuous unavoidable” operation.
When selecting a shunt trip breaker, you also have to consider the circuit breakers it will be protecting. You want to select a shunt trip breaker with a current rating that is significantly lower than the current rating of the circuit breakers it will be protecting.
Where to buy shunt trip breakers?
In case you want to buy shunt trip breakers in China, ensure that you get them from the right sources. By this, I mean reputable manufacturers and suppliers.
They are the only ones who can assure you of g quality and genuine shunt trip breakers for sale.
We know that finding such manufacturers and suppliers can be quite a hectic task. To make things better, you should consider using a sourcing agent. They will ensure that the products you are buying are genuine and authentic.
ICRFQ is one of the trusted sourcing agents for electrical components in China. We have an extensive list of electrical components manufacturers and suppliers in China.
We will assist you in finding the right vendors to buy shunt trip breakers in China.
Final Words: Is a Shunt Trip Breaker Worth it?
Shunt trip breakers are important devices that protect circuit breakers from nuisance tripping. So, it is a must-have electronic component for your home or even commercial place.
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