Image credit: AutomationDirect | Newark/element14 | Littelfuse   Circuit breakers are automatic electrical switches designed to interrupt current flow in the event of an overload or short circuit.   Basic Information   Basics of Circuit Protection Electrical circuits can experience several conditions which pose danger to associated equipment or the circuit itself, namely current overload and short circuits. An...
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Q & A on Circuit Breakers

We asked our users for their input on Circuit Breakers. Here are the results of 523 users familiar with Circuit Breakers.

Who Took Our Poll? | Design Trends | Applications and Use | Features | Buying Advice

Who Took Our Poll?Top

Design TrendsTop

Q:
What new technologies are influencing circuit breaker design?
80 answers
Answers:
Circuit breaker design for low voltage - according to me, nothing much has revolutionized in the last few decades except that the size has been reduced. Trip units have become digital or microprocessor based, but the arc quenching technology for LV still remains very much the same. In medium voltage also vacuum, SF6 have come quite sometime back, so there is no real revolution. The researchers are only looking into the tripping units.
~Technical Support, Singapore
Materials that the breakers are being made from. With the emphasis on safety being the hot topic of late, breakers can be made more safe so as not to blow apart into a million little pieces upon a overload or short circuit, and hurting a maintenance person or an electrician.
~Warren C, Senior Electrical Designer, Columbus, OH
Hybrid vehicles and high voltage, high current applications in heavy vehicles, load monitoring and reporting via data bus communication. Software settable devices for multiple applications.
~Degory H, Senior Project Engineeer, Dallas, TX
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Q:
From your perspective, which companies are creating the most innovative circuit breakers?
87 answers
Answers:
There is not a lot of innovation in the world of CBE manufacturers, as critical masses are seldom achieved with new products and companies are reluctant to commit to major investments. Today's strongest global players are without a doubt Sensata Technologies and Carling Technologies.
~Mark P., General Management, Sevilla, Spain
I can not talk about innovation as - in the nuclear industry - that is secondary to reliability and safety. My systems includes breakers from ABB and Schneiders (and their predecessor companies like ITE, Federal Pioneer, Merlin Gerin etc..)
~Thomas U., System Engineer, Clarington, Ontario, Canada
We find ABB switch gear is reasonably good.
~Milind A, General Management, Pune, India
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Applications and UseTop

Q:
What are some of the applications you have used a circuit breaker for?
132 answers
Answers:
I finally started construction work in 1951, switched a couple of contractor and was involved with all Brands and all types of Cir. Breakers, in commercial Buildings, Power plants, Reactors, Dorms, Hospitals, Factories, Stadiums, Switch yards, and you name it. I had a good enjoyable life in the Electrical Construction field.
~William (Bill) Lang, Project mnanager from 1954 on till retirement, Boonville, MO
I run coordination studies for power plants / industrial customers. Not only to properly coordinate a system, but also to mitigate HRC levels. Many times I must recommend replacing breakers to properly coordinate so some design aspects are used. I am also involved in testing breakers, usually on shutdowns by the customer.
~Engineering, Other, Ashland, MA
1.Now I am working as a design engineer and I use MCBs, MCCBs & ACBs in LV panels. 2.When I worked in VCB manufacturing plant, I involved in testing of VCBs 3.When I worked as a Substation Commissioning engineer, EHT CBs were used.
~Sreejith V, Design Engineer, Kannur, India
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Q:
Please share with us any “non-standard” applications that a circuit breaker has been used for.
28 answers
Answers:
D.U.R.T. Very fast circuit breaker based on Thomson effect technology. This circuit breaker has been made to be installed on low voltage switchboard with a very short circuit withstand, Opening time < 5 millisecond.
~Jean Bozonat, Project Manager, St Hubert, Canada
480 4000 Amp fuses acting as a main protection for multiple lineups of switchgear. The trip curve on the 4000 Amp fuses allowed extensive damage to the LV switchgear when a fault occurred.
~Mike V, Marketing/Sales, Tampa, FL
Emergency Power Off Switch. We use a low voltage release to trip the Main Disconnect when an EPO switch is activated dropping the loop to the low voltage switch.
~Ken P, Design Engineer, Tampa, FL
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Q:
Do you know of any disastrous mistakes that occurred due to the incorrect usage of a circuit breaker?
35 answers
Answers:
Incorrect protection levels set on breaker causing motors pump to shutdown, resulting in flooding a motorway tunnel roadway, closing the road.
~John B, Construction manager, Brisbane, Australia
There are hundreds of stories out there, most are caused by Human error. Be sure that a Qualified Individual is installing and energizing your equipment. In other words, don't let somebody's brother in law who "Knows a little bit about electricity" install. Recommend or work on your gear to save a little bit of money. If in doubt, call me at Coastal Power Systems and I or someone else can help you with your needs.
~Colin K, Sales, Design and Production, Houston, TX
Yes. I've seen the result of an owner not replacing a circuit breaker and wire when they have replaced a pump motor with a larger horsepower motor than was originally installed. Cost them more the second time than it would've if they'd done it right the first time of replacement.
~Warren C, Senior Electrical Designer, Columbus, OH
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FeaturesTop

Q:
What would your design or feature "wish list" be for this product?
70 answers
Answers:
Low cost bus bar connection system. Something that makes it easy and cost effective to connect between a breaker terminals and transformer low voltage bushing spades. A standard flexible connector offering may work well.
~Design Engineer, Waukesha, WI
Very reliable operation, superb arc quenching characteristics, designed for remote control, mutual "supervision" of remote and local controls (i.e. any fault in local controls & indications be observable in remote control panels and vice versa).
~Thomas U., System Engineer, Clarington, Ontario, Canada
Better instantaneous trips for easier selective coordination and to put the fuse guys in their place. Get the instantaneous trips to coordinate better at the 0.01 sec at higher amperages.
~Warren C, Senior Electrical Designer, Columbus, OH
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Q:
Is there any advice you want to share with users to help them avoid common errors in selection or usage of a circuit breaker?
41 answers
Answers:
Not all manufacturers' breakers are equal. Even if they say they are, they aren't. Look at the time current curves. Do your math and size the breaker correctly. Verify with an equipment manufacturer's specification for the minimum overcurrent protective device, be it a circuit breaker or a fuse.
~Warren C, Senior Electrical Designer, Columbus, OH
Do not allow electrical contractors to select circuit breakers. Circuit breakers should be specified by an engineer knowledgeable about electrical distribution systems. Industrial facilities should specify minimum 65ka interrupting rating circuit breakers for all 460 volt 3 phase and above applications. End users should verify breakers installed by electrical contractors meet specifications.
~David P, Engineering Consultant, Pickens, SC
Always cross check dimensions with supplier if you are using a new breaker. Heat dissipation for bus bar joints and routing of the bus bar in compact size cabinet is best done on 3D platform.
~Milind A, General Management, Pune, India
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Buying AdviceTop

Q:
Do you have any advice for people relative to buying or using a circuit breaker?
50 answers
Answers:
Know what you need before you go looking. There are a lot of questions that a salesperson will have regarding your needs. That information should be at hand to prevent multiple search and find missions. Relative info would include: System Voltage, Amperage and Interrupt Rating required. Are they replacing a breaker or adding? If adding, to a distribution panel and if so, what type? What is the application?
~Colin K, Sales, Design and Production, Houston, TX
Do not overlook the quality vendors of surplus, used, reconditioned or reconfigured electrical distribution equipment. If you have a need for adding to or extending your low or medium voltage installed base system or a short lead time for procurement and emergencies, this market segment is prepared to assist.
~Larry L, Manufacturer, Plant City, FL
Consult with a knowledgeable power systems engineer before changing circuit breaker settings. Do not allow maintenance personnel to change breaker trip settings without specific written instructions. Maintain circuit breakers per manufacturers' specified schedule for reliable operation.
~David P, Engineering Consultant, Pickens, SC
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