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Fuse or Circuit Breaker

Connector Geek

The humble electrical fuse is well over 125 years old. The first patent is attributed to Thomas Edison in 1890, but there is evidence that a device that we would recognise as a fuse was being used during the era of the American Civil War in the 1860s. In today's world of semiconductors, electronics and miniaturised devices, the fuse is a mechanical dinosaur.

Fuses are not the only solution for providing electicial protection. Circuit breakers are at least as old as fuses - once again it's that man Thomas Edison whose patent for a circuit breaker dates from 1879. Circuit breakers are electro-mechanical devices that interrupt electrical circuits, and - in critical comparison to fuses - can be reset to normal operation after the overload or overcurrent has been removed.

So, why would an engineer choose to use a fuse which, once blown, must be replaced when a circuit breaker can simply be reset? Anyone who lives in the UK is familiar with the inconvenience of a blown fuse (for those not used to our power cables, every plug is fitted with a fuse). Surely a resettable circuit breaker would be much more convenient.

However, the advantages of fuses make them highly suitable for a huge range of applications. Being mechanical devices, fuses can react to overload or overcurrent much more quickly than the electro-mechanical circuit breaker. In addition, as fuses are completely mechanical in design, they are maintenance free, sitting passively for years until the very moment they are needed.

Our friends at Eaton Bussmann are leaders in the design and manufacture of fuses. They are members of the Pro Fuse International association, a community of manufacturers who advocate the advantages and advances in fuse technology.

Pro Fuse International has created a highly informative white paper to help designers and end users in making the most appropriate choice of protection devices for low voltage equipment.

You can download the white paper here.

Eaton develops and manufactures critical circuit protection, power management and electrical safety products designed to provide innovative circuit and power electronics protection, serving the commercial, data center, electrical vehicle, food and beverage, and other markets. You can take a look at the Eaton Bussmann series of fuse products here, or click on the logo below.

Connector Geek is Dave in real life. After three decades in the industry, Dave still likes talking about connectors almost as much as being a Dad to his two kids. He still loves Lego too. And guitars.

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January 30, 2017 10:29

Enclosed HBC type fuses do have the great advantage that they just sit around for years waiting for a fault, and being enclosed they do not tend to age as do open types or the simple glass tube fuses. HBC fuses also have the added advantage of limiting the energy let through during operation, this is achieved using a fine sand in the fuse that falls into the space left by the fuse element after operation, and blocking the path of any arc that has been formed.
Fuses have many disadvantages such as needing to keep spares, fitting the correct rating and type and the old problem of some folks just bridging them out with fuse wire.
The mechanical disadvantages of circuit breakers may be alleviated by using 'Backup protection, that is using a fuse upstream of the CB that has operating characteristics that mean it will not operate before the CB has fully cleared the fault, ie the arc is extinguished. This method ensures protection in the event of the CB failing to open in the specified time.
Backup protection has been in use in the Electrical Contracting field since the introduction of Circuit Breakers.

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