A fuse is a safety device with a thin strip of conductor that protects homes from power surges. When too much electricity surges through a circuit, the fuse wire melts, halting the flow of energy.
Fuses are rated in terms of current capacity and voltage capability. They also have specific breaking capacities and response times.
Types of Fuses
Electric Fuses come in a variety of different sizes and styles and are made with a wide range of materials like ceramic, glass, plastic, fiberglass, or molded mica laminates. They are also produced in standardized package layouts that allow them to be easily interchangeable.
They are rated in terms of their current carrying capacity, which is the maximum amount of current they can carry before blowing. These fuse values are typically listed on the data sheet along with their melting and clearing I2t ratings to aid in fault coordination studies.
The I2t rating measures the energy (in terms of heat) that is let through by the fuse element when it clears a circuit fault. It is usually specified as a range for each fuse type and size and it is often used to help determine which protective devices should operate together in a fault condition. The I2t is also a good way to identify which wires in the circuit are overloaded.
The current rating of a fuse is the maximum amount of current that it can carry without blowing. The current rating is based on the melting integral of the fuse element, also known as the I2t value, which is a function of the fuse material and characteristic. This value is independent of voltage and ambient temperature.
Fuses are primarily rated in terms of their current capacity, or amps. This is because they are designed to contribute only a negligible amount of resistance to the circuits that they protect. This value is also known as the breaking capacity and should be greater than the prospective short circuit current.
This is largely accomplished by making the fuse wire as short as possible so that the heat generated during a surge doesn’t have too much time to spread beyond the fuse element and damage other components in the circuit.
A fuse’s voltage rating is the maximum amount of current it can interrupt without breaking. If a fuse with a lower rated voltage is used, it could potentially damage the circuit the fuse is protecting, resulting in a dangerous situation and possible fire or electrical failure.
The voltage ratings of fuses depend on their temperature, with the cold resistance and voltage drop increasing as the fuse increases in temperature. This is why it is important to consider the overall system characteristics when selecting a fuse and to choose small-sized fuses with low internal resistance to reduce the impact of voltage drop on the circuit.
Some fuses require safety agency approvals for use in specific applications, and Digi-Key has made it easy to filter by these parameters on the site. However, searching based on approvals first can often result in many good options being missed. This is why it is recommended to try searching for other parameters, such as current or voltage rating, before using the approvals filter.
Using the wrong fuse type for an electric circuit can lead to electrical damage and even serious injury or electrocution. The main function of fuses is to melt the wire inside during power overloads and disconnect electricity flow into the circuit.
Electric Fuses Installation has current-limiting protection and a time delay. They only allow a short burst of power surge before they blow out due to heat buildup. This protects electronic devices from damage caused by sudden spikes in current such as those generated when a garbage disposal or refrigerator is turned on.
Time-delay fuses are designed to withstand a higher level of temporary overloads and are suitable for capacitive circuits that require high inrush current such as fluorescent lamps and electric motors. This type of fuse doesn’t have a time delay mechanism, but it responds quickly to electric spikes and breaks the circuit. You can recognize a time-delay fuse by its small opening window which looks brown, cloudy, or black.