Key points for selecting fuses


Release time:

2020-07-15

When choosing a fuse, I believe everyone finds it quite troublesome, as there is no good guidance. Below, the editor from Longde Electric will list the factors involved in fuse selection, so that everyone can choose a suitable fuse based on these ideas.

Key points for fuse selection
 
I believe everyone finds it very troublesome to choose a fuse, as there is no good guidance.
Below, the editor from Longde Electric will list the factors involved in fuse selection.
Everyone can choose a suitable fuse based on these ideas.
 
1. Normal operating current: The reliable operating current of the fuse at 25°C is usually 75% of the rated current to avoid failure. For example, in an environment of 25°C, it is generally not recommended to use a fuse rated at 10A to operate above 7.5A.
2. Application voltage (AC or DC): The rated voltage of the fuse must be equal to or greater than the voltage of the application circuit.
3. Ambient temperature: The higher the ambient temperature, the hotter the fuse operates, and the shorter its lifespan. Conversely, operating at lower temperatures will extend the fuse's lifespan. The fuse will also get hotter when the normal operating current approaches or exceeds its rated value.
4. Overload current: This defines the current that needs to be protected in the circuit under fault conditions. Fault conditions can be current, or the current and the fault time that can be tolerated before damage occurs. In the matching phase between the fuse and the circuit, the time-current curve should be emphasized, but remember that the curve is based on average data.
5. Fault current: The fuse's rated breaking current must meet or exceed the circuit's fault current.
6. Pulses (current surges, inrush current, and circuit transients): Electrical pulse conditions can vary greatly in different applications. Different fuse structures may not respond the same way to given pulse conditions. The thermal cycling and possible mechanical fatigue caused by electrical pulses can affect the fuse's lifespan. Initial pulses or inrush pulses are normal for certain applications, where fuses should be selected to include thermal delay designs to accommodate normal inrush pulses while still providing protection during prolonged overloads. In selecting fuses to respond to inrush pulses, we should refer to and compare the fuse's time-current curves and I2t ratings.
7. Physical size limitations: For information regarding the length, diameter, and height of fuses, please refer to the manufacturer's data sheet.
8. Need for agency approval: Please refer to the manufacturer's data sheet for information regarding specific device agency approvals, such as UL, CSA, VDE, METI, or MITI. Military requirements need special consideration.
9. Fuse characteristics: For information on installation type/size, ease of removal, axial leads, visual indication, etc., please refer to the manufacturer's data sheet.
10. Characteristics of fuse holders and re-evaluation: For information on clips, mounting blocks, panel mounting, PCB mounting, RFI shielding, etc., please refer to the manufacturer's data sheet.
11. Pre-production application testing and validation: Validate the selection by requesting samples to be tested in actual circuits. Before evaluating samples, ensure that the fuse has a good electrical connection and that the cables used are appropriate. Testing should include lifespan testing under normal conditions and overload testing under fault conditions to ensure the fuse operates correctly in the circuit. The above are the key points related to fuse selection.

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2020-07-15

Key points for selecting fuses

When choosing a fuse, I believe everyone finds it quite troublesome, as there is no good guidance. Below, the editor from Longde Electric will list the factors involved in fuse selection, so that everyone can choose a suitable fuse based on these ideas.

2020-07-15