- How can I find out about withstand voltage performance?
Refer to each rated voltage shown on the product pages. Select a fuse with a larger rated frequency than the circuit voltage (for DC, voltage after rectification) on the short circuit expected in case of an accident. Take the following points into consideration:
- Keep in mind that rated voltage of a fuse differs between AC and DC.
- For DC, available voltage changes according to the time constant (L/R) on the short circuit. Refer to the chart titled “Application to direct-current circuit” on each product page.
- Depending on the standard observed (UL standard, CCC standard, etc.),the rated voltage may change. Be aware that the fuse may not be regarded as an approved fuse when used in a circuit exceeding the rated voltage.
- Block-off can be achieved with a fuse that you select by following the above instructions. However, adopting a fuse with more voltage as leeway will enable you to;
- Cope with voltage fluctuation
- Shorten the breaking time (mentioned below)
- Decrease the minimum breaking current
If you would use fuses in this situation that the short-circuit current di / dt = 50 [A / μs] or more, please contact us.
- How can I find out about breaking performance? (I'd like to know if the fuse can block off before the object under protection is damaged.)
For the area of (1), it appears to be protected by other protection equipment and/or current-limiting functions, and our fuses are often selected emphasizing protecting the area of (2). Also, even in cases that the shutdown l2t is larger than permissible l2t, our fuses are often used to prevent explosions, ignitions, and secondary damage.
If overcurrent time is approximately over 10 ms
Refer to the fusing characteristics curve. If the current (A) vs. time (S) curve of the fracture characteristics of the target object is positioned to the right of the fusing characteristics curve of the product, it means the fuse can block off before the object is damaged.
If overcurrent time is approximately under 1 ms
・Compensate the shutdown l2t value of each fuse using “shutdown l2t gainst the working voltage” chart.
・If the permissible l2t value for the target object is available, compare the shutdown l2t with it, and if the shutdown l2t is smaller than the permissible l2t value, it means the fuse can block off before the object is damaged.
・If only the damaging current vs. time curve of the target object is available, calculate its permissible l2t value [ = (damaging current)2 × time ] and compare in the same way as in (b).
- How can I find out about breaking capacities and performance? (I'd like to know the current value that the fuse cannot block off.)
- Refer to the breaking capacity of each fuse. Electric current exceeding the value cannot be blocked off.
Refer to the minimum breaking current of each fuse. Electric current below this value cannot be blocked off. Despite fusing, block-off may not take place, possibly causing an accident. Therefore, take the following measures:
- Using the current control function of the circuits of other protection devices, ensure that current does not flow in that area.
- Use a fuse with a rated voltage above the circuit voltage to reduce the minimum breaking current.
- How can I find out about electric durability? (I'd like to know the maximum magnitude (amperes) and the maximum rate of increase of overcurrent that a fuse can endure.)
- Read the value from the fusing characteristics curve of each fuse.
When an electric current larger than current range of a fusing characteristics curve flows, the value is calculated from the fusing l2t value of each fuse.
- [Fusing time = fusing l2t value ÷ (short-circuit current value) 2] (
- The fusing time and electric current are effective for overcurrent only once. Once such an overcurrent flows, the fuse becomes easy to cut off. For more details, refer to the material about life expectancy).
- How can I find out about fuse life expectancy against constant electric current and repetitive overcurrent?
- Details are available on this in separate documents. Please contact us for more information.
- How can I find out about environmental resistance performance?
- Heat generation: Refer to the temperature characteristics
chart of each fuse.
- Temperature characteristics: Refer to the chart titled “Compensation
"by ambient temperature.”
- Other details on environmental résistance: Contact us for more
- I’m not sure how to use the performance curves.
- Please refer to the HOW TO USE THE CATALOG. If you have any questions, please send an inquiry to us.
- Where in the circuit should I use a fuse?
- First, consider what you would like to protect with the fuse. Then, please refer to the PROTECT FUSE USER'S GUIDE for examples of applying position.