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Precautions for Use of
Fusing Components |
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Please refer to precautions foe use in the beginning
part for particulars common to all product types. |
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KOA's fuse components comply with the following safety standards:
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| JAPAN |
METI(Type B)
(The safety law for electrical appliances has been enforced
since April, 2001) |
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| U.S.A. |
UL(Underwriters Laboratories
Inc.)
UL248 |
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| CANADA |
CSA(Canadian Standards Association)
C22.2 No.248
c-UL(Underwriters Laboratories Inc.)
UL248
*c-UL is equivalent to CSA in recognition. |
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A rated voltage indicates the voltage that does not run
through electrodes after the fuse blows. In case of exceeding the
rated voltage, the circuit voltage should be applied at voltage
not higher than the rated voltage because the current may run again
or may break the elements. |
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In case of the AC waveform, the voltage of peak voltage,
but not the effective value of voltage waveform should be applied
at voltage not higher than the rated voltage. |
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An interrupted capacity indicates current and voltage that
can be interrupted when an abnormal situation arises. Make sure
beforehand that voltage and current at the time of abnormality occurring
in the circuit are within the interrupting capacity. For CCP and
TF series, the fusing current and rated voltage become an interrupting
capacity. |
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It indicates a current that interrupts a circuit. Refer
to the following list to quickly interrupt an abnormal current occurred
in the circuit: |
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| Type |
Fusing Current |
Fusing Time |
| CCF1N |
Rated Current×2 |
1s |
| CCP2B |
Rated Current×2 |
| CCP2E |
Rated Current×2.5 |
CCP2E H |
Rated Current×2 |
| TF16SN |
Rated Current×2 |
| TF10AN |
Rated Current×2 |
5s |
| TF16AT |
Rated Current×2 |
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If its fusing time is within 1 second, the variance in the
fusing time affected by the surroundings (temperature, mounting
pad dimensions, substrate material, etc.) will be negligible. But
if it is not less than 1 second, it will be largely affected by
them, so its verification should be made with an actual circuit. |
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Anti-Surge Characteristics
There are limits to applications
of transient overcurrents (inrush current, reversible current at
motor-lock, etc.) that occur in circuits. It is necessary to select
proper products that withstand such overcurrents without fusing.
Select proper fusing components considering the following conditions: |
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The transient phenomenon varies with the ambient temperature,
charging/discharging conditions of capacitors, etc. Check the wave-form
of current under such conditions that the current becomes the maximum.
Also check it beforehand under such conditions that the current
becomes the maximum if parts highly dependent on temperatures such
as thermisters, etc. are used in the circuit. |
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For a peak current observation, shorten the sampling time
of an oscilloscope to verify the maximum value of the wave-form
of the surge current. |
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If a current measuring is performed by measuring voltages
of shunt resistors, etc., use the lowest possible resistances of
them to the impedance in the circuit. |
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Calculate Joule Integral I2t (A2
s) of current wave-form
measured under conditions above and compare with the I2t-t characteristic
graph to evaluate on the following (a) to (d) criteria: |
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If a measured current wave-form shows a jagged shape just
like the figure below, evaluate it with the wave-form that connects
each peak current value to simplify the wave-form.
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(a) |
Below Rating Current Line
Impressing a stationary current will not cause any problem. |
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(b) |
Over Rating Current Line and Below Limit of
One Pulse Current Line
The repetitive impressing of a transient current will not
cause any problem. However, accumulated stress may cause some
problems if the repetitive cycle is not more than a few seconds,
so consult with us. |
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(c) |
Over Limit of One Pulse Current Line
The fusing element can suffer from stress. The repetitive
impressing may cause an open. |
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(d) |
Over Fusing Line
It causes an overcurrent impression to blow out. |
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This product is suitable both for reflow-soldering and for
flow-soldering, but an excessive heat may cause an open and change
its characteristics. |
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The part shall be soldered at the maximum temperature
of 260 . |
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If a soldering iron is used, it shall be at
350
or under and stress shall be not applied to the electrodes at a
short time. Further, pay attention that the products are not touched
directly by the top of the iron. It may cause disconnection or characteristic
change. |
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Please confirm sufficiently the evaluation of
reliability and use those that have small contractile stress at
a resin stiffening time. By contractile stress at the resin stiffening
time, fuses might be broken, resistance value may be changed and
disconnection might occur in case of resin coating/potting or molded
sealing. Further, be sure to consider the dispersion of constant
of other components in the actual circuit. There is a possibility
that heat may fill the surrounding of the fuses by shielding and
may cause the fusing characteristics to change. |
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The fusing characteristics may change when there
are components that generate heat very much around the fuses. Keep
fuses away from those parts. |
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Avoid storing components under the condition
of high temperature/high humidity (40/70%RH)
which may deteriorate solderability. |
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Also avoid direct sun light which may deteriorate
solderability and induce changes in taping strength. |
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If you have any questions about the way of selecting
fuses, please do not hesitate to ask us with the information on
rated voltage, operating temperature, wave-forms of steady-state
current and rush current, and fusing current. |
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Application Notes
Brush up your circuit
Basic Knowledge
Rated
Current Value
Stationary
Derating