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    The introduction of test method of fuse holder, attention to fuse type selection and influence of life

    Fuse seat and fuse are a kind of products that we often contact, almost every household is equipped with such a kind of protection measures to protect our safety, then about the fuse seat and fuse we know how much?

      Today, manatee fuse holder manufacturers in China will introduce some testing methods of fuse holder and what should be paid attention to when selecting fuse and what factors are related to the life of fuse and what are the influences?I believe that through today’s introduction, you will have a more comprehensive understanding of fuse holder and fuse.

      First we will introduce about what are some detection methods of fuse holder, before introduce the test method, we need to know and clear judgment standard on some of these detection methods, so as to better help us to compare and clear after the inspection, or how to how to judge the quality of such a fuse holder, few words said, the next first introduces some standards about fuse holder detection method:

      (1) according to the rated current on for one hour, the fuse will not blow.

      (2) according to the rated current power, fuse base temperature rise is less than 75 degrees

      (3) in the fuse on twice the rated current, the fuse will blow in a minute

      (4) in addition to the rated short circuit capacity, there will be no continuous arc and ignition

      Based on the above standards, we will introduce some testing methods:

      (1) temperature and voltage detection: use the power supply to fuse seat on the current and voltage, keep the voltage at 220V, and the current from 2A supply, every 4-5 minutes after increasing the current 2a-10a, rated current electrification temperature rise less than 75 degrees.

      (2) fuse time test, using a stopwatch to record and observe, in the fuse seat through twice the rated current and up the current flow, fuse fuse needs to happen in a minute, and take photos before and after the fuse

      (3) fuse sample test, provide three fuses of the same specification, respectively provide two times of rated current and other current flow, to calculate the average fusing time.

      In this way, we have completed the test of a fuse holder. According to the comparison between experimental results and expected results, we can get the result that whether the fuse holder passes the test and whether it meets the standard.

      After introduced how to determine a fuse holder, next, we will be from, which is closely linked with the fuse holder introduces the essential fuse, first of all we want to introduce is about how the fuse selection, as well as the selection of the matters needing attention, we will through the following several factors to help us to judge whether the fuse is what you need to:

      1. Rated current: pay attention to the current decrement of different certification standards. The decrement certified according to UL standard is 0.75, that is, the actual steady-state operating current should not exceed 75% of In.According to IEC standard, it is 1.0, that is, the actual steady-state operating current can be equal to In.For UL certified fuses: operating at 25℃, the operating current should not exceed 75% of the rated current of the fuse to avoid harmful fuses.Generally speaking, the optional current specification provided by the supplier is less than the standard recommended gear. It is suggested to select from the existing current specification of the supplier, and it is not recommended to require the supplier to carry out additional design.

      2. Rated voltage: the rating of the fuse shall be equal to or greater than the effective circuit voltage.

      3. Working environment temperature: the current carrying capacity test of the fuse is carried out at 25℃, which is affected by the change of environment temperature.The higher the ambient temperature, the higher the operating temperature of the fuse, the shorter its life.Conversely, operating at a lower temperature will extend the life of the fuse.Therefore, choose fuse rated current, according to the actual working environment of the fuse temperature adjustment.

      4. Electrical step-down and cold resistance: normally, the resistance of a fuse is inversely proportional to the rated current.Choose the resistance of fuse the smaller the better, so the loss of fuse power is also relatively small.The voltage drop of fuse is in dc rated current current test, because rated current small fuse has relatively large resistance, so the impact of low-voltage power is also relatively large, in the process of choosing small specification fuse should pay attention to the impact of resistance.

      5. Time-current characteristic curve: it is one of the most important basis for selecting fuse.It determines whether the fuse can effectively protect the circuit, when the fault current occurs, the correct fuse.Each type of fuse has its own time – current curve.The x-coordinate of the curve is current, and the y-coordinate is fusing time.In the selection process, this curve is used as a reference, and the key points in the curve are selected as the basis.The selection of key points is different according to the different types of fuse authentication. When selecting the fuse, it is necessary to determine the time when the protected fault current can safely exist in the circuit.

      6. Sectional capacity level: fuses with different certification standards have different breaking capacity. The rated breaking capacity of fuses must meet or exceed the maximum fault current in the circuit.When the protected system is connected directly to the power input circuit and the fuse is placed in the power input section, it is important to use a high breaking power fuse.In most secondary circuits, especially when the voltage is lower than the supply voltage, a fuse with a low breaking capacity is sufficient.

      7. Nominal melting heat energy: in the case of fuse must withstand high current, the current large and short duration pulse, such as the impact current and starting current, flood current, and other similar “pulse” type of circuit transient value, the fuse should be able to withstand such high current energy, abnormal circuit should not occur.The nominal melting heat rating of fuses is determined in the laboratory. There is only one nominal melting heat rating for each fuse specification.

      8. Durability (life) : the life of the fuse is relatively long. When the fuse is selected correctly, it is generally unnecessary to replace the fuse due to life reasons.

      According to the actual working conditions of the fuse, choose different shapes/sizes.There are usually the following options:

      Tube shape: glass tube – low breaking ability, ceramic tube – high breaking ability, etc.

      Micro: resistance type, surface paste type, film type, etc.

      Melt structure: round wire, flat wire, straight wire, wave type, etc.

      Combined melt: tin ball – slow melting delay, etc

      10. Certification requirements: fuse mainly adopts UL certification standards, IEC standards, due to the fuse of the IEC standards and UL standard in terms of content and specification content difference is bigger, so by the two kinds of standard authentication fuse cannot replace each other, at the same time in respect of the same kind of fuse and no way to get these two standard certification.

      11. Marking: according to the requirements of safety specifications, the fuse (fuse holder) of the circuit board shall be accompanied by the following marking of the fuse: rated current, rated voltage, fuse breaking characteristic, explosion proof characteristic, etc., and shall be accompanied by the safety warning mark of replacing the fuse.For example, we choose a fuse with rated current 2A, rated voltage 125V, fast breaking characteristic and low explosion proof characteristic. The screen mark of the fuse holder on the circuit board is: F2AL,125V;For internal fuses (such as wire-mount fuses, panel mount fuses), provide a clear cross-reference table containing instructions in the maintenance documentation.

      12. Fuse holder: select appropriate fuse holder parts and installation methods, such as fuse holder, installation box, panel installation, shielding installation, etc.Be careful not to use a silver-plated fuse holder.

      13. Selection of welding and sleeve: welding fuse and fuse holder should not be used in the process of silver-plated welding. Heat absorption devices are recommended.Fuse sleeve can insulate the exposed part of fuse, protect it when working with electricity, and prevent the risk of fuse explosion.Therefore, it is recommended to choose fuse sleeve when using glass tube fuse with low breaking ability in ac system.

      Finally, we will introduce some factors that affect the life of fuses, to help you better protect fuses:

      (1) working environment temperature: the environment temperature is too high to damage the life of the fuse seat.A common fuse holder where tin begins to diffuse into the wire at a temperature of about 160 degrees;The temperature at which the melt begins to oxidize more vigorously is about 200 degrees.The life of fuse will be shortened gradually with the oxidation, multiple diffusion, thermal stress fatigue and so on.Therefore, it is suggested that the delay fuse holder should not work above 150℃ for a long time, and the normal fuse holder should not work above 175~225℃ for a long time.

      (2) pulse current: pulse impact, will generate thermal cycle, which leads to the diffusion of the fuse, oxidation, thermal stress, and even accelerate.The fuse holder will age gradually with the increase of pulse energy and frequency.The impact life of the fuse holder depends on the percentage of I2t of the pulse in the fuse itself.Normally, should be less than 20%, so the fuse can withstand more than 100,000 times of impact.

      (3) contact parts: fuse holder contact pipe clamp, and connect the length of the wire, cross-sectional area, etc.Fuse holder and contact resistance of pipe clamp, damaging to life, the UL standard, test when the fuse and the pipe clamp Ω contact resistance is less than 3 m.When contact resistance is high, the clamp does not dissipate heat but generates heat and transmits it to the fuse.


    Post time: Aug-12-2019
    
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