Do you know the detection method of inductive coil
Information from:internet Published on:2022-03-02
(1) When selecting and using inductive coils, we should first think of the inspection and measurement of the coils, and then judge the quality and advantages and disadvantages of the coils. In order to accurately detect the inductance and quality factor Q of inductance coil, special instruments are generally required, and the test method is more complex. In practical work, this kind of detection is generally not carried out, but only the on-off inspection of the coil and the judgment of the Q value. The DC resistance of the coil can be measured by using the resistance gear of the multimeter, and then compared with the originally determined resistance value or nominal resistance value. If the measured resistance value is much larger than the originally determined resistance value or nominal resistance value, or even the pointer does not move (the resistance value tends to infinity x), the coil wire can be judged to be broken; If the measured resistance is very small, it is difficult to judge whether it is a serious short circuit or a local short circuit. In these two cases, it can be determined that the coil is broken and cannot be used. If the measured resistance is not much different from the original determined or nominal resistance, it can be determined that the coil is good. In this case, we can judge the quality of the coil according to the following situations, that is, the size of Q value. When the inductance of the coil is the same, the smaller the DC resistance is, the higher the Q value is; The larger the diameter of the wire used, the larger the Q value; If multi strand winding system is adopted, the more strands of conductor, the higher Q value; The smaller the loss of the material used in the coil frame (or iron core), the higher its Q value. For example, when high silicon steel sheet is used as iron core, its Q value is higher than that when ordinary silicon steel sheet is used as iron core; The smaller the coil distributed capacitance and magnetic flux leakage, the higher the Q value. For example, the Q value of the coil of honeycomb winding method is higher than that of flat winding and higher than that of random winding; When the coil has no shield and there are no metal components around the installation position, its Q value is high. On the contrary, the Q value is low. The closer the shield or metal component is to the off-line coil, the more serious the Q value decreases; The position of magnetic core shall be properly arranged; The antenna coil and oscillation coil should be perpendicular to each other, which avoids the influence of mutual coupling. (2) The coil shall be visually inspected before installation Before use, check whether the structure of the coil is firm, whether the wire turns are loose and loose, whether the lead contacts are loose, whether the magnetic core rotates flexibly, whether there are sliding buckles, etc. After these aspects are checked and qualified, the installation can be carried out. (3) If the coil needs to be fine tuned during use, the fine-tuning method shall be considered Some coils need to be fine tuned during use, and it is inconvenient to change the number of coils. Therefore, the method of fine tuning should be considered when selecting. For example, a single-layer coil can adopt the method of removing the number trap coil near the end point, that is, wrap 3 ~ 4 turns around one end of the coil in advance. During fine adjustment, the inductance can be changed by moving its position. Practice shows that this adjustment method can realize fine adjustment of ± 2% - ± 3% inductance. For coils used in short wave and ultrashort wave circuits, half a turn is often reserved for fine adjustment. Move or turn this half turn to change the inductance and realize fine adjustment. The fine adjustment of multi-layer segmented coil can be realized by moving the relative distance of one segment. The number of turns of the movable segment shall be 20% - 30% of the total number of turns. Practice has proved that this fine-tuning range can reach 10% - 15%. For a coil with a magnetic core, the coil inductance can be fine tuned by adjusting the position of the magnetic core in the coil tube. (4) When using the coil, pay attention to maintaining the inductance of the original coil Do not change the shape of the coil when the coil is in use. Size and distance between coils, otherwise it will affect the original inductance of the coil. In particular, the higher the frequency, that is, the fewer coils. Therefore, the high-frequency coil used in TV is generally sealed and fixed with high-frequency wax or other dielectric materials. In addition, it should be noted that during maintenance, do not arbitrarily change or adjust the position of the original coil to avoid detuning fault. (5) The adjustable coil shall be installed for easy adjustment The adjustable coil shall be installed at the easily adjustable position of the machine, so as to adjust the inductance of the coil and achieve the best working state.
