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Views: 1 Author: Site Editor Publish Time: 2024-09-24 Origin: Site
When using an inductive coil, the first step is to check whether the inductance meets the requirements. This can be done using an inductance tester, which can not only measure the inductance, but also measure the Q value of the coil.
When a short circuit occurs in the coil, it will greatly increase the loss and even render it unusable. The short circuit of the coil should be measured using a coil short circuit tester.
In the use of inductive coils, if there is no specialized measuring instrument, a multimeter can be used for simple quality judgment. You can first use a multimeter to measure the DC resistance of the coil, and then compare it with the originally determined or nominal resistance value. If the measured resistance is infinite, it can be concluded that the coil is disconnected; If the measured resistance value is much smaller, it can be determined that there is a short circuit in the coil. Both of these situations indicate that the coil has quality issues and cannot be used anymore. If the detected resistance is not significantly different from the original determined or nominal resistance, it can be considered that the quality of the coil is basically good.
Some coils require fine-tuning of inductance during use, and common methods include:
① Single layer coil fine-tuning method. By changing the spacing between the coils during fine-tuning, the inductance can be adjusted. For coils used in short wave or ultra short circuits, a half turn is often left at the end of the coil as a fine-tuning, and moving or folding this half turn can change the inductance.
② Fine tuning method for multi-layer coils. For multi-layer coils that you want to adjust, you can generally use 20% -30% of the total number of turns as segmented winding, and move the relative distance between each other to fine tune the inductance by 10% -15%.
③ Fine tuning method with magnetic core coil. The inductance can be changed by adjusting the position of the magnetic core in the coil.
The measures taken to increase the Q value of the coil are as follows:
① Select the wire for winding the coil according to the operating frequency. Inductive coils operating in the low-frequency range should be wound with insulated wires such as enameled wire. For inductive coils operating at frequencies between tens of kilohertz and two megahertz, multi stranded insulated wires should be wound to increase the effective cross-sectional area of the conductor and reduce the impact of skin effect, which can increase the Q value by 30% -40%. For inductive coils with a working frequency higher than 2MHz, a single thick wire winding should be used, with a wire diameter generally between 0.3-1.5mm.
② Select high-quality skeleton to reduce dielectric loss. Usually, for inductance coils that require low losses and high operating frequencies, high-frequency dielectric materials such as high frequency ceramics, polytetrafluoroethylene, polystyrene, etc. should be selected as the skeleton. For inductance coils operating at ultra-high frequencies, they can be wound in a boneless manner.
③ When selecting an inductor coil with a magnetic core, the number of coils and their resistance can be greatly reduced, which is beneficial for improving the Q value
④ Reasonably choose the size of the shielding cover. After adding a shielding cover to the coil, it will increase the loss of the coil and reduce the Q value. Therefore, the size of the shielding cover should not be too large or too small. Generally speaking, the ratio of the shielding cover diameter to the coil diameter is 1 6-2.5 is recommended, as it can reduce the Q value by less than 10%.
Inductive coils with small distributed capacitance should be selected for high-frequency circuit operation. The use of ribbed skeleton or skeleton free winding coils can reduce distributed capacitance by 15% -20%. The use of segmented winding multi-layer coils can reduce distributed capacitance by 1/3-1/2 for multi occupancy wire trays. It is necessary to use coils with small diameters, small winding lengths, or large winding thicknesses because the distributed capacitance of coils with this structure is small.
It should be pointed out that after immersion treatment or coating, the distributed capacitance of the coin ring will increase by 20% -30%. Although immersion treatment or coating can help prevent moisture in the coil, its advantages and disadvantages should be weighed when using it.
It is aimed at the situation where the magnetic fields of each coil are isolated without contact. If there is contact between the coils with the field, it should be treated separately. When making homemade coils, it is necessary to ensure the firmness of the mechanical structure, and the coils must not have loose turns.
Coils with taps should be connected to the circuit only after the tap markings are clearly visible. For self-made coils with taps, tap markings should be made. The coil is prone to breakage when exposed to moisture, or may form a breakdown short circuit due to poor insulation, so it should be prevented from being used under high humidity conditions.
During installation, the assembly position of the coil and the relative position of other electronic components should be arranged reasonably to prevent affecting the normal operation of the whole machine.
