The vast majority of electronic components, such as resistors, capacitors. Speaker, are the production sector in accordance with the prescribed standards of production and the series finished for selection. And as only a part of the inductor choke coil, the low-frequency choke coil, oscillating coils and LG fixed inductor coil is produced according to the required standards of products, most of the inductor is non-standard items, they tend to be based on actual needs, create their own. Since the inductance of the coil is extremely broad application, such as LC filter circuit, tuning amplifier circuit, an oscillator, a balanced circuit, decoupling circuits, etc. will be used inductor. To properly make good use of the coil, or a more complex thing; some knowledge mentioned here, some practical experience, according to some people, only for reference.

First, the inductor series and parallel

Each inductor only have a certain inductance. If the total inductance of the two or more than two inductor in series is increased, the total inductance in series as follows:

L String = L1 + L2 + L3 + L4 ......

After the total inductance coil connected in parallel is to reduce the amount of total inductance parallel connection is:

And L = 1 / (1 / L1 + 1 / L2 + 1 / L3 + 1 / L4 + ......)

Is calculated as described above, the magnetic field of each coil is the case for each spacer without contact, brought into contact with each other if the magnetic field, otherwise considered necessary.

Second, the inductance of the detection coil

When selecting and using inductors, we must first think to check the measurement coil, and then to judge the quality is good or bad and the merits of the coil. For accurate detection of the inductor coil inductance and quality factor Q, generally require specialized equipment and test methods more complicated. In practice, this detection is generally not carried out only to check off and Q values determine the size of the coil. You can first use a multimeter resistance profile measuring coil DC resistance, and then determine the resistance or the original nominal resistance compared to the resistance if the measured resistance value than the original determining or increasing the nominal resistance of many, even the pointer does not move (resistance tends to infinity X can be judged coil disconnected; if the measured resistance is very small, it is determined if a serious short circuit Wan partial short is difficult to compare these two situations arise out of people, it can determine the coil is bad, can not use. If the sense resistor and the original determination or less nominal resistance, can determine this coil is good. In this case, we can according to the following situations, to determine the size of the quality of the coil that is the Q value. inductance of the coil is the same, the DC resistance, the higher the Q value; the larger the diameter of the wire, the greater the Q value; if the use of multi-strand wire wound, the more the number of shares wires, Q value, the more high; loss bobbin (or core) materials used in the smaller, the higher the Q value e.g., high silicon steel sheet do core, its Q value is compared with ordinary silicon steel core made high; coil distributed capacitance and magnetic flux leakage is smaller, the higher its Q value, for example, honeycomb coil winding method, is high Q value than the flat wound, also higher than mess around; coil no shield around the mounting location when no metal components , its Q value is high, on the contrary, the lower the Q value closer shield or metal ring member off, the more severe its Q value decreases;. of the high-frequency coil has a magnetic core, and the Q value as compared with the core days high; core loss smaller, the higher its Q value.

Low-frequency choke coil used in the power filter, the size of its Q value and less important, and the inductance L of the size of the filtering effect but then a greater impact. Note that the low-frequency choke coil in use by a large multi-DC, in order to prevent magnetic saturation, the core requirements along the plug, it has a large air gap. To prevent the occurrence of the coil and the core breakdown, insulation between the two should meet the requirements. Therefore, prior to use should be carried out between the coil and core insulation resistance testing. Detection of specific methods and transformer insulation resistance of the same (see also detect transformer).

For high-frequency coil inductance L due to the test up more trouble, are generally based on use effect the appropriate adjustments in the circuit to determine the suitability of inductance.

A plurality of windings of the coil, but also with a multimeter to test whether a short circuit between the coil windings; for having a core and a metal shield of the coil, to measure its winding and the core or metal shield short circuit between the hood.

Third, the coiled Notes

Coil in actual use, there are a considerable number of varieties of the inductor is non-standard parts, are carried out according to need targeted wound. When the self-winding, to note the following:

(1) The circuit requires, winding method selected

When winding hollow coil, should be based on the requirements of the circuit, the size and the size of the diameter of the inductance coil bobbin determine winding method. Inter-wound coil for use in high frequency and ultra high frequency circuit, the number of turns is less than three laps to 5 times, you can not skeleton, you can have good characteristics, high Q value, up to 150-400 , stability is also high. Single-layer close-wound coil is suitable for short-wave, medium-wave circuit, which can reach 150-250 Q value, and high stability.

(2) Ensure that the coil-carrying capacity and mechanical strength, choose the appropriate wire

Should not use too small a wire coil around the system, so as not to increase the coil resistance, so that the Q value decreases. Meanwhile, the wire too small, its carrying capacity and mechanical strength are small, easily blown or touch disconnected. Therefore, to ensure carrying capacity and mechanical strength of the coil of the premise, to use the appropriate wire winding.

(3) coiled tap should be clearly marked with a tap of the coil should be clearly marked, so easy for installation and maintenance.

(4) the characteristics of the different frequency coil, using different core materials

Different operating frequency coils have different characteristics. Inductance coil in the audio section of work, usually silicon steel or permalloy as the core material. As the low-frequency ferrite core material, its large inductance can be up to a few tens of Hang Hang. Among hundreds of thousands of hertz to several megahertz, such as coil AM broadcast segment, usually ferrite cores, and multi-strand insulated wire. Above a few megahertz frequency, high frequency ferrite coil as the core, is also commonly used hollow coil. This situation should not use multi-strand insulated wire, and should adopt a single strand of thick silver-plated wire wound. At 100MHz or more, generally can not use ferrite core, only use hollow coil; If you want to make fine-tuning, the available steel core. Choke coil for use in high-frequency circuit, in addition to the inductance and current ratings should meet the requirements of the circuit, but also must pay attention to its distributed capacitance should not be too large.

Four measures to improve the Q value of the coil taken

Quality factor Q is an important parameter reflecting the quality of the coil, improve the Q value of the coil, it can be said to be one of the priorities of the coiled should be noted. So, how to improve the coiled Q value of it, here are specific ways:

(1) According to the operating frequency, the choice of the coil wire

Working in low frequency inductor, the general enameled wire with insulation and other wound. Operating frequency is higher than the tens of thousands of Hz, but lower than the circuit of 2MHz, the use of multi-strand insulated wire coiled, so that can effectively increase the surface area of the conductor, which can overcome the influence of the skin effect, so that the Q value than the same 30% -50% of single wire cross-sectional area of the wound coil is high. At frequencies above 2MHz circuit, inductors should adopt a single thick wire winding, wire diameter is generally 0.3mm-1.5mm. Inductance coil is wound between the commonly used silver-plated copper wire, in order to increase the conductivity of the wire surface. Then should not use multi-strand wire around the system, because the multi-strand insulated wire at a high frequency, the coil insulation media will cause additional losses, the effect of anti-inferior to single wire in place.

(2) selection of high quality coil, reducing dielectric loss

At higher frequencies are required, such as short-wave band, because the average coil, its dielectric loss increased significantly, therefore, should be used in high-frequency dielectric material, such as high-frequency ceramic, Teflon and polystyrene as a skeleton, and using inter wound around the law.

(3) a reasonable choice of coil sizes, can reduce the loss of certain single-coil outer diameter (φ20mm-30mm), when the winding length L and the ratio of the outer diameter D of L / D = 0.7, its loss is minimized; the outer diameter of a certain multilayer coil L / D = 0.2-0.5, with t / D = 0.25-0.1, its loss is minimized. By winding thickness t, meet between the winding length L and the outer diameter D 3t + 2L = D case, the loss is minimal. Using the shield coil, its L / D = 0.8-1.2 when the best.

(4) Selected reasonable shield diameter

With a shield, it will increase the loss of the coil, so that the Q value decreases, so the size of the shield should not be too small. However, the size of the shield is too large, it will increase the volume, and thus to select a reasonable shield diameter.

When the shield coil diameter than the diameter Ds and D satisfy the following values namely Ds / D = 1.6-2.5 when, Q value is not more than 10% lower.

(5) The core can significantly reduce the number of turns

Coil used in the core, reducing the number of turns of the coil, not only to improve the resistance value of the coil is reduced, enabling the Q value, and reduce the volume of the coil.

(6) suitably selected coil diameter bigger, which will help reduce the loss at possible conditions, the election was larger diameter of the coil, the volume increases some, losses are reduced in favor of the coil. Usually the receiver, single coil diameter take 12mm-30mm; multilayer coils take 6mm-13mm, but consider the volume, and it is not out of range of 20mm-25mm.

(7) to reduce the distributed capacitance of the coiled

Try to use skeleton way coiled or wound on a coil skeleton ribs, distributed capacitance can be reduced by 15% -20%; segmentation method can reduce the multi-layered coil winding distributed capacitance of 1/3 ~ l / 2. For the multi-layered coil, the smaller the diameter D, a length L smaller winding or windings thickness t is larger, the smaller the distributed capacitance. It should be noted that: After Man stain and seal-coated coil, the distributed capacitance will increase 20% -30%.

In short, coiled, always improving the Q value, reduce losses, as a key consideration.

Fifth, coils, installation should pay attention to the problem

Any electronic device electronic component mounting board, is supported by engineering and technical personnel in accordance with the performance characteristics of the use of a variety of components, carefully arranged, comprehensive layout, rational design out. As the coil using the installer, pay attention to the following several issues on it.

Mounting position (1) shall meet the design requirements of the coil

Position of the coil assembly and the relative position of the various elements of other provisions designed to meet, otherwise it will affect the normal operation of the machine. For example, a simple transistor radios in the high-frequency choke coil and magnetic antenna location should be appropriate and reasonable arrangement; an antenna coil and oscillation coil should be perpendicular to each other, which avoids the effects of mutual coupling.

(2) coil prior to installation, to conduct visual inspection

Before use, check the coil structure is solid, the turns are loose and loosening, lead contacts loose, core rotation is flexible, with or without the slider and the like. After passing the examination of these aspects, then install it.

(3) the need to fine-tune coil during use, it should consider trimming method

Some coil during use, the need for fine-tuning, rely on changing the number of turns and very inconvenient, therefore, the choice should be taken into account to fine-tune the method. For example, the number of single-coil may be removed * sleepy coil method endpoint, namely the end of the coil advance on three laps around 1-4 laps, in the fine-tuning, moving its location can change the inductance. Practice has proved that this method can achieve fine tuning adjustment ± 2% - ± 3% of the inductance. Coils in the HF and VHF circuits, often leaving a semi-circle as a spinner, remove or turn off this half-circle so that the inductance change, achieve fine-tuning. Multi-segment coil of fine-tuning, you can move a segment of the relative distance to achieve, the number of laps movable segments should be 20% -30% of the total number of turns. Practice has proved that: This fine-tuning range of up to 10% -15%. Coil has a core, you can adjust the position of the core in the coil tube to achieve fine tuning coil inductance.

(4) using a coil should keep the primary coil inductance

Coil in use, it should not change the shape of the coil. Size and distance between the coils, otherwise it will affect the original coil inductance. In particular, the higher the frequency, the fewer number of turns of the coil. Therefore, the high-frequency coil is currently used in television, usually fixed with a high-frequency sealing wax or other dielectric materials. Additionally, it should be noted in the maintenance, do not change or adjust the position of the primary coil to avoid detuning fault.

Installation (5) adjustable coil should be easy to adjust

Adjustable coil should be installed in the machine easy to adjust the position in order to adjust the amount of inductance coil to achieve the best working condition.