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Application of hollow coil and description of main parameters

Application of air core coil
Air-core coils are mainly used for induction receiving, focusing, magnetic cards, magnetic heads, high current coils, low voltage electrical appliances, industrial controls, household appliances, car electronics, SMT placement, mobile phones, wireless transceivers, electronic navigators, power conditioners, amplifiers, Suppliers and filters. Primary parameters of the air-core coil
1, the amount of inductance
The inductance L is an inherent characteristic of the coil itself, regardless of the magnitude of the current. The amount of inductance is generally indicated by a specific designation.
2, the resistance
The magnitude of the inductance coil's resistance to AC current is called XL, and the unit is ohm.
3. Quality factors
The quality element Q is a physical quantity indicating the quality of the coil, and Q is the ratio of the inductive reactance XL to its equivalent resistance, namely: Q = XL / R.
The higher the Q value of the coil, the smaller the loss of the loop. The Q value of the coil is related to the DC resistance of the wire, the dielectric loss of the skeleton, the loss caused by the shield or the iron core, and the influence of the high-frequency skin effect. The Q value of the coil is generally from several tens to several hundreds.
4, distributed capacitance
The capacitance existing between the turns and turns of the coil, the coil and the master, and between the coil and the shield is called a distributed capacitance. The presence of the distributed capacitance reduces the Q value of the coil and the stability is deteriorated, so the smaller the distributed capacitance of the coil, the better.
The role of the air core coil
1, air-core coil blocking effect
The self-induced electromotive force in the air-core coil coil is always resistant to the current in the coil. The air-core coil has a blocking effect on the alternating current, and the magnitude of the obstruction is called the inductive reactance xl, and the unit is ohm. Its relationship with the inductance l and the alternating current frequency f is xl=2πfl.
2, tuning and frequency selection
The air-core coil and the capacitor are connected in parallel to form an lc tuned circuit. That is, the natural oscillation frequency f0 of the circuit is equal to the frequency f of the non-AC signal, and the inductive reactance and capacitive reactance of the loop are also flat, so the electromagnetic energy oscillates back and forth between the inductor and the capacitor, and the resonant appearance of the lc loop. At the time of resonance, the inductive reactance and capacitive reactance of the circuit are reversed, the inductive reactance of the total current of the loop is the smallest, and the current amount is the largest (referring to the AC signal of f="f0"). The lc resonant circuit has the function of selecting a frequency and can An AC signal of a frequency f is selected.
Air-core coil equipment and application matters
The electronic component equipment board in any electronic equipment is carefully arranged, fully planned, and reasonably planned by the engineering and technical personnel according to the functional characteristics of various components used. As a user of the air core coil, pay attention to the following problems.
(1) The equipment orientation of the air-core coil should meet the planned needs
The orientation of the device of the air-core coil and the relative orientation of other various elements must conform to the planned rules, otherwise it will affect the normal operation of the whole machine. For example, the orientation of the high-frequency choke coil and the magnetic antenna in the simple semiconductor radio should be properly arranged; the antenna air-core coil and the oscillating air-core coil should be perpendicular to each other, which prevents the mutual coupling.
(2) The air core coil is in front of the equipment for visual inspection
Before use, check whether the structure of the air-core coil is robust, whether the wire is loose or loose, the wire contact is loose, the core rotation is active, and there is no slip. After all these aspects have been checked, the equipment will be carried out.
(3) The air-core coil needs to be fine-tuned during the application process, and the fine-tuning method should be considered.
Some air-core coils need to be fine-tuned during the application process, and it is very inconvenient to change the number of air-core coils. Therefore, the method of fine-tuning should be considered when selecting. For example, a single-layer air-core coil may be selected by moving a plurality of trapped air-core coils at the end, that is, three to four turns are wound on one end of the air-core coil in advance, and the amplitude may be changed by moving the orientation during fine adjustment. Practice has proved that this scheduling method can finish fine-tuning the inductance of ±2%-±3%. Air-core coils used in short-wave and ultra-short-wave circuits often leave a half-turn as a fine-tuning. Moving or turning this half-turn causes the inductance to change and finish fine-tuning. The fine adjustment of the multi-layer segmented air core coil can be completed by moving the relative distance of one segment, and the number of turns of the movable segment should be 20%-30% of the total number of turns. Practice has proved that this fine-tuning plan can reach 10%-15%. The air core coil with the magnetic core can complete the fine adjustment of the inductance of the air core coil by scheduling the orientation of the magnetic core in the air core coil tube.
(4) The use of air-core coils should pay attention to the inductance of the original air-core coil
In the application of the air-core coil, do not arbitrarily change the shape of the air-core coil. The distance between the size and the air-core coil, otherwise it will affect the inductance of the air-core coil. In particular, the higher the frequency, that is, the smaller the number of turns of the air-core coil. Therefore, the high-frequency air-core coils selected in the TV set at that time are generally sealed and fixed with high-frequency wax or other media materials. Others, should pay attention to the repair, do not arbitrarily change or adjust the orientation of the original hollow coil to prevent the occurrence of detuning.
(5) The equipment of the adjustable air-core coil should be easy to adjust
The adjustable air-core coils should be placed in an easy-to-schedule orientation of the machine to facilitate adjustment of the inductance of the air-core coils to optimum operating conditions.

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