The hollow coil is mainly used in the induction of acceptance, focusing, magnetic card, magnetic head, large current coil, low voltage electrical appliances, industrial control, home appliances, automotive electronics, SMT mount, mobile phone, wireless transceiver, electronic navigation device, power regulator, amplifier, supply and filter etc..
The main parameters of the hollow coil
1 inductance
The inductance L is the inherent characteristic of the coil, independent of the magnitude of the current. Inductance is usually indicated by a particular title.
2, inductance
Stop the effect of induction coil on the size of the current communication unit is called inductance XL, ohm.
3, quality factors
Q is a quality factor that physical quality of the coil, the ratio of Q to XL and equivalent inductance resistance is Q=XL/R.
The higher the Q value of the coil, the smaller the loop loss. 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 iron core, and the influence of the high-frequency skin effect. The Q value of a coil is usually tens to hundreds.
4. Distributed capacitance
Turn and turn coil capacitor, coil and coil and shield plate, are called distributed capacitance. The existence of distributed capacitance reduces the Q value of the coil and the stability becomes worse, so the smaller the distribution capacitance of the coil is, the better.
The effect of a hollow coil
1, hollow coil blocking effect
The self inductance in the hollow coil always changes with the current in the coil. Stop communication effect on hollow coil current, the size of said block effect inductance XL ohms. Its relationship with inductance L and communication frequency f is xl=2 PI fl.
2, tuning and frequency selection effect
The hollow coil and the capacitor are connected in parallel to form a LC tuning circuit. The natural vibration frequency of the F0 circuit and non communication signal frequency f inductive and capacitive reactance is flat, the loop is also flat, so the electromagnetic energy in the inductance and capacitance and resonant vibration, this scene LC circuit. When the resonant circuit inductance and capacitance equivalent and reverse current circuit, the total inductance current minimum, maximum amount (f= "F0" communication signal), LC resonant circuit has selected frequency effect, can pick out the communication signals at a frequency of F.
Hollow coil installation and application notes
The installation boards of electronic components in any electronic equipment are carefully organized, comprehensively arranged and rationally planned through the functional characteristics of various components used by the engineers and technicians. As an application of the air core coil, it is possible to pay attention to some of the following questions.
(1) the installation position of the hollow coil shall be in accordance with the plan request
The relative azimuth orientation and various other components installed hollow coil to fit the planning rules, or will affect the normal operation. For example, high resistance semiconductor radio simple flow in the ring and the magnetic antenna range due to the reasonable organization; antenna air core coil and the vibration of air core coils should be perpendicular to each other, which avoids the influence of coupled to each other.
(2) the hollow coil shall be examined before installation
Before use, we should check whether the structure of the air core coil is firm or not, whether the wire turns loose or loose, whether the lead joint is loose or not, whether the core rotation is sensitive or not. These aspects are checked, and then installed.
(3) the fine tuning method should be considered when the hollow coil needs to be fine tuned in the process of application
Some hollow coil in the use process needs fine-tuning, relying on changes in the number of hollow coil coil is very inconvenient, and therefore should be chosen when considering fine-tuning method. For example, a single layer hollow coil can adopt a method of removing a hollow coil with an end point of a plurality of points, that is, winding 3 or 4 circles at one end of the hollow coil in advance, and the inductance can be changed when the position of the hollow coil is moved at fine trimming. Practice proves that this method can complete the inductance conditioning 2% + 3% + fine-tuning. The use of air core coils in HF and VHF circuits, often set aside half circle as trimming, remove or turn the half circle to the inductance change, complete adjustment. The fine tuning of a multi-layer segmented air core coil can be accomplished by moving a segment of the relative spacing, and the number of movable segments shall be 20% to 30% of the total number of turns. It is proved that the fine scale of up to 10% to 15%. An air core coil with a magnetic core can adjust the orientation of the magnetic core in the hollow coil tube by completing the adjustment of the inductance of the air core coil.
(4) the use of hollow coil should pay attention to adhere to the inductance of the original hollow coil
In the application of the hollow coil, do not arbitrarily change the shape of the hollow coil. The spacing between the big and the hollow coils otherwise affects the inductance of the hollow coil. Especially, the higher the frequency, the less the number of turns. Therefore, the high frequency hollow coil used in TV sets is usually sealed with high frequency wax or other medium. In addition, it should be noted that in the repair, do not arbitrarily modify or adjust the orientation of the original hollow coil, to avoid causing harmonic problems.
(5) the installation of the adjustable hollow coil should be easy to adjust
The adjustable hollow coil shall be installed in the easily adjustable position of the machine so as to adjust the inductance of the hollow coil so as to achieve the best operation condition.
