An inductance coil is a wire wound round and round on an insulating tube that is insulated from each other, and the insulating tube may be hollow, or may contain an iron core or a magnetic powder core, referred to as an inductor. In l, the units are Henry (h), Millihenry (MH), Micro Henry (uh), 1h=10^3mh=10^6uh.

Inductance is classified according to the form of inductance: fixed inductance, variable inductance. Classification by magnetic properties: hollow coil, ferrite coil, iron coil, copper coil. Classified by work property: antenna coil, oscillation coil, choke coil, notch coil, deflection coil. Classification by winding structure: single coil, multi - coil, honeycomb coil.

The main characteristic parameters of the inductance coil

The inductance value L represents the intrinsic characteristics of the coil and is independent of the current. Except for the special inductance coil (color-coded inductance), the inductance quantity is generally not specially marked on the coil but marked with a specific name.

2. Inductive XL The inductive coil's blocking effect on ac current is called inductive XL in ohm. Its relation to inductance L and alternating current frequency F is XL =2 f.

Quality factor Q Quality factor Q is a physical quantity that represents the coil quality. Q is the ratio of inductive resistance XL to its equivalent resistance, that is, 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 frame, the loss caused by the shield or core, and the influence of the high frequency skin effect. The q values of coils are usually in the tens to hundreds.

4. The capacitance between turns of distributed capacitance coil, between coils and shield, between coils and base plate is called distributed capacitance. The existence of distributed capacitance reduces the q value of the coil and makes the stability worse, so the smaller the distributed capacitance of the coil is, the better.

Three, common coil

Monolayer coil A monolayer coil is an insulated wire wound round and round a paper tube or bakelframe. Such as the wave antenna coil in a transistor radio.

2. If the plane of the wound coil is not parallel to the rotating plane, but intersects at a certain Angle, the coil is called the honeycomb coil. The number of times the wire bends back and forth, often called the number of folds. The advantages of beehive winding method are small volume, small distributed capacitance and large inductance. Honeycomb coils are wound by honeycomb winding machine. The more folding points, the smaller the distributed capacitance.

3. The inductance of ferrite core and iron powder core coil is related to whether there is a magnetic core or not. Inserting ferrite core into hollow coil can increase inductance and improve coil quality.

Copper coil Copper coil is widely used in the ultra-short wave range. The position of the copper core in the coil is used to change the inductance. This kind of adjustment is more convenient and durable.

5, color code inductor color code inductor is an inductor with a fixed amount of inductance, the method of marking the amount of inductance is the same as the resistance by color ring.

6. Choke coil (choke coil) The coil that restricts the flow of alternating current is called choke coil, which is divided into high-frequency choke coil and low-frequency choke coil.

Deflection coil Deflection coil is the load of the output stage of the TV scanning circuit. Requirements for deflection coil: high deflection sensitivity, uniform magnetic field, high Q value, small volume and low price.