Introduction
inductive coil is a device that operates using the principle of electromagnetic induction. When there is a current flowing a wire, a certain electromagnetic field will be generated around the wire, and the wire of this electromagnetic field itself will act on the wire in this electromagnetic field range. The role of the wire generated by the electromagnetic field itself is called "self-sensation", that is, the changed current generated by the wires produces a change in magnetic field. This magnetic field further affects the current in the wire; the role of other wires in this electromagnetic field , Called "mutual feel".
The electrical characteristics of the inductor coil and the opposite of the capacitor, "pass the low frequency, and high frequency". The high frequency signal will encounter a lot of resistance when the inductor coil is passed, and it is difficult to pass; the resistance to the low frequency signal is smaller, that is, the low frequency signal can be easier to pass it. The electrical resistance of the inductor coil is almost zero.
resistance, capacitance and inductance, they have a certain resistance to the flow of electrical signals in the circuit, which we call "impedance". The impedance of the inductor coil to the current signal is utilized to use the self-sensing of the coil. The inductor coil sometimes we simply refer to "inductance" or "coil", expressed by the letter "L". When the inductor coil, the number of coils around the coil should generally be referred to as the "turns" of the coil.
Main performance indicators
The performance indicator of the inductance coil is mainly the size of the inductor. In addition, the wire to the inductor coil generally has a certain resistance, usually this resistance is small, and it is negligible. However, when the current flowing in some circuits is very large, this small resistance of the coil cannot be ignored, because a lot of current consumes power on this coil, causing the coil to fever or even burning, so sometimes it is necessary to consider The electric power in which the coil can be affected.
inductance
The inductance amount L represents the inherent characteristics of the coil itself, independent of the current size. Except for specialized inductance coils (color code inductance), the amount of inductance is generally not specifically marked on the coil and is labeled in a specific name. The inductance is also called self-sensing, and is a physical quantity that represents the self-inductive ability of the inductor. The size of the inductor inductor is mainly dependent on the number (number of turns) of the coil, the winding method, the material without core and magnetic core, and the like. Typically, the more coils, the more densely wounded coils, the greater the inductance. Coles with magnetic core are larger than the coil of the coreless coil; the larger the magnetic magnetic magnetic rate, the greater the amount of inductance.
The basic unit of the inductor is Henry (referred to as Heng), expressed in the letter "H". Common units have millions (MH) and microencorn (μH), the relationship between them is:
1H = 1000MH
1MH = 1000μH
Initiation
inductive coils on AC current hinders the size of the size, the unit is ohmic, symbol ω. It is related to the relationship between the inductance L and the AC frequency f, XL = 2πfl
Quality Factors
Quality factor q is a physical quantity of the coil quality, Q is an induced anti-XL and its equivalent The ratio of the resistance, q = xl / r. It refers to the ratio of the sensor resistance to its equivalent loss when the inductor is operating at an alternating current voltage of a certain frequency. The higher the Q value of the inductor, the smaller the loss, the higher the efficiency. 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 core, and the impact of high-frequency skin effects. The Q value of the coil is usually tens to several hundred. The high and low inductor quality factor is related to the DC resistance of the coil wire, the dielectric loss of the coil skeleton, and the loss caused by the core, shield, and the like.
Distributed capacitor
Any inductor coil, between the turns and turns, between the layers, between the layers, between the coils, the coils and magnetic shields, etc. The capacitor, which is called the distribution capacitance of the inductor coil. If these distribution capacitors are integrated, it is an equivalent capacitor C which is parallel to the inductor coil. The presence of distributed capacitors reduces the Q value of the coil, and the stability is varied, so the smaller the distribution capacitance of the coil.
Rated current
Rated current means the maximum current value allowed by the inductor when working properly. If the operating current exceeds the rated current, the inductor will change the performance parameters due to fever, and even burn it due to overcurrent.
Allowing deviations
Allow deviation refers to the allowable error value of the inductance amount and the actual inductance of the sensor.
Generally used in the circuit in the circuit of oscillation or filtering is high, the allowable deviation is ± 0.2 [%] ~ ± 0.5 [%]; for coupling, high frequency blocking, etc. The accuracy requires not high; the allowable deviation is ± 10 [%] ~ 15 [%].
Classification
Classification of inductive coils commonly used in the circuit has roughly in such a few:
Press inductive form: fixed inductance, variable inductance.
Classified by magnets: empty core coil, ferrite coil, iron core coil, copper core coil.
Classified by working nature: antenna coil, oscillating coil, choke coil, a trap coil, and a deflection coil.
Press the winding structure: single layer coil, multi-layer coil, hive type coil, wound coil, a coil, a tire coil, a hive type coil, and a coil.
Common coil
1, single layer coil
single layer coil is a circle of insulated wires Cartridge or rubber wooden skeleton. Such as a transistor radio wave antenna coil.
2, hut coil
If the wound coil, its plane is not parallel to the rotating surface, but intersects a certain angle, this The coil is called a hive coil. And the number of times the wire is rotated back and forth, and it is often referred to as a depreciation. The advantage of the hive-style winding is that the size is small, the distributed capacitance is small, and the inductance is large. The hive coils are winded with hive windows. The more depreciation, the smaller distribution capacitance
3, ferrite core and iron powder coil < / p>
The inductance size of the coil is related to the magnetic core. Insert the ferrite core in the hollow core coil, increase the inductance and improve the quality factors of the coil.
4, the copper core coil
The copper core coil is used in the ultra short wave range, and the inductance amount is changed by the position of the rotating copper core in the coil. This adjustment is relatively convenient and durable.
5, color code inductor
color code inductor is an inductor with fixed inductance, its inductance The logo method is the same as the resistance to mark the ring.
6, blocking ring ( choke )
limit the coil passing through the AC Weighing blocking ring, high frequency barrier circle and low frequency blocking ring.
7, deflection coil
deflection coil is the load of the TV scan circuit output stage, the deflection coil requirements: high deflection sensitivity, uniform magnetic field, Q value High, small size, low price.
Effect
Turning effect
The self-sensing power in the inductor coil is always competing with the current in the coil. The inductive coil has an impediment that the AC current is hindered, and the size of the inhibitory is an ohm. It is associated with the relationship between the inductance L and the AC frequency f, and the inductor can be divided into high frequency damping coils and low frequency blocking coils.
Tuning and SETE effect
inductive coils and capacitors can form an LC tuning circuit. That is, the inherent oscillation frequency f0 of the circuit is equal to the frequency f of the non-AC signal, the sensing resistance and capacity of the circuit are also equal, so that the electromagnetic energy is inductively, the capacitance is returned to the oscillate, the resonance of the LC circuit. The sensing resistance and resistance of the resonance is inversely, and the total sensor of the circuit is the smallest, the amount of current is the maximum current (refers to the AC signal of F = "F0", the LC resonant circuit has the function of selecting the frequency, which can The AC signal of a frequency f is selected.
Detection
(1) When selecting and using an inductance coil, first, we must first think of the inspection measurement of the coil, and then determine the quality of the coil and the advantage of quality. To accurately detect the inductance amount and quality factor Q of the inductor coil, it is generally required for special instruments, and the test method is more complicated. In actual work, this test is generally not performed, only the coil is performed and the magnitude of the Q value is performed. You can measure the DC resistance of the coil before the multimeter resistance is measured, and then compare the original determination resistance or nominal resistance. If the measured value is larger than the original determination resistance value or the nominal resistance value, even the pointer does not move (The impedance trend is infinite large X) can be judged that the wire circle is broken; if the measured value is extremely small, it is difficult to compare the severe short or local short circuit. These two situations can be determined that this coil is bad and cannot be used. If the detection resistor is not large to the original or nominal resistance, it can be determined that this coil is good. In this case, we can determine the size of the Q value according to the following cases. When the amount of the coil is the same, the smaller the DC resistance, the higher the Q value; the larger the diameter of the wire used, the greater the Q value; if the multi-strand is wound, the more the wires of the wire, the more Q value High; the smaller the loss of the material used in the coil skeleton (or iron core), the higher the Q value. For example, when the silicon silicon steel sheet is made of iron core, its Q value is high when it is used as a common silicon steel sheet, and the smaller the coil distribution capacitance and the leakage, the higher its Q value. For example, the hut-like winding coil, its Q value is high, and is higher than the chaos; the coil has no shield, and when there is no metal member around the mounting position, the Q value is high, the opposite, then Q value Lower. The closer the shield or metal member, the more severe the Q value decrease; the position of the magnetic core should be properly arranged properly; the antenna coil and the oscillation coil should be perpendicular to each other, which avoids the effects of mutual coupling.
(2) The coil is in front of the installation
Before using it, check whether the structure of the coil is secure, whether there is loose and loose phenomenon, and the lead contact is There is no looseness, whether the core rotation is flexible, there is no slip button, etc. These aspects are checked, and they are installed.
(3) The coil needs to be fine-tuning in the use process. Some coils should be considered in the process of use, and it is necessary to perform fine-tuning during use. It is very inconvenient to change the number of wire circles. Therefore, the fine-tuning method should be considered when choosing. For example, the single layer coil can be used to remove the endpoint of the number of portions, i.e., a 3-turn-4 lap in one end of the coil, and moving its position, moving its position can change the amount of inductance. Practice has proven that this adjustment method can achieve a fine-tuning ± 2% - ± 3% inductance. The coil is applied in short-wave and ultra-short wave circuits, often leaves a semi-circle as fine-tuning, removing or folding this half turn makes the inductance change, and realize fine-tuning. The fine-tuning of the multilayer segmented coil can move a relative distance from a segment to be realized, and the number of turns of the movable segment should be 20% -30% of the total number of circles. Practice proves that this fine-tuning range can reach 10% -15%. The coil having the core can achieve fine-tuning the amount of coil inductance by adjusting the position of the magnetic core in the coil tube.
(4) Use the coil to take care of the inductance amount of the original coil
Coil in use, do not change the shape of the coil. The distance between the size and the coil, otherwise it will affect the original inductance of the coil. In particular, the higher the frequency, the less the total number of times. Therefore, the high-frequency coil used in the television set is generally sealed with high frequency wax or other media material. In addition, it should be noted that in the maintenance, do not change or adjust the position of the original coil to avoid malfunction.(5) The adjustable coil should be convenient to adjust the
the adjustable position to be installed in the machine's easy-to-adjust position, so that the electronics of the adjustment coil reaches the best work. state.
principle
Inductance is the ratio of alternating magnetic flux, the magnetic flux of the wire, the magnetic flux of the wire is produced in the wire, and the magnetic flux of the wire is produced in the wire inside and around the wire.
When the inductor passes through a DC current, only a fixed magnetic force is present, and there is no change over time; but when the AC current is passed through the AC, the magnetic line changed around it will exhibit a magnetic line that varies over time. According to the law of electromagnetic induction of the law - Magnetic electrical analysis, the changed magnetic line generates an induction potential at both ends of the coil, which is equivalent to a "new power supply". This induction potential is generated when the closed loop is formed. The protocol law knows that the total amount of magnetic line generated by the induced current should force the change of the original magnetic line. Since the original magnetic line change is derived from the change of the alternating power supply, it is seen from the objective effect, the inductance coil has the characteristics of the current change in the AC circuit. The inductor coil has a similar characteristic similar to the inertia in the mechanics, which is named "self induction" in electrical, usually in the moment of pulling the knife switch or turning on the knife switch, which is the generation of self-inductance. Very high induction potential is caused.
In summary, when the inductive coil is connected to an AC power source, the magnetic line inside the coil will change with the alternation of the current, and cause the coil to continue to generate electromagnetic inductions. This electromotive force generated by the change in the current of the coil itself is called "self-inductive momentum".
It can be seen that the inductance is only a parameter associated with the number of coils, the size and the medium, which is a measure of the inertility of the inductor coil and has nothing to do with the external current.
inductive coil point glue
inductor coil point glue is mainly for the inductive coil and the bottom plate voids, automated dot rubber operations that act as a viscous electrical circle . On both sides, it is necessary to carry out four-axis dispensing operation based on the original three-axis point rubber robot, ensuring that the size and effect of both sides of the dispensing glue.