Coil is usually referred to as a ring-shaped wire winding, the most common coil applications are: motors, inductors, transformers and loop antennas. Introduction
A coil in an electrical circuit is an inductor. Refers to the wire one by one around the wires insulated from each other, and the insulating tube can be hollow, can also contain iron core or magnetic core, referred to as inductance. Inductor can be divided into fixed inductance and variable inductance, fixed inductance coil referred to as inductance or coil. The unit is Henry (H), Mill Henry (mH), Micro Henry (uH), 1H = 10 ^ 3mH = 10 ^ 6uH.
Inductance classification
By inductive form: Fixed inductors, variable inductors.
According to the properties of magnetic guide: air-core coil, ferrite coil, core coil, copper core coil.
By nature of work: antenna coil, oscillation coil, choke coil, notch coil, deflection coil.
By winding structure classification: single-layer coil, multi-layer coil, the honeycomb-type coil.
Related parameters
Folding inductance
Inductance L represents the inherent characteristics of the coil itself, regardless of the current size. In addition to a special inductive coil (color code inductor), the inductance is generally not specifically marked on the coil, and to a specific name.
Folding inductive reactance
Inductance coil AC current blocking the size of the role of sense of resistance XL, the unit is ohm. It and the inductance L and AC frequency f relationship for the XL = 2πfL
Folding quality factor
Q is the quality factor of the coil that a physical quantity, Q is the inductance XL and its equivalent resistance ratio, 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 frame, the losses caused by the shield or the core, and the influence of the high frequency skin effect. The Q value of the coil is usually several tens to several hundreds.
Folded distributed capacitance
Between the coil turns and turns, between the coil and the shield, the coil and the bottom plate between the capacitance is known as the distributed capacitance. The existence of distributed capacitance of the coil to reduce the Q value, stability, deterioration, and thus the distribution of the smaller coil the better.
classification
Folded single-layer coil
Single-layer coil is wrapped around the insulation wire around the paper tube or bakelite skeleton. Such as transistor radios and medium wave coils.
Single-layer winding is in each stator slot is only embedded in a coil effective side of the winding, so its total number of coils is only half the total number of motor slots. Single-layer winding has the advantage of less winding number of relatively simple process; no interlayer insulation so that the utilization rate of slot; single-layer structure does not occur with breakdown breakdown and so on. The disadvantage is that the electromagnetic waveform generated by the winding is not ideal, the motor iron loss and noise are large and start performance is also slightly worse, so single-layer winding is generally used only for small-capacity asynchronous motor.
Folding honeycomb
If the wound coil, the plane is not parallel to the rotation surface, but intersect at a certain angle, this coil is called the honeycomb coil. The rotation of a week, the number of wire back and forth bending, often referred to as the number of folding points. Honeycomb around the advantages of small size, distributed capacitance, and inductance. Honeycomb-type windings are used to winding the machine to the honeycomb system, the more points break, the smaller the distributed capacitance.
The honeycomb coil is small in volume, small in capacitance, large in inductance and high in Q value. Therefore, many tuning coils, oscillation coils and high frequency chokes of the radio are wound in this manner. Other ways are good. In the factory, this coil is generally used to wrap around the hive.
Magnetic core
The size of the coil inductance and whether the core. Insert the ferrite core in the air core coil, can increase the inductance and improve the coil quality factor.
Copper core coil: copper coil in the application of more short-wave range, the use of rotating copper core in the coil position to change the inductance, this adjustment is more convenient and durable.
Special coils
Folding color code inductors
The color code inductor is a fixed inductance inductor, the inductance of the method of marking the same as the resistance to the color ring to mark.
Folding choke ring
Limit the alternating current through the coil called choke ring, sub-high frequency choke ring and low frequency choke ring.
Folding deflection coil
Deflection coil is a TV scan circuit output stage load, deflection coil requirements: high deflection sensitivity, uniform magnetic field, Q value is high, small size, low price.
The basic unit of the knitted fabric is a space-shaped curve consisting of two loops, a needle loop and a sinker arc (or extension line).
Various uses
1. Application of SMD coil: widely used in common mode filters, multi-frequency transformers, impedance transformers, balance and unbalanced transformers, EMI suppression of electronic equipment, USB lines for personal computers and peripherals, liquid crystal display panels, Differential signal, car remote control keys.
2. Fixed inductance coil includes: ring coil, choke coil, common mode coil, ferrite beads, power inductors, patch type and pin type to choose from. Widely used in the network, telecommunications, computers, AC power and peripherals.
3. High-current, high-current, surface-mount power inductors. Features: Ideal DC-DC converter inductor, high power, high saturation inductor, DC resistance is small, suitable for high current, with or reel packaging Surface mount, used in VCR power supply, VCR power supply, LCD TV, notebook computers, office automation equipment, mobile communications equipment, DC / DC converter.
4. RF Inductor Usage: Widely used in mobile phones, VCO, TCXO circuit and RF transceiver module, GPS, wireless network, Bluetooth module, communication equipment, LCD TV, camera, notebook, inkjet Video machines, video cameras, digital cameras, automotive electronics and so on.
Calculation formula
Inductance (μH) = the product of the square of the turns and the cross-sectional area of ​​the coil
Collecting Inductors Online Calculating Formula !!!
First batch
Load its inductance according to the following formula: Coil formula
Impedance (ohm) = 2 * 3.14159 * F (operating frequency) * Inductance (mH), set to 360ohm impedance, therefore:
Inductance (mH) = Impedance (ohm) ÷ (2 * 3.14159) ÷ F (Operating frequency) = 360 ÷ (2 * 3.14159) ÷ 7.06 = 8.116mH
According to this can be calculated around the number of coils:
Number of turns = [inductance * {(18 * circle diameter (inch)) + (40 * circle length (inch))}] ÷ circle diameter (inch)
Cycle number = [8.116 * {(18 * 2.047) + (40 * 3.74)}] 2.047 = 19 turns
Hollow Inductance Calculation Formula
Hollow inductance formula: L (mH) = (0.08D.D.N.N) / (3D +9 W +10 H)
D ------ Coil diameter
N - Number of coil turns
D ----- diameter
H ---- coil height
W ---- coil width
The units are mm and mH, respectively.
Hollow coil inductance calculation formula:
L = (0.01 * D * N * N) / (L / D + 0.44)
Inductance of coil l Unit: μH
Coil diameter D Unit: cm
Number of coil turns N Units: turns
Coil length L Unit: cm
Frequency inductance capacitance formula:
L = 25330.3 / [(f0 * f0) * c]
Operating frequency: f0 Unit: MHZ The title f0 = 125KHZ = 0.125
Resonance Capacitance: c Unit: PF This question is established c = 500 ... 1000pf can be determined by their own, or by the value of Q
Resonant inductance: l Unit: micro-Hang coil inductance formula
1. For toroidal coils, the following equations are available: (core)
L = N2.AL L = inductance (H)
H-DC = 0.4πNI / l N = number of coil turns (turns)
AL = inductance
H-DC = direct current magnetization I = passing current (A)
L = magnetic circuit length (cm)
L and the size of AL values, refer to Microl table. For example: to T50-52 material, coil 5 and a half laps, the L value is T50-52 (said OD is 0.5 inches), the look-up table of its AL value is about 33nHL = 33. (5.5) 2 = 998.25nH ≒ 1μH
When the current flows through the 10A, the L value of the change can be l = 3.74 (look-up table) H-DC = 0.4πNI / l = 0.4 × 3.14 × 5.5 × 10 / 3.74 = 18.47 (look-up table) Degree (μi%)
2. Introduce an empirical formula
L = (k * μ0 * μs * N2 * S) / l
among them
Μ0 is the vacuum permeability = 4π * 10 (-7). (10 minus seven power)
Μs is the relative permeability of the coil core, μs = 1 when the air coil
N2 is the square of the number of turns
S The cross-sectional area of ​​the coil in square meters
L The length of the coil, in meters
The k-factor depends on the ratio of the radius (R) to the length (l) of the coil.
The calculated inductance is in units of Henry.
The second installment
A simple inductance calculation program, only the input wire diameter of the coil diameter of the number of turns can be calculated automatically coil inductance, for the production of radio frequency circuits, oscillation circuit, resonant circuit without professional measuring instruments friends Hope to have a little bit of usefulness.
Coil inter - turn short circuit tester
In the industrial production and equipment maintenance process, the coil will often be inter-turn short-circuit fault test. But the test methods are not ideal, to the production, maintenance has brought a lot of inconvenience. The design is to detect whether the coil has a short circuit condition by sensing the oscillator. When the measured coil has no short circuit between turns, the sense oscillator starts to oscillate and has a sine wave output, and then the sine wave signal is coupled to the normal indication circuit through the coupling circuit. If there are two or more turns in the coil between the short-circuit, the short-circuit coil will form a closed loop, and the magnetic circuit to produce high damping, the oscillator stopped vibration, alarm circuit immediately sound and light alarm.