Instruction

1

Domotica to the coil additional coils. This will increase the inductance of

**coils**with constant parameters the remaining structural elements, and the variometer (**coil**with a movable core) - will shift both limit changes in inductance (top and bottom) upwards. When winding additional turns may be that they do not fit on the frame. Do not be tempted to use a finer wire than that used in the original coil, so as not to cause heating of the windings flowing through it current.2

To the coil not having a core, add such. But remember that it needs to be made of such a material, in which the operating frequency

**of the coil**does not occur losses in eddy currents. For an electromagnet operating on direct current, suitable solid steel core, for 50-Hz transformer - core, recruited from the blue plate in the higher frequency coils will have to use cores made of ferrites of different grades.3

Remember that even with the same number of turns and other parameters of the coil of greater diameter will have a higher inductance. It is clear, however, that the wire for its production will need more.

4

The ferrite is manufactured with different magnetic permeability. Replace one ferrite core in the coil to another, which is the value of this parameter above, and its inductance will increase. But it will decrease the marginal rate at which this coil can operate without any appreciable loss in the core.

5

There are

**coils**equipped with special mechanisms to move the core. In order to increase the inductance in this case, slide the core into the frame.6

A closed magnetic circuit, ceteris paribus provides a higher inductance than open. But try not to apply this decision in transformers and chokes operating in the presence of a DC component. It is able to podmanivaya and saturate a closed core, thereby, on the contrary, causing a decrease in inductance

**of the coil**.# Advice 2: Ferrite core - what it is

Ferrite cores are widely used in household appliances and radio engineering. The main objective of their use is the elimination of interferences in the control and power electrical conductors.

Ferrites are called chemical compounds of iron oxide with oxides of other metals. The composition of the substance may vary depending on the desired properties of the finished product.

Ferrite cores are produced according to the technology of powder injection. A mixture of powders containing the necessary components in carefully calibrated proportions, pressed into the billet of the necessary form, which is baked at a temperature of up to a thousand degrees. The baking may be performed in air or in special gas atmosphere. At the last stage of manufacture the product of ferrite slowly cools down within a few hours. This technology not only allows to produce alloys with desired characteristics, but also to produce products that do not require further processing

The most widely ferrite cores are used in electrical and radio engineering. Since ferrite has high magnetopause capacity and low conductivity, it is indispensable for the Assembly of low-power transformers including pulse. Also the ferrite cores are used as the means of passive protection against high frequency electrical interference. This phenomenon is most characteristic of switching networks of control devices, where even a shielded cable may be picking up interference, reducing the efficiency of signal transmission.

For the winding of transformers release ferrites U-shaped and W-shaped. Rod form ferrite products used in the manufacture of magnetic cores: for example, from ferrite cores perform for coils of high inductance. To the layman, the most frequent ferrite rings and cylinders, which are used as filters noise in the communication cables: USB, HDMI, LAN, and others. Advanced technology allows us to produce very complex structure of the product, the size of which sometimes is less than a tenth of a millimeter.

The low conductivity of the material avoids the formation of eddy currents during the magnetization reversal of the magnetic circuit. For this indicator, the ferrite exceeds even tonkolistovogo electrical steel. Also, the ferrite can be set certain properties at the stage of production, allowing in advance and with high accuracy to adapt the product to fit the needs of the particular device in which the ferrite will be used. Ferrite can actively absorb, dissipate or reflect induced noise in the cable, which is especially important in the construction of high-precision devices: small weight and dimensions of ferrite cores can be used without disrupting the layout of the equipment inside of complex devices or systems.

## The production of cores

Ferrite cores are produced according to the technology of powder injection. A mixture of powders containing the necessary components in carefully calibrated proportions, pressed into the billet of the necessary form, which is baked at a temperature of up to a thousand degrees. The baking may be performed in air or in special gas atmosphere. At the last stage of manufacture the product of ferrite slowly cools down within a few hours. This technology not only allows to produce alloys with desired characteristics, but also to produce products that do not require further processing

## The use of ferrite cores

The most widely ferrite cores are used in electrical and radio engineering. Since ferrite has high magnetopause capacity and low conductivity, it is indispensable for the Assembly of low-power transformers including pulse. Also the ferrite cores are used as the means of passive protection against high frequency electrical interference. This phenomenon is most characteristic of switching networks of control devices, where even a shielded cable may be picking up interference, reducing the efficiency of signal transmission.

## Types of ferrite cores

For the winding of transformers release ferrites U-shaped and W-shaped. Rod form ferrite products used in the manufacture of magnetic cores: for example, from ferrite cores perform for coils of high inductance. To the layman, the most frequent ferrite rings and cylinders, which are used as filters noise in the communication cables: USB, HDMI, LAN, and others. Advanced technology allows us to produce very complex structure of the product, the size of which sometimes is less than a tenth of a millimeter.

## The advantage of ferrite over similar cores

The low conductivity of the material avoids the formation of eddy currents during the magnetization reversal of the magnetic circuit. For this indicator, the ferrite exceeds even tonkolistovogo electrical steel. Also, the ferrite can be set certain properties at the stage of production, allowing in advance and with high accuracy to adapt the product to fit the needs of the particular device in which the ferrite will be used. Ferrite can actively absorb, dissipate or reflect induced noise in the cable, which is especially important in the construction of high-precision devices: small weight and dimensions of ferrite cores can be used without disrupting the layout of the equipment inside of complex devices or systems.

# Advice 3: How to calculate the inductance of the coil

An inductor can store magnetic energy during the flow of electric current. Its main characteristic is its

**inductance**, which is denoted by the letter L and is measured in Henry (H).**The inductance**depends on its characteristics.*of the coil*You will need

- the coil material and its geometrical parameters

Instruction

1

**The inductance**proportional to the linear dimensions

*of the coil is**of the coil*, magnetic permeability of the core and the square of the number of turns of winding.

**The inductance of a**wound on a toroidal core is: L = ?0*?r*s*(N^2)/l. In this formula ?0 — magnetic constant, which is approximately equal to 1.26*(10^-6) Ng/m ?r — relative magnetic permeability of core material, which depends on the frequency), s is the cross — sectional area of the core, l is the length of the middle line of the core, N is the number of turns of the

*coil**coil*.

Relative magnetic permeability and material, as well as the number of turns N are dimensionless quantities.

2

Thus,

**the inductance***of the coil*is greater, the larger the area of its cross section. This condition increases the magnetic flux through the coil when the same current.**The inductance**inductance in µh can be calculated also by the formula: L = L0*(N^2)*D*(10^-3). Here N is the number of turns, D is the diameter of*of the coil**coil*in inches. The coefficient of L0 depends on the ratio of the length*of the coil*to its diameter. For single-layer*coil*it is equal to: L0 = 1/(0,1*((l/D)+0,45)).3

If circuit

If

*coil*are connected in series, their total**inductance**equals the sum of the inductances of all coils: L = (L1+L2+...+Ln)If

*coils*are connected in parallel, the total**inductance**equal to: L = 1/((1/L1)+(1/L2)+...+(1/Ln))Note

The main parameter characterizing the properties of inductors and chokes is the inductance. The inductance of the coil depends on its size and shape, number of turns and the magnetic permeability of the medium. . Characterizes the energy losses in the coil and is determined by the ratio of its inductive reactance to active resistance

Useful advice

The physical nature of inductance. Inductors have the property to render the reactance to alternating current with little resistance to direct current. Together with the capacitors they are used to create filters performing the frequency selection of electrical signals and for generating delay elements of signals and storage elements...

# Advice 4: How to measure inductance

To measure

**the inductance**of the coil, use an ammeter, voltmeter and frequency counter (if not known, the frequency of the AC source, then take readings and calculate the**inductance**. In the case of the solenoid (coil whose length is much greater its diameter) to determine the inductance required to measure the length of the solenoid, the area of its cross section and number of turns of the conductor.You will need

- an inductor tester

Instruction

1

Measurement of inductance by the method of voltmeter-ammeter.

To find the

To find the

**inductance**of a conductor by this method, use the AC source with a known frequency. If the frequency is not known, measure its customera joining it to the source. Connect to the power supply coil,**the inductance**of which is measured. Then in series turn on the ammeter, and to the ends of the coil in parallel is a voltmeter. Passing the current through the coil, clear the readings. Accordingly, the current in amperes and voltage in volts.2

According to this data, calculate the value of inductance of the coil. For this value of the voltage divide successively by 2, the number 3.14, the values of current frequency and current. The result is the value of inductance for the coil in Henry (H). Important: the coil connect only to AC power source. The resistance of the conductor used in the coil should be negligible.

3

The measurement of the inductance of the solenoid.

To measure inductance of the solenoid take a ruler or other instrument for determining lengths and distances, and determine the length and diameter of solenoid in meters. Then count the number of its coils.

To measure inductance of the solenoid take a ruler or other instrument for determining lengths and distances, and determine the length and diameter of solenoid in meters. Then count the number of its coils.

4

Then find

**the inductance**of the solenoid. To do this, take the number of turns in the second degree, the result and multiply by 3.14, the diameter of the second degree, and divide the result by 4. The number you divide by the length of the solenoid and multiply by 0,0000012566 (1,2566*10-6). This will be the value of the inductance of the solenoid.5

If possible, to determine the inductance of this conductor use a special device. It is based on scheme, called bridge AC.

# Advice 5: How to determine the inductance of the coil

The inductance of the coil can be measured directly or indirectly. In the first case, you will need active or bridge device, and the second will have to use the generator, voltmeter and milliammeter, and then to carry out a series of calculations.

You will need

- - active or bridge meter inductance;
- - generator of sinusoidal voltage;
- - voltmeter and milliammeter AC;
- - frequency;
- - scientific calculator.

Instruction

1

To measure the inductance of the active device, connect the coil and then successively selecting the measurement range switch, select such of them to the result was approximately in the middle of the range. Read the result. If the meter has an analog scale, when reading the results, take into account the price of division, and the coefficient shown next to the corresponding switch position.

2

On the bridge device after each selector turn the knob balancing of the bridge at any of the end positions, and then rotate it all the way in the opposite direction. Find a range in which the handle is possible to balance the bridge. Having achieved the disappearance of the sound in the speaker or headphones or decreasing readings dial indicator to zero, read the indications on the scale of the regulator (but not the gauge). In this case, as in the previous case, consider the division and the factor that should be multiplied by the range statement.

3

To measure inductance indirectly assemble the measuring circuit. The AC voltmeter switched to the limit at which the upper boundary of the range corresponds to a voltage of several volts, connect the parallel output of the generator. There connect and a frequency counter. Also in parallel, they connect the series circuit consisting of the test inductors as well as milliamperemeter AC. Both devices should show the current, not the amplitude value measured value, and can be calculated for sinusoidal oscillations.

4

The generator will enable the generation of the voltage sine wave. Ensure that the voltmeter showed about two volts. Increase the frequency until then, until the readings on the milliammeter begins to decrease. Make sure that they reduce to about half the original value. Select frequency limit corresponding to the measured frequency. Read the testimony of all three devices, and then disconnect the generator and disassemble the measuring circuit.

5

Put readings in SI units. Divide the voltage across the current. Will the inductive reactance of the coil at the frequency at which the measurement was carried out. It will be expressed in ohms.

6

Calculate the inductance according to the formula: L=X/(2πF), where L is the frequency, G (Henry), X is the inductive reactance in Ohms, F is frequency, Hz. If necessary, move the result of the calculation in derived units (e.g., MH, microgenre).

Note

Do not touch the elements of the measurement circuit when it is energized.