Continuous presses. They are widely used due to the possibility of pressing in a thin layer, high productivity and less labor cost.

Belt press SH10-KPE is designed to squeeze juice from fruit and berry pulp.

The press (Fig. 1) consists of pressing conveyors 8, a feeder 4, a deflecting drum 7, a frame 3, a tension drum 1, a mechanism 2 for cleaning and washing, a pressure device 6, a belt 5.

Pressing conveyors are a structure of two necks, interconnected by supports and welded from channels, and serve to squeeze juice. On them below there are guides along which the chain slides. The pressing conveyors are mounted one above the other in such a way that the gap between them is constantly reduced, due to which the juice is squeezed out.

A twin-screw feeder with a perforated body serves to feed the pulp, the deflecting drums are the supports of the fabric filter belt. The tension drum is designed to stretch the filter belt. The mechanism for cleaning and washing is made in the form of a rotating brush and a tubular device for supplying water.

Rice. 1. Belt press SH10-KPE

The crushed mass is fed by a screw feeder inside the filter cloth, which is pre-rolled into a sleeve around the feeder body. The sleeve with the pulp is picked up by pressing conveyors. The squeezed juice flows between the slats along the surface of the conveyor and is fed into the collector. After leaving the pressing zone, the fabric is unrolled into a flat belt using a special device and the pomace is unloaded. Then the fabric is cleaned, washed and returned to the pulp loading area.

Technical specifications belt press SH10-KPE: apple productivity 3000 ... 5000 kg / h; water consumption 6.0 m 3 / h; speed of pressing conveyors 0.04 ... 0.12 m / s; installed power 28.4 kW; overall dimensions 6870x2985x2570 mm; weight 15170 kg.

Belt press PL (Bulgaria) is designed to produce apple juice and consists of an endless filtering web that runs between two vertically installed metal plate belts and two rows of vertically placed plastic rollers. The belts move in opposite directions at an angle to one another (Table 1).

The pulp is pumped into a bent filter cloth and first passes between the rollers, then enters the space between the pressing plate belts, where it is subjected to increasing pressure. The juice, flowing down the surface of the belts, is collected in the lower collector.

The strips supporting the filtering cloth diverge at the exit from the press, and the cloth is opened, the squeezes are thrown away. Next, the canvas is cleaned of residues of pomace and washed with water.

Belt press PVK-12 (Yugoslavia) consists (Fig. 2) of a supporting frame 9, a receiving hopper 2 for pulp, two endless mesh belts 3 made of polyester, which move around sixteen rollers 7 of a special design, a collection tank 6 for juice, a drive with variator 8, tensioner 4, mechanical-pneumatic device 5 for tensioning the belt and the system 1 for washing the belts.

Rice. 2. Belt press PVK-12

The pulp is fed from the hopper onto a belt, which initially runs horizontally. In this section, gravity juice is separated and the pulp is compacted into a "cake", which moves further between the stretched belts and a cascade of rollers that create pressure on the pulp and squeeze the juice. At the end of the press, the belts diverge, the "cake" falls onto the waste conveyor. The belts, returning to the place of loading, are washed with water along the way. The speed of movement of the belts and the thickness of the mash layer on them are regulated.

Apple productivity 12 t / h; installed power 3 kW; water consumption 2 m 3 / h.

Belt press "Klein" type FP (Germany) - the most advanced press of this type. It is equipped with longer belts, on the working section of which there are four zones (Fig. 3).

The press consists of a loading hopper 1, control drums 2, drive rollers 3, a device 6 for washing the belt and tension rollers 9. The press has four pressure zones: 8 - drainage, 7 - medium pressure, 5 - shear and 4 - high pressure.

The pulp is loaded into the press by a screw device that adjusts the width and height of the pulp layer on the belt. The pulp distributed on the belt passes through the drainage zone 8, where up to 20% of the juice is separated - gravity, then in the zone 7 of medium pressure, the pulp is squeezed between two belts and about 30% of the juice is released from it.

Rice. 3. Belt press "Klein" type FP

Further, the partially pressed pulp enters the shearing zone 5, where it passes around eleven pressing rollers with successively decreasing diameters, of which the first three are perforated. When moving along the rollers, the layers of pulp adjacent to the upper and lower belts are shifted (cut) one relative to the other, so the juice is released from both the upper and lower layers. In this zone, up to 40% of the juice is released. In the high pressure zone 4, a further 10% of the juice is separated. The pressed pomace is removed from the belts using a self-steering tilting scraper, which are then washed with water jets from flat nozzles.

The presses are of three types: FP-1, FP-1.5 and FP-2 with a capacity of 4, 7, 6 ... 14 and 8 ... 20 t / h, respectively; belt width 1; 1.5 and 2 m; yield of juice from apples 75 ... 82%; length and height of all types of presses, respectively 4.2 and 2.5 m, width 1.6; 2.5 and 2.8 m.

The screw press VPND-10 (Fig. 4) is designed to squeeze juice from grapes. The basis of the press is a welded frame 1 made of structural shapes. It contains a perforated cylinder 5 with bandages 6, a cast hopper 4, a special gear reducer 3, a drive motor 2, a locking housing 8, a thrust bracket 9 and a hydraulic regulator 10. Inside the perforated cylinder there are 15 conveying and 12 pressing screws.

The pressing auger has a variable diameter and pitch. Towards the exit to the bale chamber, the diameter of the screw base increases and the pitch decreases. In this case, the volume of the pressed mass decreases, and the pressure increases, which is what is achieved required degree compressing the pulp in the press. The main shaft 18 passes inside the screws, by which the pressing screw is driven in rotation in the direction opposite to the rotation of the conveying screw, and with a different frequency. Rotation is communicated to the conveying auger from the hub of the gear wheel of the reducer. From the outer upper side, the perforated cylinder is closed by a casing 7, in the lower part of the cylinder there is a collector 14 with two outlets 13 of pressed juice. The receiving hopper is equipped with a 17 collector with a 16 outlet. A pressure gauge 11 is used to control the pressure in the hydraulic system.

The pulp (crushed and whole berries without ridges) is loaded into the press hopper, where a part of the gravity juice is separated from it. Then the pulp is captured by the turns of the conveying auger and moves into the cylinder towards the pressing auger. At the junction of the augers, the pulp is loosened, which facilitates further extraction of the juice. The joint cavity of the augers resists the backward movement of the pulp into the receiving hopper and creates conditions for the normal operation of the pressing auger. The partially dewatered pulp is compressed by the pressing screw and fed into the pressure chamber, where it is subjected to maximum compression. The squeezed out dewatered pulp then enters the annular channel between the perforated cylinder and the closing cone 8 and is removed from the press. The squeezed juice is collected in a collector 14. The degree of squeezing out the mash in the press depends on the size of the annular gap, which is regulated by a hydraulic locking device.

Rice. 4. Screw press VPND-10

The screw press VG10-20A (Fig. 5) is designed to squeeze juice from grapes. The basis of the press is a frame 1 welded from shaped rolled metal. The main body part 13 is mounted on it, to which a hopper 14 is attached to the top for receiving the mass, and from the bottom there is a collector 2 for juice (wort) of the first fraction. To the flange of the main body part is attached the main perforated drum 19 with shroud rings of stiffness 18. Inside the drum, along its axis, there are two screws: transporting 3 and pressing 16. The screws are mounted on the shaft 26, and the pressing screw is rigidly connected to the shaft and the torque is transmitted to him with keys 17, the transport auger is loosely seated on the shaft. The shaft receives rotation from the electric motor 8 through a V-belt drive 10, a standard gear reducer 7 and a gear pair 5. Rotation is communicated to the conveying auger from the same drive through a chain drive 12 with a tension sprocket 4. The main shaft is installed in bearings 6 and 11, the housings of which are attached to frame. At the end of the main perforated drum there is a locking cone 20, which regulates the area of ​​the annular opening for the outlet of the pressed mass and, consequently, the moisture content of the pomace. The movement of the cone along the axis is provided by a hydraulic drive consisting of a pump 23 and two cylinders 22. The oil pump is mounted on a bracket 24 attached to the frame. A maximum pressure chamber is formed between the last turn of the pressing screw and the shut-off cone. Inside it there is a small perforated drum 27 with a cover 21 for sanitizing and a nozzle 25 for removing the wort.

Rice. 5. Screw press VPO-20A

Under the main perforated drum is a collector 28 for the wort of the second and third fractions.

The press drive is closed by a casing 9, and the main perforated drum is closed by a double-leaf casing 15.

The rotational speed of the main shaft with the pressing auger is 3.5 min-1, the conveying screw is 7.5 min-1 in the opposite direction, which ensures the movement of the pressed mass and a high yield of juice.

During the operation of the press, grape berries separated from the ridges, partially destroyed in crushers-ridges, enter the press bunker. Here the pulp (pulp) is captured by the conveying auger and fed to the pressing auger. In the section of the conveyor screw, the juice (wort) is partially separated from the mash and collected, it is of the highest quality, since it contains a minimum amount of suspended particles.

At the junction of the augers, the mass moves, that is, it undergoes shear deformations, which ensures the formation of a good drainage system of channels in the pulp for removing the wort.

The industry produces presses VPO-ZOA and VPO-50, similar in design (Table 2).

The screw press РЗ-ВП2-Ш-5 of the modernized design (Fig. 6) is used to obtain apple juice.

The press consists of a frame 4, on which a perforated cylinder 10 is mounted. Inside it, there are 8 conveying and 11 pressing screws, a hopper 7, a body 3 with obturators 2, a perforated chute 6, pallets 5 of the hopper and 9 cylinders, a locking cone 13 with a drum 12. The pressing auger is fixed on the shaft 7. There are shields inside the body: left 14 and right 15.

Thanks to the use of a wire filtering cylinder with fine perforations, open obturating devices in the housing and an intermediate support of the main shaft, the technical and operational parameters of the press have increased.

Rice. 6. Screw press RZ-VP2-Sh-5

The productivity of the press has significantly stabilized during the processing of apples, both at the technical stage of maturity with elastic fiber, and those that were stored for a long time or overripe.

In the new press, 1.5 times more gravity juice is released from the bunker zone.

Owing to the use of open occluding devices in the body of the new RZ-VP2-Sh-5 press, the conditions for the grabbing of the pulp by the auger are facilitated; therefore, there were no cases of pressing the pulp during operational tests during the entire processing season. As a result of the use of an intermediate support located in the perforated cylinder of the press, a guaranteed gap between the screw and the cylinder is provided, the possibility of friction between them is eliminated, and the reliability of their operation is increased.

Technical characteristics of the press РЗ-ВП2-Ш-5: productivity for apples 5000 kg / h; juice yield 71%; power consumption 4.5 kWh; outer diameter of screws 520 mm; overall dimensions 4600x1000x1700 mm; weight 3500 kg.

It should be noted that the quality of apple juice obtained on screw presses is lower than the quality of juice pressed on bag or belt presses.

Pulse auger presses with periodic rotation of the auger and its subsequent longitudinal movement have become widespread, which allows pressing with minimal abrasion of the pulp.

Calculation of screw presses is carried out as follows. Compressed media, which have a significant ultimate shear stress, move in the press channels in the form of a solid solid, experiencing friction against the screw and cylinder. With this movement, the change in pressure along the channel can be approximately determined by the formula

The houses under construction today are so diverse that the structures being built sometimes take on a completely bizarre look. Architects especially love to experiment with roofing, which is made flat for picnics, transparent for a winter garden, and in the form of a fancy flower.

However, the most practical are the simplest options, such as a gable roof. Consider the device rafter system gable roof in this article.

With the help of this structure, a large attic space is created that does not require special insulation, therefore it is very popular in the construction of residential buildings.

In addition, it is easy to install, unlike, for example, a four-slope one and does not require large investments during installation.

A gable roof is a structure of two rectangular surfaces, the upper parts are connected to each other, and the lower parts are supported by the walls of the house.

Thus, two triangular parts at the ends - pediments - remain uncovered at the roof. These parts are either deaf, or used to enter the attic.

It is very convenient to use the resulting attic for an additional room that can be used in warm weather. And if you make an effort and insulate it, then you will get a full-fledged room suitable for life in winter.

Main parts rafter roof are visible in the figure below:

• Mauerlat, which holds the entire structure on the walls;
• rafters that form the roof itself;
• the lathing on which the roof covering is attached;
• ridge girder connecting two roof planes at the top;
• struts and struts, additionally reinforcing the roof.

The structure of the rafters can be of two types:

• hanging;
• inclined.

Hanging rafters are fixed at only two points - on the ridge and on the walls. Therefore, their structure is subjected to two types of load - compression and bending. In addition, inclined ones, in their middle part, rest on intermediate supports, which significantly reduces bending loads.

The most effective way of constructing a gable roof rafter system is a combination of hanging and inclined rafters. This combination increases structural strength and reduces material consumption.

Due to this simplicity of construction, a gable roof has a number of advantages:

• simplicity of execution and repair in case of damage;
• low cost of work and materials;
• high wear resistance and strength;
• low probability of leaks, since such a roof does not have joints of various surfaces, the structure is almost solid;
• the possibility of arranging a full-fledged living area in the attic.

Payment

Before installing the rafter system, it is imperative to calculate it. This requires perseverance and attentiveness, all calculations must be double-checked a couple of times. Staying in the midst of work without the necessary building materials, or, conversely, buying too much will cost you much more.

If the installation of a gable roof is carried out according to a detailed design, it is necessary to select all the elements of its structure with the designation of the size and quantity of each position. Using the principles of rational cutting, add up the volumes by:

• types of lumber (lm);
• vapor barrier material (m 2);
• roofing (quantity per piece, m 2);
• insulation (m 2).

For the convenience of calculations, it is best to calculate separately the area of ​​each simple element separately, and then add up the results.

For clarity of calculations, we will calculate several roofing options for houses of the same length of 8 m and a width of 4, 5, 6, 7 and 8 m. Let us determine that the angle at the top of the roof (at the ridge C) will be the same for them - 120 °. The angles of the roof slope at the attachment points to the Mauerlat (A and B) will also be the same in this case - 30 ° each.

We start by calculating the height of the roof H, it is calculated by the formula

The length of the rafters AC according to the theorem right triangle, is calculated as half the width of the house AB, divided by the sine ½ of the angle α at the apex

AC = ½AB / sin (α / 2) + 0.5 m

To the obtained value, it is required to add the length of the eaves overhang, which ranges from 0.5 to 0.8 m.

The total amount of material that we need to make the rafters is calculated as the product of the length of one rafter by the required number of rafters.

We choose the rafter pitch from the standard range of 0.6-1 m.

For our calculation, we determine that the pitch of the rafters will be 0.7 m.

In the area where there is elevated level accumulation of snow, it is necessary to strengthen the rafter system - to install a solid crate and paired rafters.

So, from the results obtained, we will compose a table, studying which, one can understand how the width of the building affects the amount of materials required for the construction of the gable roof rafter system.

Please note that the formulas given are used to calculate the exact size of the materials. Planks, tiles, slate and all other materials are available only in certain sizes. You are unlikely to buy boards for rafters 5.12 m long. Perhaps the closest size will be 7 or even 8 m, and you will have to saw off the excess.

When calculating and buying material, be sure to take into account the fact that it is on sale only in fixed sizes that do not match yours, and some of it will go to waste.

Of course, it is better to entrust the final calculation of the amount of required materials to specialists, but using the proposed scheme, you can preliminarily determine what costs await you.

Installation

There are two ways to install the rafter system:

• mount the rafters directly at the installation site;
• mount the rafter pairs (truss) on the ground and lift them up.

The first method requires less physical effort, and the second allows you to use a wide construction site and reduces the risk of falling from a height.

A "farm" is a pair of rafter legs connected to each other in accordance with the project.

Required tool

How you prepare for the work directly depends on how quickly and efficiently you will carry it out and how comfortable it will be for you to work.

For work on the construction of the rafter system, you need:

• axe;
• hammers, different weight and type;
• nail puller;
• screwdriver;
• hacksaws or chainsaw;
• Bulgarian;
• drill with a set of drills and a countersink;
• long tape measure;
• building level and plumb line;
• pencil, marker for marking;
• construction cord;
• fastening accessories: corners, strips, nails and screws.

Making a template

To make it easier to connect the rafters into trusses and keep the same dimensions, a template should be made according to which the rafters will be cut and connected. To do this, use two long boards, connecting them in the form of the letter A in exact accordance with the dimensions future roof... Then each rafter pair is adjusted to this template and fixed, gradually forming the roofing system.

The rigidity of the structure being erected directly depends on how high-quality and firmly the rafters are fixed to each other. To increase the strength of the joints, use special metal plates.

Fastening the rafters to the Mauerlat

The most important element in the installation of the roof is the fastening of the rafters to the Mauerlat.

It can be done in two ways:

• tough;
• sliding.

Rigid fastening of the rafters to the Mauerlat eliminates any impacts on the resulting connection - shifts, turns, bends. Such strength can be achieved by fastening the rafters with support cuts, bars, metal corners, using staples and nails. Additionally, you can fix the rafters to the wall with anchors or wire.

The sliding fastening of the rafters to the Mauerlat has two degrees of freedom. This mount is recommended for roofs wooden houses... At the same time, the rafters are able to move along their longitudinal axis. To do this, they are placed in special cuts of the Mauerlat, which exclude lateral movements, but allow them to move up and down. Such restraints can also be made from two large restraining nails or a special plate.

Installing trusses

The trusses are installed at the ends of the building, and a cord is pulled tightly between them. The cord must be strictly horizontal, which is controlled by the level. If one of its ends is higher than the other, then the farm to which it is attached will need to be lowered slightly.

To eliminate the sagging of the rafter system from the load, it is required to reinforce the middle rafters with special struts.

The rest of the rafters are installed at the level of this cord with the required step and secured with braces, retaining beams and other methods provided for by the project.

Entrance metal double doors are a two-door structure. Most often these are two doors, an external and an internal one, and the external one opens to staircase, and the inner one - into the apartment. In some cases, the phrase "double entrance doors" means a double door, but this is the exception rather than the rule.

It is convenient to install double entrance doors when the width of the doorway allows it and there is no second single-leaf door to the apartment. There are house projects where a double door is provided for by design, and the architecture of the building contributes to this choice. Sometimes double doors are installed in accordance with technological constraints.

Double door: increased security for your home.

For the same reasons, double doors with transoms can be installed. Their advantage is that they can easily cover large openings.

Before you start choosing a double metal door, you should pay attention to the components of the structure. A transom is a static element of metal doors that does not open and is made of the same materials as the rest of the double door. The transom consists of an outer and an inner cover. For greater strength, it has stiffening ribs. Also, the transom must have excellent insulating properties: it does not allow heat and sound to pass through.

Dual input metal doors can be with a collapsible transom, or presented as a single piece. Due to this, such doors can close openings of different, including non-standard, sizes.

The transom can be all-welded with the door frame - then the metal structure will be one. But it can also be detachable and attached separately.

The most important thing when choosing double entrance doors is the choice of the parameters of the fixed and revolving sash. Because such a door design consists of two leaves, then in addition to the main locking mechanism, the doors are equipped with a special lock that locks the fixed leaf. Double-leaf doors are no less reliable than conventional single-leaf doors, because their design implies a profile door frame. If you want to install both metal and wooden entrance doors at the same time, then you need to carefully check their dimensions.

Most often, double metal entrance doors are installed in apartment buildings to create a vestibule in front of adjacent apartments. A common mistake in such cases is the installation of a conventional non-armored iron door without additional protective elements. Therefore, it will not be difficult for an intruder to open such a door, and in the vestibule it is much more convenient to open the locks on the other entrance doors. Therefore, you should take care of safety, and carefully approach the choice of a vestibule door.

Tambour doors serve to control access to the premises, therefore, in most cases, such doors are not insulated.

If double-leaf entrance doors are installed as external doors, then a visor above them is required in order to reduce the effect of sunlight on the doors, temperature differences and other influences.

Types of double doors

Double metal doors can be installed as independent design, or in tandem with a single-leaf wooden door. The most common installation options are:

In addition to this design, double entrance doors can consist of two leaves. This is quite convenient - if you need to bring large household appliances into the house, the second sash opens, significantly increasing the width of the opening.

Installation double doors it is advisable when the opening width is more than 110 cm.They can be installed not only in residential buildings, but also in offices, public buildings or industrial premises- wherever the non-standard width of the doorway does not allow the installation of an ordinary door. Double doors are often used as driveways.

Depending on the purpose and configuration, double entrance doors differ in the following parameters:

• door finishing (external and internal);
• type of lock systems;
• fittings;
• insulating characteristics.

Despite the fact that double metal entrance doors themselves are already irregular in shape, they can have unusual arched shape and decoration. Often together with decorative materials used by artistic forging, giving the door a sleek and stylish look.

The front door, decorated with artistic forging, will always be unique.

Pros and cons of a metal double door

Consider why double metal doors are gaining popularity and are increasingly being installed not only in office rooms, but also as an entrance door to the apartment.

1. Double metal doors provide a high level of protection. Even if one door is broken open, the second will detain the intruders until the arrival of law enforcement agencies.
2. Double doors provide much better thermal insulation than single doors. If the entrance doors do not go to the vestibule, but to the staircase, this parameter is especially important.
3. Affordable cost. Entrance metal doors are not only more reliable, but also cheaper than the ones made of wood. Almost everyone can afford steel doors.
4. If you supply metal double doors, you do not have to spend money on their maintenance. They will not require additional operating costs other than installation.
5. Metal entrance doors are durable and reliable. High-quality metal does not deform under the influence of atmospheric precipitation, it tolerates direct sunlight and physical impact well.

These benefits when installing double metal doors are very significant, but there are also disadvantages:

1. By its structure, metal does not support a healthy microclimate in an apartment.
2. Many consider metal doors to be too rough.
3. Compared to wooden doors, steel doors conduct sound well.

Double metal doors will keep your home secure.

Thus, entrance metal doors are the best value for money, they are irreplaceable for an apartment and will reliably protect you and your property.

The telescopic crown is a design of two parts: primary and secondary. It is mainly used for fixing. The primary part is a metal cap. The secondary crown is fixed to the prosthesis frame. When the two parts are joined together, a sturdy structure is formed. With its help, you can form a strong attachment of the prostheses, which at the same time can be easily removed.

Varieties of telescopic crowns

This mechanism was first tested in Germany at the beginning of the last century. The telescopic crown owes its name to its resemblance to a telescope. Its component parts move relative to each other in the same way. For practically centuries-old history this design managed to prove its practicality, ease of use and good aesthetics. These days, telescopic crowns can be excellent alternative option prostheses on implants.

There are two types of this design - cylindrical crowns and conical crowns. Basically, they differ in appearance. The earliest examples of telescopic crowns were made by artisans with cylindrical walls. They are characterized by a fairly snug fit. Today, such a design is advisable to use only among patients with absolutely healthy gums.

The telescopic conical crown is an improved version of the cylindrical crown. Its main advantage is considered to be the absence of the influence of errors that are possible at the manufacturing stage. This design does not allow for skewing or jamming when fixing the prosthesis. The main disadvantage of the improved system is the ability to detach the crowns upon contact with food.

Benefits of telescopic crowns

What kind positive sides can be noted in the application of this design?

1. The chewing load is evenly distributed over all teeth and gums.
2. Lack of influence on diction and bite.
3. Possibility of installation on implants.
4. Long service time.
5. Easy to use and maintain.
6. Keeping the tooth healthy for a long time.

These are not all the advantages of telescopic crowns. Everyone can note for themselves the positive aspects of using the design.

Disadvantages of telescopic crowns

Among the main disadvantages of this design are a long manufacturing period and high cost. However, the negative aspects are fully compensated for by the above advantages of crowns.

Installation indications

The use of telescopic crowns is advisable in the following cases:

• the presence of periodontal disease and loose abutment teeth;
• there is no financial ability to install implants;
• too few teeth for clasp dentures.

The need to use this design is still determined by the doctor.

Telescopic crowns: manufacturing steps

The production of the structure described in the article today is possible in two ways: stamping and casting. The first method is considered to be the simplest. However, when using casting, it is possible to obtain a more attractive appearance product through processing with modern materials.

Manufacturing of telescopic crowns begins with turning the patient's teeth under the inner part of the structure. Then the specialist takes impressions and sends them to the laboratory. There, technicians are already making models from them and making caps. It is very important to check the parallelism of the walls of the abutment teeth so that the structure fits accurately. After trying on the caps, a plaster cast is formed from them for casting the future model. The external crown is made taking into account a gap of 0.5-1 mm. An external structure is already being made on the basis of the resulting print.

Cost and service life

Telescopic crowns are considered relatively expensive. Its cost can vary from 5 to 11 thousand rubles. If we talk about complete prosthetics, then the final price will depend on several factors simultaneously (the material used, the number of abutment teeth, etc.). It is not possible to name it exactly.

On telescopic crowns, they are characterized by a short service life - no more than 10 years. To increase it, it is necessary to periodically visit a doctor and monitor the operation of the structure.

The Tesla coil is a high frequency resonant transformer without a ferromagnetic core, with which a high voltage can be obtained on the secondary winding. Under the influence of high voltage in the air, an electrical breakdown occurs, like a lightning discharge. The device was invented by Nikola Tesla, and bears his name.

According to the type of switching element of the primary circuit, Tesla coils are divided into spark (SGTC - Spark gap Tesla coil), transistor (SSTC - Solid state Tesla coil, DRSSTC - Dual resonant solid state Tesla coil). I will only consider spark coils, which are the simplest and most common. According to the method of charging the loop capacitor, spark coils are divided into 2 types: ACSGTC - Spark gap Tesla coil, and DCSGTC - Spark gap Tesla coil. In the first version, the capacitor is charged with an alternating voltage, in the second, a resonant charge is used with a constant voltage supply.

The coil itself is a construction of two windings and a torus. The secondary winding is cylindrical, wound on a dielectric pipe with a copper winding wire, in one layer turn to turn, and usually has 500-1500 turns. The optimal ratio of the diameter and length of the winding is 1: 3.5 - 1: 6. To increase the electrical and mechanical strength, the winding is coated with epoxy glue or polyurethane varnish. Usually, the dimensions of the secondary winding are determined based on the power of the power source, that is, the high-voltage transformer. Having determined the diameter of the winding, the length is found from the optimal ratio. Next, the diameter of the winding wire is selected so that the number of turns is approximately equal to the generally accepted value. Sewer pipes are usually used as a dielectric pipe. plastic pipes, but you can also make homemade pipe, using sheets of drawing Whatman paper and epoxy glue. Hereinafter, we are talking about medium coils, with a power of 1 kW and a secondary winding diameter of 10 cm.

A hollow conductive torus, usually made of aluminum, is installed on the upper end of the secondary pipe. corrugated pipe for the removal of hot gases. Basically, the diameter of the pipe is selected equal to the diameter of the secondary winding. The torus diameter is usually 0.5-0.9 times the length of the secondary winding. The torus has an electrical capacitance, which is determined by its geometric dimensions, and acts as a capacitor.

The primary winding is located at the lower base of the secondary winding, and has a spiral flat or conical shape. Usually consists of 5-20 turns of thick copper or aluminum wire... High frequency currents flow in the winding, as a result of which the skin effect can have a significant influence. Due to the high frequency, the current is distributed mainly in the surface layer of the conductor, thereby reducing the effective cross-sectional area of ​​the conductor, which leads to an increase in active resistance and a decrease in the amplitude of electromagnetic oscillations. So the best option for the manufacture of the primary winding there will be a hollow copper tube, or a flat wide tape. Above the primary winding in the outer diameter, an open protective ring (Strike Ring) of the same conductor is sometimes installed and grounded. The ring is designed to prevent discharges from entering the primary winding. The gap is necessary to exclude the flow of current through the ring, otherwise the magnetic field created by the induction current will weaken the magnetic field of the primary and secondary windings. The protective ring can be dispensed with by grounding one end of the primary winding, and the discharge will not harm the coil components.

The coupling coefficient between the windings depends on their relative position, the closer they are, the greater the coefficient. For spark coils, the typical value for the coefficient is K = 0.1-0.3. The voltage on the secondary winding depends on it, the greater the coupling coefficient, the greater the voltage. But it is not recommended to increase the coupling coefficient above the norm, since discharges will begin to slip between the windings, damaging the secondary winding.


The diagram shows simplest option Tesla coils ACSGTC type.
The principle of operation of the Tesla coil is based on the phenomenon of resonance of two inductively coupled oscillatory circuits. The primary oscillatory circuit consists of a capacitor C1, a primary winding of L1, and is switched by an arrester, as a result of which a closed circuit is formed. The secondary oscillatory circuit is formed by a secondary winding L2 and a capacitor C2 (a torus with a capacitance), the lower end of the winding must be grounded. When the natural frequency of the primary oscillatory circuit coincides with the frequency of the secondary oscillatory circuit, there is a sharp increase in the amplitude of the voltage and current in the secondary circuit. At a sufficiently high voltage, an electrical breakdown of air occurs in the form of a discharge emanating from the torus. It is important to understand what constitutes a closed secondary circuit. The secondary circuit current flows through the secondary winding L2 and the capacitor C2 (torus), then through air and ground (since the winding is grounded), the closed loop can be described as follows: earth-winding-torus-discharge-earth. Thus, exciting electrical discharges are part of the loop current. With a high grounding resistance, the discharges emanating from the torus will hit directly on the secondary winding, which is not good, so you need to make a high-quality grounding.

After the dimensions of the secondary winding and the torus are determined, the natural frequency of the secondary circuit can be calculated. Here it must be borne in mind that the secondary winding, in addition to inductance, has a certain capacity due to its considerable dimensions, which must be taken into account when calculating, the capacity of the winding must be added to the capacity of the torus. Next, you need to estimate the parameters of the coil L1 and the capacitor C1 of the primary circuit, so that the natural frequency of the primary circuit is close to the frequency of the secondary circuit. The capacitance of the primary circuit capacitor is usually 25-100 nF, based on this, the number of turns of the primary winding is calculated, on average, 5-20 turns should be obtained. When manufacturing a winding, it is necessary to increase the number of turns, in comparison with the calculated value, for the subsequent tuning of the coil to resonance. All these parameters can be calculated using standard formulas from a physics textbook; there are also books on the network on calculating the inductance of various coils. There are also special calculator programs for calculating all the parameters of the future Tesla coil.

Tuning is done by changing the inductance of the primary winding, that is, one end of the winding is connected to the circuit, and the other is not connected anywhere. The second contact is made in the form of a clamp, which can be thrown from one turn to another, thereby not using the entire winding, but only part of it, respectively, the inductance and natural frequency of the primary circuit change. The tuning is performed during the preliminary starts of the coil, the resonance is judged by the length of the discharges issued. There is also a method for cold tuning the resonance using an RF generator and an oscilloscope or RF voltmeter without starting the coil. It should be noted that the electric discharge has a capacity, as a result of which the natural frequency of the secondary circuit may decrease slightly during the operation of the coil. Grounding can also have a small effect on the secondary circuit frequency.

The arrester is a switching element in the primary oscillatory circuit. With an electrical breakdown of the spark gap under the action of a high voltage, an arc is formed in it, which closes the circuit of the primary circuit, and high-frequency damped oscillations arise in it, during which the voltage across the capacitor C1 gradually decreases. After the arc is extinguished, the loop capacitor C1 again begins to charge from the power source, with the next breakdown of the spark gap, a new cycle of oscillations begins.

The arrester is divided into two types: static and rotating. A static spark gap consists of two closely spaced electrodes, the distance between which is adjusted so that an electrical breakdown between them occurs at the time when the capacitor C1 is charged to the highest voltage, or slightly less than the maximum. The approximate distance between the electrodes is determined based on dielectric strength air, which is about 3 kV / mm under standard conditions environment, and also depends on the shape of the electrodes. For AC mains voltage, the static surge arrestor (BPS - beats per second) will be 100Hz.

The rotating spark gap (RSG - Rotary spark gap) is based on an electric motor, on the shaft of which a disk with electrodes is mounted, static electrodes are installed on each side of the disk, so that when the disk rotates, all the electrodes of the disk will fly between the static electrodes. The distance between the electrodes is kept to a minimum. In this version, you can adjust the switching frequency within a wide range by controlling the electric motor, which gives more opportunities for tuning and controlling the coil. The motor housing must be grounded to protect the motor winding from breakdown in the event of a high-voltage discharge.

As a loop capacitor C1, capacitor assemblies (MMC - Multi Mini Capacitor) are used from high-voltage high-frequency capacitors connected in series and in parallel. Usually, ceramic capacitors of the KVI-3 type are used, as well as K78-2 film capacitors. Recently, a transition to paper capacitors of the K75-25 type has been planned, which have shown themselves well in operation. The nominal voltage of the capacitor assembly for reliability should be 1.5-2 times higher than the peak voltage of the power supply. To protect the capacitors from overvoltage (high frequency pulses), an air arrester is installed parallel to the entire assembly. The arrester can be two small electrodes.

A high-voltage transformer T1 is used as a power source for charging capacitors, or several transformers connected in series or in parallel. Basically, novice teslastors use a transformer made of microwave oven(MOT - Microwave Oven Transformer), whose output AC voltage is ~ 2.2 kV, power is about 800 W. Depending on the rated voltage of the loop capacitor, MOTs are connected in series from 2 to 4 pieces. The use of only one transformer is not advisable, since, due to the small output voltage, the gap in the arrester will be very small, the result will be unstable results of the coil operation. Mots have drawbacks in the form of weak electrical strength, are not designed for long-term operation, they get very hot under heavy load, therefore they often fail. It is more reasonable to use special oil-immersed transformers such as ОМ, ОМП, ОМГ, which have an output voltage of 6.3 kV, 10 kV, and a power of 4 kW, 10 kW. You can also make a homemade high voltage transformer. When working with high-voltage transformers, one should not forget about safety precautions, high voltage is dangerous to life, the transformer case must be grounded. If necessary, an autotransformer can be installed in series with the primary winding of the transformer to adjust the charging voltage of the loop capacitor. The power of the autotransformer should not be less power transformer T1.

The choke Ld in the power circuit is necessary to limit the short-circuit current of the transformer in the event of a breakdown of the arrester. Most often, the choke is located in the secondary circuit of the transformer T1. Due to the high voltage, the required inductance of the choke can take large values from units to tens of henries. In this case, it must have sufficient electrical strength. With the same success, the choke can be installed in series with the primary winding of the transformer, respectively, high electrical strength is not required here, the required inductance is an order of magnitude lower, and amounts to tens, hundreds of millihenries. The diameter of the winding wire must not be less than the diameter of the primary winding of the transformer. The inductance of the choke is calculated from the formula for the dependence of the inductive resistance on the frequency of the alternating current.

The low-pass filter (LPF) is designed to exclude the penetration of high-frequency pulses of the primary circuit into the inductor circuit and the secondary winding of the transformer, that is, to protect them. The filter can be L-shaped or U-shaped. The cutoff frequency of the filter is chosen an order of magnitude less than the resonant frequency of the oscillatory circuits of the coil, but the cutoff frequency must be much higher than the arrester response frequency.


With a resonant charge of a loop capacitor (coil type - DCSGTC), a constant voltage is used, in contrast to ACSGTC. The voltage of the secondary winding of the transformer T1 is rectified using a diode bridge and smoothed with a capacitor St. The capacitance of the capacitor should be an order of magnitude larger than the capacitance of the loop capacitor C1, to reduce the ripple of the constant voltage. The value of the capacitance is usually 1-5 μF, the nominal voltage for reliability is chosen 1.5-2 times higher than the amplitude rectified voltage. Instead of a single capacitor, you can use capacitor arrays, preferably not forgetting about equalizing resistors when several capacitors are connected in series.

Serially connected high-voltage diode poles of the KTs201 type and others are used as bridge diodes. The nominal current of the diode poles must be greater than the nominal current of the secondary winding of the transformer. The reverse voltage of the diode poles depends on the rectification circuit; for reasons of reliability, the reverse voltage of the diodes should be 2 times the amplitude value of the voltage. It is possible to make homemade diode poles by serial connection conventional rectifier diodes (for example 1N5408, Urev = 1000 V, Inom = 3 A), using equalizing resistors.
Instead of standard scheme rectifying and smoothing, a voltage doubler can be assembled from two diode columns and two capacitors.

The principle of operation of the resonant charge circuit is based on the phenomenon of self-induction of the inductor Ld, as well as the use of a cut-off diode VDo. At the moment when the capacitor C1 is discharged, a current begins to flow through the inductor, increasing in a sinusoidal law, while energy accumulates in the inductor in the form magnetic field, and the capacitor is charged at the same time, accumulating energy in the form of an electric field. The voltage across the capacitor rises to the voltage of the power source, while the maximum current flows through the inductor, and the voltage drop across it is zero. In this case, the current cannot stop instantly, and continues to flow in the same direction due to the presence of self-induction of the choke. The capacitor continues to charge up to twice the power supply voltage. A cut-off diode is necessary to prevent energy flow from the capacitor back to the power source, since a potential difference appears between the capacitor and the power source equal to the voltage of the power source. In fact, the voltage across the capacitor does not reach double the value, due to the presence of a voltage drop across the diode column.

The use of a resonant charge allows for a more efficient and uniform transfer of energy to the primary circuit, while, to obtain the same result (along the length of the discharge), the DCSGTC requires less power from the power supply (transformer T1) than the ACSGTC. The discharges acquire a characteristic smooth bending due to a stable supply voltage, in contrast to the ACSGTC, where the next approach of the electrodes in the RSG can occur in time at any section of the sinusoidal voltage, including hitting zero or low voltage and, as a consequence, a variable length of the discharge (burst discharge).

The picture below shows the formulas for calculating the parameters of the Tesla coil:

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