distributed resistance. Determination of distributed resistance to the movement of the tape. Valuable Aspects of the Selection of Documents for the Fund of the Universal Scientific Library
Requirements
One of the biggest challenges facing modern car manufacturers is how to combine improved engine efficiency with reduced fuel consumption. The modern battle for the environment, expressed in the introduction of European standards, has also had a tremendous impact on the development of new technologies in the car, including ignition design. The introduction of electronic ignition control has led to an increase in the power of the electrical impulse, which improves fuel combustion and is necessary to control the emission of CO 2 in the exhaust gases.
The use of new approaches in the production of high-voltage wires is due to a number of requirements. High-voltage wires must maintain performance in the face of an increase in the average temperature of the engine compartment due to the installation of more and more equipment. With the installation of turbines and catalytic converters, these figures have become even more significant. The wires must have impeccable moisture resistance, resistance to chemicals (brake fluid, electrolyte, oil, fuel, antifreeze), have sufficient mechanical strength (for stretching when removed and vibration during operation), be elastic (for correct laying, based on geometry engine).
The main function of high voltage wires(GDP) in the ignition system is to transfer the required current to the spark plug with minimal losses. However, in parallel with the increase in the number of on-board electrical equipment, in order to avoid interference with its operation, it has also become necessary to take into account electromagnetic compatibility (EMC).
At first, the fight against interference was carried out in favor of radio and television equipment. And the law providing for the equipping of high-voltage wires with an interference suppression mechanism was passed in Europe back in 1957. Today, electromagnetic interference is a dangerous phenomenon: interference can interfere with the operation of the airbag or ABS control unit.
Electromagnetic compatibility (EMC) - the parameter of the operation of electrical equipment, which should provide suppression of electromagnetic interference - EMI (English - ElectroMagnetic Interference) and radio frequency interference - RFI (English - Radio Frequency Interference). Electromagnetic fields are created in the ignition system when current is generated and transmitted. By the time of each separation of the spark on the middle electrodes of the spark plug, the intensity of the fields increases significantly, powerful voltage peaks appear in the wire. This negatively affects the operation of the radio, mobile phone and on-board electronics. For the stable operation of automotive electronic systems, it becomes necessary to keep the intensity of these fields at a safe level. GDPs are equipped with electrical resistances that limit voltage peaks when a spark breaks off and when the ignition coil is discharged. Regulated by international standard EHK 10.00-02.
Based on EMC criteria, zero wire resistance is no longer ideal, as it interferes with the operation of electrical equipment. HPS are recommended for a certain ignition system in terms of sparking power, since a significant increase in resistance means a loss in discharge power. Unforeseen excessive resistance to GDP entails poor combustion and increased fuel consumption, late ignition and “dullness” of the engine. Under adverse conditions, the engine may not even start. Therefore, the HRP with a high distributed resistance is not recommended to be used, for example, for VAZ ignition systems.
European standards for the production of high voltage wires are regulated in ISO 3808 and ISO 6856 (for shielded wires). Also, manufacturing standards are described in the J2031 specification of the Society of Automotive Engineers (SAE). The requirements of European standards (re-approved in 2002) are more progressive than GOST 14867-79, adopted back in Soviet times. Therefore, we will consider the requirements for GDP on the basis of euronorms.
GDP must retain its conductive properties in an aggressive engine compartment environment (influence of fuel vapors, fuels and lubricants), as well as ozonation and temperature differences. High-voltage wires are divided into six classes, depending on the limiting operating temperatures (Table 1). Requirements for minimum values are initially calculated based on the temperate European climate. Standard tests of most European manufacturers imply an operating temperature range of -30 to +105/120°C. It is believed that starting and running the engine at a lower temperature is detrimental to the engine as a whole. Since the conditions of Russian operation are often much more severe, classes with suitable characteristics are recommended.
Table 1. Wire classes according to DIN-ISO 3808
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Wire class |
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Temp max, °C ±2 |
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Temp min, °C ±3 |
Wire device
The main elements of high-voltage wires are a conductive core, protective layers of insulation, contacts and protective caps.
The type of wires is distinguished based on the material, the performance of the conductive core (core) and its resistance (Table 2). We present a more extended classification of wires than in the previous issue in accordance with international practice. Usually there are four main types of modern high-voltage wires: 1 - with a copper core, 2 - with another metal core, 3A and 3B - with a non-metallic core and distributed resistance (A - low, B - high), 4 - with a non-metal core and inductive reactive resistance.
Table 2. Wire types and resistance
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wire type |
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|
Conductor |
copper |
other metals, stranded |
non-metallic with distributed resistance |
non-metallic with inductive reactance |
|
|
Resistance |
from 3000 |
from 9000 Ω/m |
nominal resistance ±20% |
||
1, 2 - GDP with a copper core (or from other metals)
Typically multi-core. They were ubiquitous in "classic" ignition systems. They are used as primary equipment in many domestic cars. To increase corrosion resistance, copper wires are often treated with tin (by tinning).
Copper wires have the so-called "zero" resistance (of the order of 0.02 Ohm / m), which ensures the transfer of energy with virtually no loss. However, for stable operation of automotive electronics, such wires need additional noise suppression resistors, which are placed in the tips. The resistance of the wire with the resistor has a value of 1 to 6.5 kOhm.
Do I need a resistor in candles if it is installed in GDP? In electronic ignition systems, the power of the spark is higher than the total resistance of the circuit from the coil to the spark plug. Therefore, the resistance of the candles will not affect the operation of the engine. In contact ignition systems, interference is suppressed in the GDP and the distributor slider. Installing spark plugs with a resistor will affect the operation of the engine in difficult conditions (low battery charge, burnt contacts, etc.) and can lead to ignition breakdowns.
3A, 3B - GDP with a non-metallic core and distributed resistance
Due to the distributed resistance along the entire length of the wire, no resistors are required. A distinction is made between type 3A GDP - with a low distributed resistance, from 3 to 9 kOhm / m (for domestic cars it may be less than 3 kOhm), and type 3B - with a large distributed resistance, from 9 to 40 kOhm / m, for cars with increased EMC requirements.
The conductive core can be made of various materials: cotton yarn impregnated with a carbon black solution, various polymeric materials, fiberglass impregnated with graphite. Impregnation is used to improve electrical conductivity. To give greater tensile strength, it is reinforced with carbon or other braid.
4 - GDP with non-metallic core and inductive reactance
The core is made of fiberglass impregnated with graphite, linen thread or Kevlar (super strong synthetic fiber). On top of the conductive core is a conductive layer of ferroplast (metal-filled electrically conductive plastic), around which a stainless steel wire is wound.
Just like in a coil, an inductive voltage (electromagnetism) occurs here. In such wires, when the current changes, a changing magnetic field is formed. There is a phenomenon of self-induction, which prevents a change in current. This phenomenon is referred to as "reactive energy" and inductive reactance as "reactance". The resistance of such wires fluctuates depending on the engine speed. One meter of such a cable, as a rule, has a noise suppression resistor from 1.8 to 2.2 kOhm.
Faults: a violation of current conductivity can occur due to a broken core or in places of poor connection of contacts. Core break occurs due to mechanical damage or loss of operational properties. The operation of the ignition system with such a malfunction can lead to a breakdown of high-voltage insulation, as well as to failure of the switch.
The copper conductor may be subject to oxidation. The carbon conductive core, having exhausted its resource, burns out inside the insulation, continuing to conduct current through the path of least resistance - a braid, impregnation or a layer of surface contaminants.
Diagnostics: It is important to consider that the resistance of the wire increases with age, aging, contamination of the silicone conductor, oxidation of the contacts, or installation of too long wire. An increase in resistance or damage to the wire of one of the cylinders affects the sparking of only this cylinder, a malfunction of the central wire affects all cylinders.
You can compare the resistance value using a multimeter measurement. A possible break in the core is also detected. To do this, you need to set it to 20 kOhm. Permissible values of wires: copper - from 1 to 6.5 kOhm, with distributed resistance - due to different lengths of wires, should be multiplied by a factor. Differences in performance from the resistance indicated on the insulation should be small.
For wires with a winding of a conductive core, this method is incorrect, since when operating in different engine modes, the value of their resistance changes. This is due to design features.
Switching to a different type of wire. When replacing a cable with a spark plug cap with a resistive wire without a tip, it is necessary to select the length of the latter so that the total resistance remains unchanged - this parameter can be measured using a standard multimeter. There is another way to assess resistance, although its accuracy leaves much to be desired: if, after replacing the ignition wires, the car radio began to provide worse sound quality, then almost certainly there is not enough resistance and it is because of this that interference occurs.
Wire insulation
The insulation prevents current leakage and ensures the safety of the core from mechanical damage, exposure to an aggressive environment in the engine compartment. One of the most important criteria for GDP is the breakdown current value - the maximum value at which the wires retain current conductivity. These values according to ISO 3808 are: for 5 mm wire - 25 kV, for 7 mm and 8 mm wire - 35 kV.
Insulation must be resistant to such conditions: atmospheric phenomena and ozone, moisture, fuel and lubricants, fuel vapors, high and low temperatures.
Due to the dual function of insulation, coating with dielectric materials is often made multilayer: the inner layer prevents current leakage, the outer one provides protection against aggressive environments. In conditions of large temperature fluctuations, an important factor is also the plasticity of insulating materials. This is essential for proper wiring in the event of a reinstallation. Experienced motorists probably remember the GDP of the Soviet automobile industry, which over time literally “froze” in one position. To avoid such phenomena in modern insulation, combined layers of elastic plastics and rubber, resistant to temperature amplitudes, are used. To increase the mechanical strength of the insulation, reinforcing braids made of fabric, fiberglass, cotton fibers, nylon or polymers are used.
Depending on the qualities of the insulating materials, the wires are classified according to the relevant categories of DIN-ISO 3808 (Table 1). The choice of insulation by the manufacturer is not accidental and depends on the working conditions in the engine compartment. This is influenced by the layout of the engine, the presence of a turbine, a catalytic converter (the temperature of which can reach the order of 500-600 ° C) and the amount of energy sent from the coil to the candle. The most common insulating materials are:
- PCV (PVC) - polyvinyl chloride or similar combinations. It is used mainly in budget versions of GDP. Refers to classes A and B (Table 1).
- EPDM - ethylene propylene rubber. Other variations of elastomers, rubber can also be used. It has excellent resistance to aggressive media and good dielectric properties. The performance characteristics are superior to PVC, belongs to classes C and D (Table 1).
- Silicone. For the first time in high-voltage wires was used in aviation. Possesses unsurpassed properties of isolation of wires from current leakage and external influences. The advantage of silicone is also the preservation of elasticity even at low temperatures. Recommended by manufacturers to work in the most difficult conditions (including on liquefied gas). The term "all-silicone wires" means the use of silicone (or non-metallic synthetic materials) both as insulation and for the conductive core. Refers to classes E and F (Table 1).
Faults:violation of the integrity of the shell. The deterioration of the insulation causes a spark to form outside the combustion chamber. As a result, the power of the spark plug drops, the engine troit. Under the influence of adverse operating conditions, the insulation ages - plasticizers evaporate from the plastic, as a result of which it becomes brittle. Insulation cracking causes ignition voltage to leak to ground. This means misfiring, unstable engine operation (in the presence of a catalyst, unburned fuel gets into it and prematurely disables it).
Important: Afterburning of the fuel in the catalyst leads to an increase in its temperature. This not only reduces its resource, but is also extremely flammable. A "clogged" catalytic converter becomes red-hot, which often leads to a fire in the car. Therefore, it is recommended to change the wires immediately if they are discolored or have been used for a very long time (even if their resistance is normal).
Causes. Accelerates premature wear of the insulation constant contact with aggressive substances (fuels and lubricants, brake fluid, antifreeze, etc.). The layer of contamination on the elements of ignition systems is conductive and increases current leakage in wet weather and with microcracks. In addition, the wear of the insulation is greatly accelerated. It is recommended to monitor cleanliness and use water-repellent sprays for GDP and other elements of the ignition system. Shell damage can also be caused by improper installation (sharp objects, such as a screwdriver), contact with hot surfaces (exhaust pipe), vibration friction against other parts.
When the engine is idling, low loads, many insulation damages do not appear, since about 10 kV is enough for a spark on a candle, and several times more is required for insulation breakdown. Therefore, the test mode should be maximum: starting the engine, abruptly opening the throttle, running the engine at low speeds under maximum load. Symptoms of breakdown of high-voltage insulation can sometimes be similar to the symptoms of contamination of the spark plug insulator from the side of the combustion chamber.
Tips and Caps
Tips (contacts) are made of metal and are often tinned to give corrosion resistance. Are intended for connection of a conductive vein with conclusions on a candle, the ignition coil and a distributor cover.
Protective caps are designed to protect the junctions of the conductive core from current leakage and environmental influences. The requirements for handpiece materials have also changed over time. The use of spark plug wells up to 20 cm deep in engine building enhances the negative impact of oil, fuel vapors, moisture and constant high engine temperature on GDP. The more brittle carbolite in the production of protective caps was replaced by various alloys of elastic and more resistant to aggressive rubber.
Important: when washing the engine, it is recommended to disconnect the GDP from the candles, then dry the engine and install the wires back. Water tends to get under high pressure to the points of contact of the GDP with candles, as a result of which carbon paths appear - sparking occurs on the ground. If the wires are not removed, moisture also condenses in the spark wells and is not completely dried. As a result, the engine may run unevenly or not start at all.
Faults:Excessive oxidation of brass or stainless steel contacts can occur due to constant high loads and be a sign of aging. This leads to an increase in the resistance of the wire and, as a result, the risk of failure of the ignition coils.
Causes. Poor quality/loose caps. In addition to natural oxidation due to resource exhaustion, it can be triggered by moisture ingress due to loose pressing of the protective cap. Often caused by careless installation or poor material quality.
Also, a problem area for conduction may be the junction of the metal contacts of the wires with the corresponding leads of the parts of the ignition system. Poor connection of contacts is often associated with inattention during installation. This can provoke heating and sparking, spark breakdown and destruction of the contacts, the core. When removing / installing the wire, carefully check the connection points.
The joints are loosened due to the constant vibration of the engine, which worsens the contact with GDP from too rigid materials. The temperature difference has a particularly strong effect on candle caps: due to heated engine parts, they can stick, due to too low temperatures, they lose their plasticity and become brittle. Increases the chance of damage to the cap when removed. Attention should be paid to the quality of the insulation of the wire and protective caps when choosing a GDP.
Troubleshooting
The times of repairing the GDP have irretrievably sunk into oblivion, if you do not take into account individual "Kulibins". This remained relevant as long as the energy intensity and power of ignition systems were low, and the forms of caps and car contacts were typical. In those days, most manufacturers produced wires with a meter in coils and carbolite protective caps separately for them.
It is important to understand that most of the malfunctions of modern GDPs cannot be repaired. The exception is oxidized contacts, which you can try to clean. For other faults, the wires must be replaced. Attempts to wrap the wires with adhesive tape, electrical tape will not help either with microcracks or with obvious damage to the insulation. Such means of isolating the conductive core are just an excuse for the car owner, but in fact they aggravate the overall picture of the engine. GDPs are supplied as a complete set, since if one wire is damaged, the rest are often also close to exhausting their resource.
Many malfunctions of the ignition elements can be detected by an audiovisual method. The following symptoms testify to this: poor starting (especially in the morning in cold wet weather), misfiring under load, engine stalling (if the center wire is damaged), uneven idling, loss of power, increased fuel consumption, radio interference. Malfunctions occur due to a break in the electrical circuit or damage to the insulation and are often accompanied by the check engine icon on the dashboard. The main ones have been listed above and can be determined by visual inspection. In the case when damage cannot be detected visually, diagnostics are necessary.
Important! It is worth noting that the common “self-diagnosis” systems, when the voltage strength is checked by touching the hand, are extremely unsafe. The voltage of non-contact electronic ignition systems reaches 40 kV, and sometimes the voltage in the network increases even more, which can lead to burns. Therefore, in order to avoid electrical injury, do not touch the GDP when the engine is running. To do this, it is recommended to use insulated pliers and work in thick rubber gloves.
The easiest way to detect insulation failure is to open the engine compartment with the engine running at night or in a dark room. In the place of "breakdown" a jumping spark will be visible. In case of leaks in the seals, microcracks in the insulation, as well as in the presence of air humidity, a glow can be observed around the GDP or other devices of the ignition system.
You can also "ring out" the current leakage by connecting a wire of suitable length to ground. To do this, it is necessary to strip the wire from both ends, connect one side to the ground, and draw the other side around the elements of the ignition system. Sparks will jump at the place of current leakage.
IN Important: Under no circumstances should the "diagnostic" wire touch the contacts of the ignition coil!
It is also possible to carry out diagnostics using a spark gap, having previously turned off the fuel supply for vehicles equipped with a catalyst. For diagnostics, you need to connect the spark gap to the wire and turn the crankshaft using the starter. With current leakage or high resistance in the secondary circuit, the spark will be pale and thin. You can simulate the operation of the arrester by fixing the tip of the wire at a short distance from the metal part of the engine. More accurate results can be obtained using a motor tester.
Consequences of working on faulty GDP
The reserves of high voltage and ignition energy must be sufficient to compensate for all electrical losses. Improper maintenance of the ignition system, the operation of faulty GDP lead to a decrease in these reserves and disturbances in the ignition and combustion processes.
With current leakage, it becomes impossible to create a sufficient potential difference across the electrodes of the spark plug. As a result, a full-fledged combustion front of the air-fuel mixture does not occur due to misfires. This causes engine shaking, increased fuel consumption and reduced vehicle performance. Burning residues, with an increased amount of hydrocarbons, burning out in the catalytic converter, disable it together with the exhaust gas sensors (“poisoning” of the oxygen sensor).
The operation of faulty GDP also directly affects the elements of the ignition system. This can lead to breakdown of the insulation of candles or oxidation of their contacts, failure of the ignition coils, distributor, switch. Lost discharge from a faulty wire can cause a fire in the engine compartment. Also, a malfunction of the GDP does not just create electromagnetic interference in the operation of on-board electronics, but actually affects its performance. The work of different vehicle systems is closely interrelated, and a malfunction of the ignition system cannot be ignored. In some cases, breakdowns in high-voltage wires lead to oil dilution, washing off the oil film from the cylinders, pressure reduction and, as a result, to mechanical damage to the engine and transmission.
Important: it is important to know that the factory (plastic) engine protection is provided by the automaker not for protection against mechanical damage, but for the aerodynamic characteristics of the car. Factory protection is designed to direct the flow of air and spray in a certain direction. Its removal violates the structural parameters of the car, and the ingress of moisture on the GDP and the ignition coil leads to ignition breakdowns.
How to avoid malfunctions
Manufacturers recommend replacing high-voltage wires without waiting for them to fail. The replacement schedule ranges from 70 to 90 thousand km or is limited to three years of operation. In any case, GDP needs regular inspection and periodic diagnostics.
In order to avoid banal malfunctions and premature failure, one should not neglect simple rules during installation:
To avoid breakage during removal, it is necessary to pull not on the wire itself, but on its protective cap. To facilitate removal, it is recommended to first turn the tip a quarter of a turn;
When removing, the tip should be removed straight without twisting. Otherwise, the ceramic insulator of the candle may be damaged;
When laying the wire, care must be taken that it does not deform and does not touch hot parts;
For optimal performance, it is necessary to ensure that the wires are installed correctly according to their length.
In most cases, solar cells have a thin frontal layer, along which current flows, collected by the contact grid. Since the power losses on the resistance are dispersed over the entire volume of this layer, more accurate models need to be considered. A diagram of a solar cell with a grid contact structure is shown in Fig. 3.12. The series resistance of the device contains the following components: - resistance of the frontal contact grid; - transient contact resistances (inversely proportional to the area of contacts); is the resistance to spreading of the surface layer (or to the flow of current in the plane of this layer), depending on the distance (here is the volume resistivity of the layer and is its thickness); - resistance of the base layer in the transverse direction - volumetric resistivity of the base layer, - layer thickness and - its area); - distributed resistance of a continuous rear contact.
Based on the total allowable value, the developer of a solar cell can find its distribution over individual components, taking into account the limited possibilities of using the materials at his disposal to create devices. A similar analysis was carried out in the development of devices with a grid contact structure.
The distributed resistance can be found approximately by considering various lumped-parameter equivalent circuits and more accurately by computer-assisted numerical methods using finite-element models. Models were studied, according to which in the equivalent circuit shown in Fig. 3.9, concentrated resistances give effects of the second and higher orders of smallness. The problem of finding the distributed resistance was solved for two-dimensional structures, as well as three-dimensional structures at a high degree of radiation concentration.
The solution of the problem in an analytical form can be useful for simple structures, as, for example, for the one-dimensional case considered below. It is believed (Fig. 3.13) that in the frontal layer the current flows in the plane of this layer, and in the base and transition - perpendicular to the plane of the device. Let us consider the elementary volume of the frontal layer bounded by planes. At the boundaries, the current density flowing along the layer, Difference, is balanced by the current density crossing the junction plane at the considered bias voltage V:
As a result of expansion in a Taylor series in the neighborhood of a point, one can obtain
Rice. 3.12. Streamlines in a solar cell with a grid contact structure, in which the thickness of the frontal layer 11 is much less than the thickness of the base layer
Rice. 3.13. Cross-sectional diagram of a solar cell with mesh front contact applied to distributed resistance analysis
Rice. 3.14. The voltage distribution between the strips of the contact grid of the element shown in fig. 3.13, during its operation near the optimal point (a) and the corresponding voltage values on the current-voltage characteristic (b)
Solution (3.17) is easy to find, assuming that is constant and equal to the current density of the corresponding maximum power, which provides the parabolic dependence shown in Fig. 3.14. If the power loss on the resistance is not very large, then this approximation is quite accurate. The power losses per unit area on the distributed resistance are directly related to the distance between the strips of the contact grid:
The (“equivalent” series resistance is . In an analytical form, a similar solution was obtained for the two-dimensional problem .
By using the finite element model, accurate results can be obtained for more complex configurations and electrical connections of diodes by finding both series and shunt distributed resistances. The essence of this method is illustrated in Fig. 3.15, which shows how the solar cell is initially presented as a long section with a width equal to half
(see scan)
Rice. 3.15. One-dimensional distributed device model used in finite element analysis
distances between the contact strips, and then this section is divided into a finite number of elements with a width. Since the line is the axis of symmetry to the right side of the element, indicated by the number "zero", no current flows.
As a test voltage on this element, you can choose, then it is easy to calculate the current flowing through the element and then the subsequent values up to the voltage and current at the output of the device. By varying the test parameter , it is possible to obtain the output current-voltage characteristic of the device even with a more complex diode characteristic. This model is quite easy to improve for solving a two-dimensional problem.
High-voltage wires are used in the car ignition system. Their properties, depending on the features of the device, may vary.
Purpose, general information
The main task of high-voltage wires is to transmit electrical impulses from the ignition coil to the spark plugs. Therefore, they must:
- withstand high voltage (up to 40,000 V),
To reduce them in the high-voltage circuit of the ignition system, additional electrical resistance is used.
Noise suppression resistor can be built into the distributor rotor (runner), spark plug or its cap in various combinations. In addition, the carbon electrode in the lid has resistance. distributor 2 .
Currently, the most effective and most common way to reduce interference is to use high-voltage wires with distributed resistance.
Device
Modern wires consist of a conductive core, insulation (protective layer), metal contacts and caps (Fig. 1).
Conductor(Fig. 2) can be of several types:
- stranded copper with a resistance of 0.02 Ohm / m (Ohm per meter of wire length). With such wires, additional jamming resistors;
- non-metallic with a metal "wrapping" - distributed resistance up to 2 kOhm / m. The central part of the core is made of fiberglass impregnated with graphite, linen thread or kevlar 3 . Often covered with a layer ferroplast 4 , which, due to its properties, also prevents the propagation of interference. A thin metal wire is wound on top. As a rule, additional noise suppression resistors are required;
- non-metallic with high distributed resistance. Wires with such a core are installed without resistors.
- cotton yarn impregnated with a soot solution. Sometimes it is reinforced from above with a cotton or nylon braid. Resistance 15-40 kOhm/m;
- polymer "vein" with a resistance of 12-15 kOhm / m. A reinforcing thread may be omitted inside it;
- fiberglass strands with graphite sprinkling.
- prevent leakage of electric current;
- protection of the core from moisture, fuels and lubricants, harmful vapors and high temperatures in the engine compartment, as well as mechanical damage.
It is made of various types of plastics (for example, PVC), silicone, rubber in various combinations. Sometimes the mechanical strength of the insulation is increased by fabric, cotton, nylon, fiberglass or polymer braid.
Metal contacts(tips) provide electrical connection of the conductive wire with the corresponding contacts (sockets, high-voltage terminals) of the spark plug and the ignition coil or the distributor cap. Primary requirements: 
The contacts to which the high-voltage wire is connected are of several types. The most commonly used are shown in Fig. 5, and at different ends of the wire they may differ.
The caps have different shapes, they are made of rubber, silicone, plastic or ebonite (photo 3). In some of them, an additional noise suppression resistor is built in (Fig. 6) or a metal screen to reduce interference. 
Faults
The main faults of the wires - electrical circuit break and current leakage.
Electrical circuit break occurs most often at the junction of the metal contact of the wire with the conductive core and other parts of the ignition system, for example, when:
- removing the wire;
- poor connection with the conclusions of the corresponding elements of the ignition system;
- oxidation or destruction of the core.
Electricity leak occurs through contaminated wires, spark plugs, a distributor cap and an ignition coil, as well as when the insulation and caps of the wire are damaged, so their dielectric properties deteriorate during operation.
At low temperatures, high-voltage wires become more rigid, and the likelihood of damage to their insulation and caps increases. In addition, due to the constant vibration that accompanies the operation of the engine, the joints are loosened, which can lead to poor contact, for example, in the distributor cap. Spark plug caps suffer the most from elevated temperatures, since they are closest to the heated engine parts and, moreover, often fail when removed.
Over time, all elements of the ignition system are inevitably covered with a layer of dust and dirt, moisture and vapors of fuels and lubricants, which are current conductors and significantly increase leakage, especially in wet weather and if the insulation is damaged. In addition, microcracks increase further from moisture and dirt.
When choosing high-voltage wires, it is advisable to focus on the recommendations of both their manufacturers and engine manufacturers.
When buying, it is useful to carefully study the packaging. It is desirable that the models of cars or engines for installation on which these wires are intended be indicated on it in Russian. The absence of an indication of the manufacturer of the wires and its "coordinates" is a sufficient condition for refusing to purchase. Also, you should not buy wires with spelling errors on the packaging, most often in the word silicon. It should be borne in mind that there is only the international standard ISO 3808 for high-voltage automotive wires, and there are no domestic ones, so the manufacturer himself determines the presence and content of the inscriptions on them.
If the ignition system gives a high-voltage pulse with low energy, for example, in cars with a contact ignition system (most rear-wheel drive VAZs), then you should not install wires with a high distributed resistance. This will reduce the power of the spark and, under adverse conditions, misfires may occur. mixtures(eg when starting a cold engine in winter) 5 .
Wire resistance can be measured with a tester. However, for wires with a winding of a conductive core, this method is not correct, since when working on an engine, their resistance value changes. This is due to their design features.
The level of interference created by both the electrical equipment of the car as a whole and high-voltage wires can be assessed using the receiver (car radio) installed in it. The procedure for such a check is given in scheme.
When choosing wires according to the insulation material, the voltage in the ignition system of a particular car should be taken into account. At its maximum values, which may be indicated in the repair manual, the insulation must not allow breakdown. Preferably wires with insulation and caps, the material of which does not become hard and brittle in the cold and withstands high temperatures in the engine compartment, such as silicone. In addition, it is less wetted by water, which means that the probability of electrical breakdown is reduced. The silicone feels waxy to the touch, and the wires made from it allow severe kinks.
During operation car, first of all, it is necessary to keep the wires clean and dry. To do this, you can, for example, periodically wipe the distributor cap, ignition coils, spark plug insulators and the wires with caps removed from the car with gasoline.
It is often possible to determine insulation breakdown during engine operation by ear (clicks are heard) or visually. If you open the engine compartment at night, then the place of the current leakage will be visible from the spark. In the dark, a glow (shine) is sometimes noticeable around the devices of the ignition system due to humidity and air ionization, for example, before a thunderstorm, or with large current leaks.
A wire break in the winding of a non-metallic conductive core (Fig. 2, b) may not manifest itself at idle speeds of the crankshaft and at low loads, while at high loads, the engine will “troit” if the wire leading to the spark plug is damaged or stall, if the central one is faulty.
Good contact in the tips prevents the loss of impulse energy transmitted to the candles. Therefore, it is advisable to periodically check whether the tips are well inserted into the sockets of the corresponding elements of the ignition system.
To prevent damage to the wire, it is recommended to remove it, starting with the cap, and not pulling out the insulation.
The tightness of the caps at the junctions of the wires reduces the oxidation of the tips and the subsequent deterioration of the contact. Therefore, it is important to put on the caps to the end, and if cracks appear on them, replace them.
The editors are grateful for the help in preparing the material of the candidate of technical sciences A.I. Feshchenko, Associate Professor of the Department of Electrical Engineering and Electrical Equipment of MADI (STU).
Interference is generated due to voltage pulses of high frequency in the ignition system. For domestic cars, their values are as follows: rotor - up to 8 kOhm, candle - 4-10 kOhm, candle cap - 4-13 kOhm, central electrode - 8-14 kOhm. Flexible artificial material with high strength. 20% polyvinylchloride compound PDF and 80% ferrite or manganese-nickel and nickel-zinc powder. You can compare the energy of a spark with one or another wire by connecting an arrester instead of candles on a car and turning the engine crankshaft with a starter. In this case, it is desirable, and on vehicles with a catalytic converter of exhaust gases, it is necessary to turn off the fuel supply. A large total resistance in the secondary circuit will make the spark paler and thinner. The arrester consists of two electrodes in an insulating housing, the distance between the ends of which is 7 mm. You can imitate the arrester by securely fastening the tip of the high-voltage wire at this distance from the metal part of the engine.
Based on site materials
The resulting expression shows that the input impedance is a function of the line parameters and , its length and load . In this case, the dependence of the input resistance on the line length, i.e. the function , is not monotonic, but has an oscillatory character due to the influence of the backward (reflected) wave. As the line length increases, both the direct and, respectively, the reflected waves attenuate more and more. As a result, the influence of the latter weakens and the amplitude of the oscillations of the function decreases.
With a matched load, i.e. at , as shown earlier, there is no backward wave, which fully corresponds to expression (1), which at , is transformed into the relation
.
The same value is determined by the input resistance at.
For some values of the line length, its input resistance may turn out to be purely active. The length of the line for which is real is called resonant. As in a lumped circuit, resonance is most clearly observed in the absence of losses. For a lossless line, based on (1), we can write
 .
|
(4) |
The study of the nature of the change depending on the length of the line based on (3) shows that at modulo varies within 
and has a capacitive character, and at - within 
and is inductive. This alternation continues further through segments of the line length equal to a quarter of the wavelength (see Fig. 1a).
In accordance with (4), a similar character, but with a shift by a quarter of a wave, will have a dependence for a short circuit (see Fig. 1,b).
The points, where , correspond to the voltage resonance, and the points, where , correspond to the current resonance.
Thus, by changing the length of the line without loss, it is possible to simulate capacitive and inductive resistances of any value. Since the wavelength is a function of frequency, a similar change can be achieved not by changing the length of the line, but by changing the frequency of the generator. At some frequencies, the input impedance of a distributed circuit also becomes real. Such frequencies are called resonant. Thus, frequencies are called resonant, at which an integer number of quarters of the wave fit into the line.
Transient processes in circuits with distributed parameters
Transient processes in circuits with distributed parameters have the nature of wandering waves propagating along the circuit in different directions. These waves can undergo multiple reflections from the junctions of different lines, from the nodal points of load switching, etc. As a result of the superposition of these waves, the picture of the processes in the circuit can turn out to be quite complex. In this case, overcurrents and overvoltages can occur, which are dangerous for the equipment.
Transient processes in circuits with distributed parameters occur with various changes in their operating modes: switching on / off the load, energy sources, connecting new sections of the line, etc. Lightning discharges can serve as the cause of transient processes in long lines.
Equations of transient processes in circuits with distributed parameters
When considering the equivalent circuit of a circuit with distributed parameters, partial differential equations were obtained
 ;
|
(5) |
 |
(6) |
Their integration with allowance for losses is a rather complicated problem. In this regard, we will consider the circuit as a lossless line, i.e. let's put and . Such an assumption is possible for lines with low losses, as well as in the analysis of the initial stages of transient processes, often the most significant in relation to overvoltages and overcurrents.
Taking into account the indicated from relations (5) and (6), we pass to the equations
Similarly, the equation for the current is obtained
 .
|
(12) |
Wave equations (11) and (12) are satisfied by the solutions
As before, direct and reverse voltage and current waves are related to each other by Ohm's law for waves
AND 
,
where 
.
When calculating transient processes, remember:
- At any moment in time, the voltage and current at any point on the line are considered as the result of the superposition of the direct and reverse waves of these variables on the corresponding values of the previous mode.
- Any change in the mode of operation of a chain with distributed parameters causes the appearance of new waves superimposed on the existing mode.
- For each wave separately, Ohm's law for waves is fulfilled.
Transients when switched on to DC voltage
open and closed at the end of the line
When the switch is closed (see Fig. 2), the voltage at the beginning of the line immediately reaches the value , and
direct square wave voltage and current are generated 
moving along the line at a speed V (see Fig. 3, a). At all points of the line, to which the wave has not yet reached, the voltage and current are equal to zero. The point limiting the section of the line to which the wave has reached is called wave front. In the case under consideration, at all points of the line passed by the wave front, the voltage is , and the current is .
Note that in real conditions, the waveform, which depends on the internal resistance of the source, line parameters, etc., always differs to a greater or lesser extent from a rectangular one.
In addition, when connected to a source line with a different law of voltage change, the waveform will be different. For example, with an exponential change in the source voltage (Fig. 4, a), the wave will have the shape in Fig. 4b.
In the example under consideration with a rectangular voltage wave, during the first run of the voltage and current waves (see Fig. 3, a), regardless of the load, they have the values, respectively, and , which is due to the fact that the waves have not yet reached the end of the line, and, therefore, the conditions at the end of the line cannot influence the process.
At the moment of time, the voltage and current waves reach the end of the line of length l, and the violation of uniformity causes the appearance of backward (reflected) waves. Since the line is open at the end, then
,
where 
And 
.