Capacitors Tutorial (page 2)
|Page 1||At this page 2|
|⚛ Definition of Capacitor - Capacity in Units||⚛ Reading Ceramic Capacitor Value Gates|
|⚛ Charging - Discharging a Capacitor||⚛ Electrolytic Capacitors|
|⚛ Capacitor Phisical Structure||⚛ Electrolytic Aluminum Capacitors|
|⚛ Capacitor behavior in continous AC current||⚛ Electrolytic Aluminum Capacitors Vertical - Horizontal|
|⚛ Characteristics of Capacitors||⚛ Code of Electrolytic Cylinder Capacitors|
|⚛ Types of Capacitors||⚛ Super Capacitors|
|⚛ Dielectric Characteristics||⚛ Variable Capacitors|
|⚛ Paper Capacitors||⚛ Adjustable Capacitors|
|⚛ Plastic Film Capacitors||⚛ Uses of Variable Capacitors|
|⚛ Mica Capacitors|
|⚛ Glass Capacitors||Page 3 (Capacitor Values and conversion Tables I)|
|⚛ Oil Capacitors|
|⚛ Ceramic Capacitors||Page 4 (Capacitor Values and conversion Tables II)|
Reading a ceramic capacitor value
Ceramic capacitors usually mark their nominal value in their body with special symbolism. Japanese capacitors write their value to their body with a three digit number where the first two denote their nominal value and the third number is the multiplier. The third number indicates the number of zeros that follow the first two digits and this value is in pF.
Below are indicative examples of ceramic capacitor values.
- 101 = 100pF
- 331 = 330pF
- 472 = 4.700pF or 4.7nF
- 224 = 220,000pF or 220nF
In some types of capacitors their nominal value is written with a dot in front followed by a number. It is the value of the capacitor in μF.
- .047 = 47000pF or 47nF
- .0022 = 2200pF or 2.2nF
Electrolytic capacitors are of constant capacity and their principle of operation is based on the principle of electrolysis. In electrolytic capacitors the dielectric is anode metal oxide. In order to form an oxide, the presence of anode metal, an electrolyte and a cathode is necessary. The cathode may be the same or different metal as the anode. The oxides used are mainly aluminum and tantalum, so we separate the electrolytic capacitors into two types: a) the electrolytic aluminum capacitors and b) the electrolytic tantalum capacitors.
Electrolytic capacitors are also divided into two types: "wet electrolytic" and "dry electrolytic". The liquid electrolytes contain a liquid component for dissolution, while in dry electrolytes the dissolution is retained by a sheet of absorbent paper or gauze interposed between the reinforcements. Capacitance depending on the state of dielectric, in liquid and solid electrolyte, depending on polarization in polarized and non-polarized and radial and axial depending on the housing. Non-polarized capacitors are only liquid aluminum electrolytic, axial or radial. Most commercial electrolytes are polarized.
The polarized electrolytic capacitors have a positive and a negative terminal, which are marked in their envelope. This means that the terminals must be polarized correctly, otherwise the capacitor will not work (for small reverse voltages) or will be destroyed (for larger reverse voltages). For the same reason, it is not allowed to apply only an alternate component. If this is required for technical reasons, then it should be overcome in a constant polarization component such that the sum of the two components does not exceed the nominal operating voltage of the capacitor and does not cause reverse polarization. For electrolytic tantalum capacitors, which are only polarized, a polarized polarization voltage of up to 5% of the nominal operating voltage is allowed.
Electrolytic capacitors should be polarized correctly to work properly, ie the anode needs a positive potential while the cathode is negative. Their reverse polarization results in destruction of the electrolytic capacitor. The reinforcements are very close, so they have great capacities.
Electrolytic Aluminum Capacitors
They are made of thin sheets of high purity aluminum. A thin oxide layer and a dielectric such as paper are interposed between the plates. The solution used (electrolysis) in the formation of the oxide is boric acid or potassium tartrate. The aluminum strip is too thin 20-40μm thick. The anode of the capacitor has on its surface the oxide. The greater the oxide surface, the greater the capacity of the thickener.
Electrolytic aluminum capacitors are cylindrical in shape and are either in horizontal or vertical form. Their great advantages are the large capacities for which they can be built, from 1μF to many thousands of μF. Their disadvantage is that they are not manufactured at very high voltages depending on their capacitance and large capacitances at high voltage are very large in size. The voltages for which they are manufactured do not exceed 450V, for capacities up to 470μF.
Electrolytic Aluminum Capacitors Vertical and Horizontal
Electrolytic aluminum capacitors are leaking and reducing their nominal capacity and load that they can hold over time. In these cases they must be changed in the circuits used. Leakage is a phenomenon that often occurs in capacitor faults. In this case, there is poor insulation of the dielectric between the reinforcements, resulting in short circuits in the circuit.
Also, the voltage at its ends must not exceed the maximum voltage given by the manufacturer because it overheats and the capacitor is destroyed.
On our left we see an electrolytic PHILIPS aluminum capacitor with a capacity of 150μF and a maximum voltage of 385V. It is usually used on pulse televisions.
Electrolytic aluminum capacitors are suitable for use in power supplies mainly for regulating the supply, but also in other circuits that are required to reduce the noise of the dc voltage.
Manufacturers typically give the following features electrical sizes:
- 1) rated operating voltage,
- 2) nominal capacity,
- 3) capacity tolerance,
- 4) operating temperature range,
- 5) DC leakage current,
- 6) rated current at 120Hz and 100KHz
- 7) loss factor,
- 8) equivalent series resistance to 100 Ohm
- 9) equivalent series induction,
- 10) Impedance at 10 or 100KHz
- 11) Capacity ratio (C_55 / C + 25) min at 120 Hz,
- 12) impedance ratio (Z_55 / Z + 25) max at 120 Hz,
- 13) equivalent series resistance ratio (ESR_55 / ESR + 25) max at 120Hz and
- 14) production date.
- Uses of Electrolytic Capacitor
LIQUID ALUMINUM ELECTROLYTE USES
- Radiation: Coupling, decoupling, timing, energy storage in telecommunication, audio-video, industrial applications, power sources and transformations.
- Coupling, decoupling, timing, isolation, energy storage in telecommunication, audio-video, general applications, crossoer.Axis:
- Power: Smoothing, filtering, switching, industry, computer, audio-video and general applications.
SOLID ALUMINUM ELECTROLYTE USES
- Radiation: Smoothing, filtering, isolation, DC / DC conversions in telecoms, audio-video, industry and telecomics.
- Axis: Elimination, isolation, filtering, timing, power sources, DC / DC converters, telecommunications, industrial applications, military and space applications.
SOLID AND LIQUID TATALIUM ELECTROLYTE USES
- Coupling, disconnection, timing, filtering, in military and space applications or where weight or volume is critical.
Code of Electrolytic Cylinder Capacitors
Different codes are used in these capacitors. The simplest case is in the liquid aluminum electrolyte, which displays the data such as capacity, operating voltage, tolerance and power, plus the elements of the climate class, rated current and date of manufacture. It is possible instead of the climate category to indicate the operating temperature range. The same applies to solid aluminum electrolytes, but they are different in shape and their nominal voltage, rated capacity, tolerance and probably the date of manufacture are listed in their enclosure.
The polarity of the terminals of these capacitors is marked in their envelope by "+" and "-", or by their length, longer is the positive, or finally with a notch in the positive terminal and arrows "-" for the negative terminal . Non-polarized liquid aluminum electrolyte capacitors have the necessary data in their envelope and have two notches usually at their ends to declare their specificity or "BIPOLAR" printed for the same reason. Multiple capacitors have a black pin to indicate the negative common and a red for the capacitor with the largest capacitance, blue for the shorter, green for the shorter than the previous and yellow for the smallest capacitance of all capacitors. The rest of the information is shown in their envelope.
Capacity tolerance is noted directly e.g. ± 20% or in letters. According to the IEC62 coding the following applies: J = ± 5%, K = ± 10%, M = ± 20%, Q = (- 10 + 30)% and T = (- 10 +75)%. E.I.A. Uses F = (- 10 + 50)% and G = (- 10 + 75)%.
These capacitors are characterized by very large capacities in a very small volume. Their behavior is between the behavior of the batteries and the electrolytic capacitors. The standard working voltages are (1.8 ~ 6.3) VDC have a capacity tolerance of (20 + 80)% and they work at temperatures (-25 + 85) and they are in the range of 0.047F to 1500F, with internal resistance 150Ωmax to 4mΩmax.
They are called double-layered, from the way the loads are spread, ie the electrochemical double layer, which is the most correct name. These capacitors are generally non-polarized, but some properties have been optimized in one of the two possible polarities, which are marked on the housing. They are not indicated as antiparasitic capacitors in power supplies. But they store a lot of energy and can supply the rest of the circuit for a few hours after the mains voltage is cut off. They are used in camcorders (clock and program memory), computers (clock and memory setup), electronic alarm clocks, electric toothbrushes, generally CMOS circuits requiring a low standby current, .
These capacitors have the same charging-discharge curves as the other capacitors. Also, there are no memory effects on overloads or overloads (such as Ni-Cd batteries). What you need to watch is the operating trend.
The different types of superconductors are radial and indicate in their enclosure the capacity, the operating voltage, the symbols "+" and "-" and sometimes the date of production.
In conclusion, they are easy to install and do not require support circuits, they do not require a charging circuit, they are short-circuited when they are destroyed, but they stop the current completely, have a long life, they have low explosion hazards due to the small amount of electrolyte and are not recommended in A.C. Because of the high equivalent series resistance (ESR) value.
Variable Capacity Capacitors
Variable capacitance capacitors are necessary where precision of the capacitance value of a capacitor in a circuit is necessary and are divided into two categories: a) variable capacitors and b) regulated capacitors.
Their difference is constructive and their use is equally different, since the variable capacitor is used in circuits where we constantly change the capacity of the capacitor (eg radio), while the variable capacitors are set once in a circuit and then their capacitance remains stable.
A variable capacitor has air as dielectric. In order to increase its capacity each of its reinforcements is made of many parallel trays which are electrically connected to each other. One group of these plates is stable and constitutes the "stator" of the variable capacitor, while the other group of plates is the mobile part and is called the "runner".
In the voids left by the stationary parallel plates, movable plates penetrate, which enter more or less in the gap depending on the angle of rotation of the capacitor shaft. When all the movable plates have penetrated into the gap, the capacitor has the largest capacity, and when the movable plates are out, it has the smallest capacity. They are mainly used on AM-FM radios to coordinate stations.
The adjustable capacitors are commercially available as trimer capacitors and are manufactured from various dielectric materials such as air, glass, quartz, mica, and others.
Mostly they have a circular shape and depending on the dielectric they use are classified in the following categories: adjustable air condensers, adjustable ceramic capacitors, adjustable glass capacitors and adjustable microwave capacitors.
They are manufactured for capacities ranging from 1pF to 3nF.
These are capacitors whose capacitance varies (manually or by motor) and set at a desired value. We know that:
C = εo εr . (S / d)
Where εo = dielectric constant of the vacuum,
εr = relative dielectric constant of the insulating material,
S = capacitor surface and
d = distance between its reinforcements.
It is obvious that a change in capacity can be achieved either by using a different ε, that is, a material, or by altering the surface of the capacitor, or the distance between the reinforcements.
If we choose a different dielectric material, then we have variable capacitors, plastic, ceramic, air etc. If we change the surface of the reinforcements we have the variable, trimmers or padders, rotary or tubular. Lastly, if we change the distance between the reinforcements, varying the compression between the insulating sheets and reinforcements, we have the variable ceramic, plastic, or disk-type mica.
Variables are commonly called control capacitors located in tuned circuits, such as e.g. On the radios to find stations. Predefined are two types:
A) the trimmers entering the co-ordinate circuit parallel, have a high Q quality factor, and constructively the trays are fixed to one another and
B) The padders that come in a row in the resonant circuit and constructively the discs are free from each other.
All types of variable capacitors exist for horizontal or vertical mounting on the chassis or the board. Also others are half-turn, ie 180°, other one turn or 360° and other multi-turn. Finally, there are variables of open or closed type.
The number of metal discs is not necessarily integer and in the low capacity capacitors we have 1 1/8, 1 1/4, 1 3/4 discs, etc. The maximum capacitance C, ηax of a variable capacitor is shown when we receive 100% of its rotations, While the minimum Cmin when set to the minimum of rotation.
The variable capacitors in terms of their capacitance variation are distinguished in linear and logarithmic. The linear ones are divided into: a) straight line capasity; b) straight line wafer or square low; and c) linear line frequency. Finally, there are also the intermediate form, the so-called midline.
The capacity-related linear arrays have semi-circular cross-sections and the capacity varies with the angle of rotation. So the frequency and wavelength will be exponentially changed. These capacitors are mainly used in measuring instruments.
Linear, in terms of wavelength, have the helical shape, while the are the frequency-linear ones, the logarithmic variable capacitors, etc. There is also a shape of a variable midline, semicircular shape with an axle mounted eccentric. This achieves something in between the frequency and wavelength linear ones.
Uses of variable capacitors
In general, variable capacitors are used in the VHF-UHF circuits of their radios, televisions and transmitters, as well as in the high-frequency tuned circuits. Single stator variables are used for fine tuning of tuned circuits and bifurcated stators for symmetry of high frequency circuits.