Craftsmen, collecting the device, often think about how to connect capacitors in parallel or in series. Far from any nominal is produced by the industry, the task of providing the design with a bunch of containers is found everywhere. In parallel, the nominal values are added, and in the case of a consistent one, a more complex formula is used. In addition, capacitors are trimmers, such as quite accurately included in the circuit where you want to provide the necessary resonance characteristics. And also required to solve the above problem.
Serial and Parallel Connections of Capacitors
When the capacitors are connected in parallel, their capacitors are added together. It is easy to calculate the desired denomination. Suppose it takes 7 microfarads, but the industry does not release such capacitors. But there are 6.8 microfarads and 200 nF.By their addition, a bundle is formed in the desired 7 μF.Factory ratings are specially selected to create any values.
When a series capacitor connection is used, the resulting value of the nominal is defined as the product of the capacitors divided by their sum. For example, if you put two identical tanks one after another, the total capacitor will earn a nominal equal to half of the original. When various capacitors are added up, it is the smaller one that makes the greater contribution. It makes no sense to consistently connect powerful tanks with weak ones. Condensers, one after the other, are selected at par approximately equivalent.
Connection details
The question arises - why use a serial connection. In physics, the topic is often considered, but it does not say why reduce the capacitance of capacitors. After all, the cost of construction from this increases, a lot of difficulties is the calculation mode. The reason is practical. The reviews have already written that the working voltage of a capacitor strongly depends on the type of dielectric and the thickness of its layer. Increasing the specified parameter is problematic.
Then it is required to make a series connection of capacitors, in which the voltage between them is divided in proportion to the capacitance ratings: the smaller the farad, the more applied. The impedance of the elements is given by the formula R = j 1 / W C, where W is the circular frequency of the circuit( f x 2 P; 6.28 f).Letter j means that the resistance of the capacitance to alternating current is imaginary( although, unlike the ideal, it is considered to be a complex number due to losses on the plates and other phenomena).
Consider how the capacitor appears in the DC circuit. Capacities will be filled with charges, and the voltage will be divided between the elements, inversely proportional to the capacities of the elements making up the circuit. Imagine a situation where the potential difference in the circuit clearly exceeds the working one. You will need to dial a serial circuit of capacitors with reduced operating voltage, sacrificing the value of capacity.
Mixed capacitor coupling is sometimes beneficial. Suppose you type part of the nominal parallel connection, and the remaining elements are designed to work with a lower voltage. Then we try to type from the last a consistent branch of the desired size in the farads.
Rows of capacitors of capacitors
The series of standard capacitors are known: E3, E6, E12, E24.After the war of the 45th year, when countries sat down at the negotiating table, it turned out that the interlocutors had two main standards on a number of tanks. The point was to be able to dial any nominal of the components by parallel connection.
It turned out that this is done in two ways:
- Take rows, where any value equals the root of the tenth degree of the dozens raised to a certain degree. Such a series is proportional to a single value: the root of the tenth power out of ten.
- The second row used similar ratios, but the root was taken to the twelfth degree. Explain from the point of view of mathematics. The standard appeal to the square root. That corresponds to degree 2. For example, the root of 9 equals 3. A cubic root is a number that is raised to a third power for a radical expression to appear. For example, the cube root of 27 also equals 3.
Now readers understand that the rows of standard capacitors are complex. So, it turned out that some countries are already using the second method, but theoretically the first one is of great benefit. For the sake of certain conditions, it was decided to use the twelfth root. There are a number of capacitors E12.All its values are proportional to the powers of tens, on which the specified mathematical operation was performed. In practice, it looks like 1, 1.2, 1.5, 1.8, etc.
Other series are multiples of this. There the root is taken, respectively, of the third, sixth, twenty-fourth, forty-eighth, ninety-sixth and even one hundred ninety-second degrees. As a result, standard rows are formed. Established their own tolerances capacitors. For example, for:
- E12 plus minus 10%.
- E24 plus minus 5%.
- For tolerances tighter than 5%, series E48 and higher are used.
Connection of capacitors
With a decrease in the degree of the root, the distance between the nominal values increases. Therefore, to cover the entire range and tolerances should be taken less tight. In practice, as mentioned earlier in the reviews, the nominal value gradually goes beyond the specified limits. People measure the real value of the tester and continue to use the product at their own risk and peril. It is worth noting that even terms( even powers of ten under the root) are excluded in the E48 and E96 series, and negative values appear for the first time in E192( for example, 10 to the power minus one).
This information will allow readers to better understand the meaning of the marking of capacitors in order to correctly type the necessary sequential and parallel chains. In addition, it is clear what values to look for with one or another tolerance, or there are none in nature. Since the 1948 congress in Stockholm, in most countries the values of capacitors have been unified. Therefore, American tanks are fully suitable for Russian conditions. Only the mains voltage across the ocean shows a different denomination, it is suggested to be careful.
The range of operating voltages is also prescribed in GOST 28884, as are the nominal values. And the interests of all countries are taken into account. Assume that 250 V capacitors are suitable for surge protectors in the Russian Federation; products with nominal values of 127 V are appropriate for the United States of America. The rows of constant voltages are isolated. In power supplies, for example, the value depends on the type of rectifier( full-wave, full-wave, etc.).It should be borne in mind that most of the capacitors in such circuits are under double load( for example, in the power supply unit of a personal computer, the voltage on the plates reaches 600 V).
How to physically connect capacitors with series or parallel chains
Terminal types
Often when assembled, the device has no clear frame before testing. You have to add or remove various elements. More often used twist. Along with the fire hazard it creates the danger of electric shock. In addition, twisting is difficult to perform for a large number of attached wires. And soldering is not an option.
Here we recommend using group terminals( terminal block, bus) in especially problematic nodes. First, buy a tire( like grounding) in the nearest hardware store. Sold together with an insulating base, which is easily mounted with screws on a wooden base. The result is a reliable bridge, and in any nest it is possible to have several lived. Difficulties are foreseen if the wiring is thin( high-frequency part).But bundles of capacitors just often recruit for power circuits, do not see a big trouble in the use of directly designed for such cases pads. Price 50 rubles apiece.
Plus: terminals can be used for debugging regularly. But, let's say, the dimensions of the case are small and do not allow to place a block inside. How to combine multiple parallel wires after testing? Methods in this regard is not provided. Either the wiring is carried out on the printed circuit board( it is permissible to specially etch a small segment as needed), or use single terminals. Similar crimped around the core, then it is permissible to unite the whole bundles with the help of threaded connections.
For example, fasten a bolt with threads upwards on a wooden plank, and install them on a solid wooden base. Described is allowed for the testing period. In the case of direct connection of equipment or electrics( for example, in a close junction box), it is possible to use an ordinary bolt. Readers will say that parallel connection of capacitors is more convenient to type by laying the separating washers between the turns of the wiring, rather than using individual terminals. Answer - try to do it, especially with high-end residential flexibility( consisting of a variety of very fine wires), you will feel the difference immediately. Especially if you often have to perform re-switching.
The capacitor in the AC circuit usually stands under low voltage, therefore, all the conductors are thin, it will seem that the terminal is difficult to compress. We recommend at the testing stage to close up a number of cores at the same time - those that will not change. And other permissible twisting done. Remember, serial and parallel connections are fundamentally different in the number of incoming and outgoing wires. From here switching methods are various.
How to check the quality of the connection of capacitors in the circuit
The ideal case when we take the appropriate type of voltmeter. It costs about a thousand rubles, given that we get a device for measuring resistance, constant and alternating voltage, currents. The nest for measuring the capacitor( see photo) consists of two narrow slots where the legs are inserted. According to the observations of the authors, there is no difference which side to insert the electrolytic capacitor. It is better to follow the instruction manual.
Socket for measuring the capacitor
It is recommended to measure nominal values prior to work, mark them or spread them out on a paper-drawn diagram, where you already have numbers( by the way, this is done in Chinese technology).Then calculate according to the formulas, what value you get and check with the tester. Does not work? This means that the quality of contacts is bad - use twists less.
