Universal mains filter and its design. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

Universal mains filter and its design. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Protection of equipment from emergency operation of the network

Comments on the article

Having once plugged the VOLNA-K radio receiver and the Pentagon-128 computer with a disk drive and power supply into the same network socket, it turned out that these devices turned out to be poorly compatible. All computer equipment gave out a powerful and wide range of radio interference, so the poor thing "WAVE" roared almost anywhere in the range from 12 kHz to 23,5 MHz. There were also interferences on TV. All this led to the idea to make and install a surge protector, that. it would not hurt if an amateur radio station was operated, but everything was postponed "for later." The spectrum of interference was very wide and the solution came by analogy with the anode choke in the output stage of a tube power amplifier. Having estimated the efficiency [1] for different frequencies, I realized that the filter should be three-section.

The classic version [2] on a ferrite ring, Fig. 1, when winding 10 turns on a 600NN K32x16x6 or 400NN K40x25x7,5 magnetic circuit and capacitors C1 ... C4 = 0,01 μF, showed the worst results. Perhaps due to the low capacitance of the capacitors, which should be at least an order of magnitude greater than 0,1 ... 0,22 uF.

Universal surge protector and its design

I failed to find pass-through (high-frequency) capacitors of such a capacity. The maximum capacitance of capacitors KTP-3 is 0,015 uF. Paper feedthrough capacitors have large capacitances, but they can effectively suppress mainly low-frequency interference of domestic and industrial origin, penetrating into the radio receiver from the AC mains.

Therefore, it was necessary to make a universal surge protector that would not pass high-frequency interference from the network to the radio receiver or transceiver when receiving, and, conversely, to the electrical one when transmitting. The network filter circuit is shown in Fig.2.

Fig.2 (click to enlarge)

Details

The filter uses capacitors C1 ... C4, C9 ... C12 - KPB - 0,022 μF - 500 V C5 ... C8, C13 ... C14 - KTP-3 - 0,015 μF - 500 V (ceramic, red with M8 thread - 0,75).

As can be seen from the diagram, ceramic and paper feed-through capacitors are connected in pairs in parallel. "Neonka" VL1 - an indicator of the inclusion of the filter in the network. Inductors L1 and L1' are wound with a conventional double mains wire, insulated (for example, from a burnt soldering iron) on seven flat ferrite rods stacked together for a magnetic antenna. The total cross section of the magnetic circuit is 4,2 cm2. The rods are tightly stacked on top of each other and wrapped with three layers of varnished fabric. A winding containing seven turns is wound on top of it. The resulting element looks more like a feed-through transformer than a choke, Fig. 3.

Universal surge protector and its design
Ris.3

Inductors L1 and L1' can also be wound on a ferrite ring with a permeability of 400 - 2000 HN. Its cross section is selected at the rate of 0,25 cm100. per XNUMX W consumed from the power network in order to avoid bias due to the asymmetry of the mains voltage. Data on the cross section of the magnetic circuit are given with some margin. In our case, the power is equal to the maximum (over the cross section) and is

Inductors L2 - 2' and L3 - 3' are wound with PEV-2 wire with a diameter of 1,5 mm. The maximum current is determined by the formula

d - wire diameter, mm j - current density, A / mm2, which can be taken as 4 ... 6 A / mm2.

At a current density of 4,5 A / mm2, the maximum current will be

It can be assumed that the filter power can reach 2000 W, since it is calculated with some margin. For normal operation, such power is unlikely to be required, but the filter is made for all occasions.

Inductors L2 - 2' are wound on ceramic rods with a diameter of 12 mm and a length of 115 mm until completely filled.

Inductors L3 - 3' - frameless, contain 9 turns each and are wound in increments to reduce the interturn capacitance and better protection against the highest frequency pickups on a mandrel with a diameter of 10 mm and a length of 41 mm.

The network filter consists of three sections, each of which operates with some overlap in a certain frequency range - L3 - 3' in the high frequency region, L2 - 2' in the medium frequency region, L1 and L1' in the low frequency region. In general, all filter sections take part in the work together.

The sketch of the filter is shown in Fig.4. Structurally, the filter is assembled in three shielded sections, which are placed in a metal case 190x190x70 mm. The inductors located in adjacent sections are connected through feed-through capacitors installed on vertical partitions. The chokes are fastened with the help of plexiglass racks 10 mm thick, in which the corresponding holes are drilled or bored.

Universal mains filter and its design. Filter Sketch
Filter Sketch

MPH connectors are used for connection. Shielded network wires from the transceiver and power amplifier are connected to it, and, having a distributed capacitance, further reduces high-frequency interference. The shielding braids of the wires are connected to the "ground" terminal, and the filter (case) itself is grounded with a short thick wire (braid of the RK-3 coaxial cable).

The filter is equipped with a conventional mains socket or sockets for connecting household equipment, such as a computer and blocks of its components.

The quality of the filter can be briefly described as follows. The Volna-K radio receiver with a connected computer was able to receive amateur radio stations on an indoor antenna, and only individual “beeps” of the computer were heard with levels of no more than 3-5 points.

Literature

1. Yu. Roginsky "Shielding in radio devices" 1970
2. Magazine "Radio" No. 10 1983

Author: A. Kuzmenko, RV4LK; Publication: N. Bolshakov, rf.atnn.ru

See other articles Section Protection of equipment from emergency operation of the network.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive

crystalline cellulose 02.07.2015

Everyone talks about cellulose fibers, pulp, but what is crystalline cellulose? The fiber consists of nanofibrils, nanofibrils - of polymer filaments, and in some areas long cellulose molecules are firmly connected by hydrogen bonds and highly ordered, while in others they have an amorphous structure.

Cellulose, purified from lignin and hemicellulose, is soft and fibrous. But if it is treated, for example, with a strong acid or an enzyme that destroys the disordered sections of the polymer, then miniature needles of nanometer diameter will remain, consisting of tightly packed fragments of glucose chains. These needles - crystalline nanocellulose (CNC) - are stronger than Kevlar and carbon fiber, and cost ten times less. Their output is about 30% of the pulp mass, they hope to bring the price in mass production to several dollars per kilogram. In addition, cellulose nanocrystals are transparent, and nanocrystalline cellulose films have interesting optical properties.

Cellulose fibers, or nanofibrils, of nanometer diameter and a few micrometers long, are also useful materials; they can be used to make nanocomposites, films for various filters, and solutions of cellulose nanofibers have unusual physical properties. Unlike many other nanoparticles, nanocellulose is completely biocompatible and does not inspire fear in the most ardent environmentalists. These materials have an important disadvantage - high hygroscopicity: even small particles of wood tend to bind water. But here the cards are already in the hands of chemists and technologists.

Hydrophobic, plastic and transparent nanocellulose films have recently been obtained by a group of Japanese researchers who have been working for many years with cellulose nanofibers oxidized with NaClO in the presence of (2,2,6,6-tetramethylpiperidin-1-yl)-oxyl (TEMPO or TO for short) and bromide. sodium. During oxidation, free surface -CH2OH groups are converted into carboxyl -COO-; the researchers called such nanofibers TOCN. In this work, the Japanese obtained films by drying an aqueous TOCN dispersion with quaternary alkylamines, molecules in which four alkyl chains are attached to one positively charged nitrogen atom. Alkylamines became counterions for carboxylate surface groups and imparted plasticity to the film - alkyl chains cover its surface and occupy the space between nanofibers.

In addition, the nanocellulose film became water-repellent: if tetra(n-butyl)-ammonium is used, then the contact angle with water reaches 100°. Such nanofibrils can be a filler in hydrophobic polymer matrices.

Other interesting news:

▪ Neanderthals are not only in Africa

▪ Samurai brushing their teeth

▪ Silicon clock, not electronic

▪ Need a bottle scanner

▪ Children's shoes with a GPS tracker

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Voltage converters, rectifiers, inverters. Article selection

▪ article Not one iota. Popular expression

▪ article What is sashimi? Detailed answer

▪ article Manufacture of printed circuit boards. HAM Tips