When operating any machine can not do without an electric motor. Many buy an electric motor with hands without any documentation. In such a situation, there is a problem with the determination of electric motor revolutions. To solve this problem, you can use several ways.
The easiest way to determine the revolutions of the electric motor is the use of a tachometer. But the presence of this instrument in a person who does not specialize in electric motors is rare. Therefore, there are ways to determine the turns on the eyes. To determine the rotation of the electric motor, open one of the electric motor covers and find the winding coil. Coils in the electric motor can be several. Choose that coil, which is in the visibility zone and to which it is easier to access. Try not to disturb the integrity of the electric motor, do not deliver the details. Do not try to disconnect the parts with each other.
All major characteristics of the electric motor must be indicated on the metal tag, located on its housing. But in practice the tag or is missing, or the information erased during operation.
Whatever the machine you collect, probably more than once, experiencing the machine, thought: you need a tachometer. But he was all the time on your hand, of course, if you have such simplest components as a small motor and a voltmeter. Get acquainted with the proposed device, and make sure that literally in five minutes at your disposal will be a compact and accurate homemade tachometer.
So, proceed to the assembly. As already mentioned, the home-made tachometer consists of two main parts: a motor who works from direct current and voltmeter. If you do not have such a motor, it can be easily bought on the flea market at the price of loaf of bread or cheaper, at the price of two loaves you can buy a new one in the electronic component store. If there is no voltmeter, it will cost more a motor, but on the same flea market its price will be quite acceptable. The voltmeter connects to the contacts of the motor, and everything, the tachometer is ready. Now you need to experience the finished tachometer in the work. When rotating the shaft of the motor generator, voltage will be created proportional to the rotational speed. Consequently, the speed of the rotation will be proportional to the voltmeter.
You can graduate such a tachometer in different ways. For example, build a reference graph of the dependence of the voltage from the frequency of rotation of the anchor or make a new Voltmeter scale, on which the revolutions number is recorded instead.
Since the schedule reflects a linear dependence, it is enough to mention two or three points and spend directly through them. Receipt of control points is the most problematic stage of preparation of a self-made tachometer to work. If there is access to branded machines, checkpoints are easy to get, clinging the rubber tube, bowed to the motor shaft, in the cartridge of the drilling or lathe and the machine and including the machine on various transmissions, fix the testimony of the voltmeter (the spindle speed on each transmission is indicated in the passport of the machine). Otherwise, it will have to use either a drill for calibration, or the engine at operating mode for which the rotational speed is known. And even if the voltage on the motors' contacts were measured only for one rotation frequency, the second point is the intersection of axes (x) and (y) (that is, the numbers of revolutions and voltage), however, the accuracy of measurements on the dependence of two-point fiction will be low.
To measure the speed of rotation, the engine of the test engine is connected to a slightly segment of the rubber tube or using various adapters. If the voltmeter rolls when measuring high speeds of rotation, a switch with additional resistors is entered into the circuit. Required the schedule for each position of the switch.
The device features can be significantly expanded. If we make a roller friction adapter with a diameter of 31.8 mm, the tachometer will measure and linear speed expressed in meters per minute. For this, the number of revolutions per minute, defined on schedule, divided by 10.
The accuracy of measurement depends almost only on the thoroughness of building the schedule and the price of the voltmeter division. A similar simplest and very cheap home-made tachometer can find a wide application throughout where you need to quickly determine the frequency or speed of rotation of the shafts, pulleys and other parts.
Digital tachometer from smartphone do it yourself
If you are an iPhone owner, I also advise you to establish the best turning measurement application shown below. And do not stop on the strobe from the flash of the phone, it will only help you understand how the stroboscope tachometer works. Making it yourself very simple electronic circuitsYou will get stroboscopic and laser tachometers not inferior (and in some situations superior) branded tachometers. Schemes, photos and description of tachometers will find in this application. Video with demonstration of this application, see below.
Homemade Stroboscopic Tachometer from iPhone with your own hands
Homemade laser (optical) tachometer from iPhone with your own hands
Comparative measurements of engine speed with laser and stroboscopic tachometers
When using the content of this site, you need to put active links to this site visible by users and search robots.
Repair daily engage in thousands of people around the world. When it is fulfilled, everyone begins to think about the subtleties that accompany the repair: in what color scheme to choose wallpaper, how to choose the curtains in the color of the wallpaper, put the furniture to get the furniture single style premises. But the most important thing is rarely wondering, and this main thing is to replace wiring in the apartment. After all, if something happens to the old wiring, then the apartment will lose all its attractiveness and will become absolutely not suitable for life.
How to replace the wiring in the apartment knows any electrician, but this is under power to any ordinary citizen, but when performing this type of work, it should choose high-quality materials to get a secure electrical network indoor.
The first action that needs to be performed plant future wiring. At this stage, it is necessary to determine which locations will be laid wires. Also at this stage you can make any adjustments to the existing network, which will allow the lamps as comfortable as possible in accordance with the needs of the owners.
12.12.2019
Nercho-separable instruments knitted sub-sectors and their maintenance
To determine the extensibility of hosiery products, the device is used, the diagram of which is shown in Fig. one.
The design of the device is based on the principle with automatic rocker equilibration by the elastic forces of the test products acting at a constant speed.
Weight rocker is an equal deploying round steel rod 6 having an axis of rotation 7. It is attached to its right end using a paw bayonet lock or a sliding track shape 9 for which the product dresses. On the left shoulder, the cargo suspension 4 is highlighted, and its end ends with an arrow 5 showing the equilibrium state of the rocker. Before the testing of the product, the rocker is leading to the equilibrium of the movable gay 8.
Fig. 1. Diagram of the device for measuring the extensibility of humene-socks: 1-receiver, 2 - left ruler, 3 - engine, 4 - cargo suspension; 5, 10 - arrows, 6 - rod, 7 - axis of rotation, 8 - weight, 9 - Form of a trace, 11-tensile lever,
12-carriage, 13 - chassis screw, 14 - right line; 15, 16 - Screw gears, 17 - worm gearbox, 18 - connecting coupling, 19 - electric motor
To move the carriage 12 with the tensile lever 11 serves the chassis screw 13, at the bottom end of which the screw gear 15 is fixed; Through it, the rotational movement is transmitted to running screw. The change in the direction of rotation of the screw depends on the change in rotation 19, which, with the help of the coupling 18, is associated with worm gear 17. On the shaft of the gearbox is planted by a screw gear 16, directly reporting the movement of the gear 15.
11.12.2019
In pneumatic actuating mechanisms, the permutational effort is created due to the impact of compressed air on the membrane, or the piston. Accordingly, the mechanisms of membrane, piston and bellows are distinguished. They are designed to install and move the gate of the regulating organ in accordance with the pneumatic command signal. The full working stroke of the output element of the mechanisms is carried out when the command signal changes from 0.02 MPa (0.2 kg / cm 2) to 0.1 MPa (1 kg / cm 2). The limit pressure of compressed air in the working cavity is 0.25 MPa (2.5 kg / cm 2).
At the membrane rigid mechanisms, the rod makes a reciprocating movement. Depending on the direction of the movement of the output element, they are divided into direct operational mechanisms (with the increase in the pressure of the membrane) and reverse action.
Fig. 1. Membrane design executive mechanism Direct Action: 1, 3 - Covers, 2-Membrane, 4 - Land Disk, 5 - Bracket, 6 - Spring, 7 - Stow, 8 - Support Ring, 9 - Adjusting Nut, 10 - Connecting Nut
The main structural elements of the membrane actuator are a membrane pneumatic chamber with a bracket and a movable part.
The membrane pneumatic camera of a direct action mechanism (Fig. 1) consists of covers 3 and 1 and membrane 2. Cover 3 and membrane 2 form a hermetic working cavity, the cover 1 is attached to the bracket 5. To the moving part include the reference disk 4 to which the membrane is attached 2, rod 7 with connecting nut 10 and spring 6. The spring is resting in one end to the reference disk 4, and the other through the support ring 8 into the adjusting nut 9, which serves to change the initial tension of the spring and the direction of the rod movement.
08.12.2019
To date, there are several types of lamps for. Each of them has its pros and cons. Consider the types of lamps that are most commonly used for lighting in a residential building or apartment.
First type of lamps - incandescent lamp. This is the cheapest view of the lamps. The advantages of such lamps include its cost, ease of device. Light from such lamps is the best for the eyes. By cons of such lamps include low life and a large amount of electricity consumed.
Next type of lamps - energy-saving lamps. Such lamps can be found absolutely for any types of bases. Present an elongated tube in which special gas is located. It is gas that creates a visible glow. In modern energy-saving lamps, the tube can have the most diverse shape. Pluses of such lamps: low power consumption compared to incandescent lamps, day glow, big choice Codles. By cons of such lamps include the complexity of the design and flicker. Flicker usually unnoticed, but the eyes will be tired of light.
28.11.2019
Cable assembly - The type of mounting node. The cable assembly is several local, ended on both sides in the electrical workshop and linked to the bundle. Installation of the cable route, is carried out by placing the cable assembly in the fixing device of the cable route (Fig. 1).
Ship cable route - electric line mounted on a vessel from cables (cable beams), cable route devices, sealing devices, etc. (Fig. 2).
On the vessel, the cable track is placed in hard-to-reach places (on sides, subwoulder and bulkheads); They have up to six turns in three planes (Fig. 3). On large courts, the greatest length of the cables reaches 300 m, and the maximum cross-sectional area of \u200b\u200bthe cable route is 780 cm 2. On separate ships with a total cable length over 400 km, cable corridors provide for the placement of the cable route.
Cable runs and cables passing on them are divided into local and trunk depending on the absence (presence) of sealing devices.
The main cable tracks are divided into tracks with elder and passing boxes, depending on the type of cable box. It makes sense to choose tools for technological equipment and technology of mounting the cable route.
21.11.2019
In the field of development and production of instruments of kipia, the American company Fluke Corporation occupies one of the leading positions in the world. It was founded in 1948 and from that time constantly develops, improves technology in the field of diagnosis, testing, analysis.
Innovation from the American Developer
Professional measuring equipment from a multinational corporation is used when servicing heating, air conditioning and ventilation systems, refrigeration installations, air quality checks, electrical parameter calibrations. Fluke's corporate store offers to purchase certified equipment from the American developer. Full the lineup Includes:- thermal imagers, insulation resistance testers;
- digital multimeters;
- electric energy quality analyzers;
- rangefinders, vibrors, oscilloscopes;
- temperature calibrators, pressure and multifunctional devices;
- visual pyrometers and thermometers.
07.11.2019
Use a level gauge to determine the level of different types of liquids in open and closed storage facilities, vessels. With it, they measure the level of the substance or distance to it.
To measure the level of fluid, sensors are used, which differ in type: a radar level gauge, microwave (or waveguide), radiation, electric (or capacitive), mechanical, hydrostatic, acoustic.
Principles and features of working radar levels
Standard devices do not determine the level of chemically aggressive liquids. Only a radar level gauge is able to measure it, as it does not come into contact with fluid when working. In addition, radar levels are more accurate compared, for example, with ultrasound or with capacitive.At the speed of rotation asynchronous electric motor Usually understand the angular frequency of rotation of its rotor, which is shown on the nameplate (on the engine nameplate) in the form of the number of revolutions per minute. The three-phase engine can be used from a single-phase network, for this in parallel with one or two windings, depending on the network voltage, but the engine design will not change.
So, if the rotor under load performs 2760 revolutions per minute, it will be equal to 2760 * 2p / 60 radians per second, that is, 289 Rad / s, which is not convenient for perception, so they are simply written on the plate "2760 rpm". With regard to the asynchronous electric motor, these are turns taking into account the slide s.
Synchronous speed this engine (excluding slipping) will be equal to 3000 revolutions per minute, because when powering the stator windings with a network current with a frequency of 50 Hz, every second magnetic flux will perform in 50 full cyclic changes, and 50 * 60 \u003d 3000, so it turns out 3000 revolutions per minute - synchronous speed of an asynchronous electric motor.
As part of this article, we will talk about how to determine the synchronous speed of rotation of an unknown asynchronous three-phase motor, simply looking at its stator. By appearance The stator, by the location of the windings, by the number of grooves, can easily determine the synchronous turnover of the electric motor if you do not have a tachometer at hand. So, let's start in order and analyze this issue with examples.
3000 revolutions per minute
About asynchronous electric motors (see -) It is customary to say that one or another engine has one, two, three or four pairs of poles. The minimum is one pair of poles, that is, at least two poles. Take a look at the drawing. Here you see that two successively connected coils for each phase are laid into the stator - in each pair of coils one is located opposite the other. These coils and form a pair of poles on the stator.
One of the phases is shown for clarity in red, the second is green, the third is black. The windings of all three phases are arranged equally. Since three of these windings are powered in turns (three-phase current), then for 1 oscillation of 50 in each of the phases - the magnetic stream of the stator will turn on the total 360 degrees, that is, it will make one turn for 1/50 seconds, it means 50 turns will be give me a sec. It comes out 3000 revolutions per minute.
Thus it becomes clear that to determine the synchronous revolutions of the asynchronous electric motor, it suffices to determine the number of pairs of its poles, which is easy to do, removing the lid and look at the stator.
The total number of stator grooves are divided into the number of grooves per section of the winding of one of the phases. If it turns out 2, then you are the engine with two poles with one pair of poles. Consequently, the synchronous frequency is 3000 revolutions per minute or approximately 2910, taking into account sliding. In the simplest case, 12 grooves, 6 grooves per coil, and such coils 6 - two each of the three phases.
Please note the number of coils in one group for one pair of poles may not be required 1, but also 2 and 3, however, for example, we looked at the option with single groups per pair of coils (we will not focus on this article at the winding methods).
1500 revolutions per minute
To obtain a synchronous speed of 1500 revolutions per minute, the number of stator poles are doubled that for 1 oscillation of 50 magnetic flow would make only half turn - 180 degrees.
For this, 4 winding sections are made for each phase. Thus, if one coil ranks a quarter of all grooves, then you are an engine with two pairs of poles formed by four coils on the phase.
For example, 6 grooves from 24 occupies one coil or 12 out of 48, which means that you are an engine with a synchronous frequency of 1500 revolutions per minute, or taking into account the slip of approximately 1350 revolutions per minute. In the photo above, each section of the winding is made in the form of a double coil group.
1000 revolutions per minute
As you already understood, to obtain a synchronous frequency of 1000 revolutions per minute, each phase forms three pairs of poles so that for one oscillation of 50 (hertz), the magnetic flux would turn on only 120 degrees, and would turn the rotor accordingly.
Thus, at least 18 coils are installed on the stator, each coil ranks the sixth of all the grooves (six coils on the phase - three pairs). For example, if the grooves 24, then one coil will take 4 of them. It turns out the frequency, taking into account the slip of about 935 revolutions per minute.
750 revolutions per minute
To obtain a synchronous speed of 750 revolutions per minute, it is necessary that three phases form four pairs of moving poles on the stator, it is 8 coils on the phase - one opposite the other - 8 poles. If for example, 48 points fall on the coil for every 6 grooves - in front of you an asynchronous engine with synchronous turns of 750 (or about 730, taking into account the slip).
500 revolutions per minute
Finally, to get asynchronous engine With a synchronous speed of 500 revolutions per minute, 6 pairs of poles are needed - 12 coils (poles) on the phase so that for each oscillation of the network, the magnetic flux would turn by 60 degrees. That is, if for example the stator has 36 grooves, while the coil accounts for 4 grooves - in front of you a three-phase engine for 500 revolutions per minute (480, taking into account the slip).
