Engine dks 1 connection diagram. Basic technical data of DC electric motors. in the tape drive mechanism

Electric motors that have an absolutely rigid or rigid mechanical characteristic are used as the driving motor. Synchronous electric motors have absolutely rigid characteristics. Since the starting torque of the latter is zero, synchronous electric motors with asynchronous start are used in tape recorders. Synchronous electric motors have large dimensions and weight and, compared to asynchronous ones, have lower efficiency. Therefore, they are used mainly in professional tape recorders. The exception is the SD-6 synchronous reluctance motor, developed for the Yauza-212 tape recorder. As the leading electric motor in household tape recorders, asynchronous capacitor electric motors are used, which have rigid characteristics that make it possible, with the correct development of the tape drive mechanism, to obtain a deviation of the average tape speed from the nominal value that does not exceed the established standards. They have high efficiency and power factor, high starting torque, and the ability to reverse.

The rewinding motor must have a soft mechanical characteristic, since its speed must vary depending on the amount of tape on the reel. Only under this condition can the necessary tension of the tape be ensured and its tight winding on the reel. In addition, it must have a sufficiently large starting torque necessary for the normal operation of the tape transport mechanism at any ratio of tape to reels.

Table 2-2

Basic technical data of DC motors

The designs of modern tape recorders use small electric motors in the axial direction. One of them is the KD-6-4, which replaced the KD-3.5 electric motor. It is widely used in tape recorders of the second and third classes developed in recent years (“Mayak-202”, “Jupiter-202 stereo”, “Astra-205”, “Saturn-301”, etc.) and is unified for network reel-to-reel tape recorders being developed again.

In the tape drive mechanisms of portable tape recorders operating from autonomous power sources, DC commutator motors are used. The main requirements for them are the following: possibly lower current consumption from power supplies at rated load, possibly lower voltage of power supplies, stability of rotation speed and possibly smaller dimensions and weight.

To maintain a constant speed of rotation of the electric motor when the voltage of the power sources changes, centrifugal regulators are used. The principle of operation of the regulator, which is mounted directly on the electric motor shaft, is that it carries out electrical switching when the motor armature reaches the maximum and minimum permissible speed. These switchings, through a special control circuit, stepwise change the voltage at the armature of the electric motor, maintaining its speed within certain limits. In table Table 2-1 shows the main types and characteristics of alternating motors, and table. 2-2 - direct current, used in domestic household tape recorders.

2-5 Controlling the tape recorder

and automation units

in the tape drive mechanism

The following operating modes are typical for tape recorders: “Stop”, “Short-term stop”, “Record”, “Playback” and “Rewind”. Depending on the required mode, individual nodes of the tape drive mechanism are turned on and the amplifier is switched. In the “Stop” mode, electrical power is supplied only to the amplifier, and the electric motor is turned off; in the “Short-term stop” mode, power is supplied to the amplifier and electric motor, but the tape transport mechanism does not work; in the “Record” mode, the amplifier is switched to the recording mode, the erasure and bias generator is turned on, and the tape transport mechanism pulls the tape evenly along the working surfaces of the magnetic heads; in the “Playback” mode, the amplifier is switched to the playback mode and the tape-pulling mechanism evenly pulls the tape; In the “Rewind” mode, the pressure roller is retracted from the drive shaft, and the tape is removed from the magnetic heads and the tape is wound at high speed onto the right or left reel. High-end tape recorders also have an “Auto-Stop” mode. In this mode, the movement of the tape stops when the roll on the reel ends or it breaks.

Rice. 2-7. Hitchhiking design

The selection of a specific operating mode is carried out by a switch for the type of work, with the help of which the necessary electrical and mechanical switchings are made. For switching, keyboard, push-button, biscuit and cam switches are used. With their help, electric motors, electromagnets are turned on, and with the help of levers and rods - the necessary influence of the nodes of the tape drive mechanism. In some tape recorders, the transition to different operating modes is made by one double switch. In this case, a cam switch is installed in the upper part of the axis, which controls the operation of the tape drive mechanism. It is connected to the units and the braking device by rods and control levers. A biscuit switch is mounted on the lower part of the axis, with the help of which switches are made in the amplifier.

To avoid errors when operating the tape recorder, its design must include mechanical or electrical locking. This eliminates the possibility of rewinding the tape if the tape recorder is turned on for recording or playback, and vice versa, if the tape recorder is turned on for fast rewinding of the tape, the possibility of recording or playback is eliminated. If a push-button or key switch is used with fixation of all operating modes of the mechanisms, then the transition from one mode to another occurs after pressing the “Stop” button or key. Cassette tape recorders use push-button and lever switches with partial locking. Such switches are fixed only in recording and playback modes. The tape rewind mode is performed by holding the lever handle or button pressed. The operating mode is changed by releasing the lever handle or button, and the movement of the belt stops.

Adaptations and devices that increase the operational convenience of using a tape recorder include systems such as hitchhiking and tape quantity counters. In Fig. 2-7 shows one of the hitchhiking options used in tape recorders of the Astra models. Violation of the movement of the magnetic tape 1 fixed with a spring lever 2, which is under the action of a spring 3 tends to turn clockwise, but is held in place by the tension of the tape. The executive mechanism is contact groups 4, included in the power supply circuit of the electric motor. If the tape breaks or ends, the lever 2 turns clockwise, opens the contact group 4 and thereby turns off the electric motor.

Tape counters are used to quickly find the desired recording on a magnetic tape. Any revolution counter that works in both directions depending on the direction of tape movement and can be reset by setting the numbers to the zero position can be used as a magnetic tape counter or an indicator of the recording location. The meter is connected by a rubber belt to the receiving or supply unit.

Rice. 2-8. Digital mechanical counter

In Fig. 2-8 shows the counter used in the Vesna-201 stereo tape recorder. A worm 7 and a pulley 5 with a groove for a rubber belt, which transmits rotation to the counter from the left spool, are mounted on a vertical axis. Rotation is transmitted to the horizontal axis through a worm and worm gear 6. The horizontal axis with its gear transmits rotation to the first drum 4. When is the first drum turns one turn (by 10 divisions), then he turns the second drum 3, showing tens of revolutions, per 1/10 of a revolution. In a similar way, rotation from the second reel is transferred to the third reel 2, which shows hundreds of revolutions. The counter readings are proportional to the revolutions of the subcoil. The meter is equipped with a reset handle 1, with which all drums are set to the zero position.

Some tape recorders use simpler counters, which are a metal plate with numbers and divisions printed on it, indicating the playing time or footage of the tape. Such a ruler is mounted on the front panel of the tape drive mechanism, directly under the tape reel.

2-6. Magnetic tapes

In tape recorders, magnetic tape is used as a sound carrier. It consists of a base and a working layer applied to it on one side. The base material is cellulose diacetyl, cellulose triacetate or polyethylene terephthalate (lavsan). Ferromagnetic powders are the most widely used material for the working layer.

In household reel-to-reel tape recorders, a tape width of 6.25 is used, and in cassette tape recorders - 3.81 mm. The tapes have a total thickness of 18, 27, 37 or 55 microns. The tape is marked on the basis of GOST 17204 - 71. The designation of a specific type of magnetic tape consists of five main elements. The first element is a letter index indicating the main purpose of the magnetic tape. Depending on the purpose of magnetic tapes, the following letter indices are installed: A - sound recording; T - video recording; B - computer technology; And - accurate magnetic recording. The second element is a digital index (from 0 to 9), indicating the base material: 2 - cellulose diacetyl; 3 - triacetylcellulose; 4 - polyethylene terephthalate (lavsan). The third element is a digital index (from 0 to 9), indicating the total nominal thickness of the magnetic tape: 2 - from 15 to 20; 3 - from 20 to 30; 4 - from 30 to 40; 6 - from 50 to 60 microns. The fourth element is a digital index (from 01 to 99), indicating technological development. The fifth element is the numerical value of the nominal width of the magnetic tape, expressed in mm. After the fifth element, additional letter indices are indicated: P - for perforated tapes; R - for tapes intended for radio broadcasting; B - for tapes intended for household magnetic recording equipment.

Example designations. The common magnetic tape A4402-6 (formerly type 10) is deciphered as follows: tape for sound recording (A), with a lavsan base (4), thickness 37 microns (4), second technological development (02), width 6.25 mm ( 6).

Magnetic recording enthusiasts often use tapes made in the GDR. In the GDR, the standardized symbols for magnetic tapes, like in our country, consist of five elements. The first is a letter designating the base material (for example, WITH - cellulose acetate); the second element is a letter indicating the type of ferromagnetic powder (for example, powder type R or S); the third is a two-digit number indicating the total thickness in microns; the fourth element is a letter indicating the design features of the tape, for example V- non-perforated tape. The fifth element is a number indicating the width of the tape in rounded mm. Example of designation: recording tape CR50V6 stands for: magnetic tape with cellulose acetate base, with type powder R, 50 microns thick, non-perforated 6.25 mm wide.

Rice. 2-9. Arrangement of recording tracks on a 6.25 mm wide tape:A - monophonic two-track phonogram; b - stereophonic two-track phonogram:V - - monophonic and stereophonic four-track phonogram

In accordance with the old designations, tape types 2, 6, 9 and 10 are used in household tape recorders. Tapes of types 2, 9 are not currently available. Type b tape has a thickness of 55 microns, type 10 - 37 microns. The basis of type B tape is diacetylcellulose or triacetylcellulose, the basis of type 10 tape is lavsan (the tape is more flexible, fits more tightly to the magnetic heads, and has higher mechanical strength). The working layer of the tapes is ferromagnetic iron oxide powder; its particles are needle-shaped and significantly smaller in size, which dramatically increases the electrical properties of the tapes (higher sensitivity, lower nonlinear distortions and intrinsic noise).

The most common types for reel-to-reel tape recorders are A4402-6B, A4407-6B, A4409-6B, and for cassette tape recorders - A4203-3 and A4204-3. It should be remembered that each tape recorder is designed to work with a certain type of tape, which is indicated in the factory instructions attached to it. So, for example, a tape with a lavsan base should not be used on tape recorders of older models that have large dynamic loads (tape jerks when starting and stopping and high tension).

In order to save magnetic tape in household tape recorders, recording is carried out along two tracks in mutually opposite directions. The position of the beginning and end of both tracks is standardized and corresponds to Fig. 2-9a. The outer edge of the recording tracks should line up with the edge of the tape. Between the recording tracks there must be a gap of at least 0.75 mm wide, located symmetrically relative to the center line of the tape. The transition from the first track to the second can be accomplished by turning over and moving the reels (without rewinding the tape). In more advanced tape recorders (with two sets of heads, shifted relative to each other in height), the transition from one track to another is carried out by simply pressing the key of the electrical switching head and the direction of rotation of the electric motor.

Information book L 1979 Gruev, I.D. ... Lepaev, D.A. Repair household electrical appliances, electric players and..., V.D. Inspection and testing radio equipment M 1970 Manovtsev, A.P. ...

Turn on the dosimeter, for which set the dosimeter switch to the position NUTRITION(Fig.6c). Make sure that the battery voltage is not lower than the minimum permissible value by pressing the button COUNTER. NUTRITION-DOSE(Fig. 7a). In this case, the indicator light should light up (Fig. 7b). Set the type of work switch to position SEARCH.

In the presence of natural background radiation, the dosimeter should deliver up to 5 sound and light pulses per minute. Depending on the intensity of ionizing radiation, the repetition rate of sound and light signals changes. When monitoring hard beta radiation, the dosimeter should be positioned towards the intended radiation source on the side with the slots.

Mode SEARCH can be used to localize a source of ionizing radiation.

Measuring exposure dose rate (EDR)

DER measurement can be carried out at any position of the switch for the type of work. The exposure dose rate P, A/kg (mR/hour), should be determined in accordance with the formula:

P = p∙K,

Where P

K= 1 mR/h.

The measurement and output of the DER value is carried out in two cycles:

a measurement cycle that lasts 3-5 seconds, when the radiation situation can be judged by the rate of change of values ​​on the digital display;

cycle of displaying the DER value on a digital display, the duration of which is also 3-5 seconds.

When the DER exceeds 999.9 mR/hour in the THRESHOLD, the digital display overflow alarm is activated in the form of repeating sound and light signals lasting (4 ± 2) seconds. To stop the overflow alarm, the dosimeter should be removed from the irradiation zone with an DER of more than 999.9 mR/hour, after which the dosimeter will function normally.

Exposure dose (ED) measurement

The DE value is accumulated and measured from the moment the dosimeter is turned on at any position of the switch for the type of work. Exposure dose D, C/kg (mR), is determined in accordance with the formula:

D = n∙K,

Where P- readings of the dosimeter digital display,

K= 1 mR.

To display the value of the accumulated DE you need to click on the button COUNTER. FOOD- DOSE. In this case, the dot after the third digit on the digital display goes out. When the switch for the type of work is moved to the position THRESHOLD the dosimeter is switched to the accumulated DE signaling mode in 1 mR increments.

When an exposure dose of 4096 mR accumulates, an alarm is activated in the form of continuous sound and light signals. To stop this alarm and return the dosimeter to its initial state, the dosimeter should be turned off and on again.

Gamma background measurement. The sensitivity of the SBM-20 gas-discharge counter, usually used in household dosimeters, makes it possible to measure dose rates starting from 5-10 µR/hour. If you turn on the dosimeter in a clean area, then after completing the measurement cycle, it will show the value of the natural background radiation. In the Odessa region, the gamma background value is usually 10-20 μR/hour. and can change during the day, year, eleven-year cycle of solar activity, as well as from cataclysms occurring in the universe and in the bowels of the Earth. To eliminate the random nature of the readings from measurement to measurement, it is necessary to use the following technique: make 5-10 measurements of the gamma background, sum up all the results and divide the resulting amount by the number of measurements, i.e. find the arithmetic mean. The greater the number of measurements, the higher the accuracy of the result.

The level of contamination of the area is assessed at a distance of 1 meter from the surface of the earth, away from stone buildings (no closer than 30 m), since building materials, especially granite, may have an increased level of radiation.

To assess contamination of food and feed by external gamma radiation, the method “ direct measurement» from a distance of 1-5 cm and examining objects weighing at least 1 kg and 1 liter.

For the above assessments of radioactive contamination, 5-10 measurements are made and the arithmetic average is determined. Then the value of the natural gamma background, measured earlier using the same method, is subtracted from the resulting value. The resulting difference will represent the level of radioactive contamination of the object under study.

Generator of traveling (rotating) magnetic field

Rice. 1. Rotating magnetic field generator: side view, front view (model version).

The rotating magnetic field generator is a permanent ring six-pole magnet made of barium ferrite, mounted on the axis of the electric motor.

Electric motor DKS-1-U4

The direction of magnetization is axial. An electric motor of the DKS-1-U4 type (rotation speed 2750 rpm) is installed on a U-shaped chassis made of plexiglass (polymethyl methacrylate). The front panel of the chassis serves to protect against mechanical contact with the rotating magnet.

An analog pulse teslameter was used to monitor magnetic induction. The circuit for measuring magnetic induction is shown in Fig. 2.

Rice. 2. Scheme for measuring magnetic induction.

The frequency of change of the magnetic field is about 140 Hz. The amplitude of magnetic induction at a distance of 10 mm from the front panel is 18 mT, near the front panel 70 mT.

To measure the intensity of the induced vortex rotating electric field, measuring coils were used, the appearance of which is shown in Fig. 3.

Rice. 3. Measuring coils of various sizes.

The measuring coil is a cylindrical frame with a narrow slot. 1 meter of wire is wound into the slot. The radius of the frame (taking into account the dimensions of the slot and winding) is equal to the radius of the contour on which it is necessary to measure the electrical intensity. In this case, the electromotive force (EMF) of the coil, which arises due to a change in the magnetic flux passing through its cross section, is numerically equal to the electrical intensity of the induced electric field (more precisely, the integral of the electrical intensity along the circuit, i.e., the average value of the intensity). EMF measurements can be made using an oscilloscope or an alternating voltage voltmeter. The electrical voltage measurement circuit is shown in Fig. 4.

Rice. 4. Circuit for measuring the intensity of the induced electric field.

The amplitude of the electrical intensity at a distance of 10 mm from the front panel is 50 mV/m, near the front panel - about 200 mV/m.

The magnetization of the permanent magnet was carried out using a pulse magnetization installation as part of a 6-pole axial magnetizing device and a powerful current pulse generator.

By increasing the number of magnet poles, the speed of its rotation, and also using magnets with higher energy (samarium-cobalt, neodymium-iron-boron), it is possible to achieve a significant (by an order of magnitude or more) increase in the intensity of the induced electric field. It is also possible in some cases to eliminate the external drive by using the multi-pole magnet itself as the rotor of a brushless motor.

Possible applications:

1. Devices for demagnetization of steel products, including massive ones, with a large surface.
2. Design of magnetic couplings.
3. Testing of electromagnetic components of electric generators.
4. Induction heating of conductive objects.
5. Physiotherapeutic effects on the human body.

1. Analog pulse teslameter with Hall sensor type PHE for measuring magnetic field induction
2. Generator of powerful current pulses, unipolar
3. Generator of powerful current pulses (capacitive energy storage)
4. Permanent magnets: Handbook / Altman A. B., Gerberg A. N., Gladyshev P. A. et al.; Ed. Yu. M. Pyatina. — 2nd ed., revised. and additional - M.: Energy, 1980. - 488 p., ill.
5. Installations for pulsed magnetization and demagnetization of permanent magnets
6. Device for 6-pole axial pulse magnetization of ferrite rings with a diameter of up to 70 mm

Glossary of terms:

• Engine (motor)— converter of source energy into mechanical energy of movement.
• Demagnetizer— device (installation) for demagnetization.
• Magnetic induction- a vector numerically equal to the limit of the ratio of the force acting from the magnetic field on a conductor element with electric current to the product of the current and the length of the conductor element, if the length of this element tends to zero, and the element is so located in the field that this limit has the greatest value , and directed perpendicular to the direction of the conductor element and to the direction of the force acting on this element from the magnetic field, and from its end the rotation along the shortest distance from the direction of the force to the direction of the current in the conductor element should be visible as occurring counterclockwise.
• Multi-pole magnet- a permanent magnet having more than one pair of magnetic poles.
• Electric field strength- the force acting from the electric field on a unit positive point electric charge.
• Neodymium-iron-boron(English Ne-Fe-B) - a hard magnetic material based on a compound of iron, neodymium and boron with the composition Nd 2 Fe 14 B, Nd 3 Fe 16 B, Nd 4 Fe 28 B 3.
• Demagnetization- a procedure that makes it possible to reduce the residual magnetization of a sample to such values ​​that it can be neglected.
• Samarium-cobalt(eng. Sm-Co) is a hard magnetic material based on the intermetallic compound of samarium and cobalt with the composition SmCo 5. In the brand designation (for example, KS37), the letters indicate the composition (K - cobalt, C - samarium), and the number (37) - the percentage of samarium.
• Teslameter (Gaussmeter)- a device for measuring magnetic induction.
• Barium ferrite— hard magnetic material based on iron and barium oxides with the composition BaO·6Fe 2 O 3 . In the brand designation (for example, 19BA190), the first number (19) indicates the energy product (in kA T/m), the first letter is the ferrite composition (B - barium), the second letter is the properties (A - anisotropic, I - isotropic), the second number (190) is the coercive force of magnetization (in kA/m).
• Electromotive force (EMF) - the work of forces creating an electric current to move a single positive electric charge along the section of the electrical circuit under consideration.

27.04.2004
09.09.2005
22.06.2010

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