Common industrial ones used to account for products and raw materials include commodity, automobile, carriage, trolley, etc. Technological ones are used for weighing products during production in technologically continuous and periodic processes. Laboratory tests are used to determine the moisture content of materials and semi-finished products, conduct physical and chemical analysis of raw materials and other purposes. There are technical, exemplary, analytical and microanalytical.

They can be divided into a number of types depending on the physical phenomena on which the principle of their operation is based. The most common devices are magnetoelectric, electromagnetic, electrodynamic, ferrodynamic and induction systems.

The diagram of the magnetoelectric system device is shown in Fig. 1.

The fixed part consists of a magnet 6 and a magnetic circuit 4 with pole pieces 11 and 15, between which a strictly centered steel cylinder 13 is installed. In the gap between the cylinder and the pole pieces, where the uniform radial direction is concentrated, a frame 12 made of thin insulated copper wire is placed.

The frame is mounted on two axes with cores 10 and 14, resting on thrust bearings 1 and 8. Counteracting springs 9 and 17 serve as current leads connecting the frame winding to the electrical circuit and input terminals of the device. On the axis 4 there is a pointer 3 with balance weights 16 and an opposing spring 17 connected to the corrector lever 2.

01.04.2019

1. The principle of active radar.
2. Pulse radar. Principle of operation.
3. Basic time relationships of pulse radar operation.
4.Types of radar orientation.
5. Formation of a sweep on the PPI radar.
6. The principle of operation of the induction lag.
7.Types of absolute lags. Hydroacoustic Doppler log.
8.Flight data recorder. Description of work.
9. Purpose and operating principle of AIS.
10.Transmitted and received AIS information.
11.Organization of radio communications in AIS.
12.Composition of shipboard AIS equipment.
13. Structural diagram of ship's AIS.
14. Operating principle of SNS GPS.
15.The essence of differential GPS mode.
16. Sources of errors in GNSS.
17. Block diagram of a GPS receiver.
18. Concept of ECDIS.
19.Classification of ENC.
20.Purpose and properties of the gyroscope.
21. The principle of operation of the gyrocompass.
22. The principle of operation of a magnetic compass.

Connecting cables— a technological process for obtaining an electrical connection between two sections of cable with the restoration of all protective and insulating sheaths of the cable and screen braids at the junction.

Before connecting the cables, the insulation resistance is measured. For unshielded cables, for ease of measurement, one terminal of the megohmmeter is connected in turn to each core, and the second - to the remaining cores connected to each other. The insulation resistance of each shielded core is measured when connecting the leads to the core and its screen. , obtained as a result of measurements, must be no less than the standardized value established for a given cable brand.

Having measured the insulation resistance, they move on to establishing either the numbering of the cores, or the directions of laying, which are indicated by arrows on temporarily attached tags (Fig. 1).

Having completed the preparatory work, you can begin cutting the cables. The geometry of the cutting of the cable ends is modified in order to ensure the convenience of restoring the insulation of the cores and sheath, and for multi-core cables, also to obtain acceptable dimensions of the cable connection.

METHODOLOGICAL GUIDE TO PRACTICAL WORK: “OPERATION OF SPP COOLING SYSTEMS”

BY DISCIPLINE: " OPERATION OF POWER INSTALLATIONS AND SAFE WATCH KEEPING IN THE ENGINE ROOM»

COOLING SYSTEM OPERATION

Purpose of the cooling system:

• heat removal from the main engine;
• heat removal from auxiliary equipment;
• heat supply to the OS and other equipment (GD before start-up, VDG maintenance in “hot” reserve, etc.);
• intake and filtration of sea water;
• Blowing out Kingston boxes in the summer to prevent them from becoming clogged with jellyfish, algae, and dirt, and in the winter to remove ice;
• ensuring the operation of ice chests, etc.

Structurally, the cooling system is divided into fresh water and intake water cooling systems. ADF cooling systems are performed autonomously.

Rice. 1. Diesel cooling system

1 - fuel cooler; 2 - turbocharger oil cooler; 3 - expansion tank of the main engine; 4 - main engine water cooler; 5 - main engine oil cooler; 6 - Kingston box; 7 - sea water filters; 8 - Kingston box; 9 - VDG receiving filters; 10 - VDG sea water pumps; 11 - fresh water pump; 12 - main and backup main water pumps; 13 - oil cooler VDG; 14 - water cooler VDG; 15 - VDG; 16 - expansion tank VDG; 17 - shaft line support bearing; 18 - main thrust bearing; 19 - main engine; 20 - charge air cooler; 21 - water for cooling compressors; 22 - filling and replenishing the fresh water system; 23 - connection of the internal combustion engine heating system; 1op - fresh water; 1oz - sea water.

23.03.2019

During operation, its winding gradually fails, taking on the influence of various negative factors. You can restore the engine's functionality by rewinding it. The procedure must be performed when signs of damage occur.

Causes and signs of winding wear

The motor winding is rewinded when such “symptoms” occur as extraneous noise and knocking, accompanied by a violation of the integrity and loss of elasticity of the insulation. This happens for several reasons. The main ones are:

• exposure to natural phenomena, including high humidity, temperature fluctuations;
• ingress of machine oil, dust and other contaminants;
• improper operation of the power unit;
• influence of vibration loads on the motor.

Temperature issues are a common cause of wear, stretching, and loss of integrity. When overheated, excessive overvoltage occurs, which makes the winding sensitive to external influences. The slightest shocks and vibrations lead to breakdowns.

Another common cause of failure of electric motor windings is the failure of bearings, which, due to overloads or temporary wear, can shatter into small pieces, which leads to burnout of the windings.

When operating any machine, you cannot do without an electric motor. Many people buy an electric motor secondhand without any documentation. In such a situation, a problem arises with determining the speed of the electric motor. To solve this problem, you can use several methods.

The easiest way to determine the speed of an electric motor is to use a tachometer. But the presence of this device in a person who does not specialize in electric motors is very rare. Therefore, there are ways to determine revolutions by eye. To determine the motor speed, open one of the motor covers and locate the winding coil. There can be several coils in an electric motor. Choose a reel that is within sight and easier to access. Try not to damage the integrity of the electric motor; do not remove parts. Do not try to disconnect the parts from each other.

Examine the coil carefully and try to approximately determine its size relative to the stator ring. The stator is the stationary part of the electric motor, the rotor is movable and rotates inside the stator. You don't need a ruler or precise calculations. The entire procedure is determined by eye.

The rotor rotation speed is 3000 rpm if the coil size covers half of the stator ring. The rotor speed is less than 1500 rpm if the size of the coil covers a third of the ring. The rotor speed is 1000 rpm if the size of the coil is one fourth of the ring.

There is another way to determine winding speed. The windings are located inside the stator. To do this, it is necessary to count the number of slots occupied by sections of one coil. The total number of core slots is the number of poles: 2 – 3000 rpm, 4 – 1500 rpm, 6 – 1000 rpm.

All main characteristics of the electric motor must be indicated on a metal tag located on its body. But in practice, the tag is either missing, or the information has been erased during use.

Each vehicle with an internal combustion engine is equipped with a device for measuring the crankshaft speed - a tachometer. Read about what a tachometer is and why it is needed, what tachometers are used on vehicles today, how they are designed and work.

What is a tachometer and why is it needed in a car?

Automotive - a device for measuring and indicating the engine crankshaft speed. The device constantly displays the current speed of the power unit, which allows you to solve several problems:

• Select the optimal gearbox and vehicle speed in various conditions. It is according to the tachometer readings that it is easiest to choose the right moment to switch from low to high gear and vice versa;
• Select the optimal engine operating mode. Internal combustion engines develop the greatest torque in a narrow range of crankshaft speeds, and it is the tachometer that is the easiest way to monitor the achievement of this mode;
• Timely identify faults that lead to uneven engine operation at idle and in all modes. Some malfunctions of the power supply system, ignition and other systems lead to the fact that the engine speed “floats”, which is easy to track on the tachometer.

Despite the widespread introduction of electronic control systems that select optimal engine operating modes under changing loads, tachometers do not lose their relevance. This device is important for the proper operation of vehicles, so today it is necessarily present on cars and trucks, tractors and special equipment.

Types and types of tachometers

Tachometers used in transport are divided into several types according to the principle of operation, the method of signal processing and indication, the method of connection and applicability.

According to the principle of operation and method of connection, tachometers are:

• Mechanical/electromechanical (centrifugal, magnetic) with direct drive;
• Electric with connection to the engine ignition system - electronic (pulse);
• Electric with connection to an electric generator - electric machine.

Connecting an electronic tachometer to a contactless ignition system

Connecting an electronic tachometer to a contact ignition system

According to the method of signal processing, tachometers are either analog or digital.

According to their applicability, tachometers are divided into several groups:

• For gasoline engines with contact and non-contact ignition systems - connection directly to the primary (low-voltage) circuit;
• For all types of engines with an electronic control unit - connection to the ECU, the unit itself uses signals from the ignition system or the crankshaft position sensor to control the tachometer;
• For diesel engines - connection to a generator.

As a rule, tachometers are manufactured for use on certain brands and models of cars, tractors and other equipment; some devices can be used on various vehicles equipped with the same engines, ignition systems, etc.

Tachometer device

It consists of several main components: a measuring unit or signal converter, an indication unit and auxiliary components.

The measuring unit of mechanical and electromechanical tachometers is most often magnetic, similar to a conventional speedometer (in essence, the speedometer is a tachometer that measures the speed of rotation of the secondary shaft of the gearbox or wheel). This speedometer is connected to the engine with a flexible shaft.

The measuring unit in electrical devices can be built using analog circuitry using transistors or using digital circuitry based on specialized microcircuits. This unit receives a signal from the sensor, ECU, generator or ignition system, processes it in accordance with the preliminary settings, and the converted signal is sent to the display unit.

The display block can be of several types:

• Pointer indicator (with pointer drive by milliammeter);
• Digital indicator based on liquid crystal or LED display;
• Indicators with a linear LED scale - the role of an arrow is played by a line of LEDs of different colors.

Cars usually use dial indicators, which are easier to read and allow you to immediately determine in which mode the engine is operating. Digital and LED indicators are most often installed during tuning; they are also used in simple tachometers for motorcycles, diesel generators, etc.

The tachometer scale is divided into several zones, marked in different colors:

• Low speed zone - in this speed range the engine is unstable, the zone may be marked in red;
• Optimal speed zone (?green zone?) - in this range the engine develops the greatest power and torque, usually the zone is marked in green;
• High speed zone - this speed range is conditionally dangerous for the engine; usually this zone is marked in yellow or a line above the red zone;
• High speed zone (?red zone?) - this speed range is dangerous, the engine is overloaded and operates with low efficiency, this zone is marked in red.

The speed scale can be graduated in units or in tens, indicating the multiplier - x100 or x1000, the unit of measurement of revolutions - r/min or min -1.

The entire structure is housed in a housing that can be mounted in the dashboard or installed separately. In this case, tachometers can be equipped with different configurations:

• Device without additional functions;
• Tachometer with various indicators;
• A tachometer combined in one housing with other instruments - speedometer, odometer, hour meter, etc.

Separately, we need to talk about the operating principle of the most common types of tachometers.

Operating principle of magnetic tachometers

The operation of a magnetic tachometer is based on the phenomenon of induction of eddy currents (Foucault currents) in a non-magnetic disk by a rotating constant field. In its normal state, an aluminum or copper disk does not have magnetic properties, but if you place it in a rotating magnetic field, eddy currents arise in it. These currents interact with the magnetic field, so the non-magnetic disk also begins to rotate after the magnet.

To operate the tachometer, an arrow is attached to the disk, on the shaft of which a return spring is attached. The magnet is connected to the crankshaft or one of the transmission shafts via a flexible shaft. The higher the engine speed, the faster the magnet rotates, and the higher the force deflecting the non-magnetic disk fixed by the spring - all this is reflected in the position of the arrow.

Operating principle of electric tachometers

Electric tachometers use electrical signals or individual pulses to measure. Electrical signals proportional to the crankshaft speed in a gasoline engine are generated by the ignition system and an electric generator, and in a gasoline engine only by the generator. The necessary signal can also be received from the electronic engine control unit.

The simplest way to operate is a tachometer connected to an electric generator. The generator is driven from the crankshaft via a V-belt drive, so the generator rotor speed is always proportional to engine speed. And the magnitude of the EMF generated on the winding depends on the rotation speed of the generator rotor, which is used to connect an electric machine tachometer. In essence, the device is a voltmeter that measures the voltage on the generator and converts it into crankshaft speed readings. The tachometer is connected to the generator through a special connector, which requires adjustment of the device to the specific generator.

The operation of the electronic tachometer connected to the ignition system is a little more complex. The ignition system generates current pulses necessary to produce a spark in the spark plugs. In this case, the frequency of sparking is directly related to the frequency of rotation of the crankshaft - otherwise the fuel-air mixture in the cylinders would not be ignited in time. The frequency of sparking depends on the number of engine cylinders and the order of their operation. In four-cylinder engines, the ignition system generates two sparks per revolution of the crankshaft - one spark for every 180°. It is this circumstance that is used to operate electronic tachometers - the measuring unit measures the sparking frequency and converts it into engine speed readings. An electronic tachometer is connected to the primary (low-voltage) circuit of the ignition system and measures the number of pulses per unit of time, which is why this type of device is often called pulse.

Simple tachometers for motorcycles and other devices with one- or two-cylinder two-stroke internal combustion engines operate on the same principle, but such devices are connected to the high-voltage part of the ignition system. Connection - using a wire wrapped around a high-voltage (spark) wire. In this case, the number of pulses on the spark plug is directly measured and this parameter is converted into readings of the engine speed.

— the device is simple and reliable, this device can operate without failures throughout the entire life of the vehicle. But in the event of a breakdown, the device should be replaced as soon as possible - only in this case will the engine operate and the vehicle operate in optimal mode.

Old and used Soviet-made asynchronous machines are considered the highest quality and most durable. However, as many electricians know, the nameplates on them can be completely unreadable, and the motor itself could have been rewound. You can determine the rated speed by the number of poles in the winding, but if we are talking about machines with a wound rotor or there is no desire to disassemble the housing, you can resort to one of the proven methods.

Determining speed using a graphical drawing

To determine the engine rotation speed, there are round graphic drawings. The point is that a paper circle with a given pattern glued to the end of the shaft when rotated forms a certain graphic effect when illuminated by a light source with a frequency of 50 Hz. Thus, by going through several figures and comparing the result with the tabular data, you can determine the rated rotation speed of the engine.

Typical characteristics for installation dimensions

Industrial production in the USSR, like most modern ones, was produced according to state standards and has an established conformity table. Based on this, you can measure the height of the center of the shaft relative to the landing plane, its and rear diameters, as well as the dimensions of the mounting holes. In most cases, this data will be enough to find the desired engine in the table and not only determine the rotation speed, but also establish its electrical and useful power.

Using a mechanical tachometer

Very often it is necessary to determine not only the nominal characteristics of an electric machine, but also to know the exact number of revolutions at a given moment. This is done when diagnosing electric motors and to determine the exact slip coefficient.

In electromechanical laboratories and in production, special instruments are used - tachometers. If you have access to such equipment, you can measure the rotation speed of an asynchronous motor in a few seconds. The tachometer has a pointer or digital dial and a measuring rod, at the end of which there is a hole with a ball. If you lubricate the centering hole on the shaft with viscous wax and press the measuring rod tightly against it, the exact number of revolutions per minute will be displayed on the dial.

Using a strobe effect detector

If the engine is in use, you can avoid having to uncouple it from the actuator and remove the rear casing just to get to the alignment hole. The exact number of revolutions in these cases can also be measured using a strobe detector. To do this, a longitudinal white mark is applied to the motor shaft and a light catcher of the device is installed opposite it.

When you turn on the engine, the device will determine the exact number of revolutions per minute based on the frequency of the appearance of a white spot. This method is used, as a rule, for diagnostic examination of powerful electrical machines and the dependence of rotation speed on the applied load.

Using a cooler from a personal computer

To measure engine speed, you can use a very original method. It uses a blade cooling fan from a personal computer. The propeller is attached to the end of the shaft using double-sided tape, and the fan frame is held manually. The fan wire is connected to any of the motherboard connectors, where measurements can be taken, without the need to supply power to the cooler itself. The exact speed reading can be obtained through the BIOS utility or a diagnostic utility running under the operating system.