UDK 629.421

S. MULENGA, BEng. KSPEU

Supervisor: Prof. IDIATULIN R.G., Doc. Tech. Sc.

Copyright © Mulenga S., BEng, Kazan 2006.

1. Electromechanics and social progress
2. The development of electrical machines
3. Transport and electromechanics
4. Concise characteristics of Electrical rolling stock of city transport
5. Fundamental attributes to Traction Electro-equipment and its classification.
6. Excitation System of Traction Motors
7. Control systems and their classification

Bibliography

1. Electromechanics and social progress

The development level of material culture of human community in the first place is defined by formation and use of energy sources. The use of steam, and in the last 100 years electricity, accomplished technical revolution in industry and came out to be the influential solution to the development of social interrelations.

At present, in the more developed countries, for one person up to 10 kilowatts of all forms of energy is used. This is almost 100 times more than man power, which 200 years ago was the basis in industry and agriculture.

With complete fundamentals, one can say that technical and cultural levels of development of a state is defined by the quantity of electrical power produced per capita.

Almost all electrical energy (without regard of the chemicle resourses) is produced by electrical machines. Besides that, electrical machines may work not only as generators, but also as drivers which transform electrical energy to mechanical. Possessing high energy indicators and a little relatively with other transformers of energy, (waste products) for a unit power, ecologically clean (unpolluting) electromechanical transformers have in the life of human community a useful meaning.

First town electrical power stations appeared at the end of 19 th centuary. At present, the overall power of electrical power stations on earth is equal to about 4 000 million kilowatts.The energy produced is about 25 000 billion kilowatt.hour in a year. If in the future production of electrical power will grow like wise, then sooner in the years to come, electrical energy production will be 0,1% of all the energy that the earth recieves from the sun. Production of electrical energy is becoming global and of influence to our environment.

Electrotechnical industries produce every year million electrical machines for all sectors of society (i.e. agriculture, e.t.c). Without electrical machines, there can not be development in any complex scientific program. Without exaggeration, electromechanics defines technical progress in large amounts of fundamental sectors of industries.

On thermal and atomic electrical power stations, high input rotation electrical machines for generators are used - turbo generators with frequency of 3 000 and 1 500 rotations per minute.

Fig 1. Grouth of unit power of turbo generators

On hydro-power stations low rotation input generators of electrical energy are used. For 30 years, by the works of electromechanical engineers was a success to increase the power of turbo generators in 10 times. Increasing the power of turbo generators became possible by the result of betterment of cooling system of the machines (generators).

Initially air was used for cooling then hydrogen, and in the later constructions, internal cooling of conductors of windings is accomplished by water or air.

At present, turbo generators working with 500 and 800 Mwatts. A Kostromskoi thermal electrical station uses turbo -generators of power 1200 Mwatts. For atomic electrical stations - turbo generators of power 1 000 Mwatts with frequency of rotation 1500 and 3 000 rotations per minute and power 1600 Mwatts on 1 500 rotations per minute. These are the most biggest and most economical power plants made by man. With efficiency for 1200 Mwatts , 99,2% and 0,5 kg/kwatt of waste materials.

In order to deeply understand the principles and criteria for development of any scientific knowledge, its inevitable to know its history. The motor that was designed by M. Faraday (Fig. 2) consists of a permanent magnet 1, around which rotates a conductor with current 2. Sliding contact is afforded by mercury that is contained in a vessel 3, and the upper support 4.

Faraday's motor with direct current in the conductor and permanent magnetic field, provided by the permanent magnet affords conversion of electrical energy to mechanical.

In 1799 Italian academician A. Volt made an electrochemicle generator which was made of zinc and copper disks, divided packing, immersed in acid.

Russian academician V.V. Peter in 1802 made a battery from 4200 copper and zinc plates which was had electromotive force of 1700 volts and output power of 85 watts. He was the first to observe the electric arc.

Faraday in 1831 undertook a thousand experiments and had shown the possibility of "converting magnetizm to electricity" and invented the law of ELECTROMAGNETIC INDUCTION.

Fig2. Motor designed by M. Faraday in 1821 (1-permanent magnet, 2-conductor, 3-mercury, 4-support)

Transport - it is a strategically important complex, by a high index that defines the power of a nation, such that it provides the needs of society in terms of transporting cargo and passengers.

Communal ownership, characteristically for socialistic periods in Russia has changed for many forms of transport to other forms of ownership - mainly due to auctioning and privatization. If questions of control (coordination) on forms of transport arise, they may spread on separate ministries of transport, then at present they (except railway transport) concentrate on the Russian ministry of transport. On market conditions, several changes affected the transition from unitary systems of transport. The appearance of competition due to new forms of transport must not be considered as a hindrance of one form of transport by another but as an occurrence (phenomenon) that is stimulating development of transport, search for new progressive technology of transportation for reducing the cost of transportation services and increasing delivery speed. Reduction of costs and transportation time expands the sphere of exploiting a form of transport and consequently raises its importance on the market of transportation services.

The cost of transport services realistically is defined by the final cost of delivered Cargo, that is why the clients look for possible ways to transport their goods by the cheapest forms of transport. Transporting passengers is important to society. Expenditure on transport is not supposed to exceed a certain percentage of the family budget. In many countries of the world, expenditure on transport has been dotted for specific(separate) population layers.

Market conditions have intensified research for each transport company by their niche on the transport services.

Its important to note that as the territory of Russia is large, there is well defined spheres of application of each form of transport: based on distance, speed and form of Cargo (example-transporting cheese over a long distance by rail is preferred). There are regions practically with one form of transport, for example further regions in Siberia, and the Further East. Besides there exists regions (and business areas) where the client may choose the form of transport depending on their requirements.

Modern market conditions of running the business, expanding international relations and home affairs of a country, requires specialists with high qualifications, with wide scope , not only with knowledge of one form of transport, but also with understanding specifics of each form and capability of working in conjunction with other specialists especially in multi and inter-modal delivery.

In the area of transport, specialists must have the potential to quantify and qualify real situations of business in the transport system, understand and work out a direction by technical and technological politics on transport for normal functioning of all branches of transport to uphold and develop the national economy.

At present, competition of different forms of transport or technology must be based not only on the economy, but also on the ecology and general safety-that is, with consideration of logistical principles.

Absolutely naturally, interaction of forms of transport, coordination of their operations and most importantly competition must be regulated by the STATE.

Electrical transport is defined as one who’s movement is aided by electrical traction motors.

City Electrical transport- It is a massive communal transport system which is meant for commuting the public. It must have in place: high reliability and safety of movement; maximum comfort for passengers at minimum transportation costs; necessary cleanliness and regular movement on its route; high speed and required conveyance; minimum noise, made by the rolling stock.

Main forms of city electrical transport- Tram cars, trolley buses, and metropolitan. In separate situations mono-railroads are used, heat-electrical , Electro-mobile transport and so forth.

Trolley bus - form of city electrical transport without rail-contact . Advantages: for organization of its movement, it does not require special “path” equipment , guarantees safety and comfort of loading and off loading passengers as a result of direct stopping at the bus stop by the road side. In comparison with rail transport, trolley buses are more noiseless. In comparison with motor vehicles (buses), they do not produce combustion waste products.

Disadvantages of trolley buses: higher electrical power consumption and complicated condition of electrical current tapping system in comparison with tram cars; minimal shunting in comparison with autobuses and necessity of equipment for contact network and sub station that are a precondition and requires high investments on construction.

Electrical motors, control systems and sources of power supply form traction electrical equipment for electrical rolling stock.

Attributes to electrical equipment are defined by the condition of its functionality. In comparison with electrical equipment of station installations traction electrical equipment works in more difficult conditions and it is characterized mainly by the following:

1. Due to roughness of the road, and oscillations and vibrations of mechanical parts of the rolling stock, electrical equipment works under impulses and shaking. This entails more mechanical and electrical strength.
2. On movement of the rolling stock, dirt and moisturized air ( sometimes water and snow) penetrates in electrical equipment. For this reason insulating material and insulated parts must have moisture resistance, and all metallic parts- reliable anticorrosion coating.
3. Nominal voltage, used on city electrical transport, is relatively high, compared to that of the industrial installations. This raises high attributes to commutation reliability of electrical traction motors and other high voltage auxiliary electrical machines, which are as well calculated for work in conditions of transient processes related to changes (abrupt) in voltage in contact network.
4. Electrical rolling stock works with abrupt changing of load as path profile changes; parameters of air (moisture and temperature), which cools electrical equipment, changes in wide ranges, which enforces relatively high changes in temperature of windings and electricity conducting parts of electrical equipment.
5. Space for installation of electrical equipment on the rolling stock is limited, that is why traction electrical equipment must have possibly small sizes and weight.

Excitation system of traction motors-

i). in series

iii) independent excitation

**Note- Motors of parallel excitation are not used as traction motors

Motors of “series” excitation have the following advantages in comparison with parallel excitation:

In conditions of abrupt change of load, they show natural traction characteristics v(F) , which afford best usage of rolling stock and power supply equipment.

For example, with large load (on uphill or at starting) these motors with the rise of current automatically reduces speed and increases magnetic flux, which enforces reduced overload of current on motor windings. When load reduces , speed automatically increases and magnetic flux reduces. These qualities afford more proportional load on electrical equipment and power supply system (Traction sub station and its network);

-with parallel work of motors much more equally spreads load between its circuits;

-best works in transient conditions as a result of large commutation stability towards ring fire on the collector, less amounts of maximum values of transient current, less voltage ( and mechanical stress) on the insulation of excitation windings and mechanical forces on the spindle of the motor.

When controlling traction motors, the following operations are carried out:

- connecting traction motors to the contact network and disconnecting them by the operator or automatically (for example, when there is overload, short circuit, disappearance of voltage in the contact network, increase of voltage more than the limit);

-reconnecting levels of starter rheostats and breaking rheostats.

-reconnecting levels of excitation circuit for changing magnetic flux of traction motors.

-reconnecting traction motors from one group to another.

-reconnecting circuit of traction motors from traction to breaking and vice versa.

-connecting breaking circuit, reconnecting the circuit from one form of breaking to another(for example, from recuperating to rheostat form or from rheostat form to mechanical);

-changing the direction of movement of rolling stock (reversing the direction of rotation of traction motors)

-switching off traction motors when there is a technical fault (accident)

Not all the above mentioned operations are used on all forms of electrical rolling stock. For example, on many trolley buses and some types of trams, they do not operate regrouping traction motors on starting.

Control systems of traction motors depending on the type of starter apparatus is divided in "step" and "smooth" and also on the method of action of electrical apparatus - i.e. system of direct and system of indirect (distant) control.

Any control system needs to have in consideration the following general attributes:

• operation of traction motors must be simple and easily manipulated (using pedals, or handle bars for control), and its not necessary to use more than one handle or pedal at the same time. All handles and peddles must be interlocked with respect to each other so that no control mistakes can occur and afford at any moment.
• Minimal size and weight regulating apparatus, and minimal costs of control systems and costs of servicing apparatus.
• Failure of work of any electrical apparatus does not call for a wrong operation (example traction process in place of breaking e.t.c)
• Apparatus must work reliably

ISBN 5-7695-1988-6