ABSTRACT
to theme of the qualification master’s work
“Research and Development of the Tractive Alternating-Current Drive of an Battery Locomotive with the Automatic Control System”

CONTENT

INTRODUCTION
1. PURPOSES AND RESEARCH TASKS
2. URGENCY OF THE THEME WORK`S
3. SCIENTIFIC NOVELTY
4. PLANNED PRACTICAL OUTCOMES
5. REVIEW OF RESEARCH AND DEVELOPMENT TO THE THEME
6. THE SUMMARY OF OWN RESALTS
CONCLUSION
LIST OF THE USED LITERATURE

INTRODUCTION

1. PURPOSES AND RESEARCH TASKS

During fulfilment of master`s work the following purpose is put – to justify a feasibility noncollector an alternating current motor in structure of the tractive an battery locomotive alternating-current drive with the automatic control system.

Parsing merits and demerits of direct current motor (DCM) as thrust organ of mine locomotive (ML), the research problem is formulated in the field of perfecting the electric drive which guidance system should ensure:

• the smoothly varying increase of a tractive effort at a breakaway from a place;
• dispersal of the composition with the desired acceleration;
• service braking with given accuracy of a shut-down;
• emergency brake application in case of need;
• maintaining of speed in the given limits;
• limitation of mode of behaviors in allowable limits;
• safety control of motion.

One of alternatives of construction of the electric drive is application of the thyratron motor (TM). Therefore we secrete following tasks: research of processes and the scientific substantiation of parameters of a TM with the self-excited inverter for conditions of a mine electric locomotive; the substantiation of structure of the electric drive with an automatic control system; a rational design of the power electric drive with an automatic guidance system on the modern base of power semiconductor elements and microprocessor technique.

Object of research is the mine battery locomotive with an automatic control system.

Subject of research is the tractive electric drive of a battery locomotive on the basis alternating current motors

Methods of research consist of realization of a mathematical model of the generalized ac machine with the help simulation in Matlab of software tools and mathematical calculations.

2. URGENCY OF THE THEME WORK`S

Poor reliability of a direct current motor in structure of the tractive electric drive, his seller's price, stipulates necessity of development of alternate systems of electric drives on the basis alternating current motors. One of alternatives is a construction of the electric drive on the basis the thyratron motor having some similarity of speed-torque characteristics and a direct current motor dispossessed a limitation for the lack of a collector unit. Application together with them of the adjustable autonomous voltage inverter would allow to decide a problem of the electric drive perfecting of a mine battery locomotive.

In this connection the research problem of processes and the scientific substantiation of parameters of a TM with the autonomous inverter for working conditions of a mine electric locomotive is actual.

For this purpose more steep study of processes in system «autonomous inverter – TM» is necessary with the purpose of the scientific substantiation of parameters of converter circuits, the engine and the automatic control system.

3. SCIENTIFIC NOVELTY

Scientific novelty of activity is supposed in following two points:

• Development of a mathematical model of the tractive electric drive on the basis of the thyratron electromotor as inquest of development of the generalized model;
• Reputed mathematical ratios and techniques allow to justify hereinafter rational parameters of a drive of a mine battery locomotive.

4. PLANNED PRACTICAL OUTCOMES

During researches, the bound with development of the tractive alternating-current drive of a battery locomotive and an automatic control system, such practical outcomes, as are planned:

• making of a laboratory bench for researches of the thyratron drive;
• development of algorithms of activity and software for a microcontroller of an automatic control system the electric drive;
• Development of the principal diagram of a control package by the alternating-current drive of a battery locomotive (on the basis the thyratron motor).

5. REVIEW OF RESEARCH AND DEVELOPMENT TO THE THEME

Now mine electric locomotives are equipped by direct-current electromotors with a series excitation that is stipulated by comparative ease of speed control, and also the softness of a speed-torque characteristic of the engine promoting levelling of loads at concurrent operation of two engines.

In practice change of an engine speed implements by means of amplitude (rheostatic systems) or pulsed (thyristor systems) voltage control of an anchor winding [1,2]. The most effective is the last way.

At the given method the tractive electric drive periodically is connected and unplugged.

In this case the mean medium voltage on the engine constitutes:

(5.1)

Where E – EMF of the power source; t_B and t_O the duration of accelerated and delayed motions; T = t_B + t_O – the period of repetition relevant to the given pulse repetition rate.

Change of an average value of voltage entails change of angular rate of the tractive motor according to expression:

(5.2)

The first version of an impulse drive for an industrial contact - battery locomotive has been developed in 1968 in Dnepropetrovsk institute of a railway engineers transport. And the control system of DCSEM speed represented two converters included under the scheme (fig. 5.1) and working with phase shift on a floor of a period [3].

Figure 5.1 – Pulsed DC voltage regulator

Now for the automation of electric mine battery locomotive with thyristor control are used apparatus TERA (locomotives ARP-8, ARP-14). The power circuit of the control equipment is represented by the pulse thyristor circuit breaker (PTB). PTB scheme has large losses in the circuit switching because of the need to produce cycles of charging and recharging of commuting capacitors and large dimensions commutating circuit. But It is more reliable, especially when running on low power supply [2].

Other development trend is implementation of a contactless way of a transmission of electrical energy from an electricity. What has been realized in the Dnepropetrovsk Mining Institute under the leadership of Dr. G. Pivnyak. High-frequency electric locomotive V14-900 are powered from an AC circuit frequency 5 kHz by means of electromagnetic induction between the isolated contact conductor and the current collector and provided intrinsic a contact tractive line. It was had a dc-drive [4].

Limitation of a dc drive require application in a tractive drive of an electric locomotive of more reliable and cheap alternating-current commutatorless motors or thyratron motors.

One of versions is use of an asynchronous motor with the cage rotor as a tractive organ which is alternative to a DC motor and is dispossessed its limitation.

In 1985 year by J.Dzidovskiy, M.Hefchits and F.ShChutskiy (Poland) [5] has been developed the asynchronous electric drive for mine locomotives. In the capacity of the convertor has been applied the autonomous inverter. It was plumped on a three-phase bridge with personal commutation of thyristors, and worked in a mode of pulse-width modulation (PWM). The given guidance system has allowed to receive tractive characteristics relevant to a DC motor. However defect of the given scheme has a large number of elements of forced commutation, which reduces the reliability of the power circuit. And also a small of an output voltage of the inverter, is stipulated by a low level voltage on accumulator battery (АB) of mine locomotive [6].

The further perfecting of main circuits went on the basis of developments, the bound with application of power keys with full roadability – IGBT-transistors. Made in 1990 in the republic of South Africa the prototype of a miner battery locomotive on a slip-ring motor had the convertor consisting of power transistors that has allowed to simplify a power part, having excluded links of forced commutation and to increase thus reliability of the convertor [7]. Its power part is introduced by three-phase bridge of the autonomous voltage inverter(AVI) , in mode PWM ensures the sinusoidal form of an output voltage with control band of 0,3..35 Hz and an output voltage 5..55 V. However, this converter has the disadvantage - low output voltage converter.

Work on the Exploration of the valve jet motor (VJM), held G. Demchenko, under the leadership of Dr. M. Dudnik in DonNTU [8], indicates the possibility of its use as a traction drive of ML. However, a number of difficulties associated with the need for a valve of the converter with a control system and special VJM

But the most perspective construction version of the power electric drive is application of the brushless motor on the basis the synchronous machine with excitation located on a rotor of permanent magnets, the theoretical basis for this is considered in [9, 10, 11].. Application of permanent magnets on a curl enables to save of the brush contact, the moment of inertia of a curl decreases, there is no necessity for the complex cooling system. Besides the given electric machine has a high static accuracy and a wide range of speed regulation. However, it has higher cost, than asynchronous on the score of permanent magnets.

6. THE SUMMARY OF OWN RESALTS

DC motors with series excitation, used in mine locomotives have a number of shortcomings such as: low life and reliability of the collector node, anchor and pole motor windings, heightened labour input of their service. In turn, the downtime caused by maintenance work, reduce the effectiveness of the technological process of transportation of the rock mass. The above-stated shortcomings showed necessity the search for alternative solutions when creating a controlled battery electric locomotives are used in mining. One alternative is to use thyratron motors (TM) based on synchronous machines.

The classical form of traction characteristics is composed of three parts: rigid, soft and the constant power (the characteristics 2) (fig. 6.1) [12, 13]. The characteristics are represents "tractive area", limiting possible operating modes of a drive. At the maximum speed is (corresponding to line 1) impose restrictions on the security requirements and the path, line 3 is responsible for limiting traction at clutch.

Figure 6.1 – The classical tractive characteristics of the electric locomotive drive

To the electric drive of a mine electric locomotive often overloading, which take place in modes of starting and braking. The work of the electric motor and brake modes, and variable loads cause considerable fluctuations in power which is consumed by a drive.

From the above, the basic requirement of the actuators is its steady work throughout the range of variation of traction effort provided the limited energy of AB.

Perspective version of construction of the thrust electric drive is application brushless DC motor (BDCM). It is the magnetoelectric synchronous machine with trapezoidal distribution of a magnetic field and the rotor position sensor (RPS), and as semiconductor commutator (SC) (fig. 6.2). On output SC and accordingly on windings of the synchronous machine rectangular voltage is formed. Possible versions of construction of the electric drive and the control systems are adduced in [11, 14, 15].

Figure 6.2 – Functional model of BDCM

Speed control and a driving torque of the engine implements by means of a mean current on the autonomous inverter with use pulse-width modulation (PWM).

Researched by a TM it is considered in rotaried coordinate system d – q, which is oriented on the rotor flux vectorФ_f (fig. 6.3). The TM will develop a maximum drive moment if between a vector i_q and Ф_f there will be the angle Θ = 90. For maintenance of it conditions a guidance system, with the help RPS should form a current and voltage in stator windings specially.

Figure 6.3 – Spatial placement of the rotating coordinate system oriented along the vector Фf

In the operator form dynamic model of the TM is described by the equations [16]:

(6.1)

where n – number of pole pairs;
Ф_f – the flow of the rotor of permanent magnets;
ω – angular frequency of rotation of the rotor field;
L₁ – the reduced inductance of rotor phase;
T_s=L₁/R₁ – time constant of the engine;
M_c – moment of resistance;
J – moment of the rotor inertia .

From these expressions follows, that at Ф_f = const the electromagnetic moment of the engine is determined by a quadrature-axis current i_1q. Therefore, the most economic mode of behavior of the TM is such at which equality to zero of a current i_1d is ensured. That corresponds to the least value of the current consumed at the given load.

Under condition of limitation of consumption of electrical power from AB this mode can be executed at a feed of a TM from the autonomous voltage inverter (AVI) under the law of commutation 120°. The control system is based on the use of an inverter (UZ), built on IGBT-transistors, not only to switch phases, but also for pulse-width modulation voltage applied to the stator. This inverter operates in the autonomous voltage inverter and a free-wheeling diode (fig. 6.4).

Figure 6.4 – Principal diagram AVI`s of the traction electric drive

Apparently from simultaneous equations (6.1) constituting voltage u_1d and u_1q simultaneously depend on constituting currents on the axes d – q. For removal of this connection into models of a TM we shall enter additional artificial EMFs:

(6.2, 6.3)

In the separation of control channels of the equation of voltage will be:

(6.4, 6.5)

For maintenance necessary dynamic and direct current characteristic the electric drive is constructed by a principle of slave control system. Synthesis of controllers in the system of a TM implements analogously, as well as for a DC motor. The block diagram is shown in fig. 6.5.

Figure 6.5 – Calculated structural diagram of the TM control system.

The scheme is designated: W_п(p) – a transfer function of the power converter; W₁(p), W₂(p) – a transfer function of the TM, according to ts electrical and mechanic parts; К_п, Т_п – gain and the smallest time constant of the power converter; Т_м – electromechanical time constant of the engine; W_рс, W_рт – a transfer function of a speed regulator and a current; К_т, К_с – coefficients of the current feedback and speed; ω_з, I_з – an assigning signal on speed and a current.

Setting up a guidance system of the TM on a modular optimum, transfer function of adjusters look like:

(6.6, 6.7)

In our case we shall be set by the electromotor power of 20 kW, the equivalent to a DC motor, used on mine locomotives.

In accordance with the traction diagram (fig. 6.1) the power consumed by the engine must remain independent at different load on the motor. Based on the limited energy storage battery, should be optimized power consumption, which is solved using the block current limiter (BCL), the current limit is determined from the expression:

(6.8)

Algorithm of tehe BCL is shown in fig. 6.6.

Figure 6.6 – Algorithm of the BCL

Figure 6.7 – The block diagram of a researched model of the TM

Set of natural and artificial speed-torque characteristics of a TM with different Р_опт are shown in fig. 6.7 a).

Figure 6.8 – Simulation results: a) the tractive characteristics of the TM, b) the dependence of the power consumption from the resistance on the shaft

Natural mechanical characteristics of a TM, which using in the control system with a subordinate regulation (fig. 6.5) are rigid enough (fig. 6.8 а)). At optimization on a current of the task on current regulator CR with the help of the unit of limitation of a current the BLC, we receive artificial speed-torque characteristics. Which are analogous to mechanical characteristics of a DC series-wound motor. Also as a result of modeling was obtained by graphical relationship between power consumption and resistance on the shaft (fig. 6.8 b)). Their schedule it is visible, that at change of the load, consumed power of the TM remains constant.

Thus, the received characteristics of the thyratron motor, answer necessary conditions of the traction drive control (fig. 6.1). At change of a load on the engine the consumption of power remains practically to a stationary value that confirms possibility of using of the TM in the actuating system of a mine electric locomotive in conditions of limitation of an electric intensity of the accumulator battery

Given the requirements for the control system discussed above and in [13], it is advisable to implement it based on microprocessor technology. Sample block diagram of control system traction drive is shown in fig. 6.9. It uses a microcontroller with PWM functions (AT90PWM3) [17]. In the figure the control signals from the remote control electric locomotive machinist (B) enter the ports of the microcontroller (MC). At the MC with the current sensor (I) and the rotor position sensor (D) received information that the software is handled in accordance with control signals are generated control signals to the driver inverter power switches (G) and the device driver is braking (J). In the diagram A, E – PSU; C – battery, F – synchronous machine, H – autonomous voltage inverter, L – power key and the resistance of the dynamic brakes.

Figure 6.9 – Block diagram of traction thyratron drive control system: 1 – Control system, 2 – the power part 3 – signal speed reference, 4 – signal "start / stop", 5 – the value of current motor
(animation: volume – 25,7 KB; size – 700 x 435; number of shots – 8; delay between shots – 2000 ms; delay between the last and fist shots – 0 ms; number of repetition cycles – infinity)

Thus, the thyratron motor becomes actual than DCM. Besides its control system, with minor changes similar to the control system of DCM. Consideration of the structure thyratron motor with automatic control is promising, with flawed source of electric drive, in addition decreases the moment of inertia of the rotor, there is no need for complex cooling system in the absence of shock heated rotor windings. But it must be noted that the use of AVI makes the issue of how the cooling power switches.

Further research in this area should address the constructive development of electric drive with automatic control system on the basis of modern power semiconductor devices and microprocessor technology.

CONCLUSION

The application in traction motor ML DSWM has several disadvantages associated with the design of the electric motor, which entails its low reliability and low lifetime. These motors are expensive and because of frequent breakdowns required repair, which affects the whole technological process of transport. In connection with this current problem is the use as traction drive with AC motors, which has a high reliability and lower cost. Also becomes relevant issue to build a system of automatic control system for the drive.

Consideration of technical solutions in the field of electric traction motor drive, showed the possibility of other schemes of electric drive. One option is to use asynchronous motor with cage rotor as traction body, which is an alternative to DC motors and deprived of its shortcomings.

But the most promising option for the construction of electric power is the use of TM-based synchronous machine with excitation located on the rotor of permanent magnets. In the moments that are close to nominal, its characteristics are quite close to the characteristics of the DC motor and, given that its management is necessary to change the supply voltage (output voltage of the inverter), a control system according to the engine, to some extent, should resemble the control system of DCM – slave control system for speed and current. However, the power consumed by the engine must remain independent at different load on motor. Based on the limited energy storage battery, should be optimized power consumption, which is solved using the block current limiter (BCL).

Furthermore the structure of construction TM has a number of features associated with the presence of cross-linking and reactive moment that must be considered when building automatic control system electrically.

As a result of this work was developed by the initial structure of the electric system of automatic control, a mathematical model of the system AVI-TM with the current regulator and the speed and block current limiting BCL.

According to the results of mathematical modeling were obtained artificial mechanical characteristics that are similar to the mechanical characteristics of the DC motor with series excitation. A graphic of the relationship between power consumption and drive point resistance on the shaft can be seen that when the load, power consumption by the TM remains constant.

But it should be noted that the use of the AVI makes the issue of how the cooling power switches.

Further research in this area should address the constructive development of electric drive with automatic control system on the basis of modern power semiconductor devices and microprocessor technology.

LIST OF THE USED LITERATURE

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When writing this Abstract master work was not yet completed. Date of final completion: Dec. 1, 2010. Full text of the work and materials on the topic can be obtained from the author or his supervisor after that date.