Abstract
Introduction
The use of harvesters and plows – the most efficient and fastest
way to
coal mining. But it is also the most difficult feasible. Harvesters and
plows are mechanisms of the automation which should
be as deep. This is necessary to improve the safety of the extraction
of coal and minimizing the cost of repairs.
1.
Theme urgency
The priority areas of the automation in the mining industry are those
that are aimed at improving safety of operation of technology systems
and facilities for staff. The specific conditions of the abatement in
the slaughter – it is an explosive technological environment, a
dispersed character of works, the difficulty of movement of people and
the increased risk of mining and tunneling equipment. These conditions
are increasingly complex. This is due to a decrease in the stock of
natural resources. Therefore, extension of working faces is increasing
the depth and development
of coal seams.
Modern
security systems
personnel working faces are imperfect. Therefore the theme is urgent
and new research and development necessary to.
2.
Goal and tasks of the
research
The main goal of research is the development of protection device of
the combined electric network of the multidrive haulage system of the
mining machine.
Tasks of the research
are:
1.
Analysis of existing methods
for detecting leakage of electric current.
2.
Defining the parameters of
the investigated area the mains and requirements to the developed
device.
3.
Justification of the method
support conductances
for leak detection and
computer modeling.
4.
Determination of parameters
of system performance.
5.
Development of structural
and circuit design solutions.
3.
The automation system
One of automation systems of this process equipment is
КД-А
. The equipment is designed to control of
mechanisms by systems КД-80, КД-90, КМ-103 rendered haulage systems of
harvesters КА-80, КА-90, К-103М, 1К101УД, 1К101УД-04, ГШ200В, УКА 200,
УКД-250. This equipment provides the modes of the load and speed which
are specified. Scheme of the automation system is shown in Figure 1.
Figure 1 – Block diagram of the automation process of coal
mining
(animation: 8 frames, 7 cycles of repeating, 150 kilobytes)
In Figure 1, indicated
by: 1 –
drive of the haulage system; 2 – speed
sensors; 3 – regulator of the load and speed; 4 – control unit; 5 –
control unit of the combines engine; 6 – control unit of the haulage
engines; 7 – the harvester UKD-250;
8 – auxiliary cord; 9 – power cord.
4.
The control and protection system
The electric power network of electromagnetic slip brakes of the drive
mining machines are the most susceptible link in the automation system.
Damage to the cable can cause a short circuit of electric circuits, the
leakage current to the ground, damage to elements of automation system
and other emergency situations. One of effective methods to prevent the
development of an emergency is an automatic control and protection
against leakage to the ground in power circuits of electromagnetic slip
brakes.
The
main parameters –
performance, response speed, maximum and minimum allowable values of
the currents and resistances, the safety requirements specified in ГОСТ
22929–78 Аппараты защиты от токов утечки рудничные
для сетей напряжением до 1200 В
[2].
As
a result, a critical
analysis of methods for determining an equivalent resistance by the
combined electrical network relative to the ground, was chosen as the
method support conductivities. They are connected to the poles of a
voltage converter (semiconductor controlled rectifier) [6]. The method
involves alternately connecting of two support conductivity to the DC
link in order to detect possible leaks to the ground. By measuring the
difference between the bias voltage of the artificial neutral Usm , can
be clearly estimate the value of the equivalent resistance Re of the
ground leakage.
In
order to determine the
dependence of the refined Usm=f(Re) was carried out computer
simulations. Schematic diagram of the investigated area network is
shown in Figure 2.
Figure
2 – Diagram of the investigated section of the mains
The diagram elements are indicated:
Uc – three phase low voltage
winding of the power transformer;
R1–R7 – resistance forming an
artificial neutral;
Ry1–Ry3 – resistance to leaks;
DC – phase
controlled rectifier circuit for Larionov;
ion – managed
conductivity;
EMS – electromagnetic clutch
slip.
The
letters A, B, C – indicate locations of leaks in the network
simulation, K1-driven key that allows the network connects the
electromagnetic clutch slip.
Graphs
of the artificial neutral bias voltage have been obtained during the
simulation (Fig. 3).
Figure 3 – Graphs of
voltage bias the artificial
neutral;
Figure 3 shows graphs of the following bias artificial
neutral:
a)
bias voltage without neutral
leakage current;
b)
the bias voltage at the
neutral-phase leakage;
c)
the bias voltage at the neutral
single-pole leakage.
Found
that the amplitude of the AC
bias voltage neutral corresponds
uniquely to equivalent conductivity of the mains to ground for all
possible combinations of lower conductivity (symmetrical AC, two pole,
single phase, two-phase and single-pole).
The analytical dependence of the bias voltage neutral on the equivalent
resistance (1) was obtained by the method of least squares, using the
approximation dependence obtained in computer experiments (Fig. 4).
Figure 4 – Dependence of the bias voltage neutral on the
equivalent
resistance
Conclusion
The
resulting dependence can
get the source data to develop a new system of control and protection
of electrical power supply of the electromagnetic clutch slip drive
mining machines.
When writing this
abstract the
master's qualification work is not completed. Date of final completion
of work: December, 2012. Full text of the work and materials on work
theme can be received from author or his scientific supervisor after
that date.
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