Технические науки/6. Электротехника
и радиоэлектроник
Candidate of Science Sergey Dozorov
JSC “Gazprom Transgaz St. Petersburg” Engineering
and technical center
Current dependence of
loading on loading resistance value for different schemes of current sources.
In
modern practice the system of conversion, transfer, distribution and
consumption of electric energy is accepted at a constant tension. The value of loading
current In depends only on the value of receiver resistance
(loading) of Zn and at variable loading, that is at change of its resistance, and In
current respectively changes.
In
practice there are some cases when there is a need to support invariable a
preset value of loading current irrespective of change of its resistance, that
is the systems of distribution and consumption of electric energy providing
independence of current of loading of loading resistance value, such systems
received the name of the systems of the stabilized current (SSC). [1]
Thanks
to the using of inductance and capacity transformers (ICT) SST gained
considerable distribution in electrotechnological practice. Primary benefits of
ICT are simplicity, reliability,
profitability. However they have also some shortcomings such as insufficiently
good mass-dimensional indicators, complexity at implementation of smooth
regulation of current over a wide range, etc. These shortcomings were solved by
use of the transformer and capacity transformers (TCT) and new schemes of
regulation of output loading current. Application of TCT as sources of
invariable current allows to lower mass-dimensional indicators of SSC
significantly.
In TCT [2] the function of a throttle
and the power transformer are combined in
one device – it is
the transformer with purposefully provided values of inductance magnetization
and dispersion (drawing 1).
Drawing 1. - Equivalent TCT circuit
In this
case the oscillating circuit which is also configured on the frequency of a
power line is formed by the condenser C and the inductance L1 which is the sum of inductance of magnetization and
inductance of dispersion of the primary winding of the transformer. [3]
Dependence
researches of accuracy of stabilization of current of loading on the value of
resistance of loading confirm operability of TCT.
On
drawing 2 there are the studied schemes
of sources of invariable current T-shaped ICT – a), T-shaped ICT with capacity – b), Shteynmetts's scheme – in),
P-shaped ICT –), TCT with the
compensating capacity – d), executed in the program of circuitry modeling Micro-Cap9.
Consistently with inductance the resistors of 0,2 Ohms considering active
resistance of inductance are switched on.
At
contrastive analysis of the main four schemes ICT and the schemes TCT working
for identical loadings it is necessary to consider that values of the
equivalent jet Lэ and Cэ elements are identical to all schemes, except the
T-shaped scheme with magnetic communication of inductive elements (drawing 2, a), at which inductance of L1 = L2 = Lэ/2, and capacity C=2Сэ.
a) b)
c) d)
e)
Drawing 2. - Schemes of the studied sources of invariable current.
Equivalent
wave resistance of the concrete scheme IEP can be determined as
.
Let's determine the
equivalent wave resistance of the studied schemes:
Ohm,
Let's
define effective values of currents of loading at value of value of resistance
of loading equal to wave resistance
.
On
drawing 3 the dialog box of the program in which elements of schemes for which
modeling of signals is made [4] are specified is presented.
Drawing 3. - Dialog box of the program for determination of effective
values of loading currents.
On
drawing 4 a) and 4 b) results of numerical calculation of effective value of
current of loading at value of value of resistance of loading are presented
.
Drawing 4 a). - Effective values of currents of loading at 
Drawing 4 b). - Effective values of currents of loading at 
for TEP
Let's
define how effective value of current of loading at change of value of
resistance of loading will change. For this purpose we will enter coefficient
of a deviation of effective value of current of loading 
which we will determine by a formula:
,
where 
- range change of the loading current operating value, 
- effective value of current of loading at value of resistance of
loading
.
We will
make researches for three ranges of change of value of resistance of loading
:
a) from 
to
, b) from 
to 
, c) from 
to
.
Results
of coefficient calculation of effective value deviation of load current 
for different ranges of loading at value of wave resistance of a circuit
of 10,6 Ohm are presented in Table.
|
Parameter |
The studied scheme |
||||||
|
The T-shaped ICT |
The T-shaped ICT with capacity. |
Shteynmetts's scheme |
The P-shaped ICT |
TCT |
|||
|
|
20,571 |
20,547 |
20,552 |
20,946 |
20,940 |
||
|
Rn = 1-10, Ohm |
|
0,377 |
0,351 |
0,357 |
0,146 |
0,156 |
|
|
|
1,833 |
1,708 |
1,737 |
0,697 |
0,745 |
||
|
Rn = 10-50, Ohm |
|
1,575 |
1,587 |
1,589 |
0,937 |
0,979 |
|
|
|
7,656 |
7,724 |
7,732 |
4,473 |
4,675 |
||
|
Rn = 1-50, Ohm |
|
1,952 |
1,938 |
1,946 |
1,083 |
1,135 |
|
|
|
9,489 |
9,432 |
9,469 |
5,170 |
5,420 |
||
, A
, A
, %
, A
, %
, A
, %From Table
1 it is visible that during the work on a resistive load of TCT well stabilizes
output current and possesses significantly smaller mass-dimensional indicators,
than other schemes of sources of current. Current of loading remains invariable in broad range of change of
value of resistance of loading.
Literature:
1.
Использование
индуктивно-емкостных преобразователей для стабилизации мощности, потребляемой
переменной нагрузкой / И.В. Волков, К.А. Липковский, М.М. Александров //
Проблемы технической электродинамики – Киев: Наукова думка, 1972, вып.35
2.
Патент - 77517 РФ, МПК
Н02М 5/06. Индуктивно-емкостный преобразователь. / С.А. Дозоров, В.М. Опре,
И.В. Саенко, А.А. Новик, П.А. Кошелев, С.В. Парамонов; CПбГЭТУ «ЛЭТИ» - №2008118172/22; Заяв. 06.05.2008;
Опубл. 20.10.2008., Бюл. № 29.
3.
Трансфарматорно-емкостный
стабилизатор тока / С.А Дозоров, П.А.Кошелев, В.М. Опре и др. // Вестник
Саратовского государственного технического университета. – 2012. - №2 (66) – С.
59-65.
4.
Амелина
М.А., Амелин С.А. Программа схемотехнического моделирования Micro-Cap 8 /
М.А.Амелина, С.А.Амелин // М.:Горячая
линия-Телеком, 2007. - 464 с.