RU2192091C1 - Direct-current drive - Google Patents

Abstract

FIELD: electrical engineering; high-speed induction motor drives. SUBSTANCE: ac drive has three-phase induction motor whose rotor speed is up to 12 000 rpm; its stator slots accommodate three groups of half-windings similar in design; half- windings related to same group are disposed in same slots and connected through transistor switches as follows: one pair of half-windings connected in parallel opposition is fed with phase voltage of power supply; other pair of half-windings connected in parallel opposition whose turn number is

Description

 The invention relates to an electric drive, in particular to an alternating current electric drive of increased frequency with asynchronous electric motors, and can be used to drive machines and mechanisms with a speed of working bodies up to 12000 rpm, for example shearing machines, centrifuges, power tools, etc.

 A known frequency multiplier for powering high-speed asynchronous electric drives [1], allowing to obtain a supply voltage with a frequency of 200 Hz, made on a rod transformer using additional DC magnetizing windings and self-magnetizing windings with fourth harmonic currents closed to the capacitor. The disadvantages of this device are: rather low efficiency, significant material consumption, a large number of controlled semiconductor elements. Also known is an AC electric drive [2], containing an electric motor, in the grooves of the stator magnetic circuit of which there are four windings, in turn connected to each other are counter-parallel connected lockable thyristors. The disadvantages of this device are: the need for the formation of control pulses of reverse polarity needed to lock the thyristors, which complicates the control circuit of the thyristors; uneven loading of the phases of the supply network; subharmonic components of the magnetizing force, negatively affecting the mechanical characteristics of the electric drive.

раз больше числа витков в полуобмотках первой группы и включены в диагонали управляемых двухполупериодных выпрямительных мостов, подключенных к линейному напряжению источника питания, причем полярность подключения к напряжению источника питания полуобмоток первой группы противоположна полярности подключения полуобмоток второй группы, а угол включения управляемых вентилей управляемых двухполупериодных выпрямительных мостов больше π/2.
Недостатками этого устройства являются: использование только конечной части синусоиды питающего напряжения; частота вращения рабочих органов до 6000 об/мин.Closest to the proposed invention and adopted by the authors for the prototype is an AC electric drive [3], containing a three-phase asynchronous electric motor, in the grooves of the stator magnetic circuit of which there are two groups of half-windings, the half-windings of each phase of both groups are laid in the same grooves, the half-windings of one group are included in the diagonal of controlled half-wave rectifier bridges connected to the phase voltage of the power source, and the semi-windings of the second group have the number of turns in

times the number of turns in the semi-windings of the first group and are included in the diagonals of the controlled half-wave rectifier bridges connected to the linear voltage of the power source, the polarity of the connection to the voltage of the power supply of the semi-windings of the first group is opposite to the polarity of the connection of the semi-windings of the second group, and the angle of the controlled valves of the controlled half-wave rectifier bridges greater than π / 2.
The disadvantages of this device are: the use of only the final part of the sinusoid supply voltage; rotation frequency of working bodies up to 6000 rpm

 The aim of this invention is to increase the rotational speed of the rotor of a three-phase asynchronous motor up to 12000 rpm, increase the power factor of the electric drive through the use of the initial and final parts of the sinusoid of the supply voltage.

раз больше числа витков первой пары, к линейному напряжению источника питания, имеющему фазовый сдвиг по отношению к фазному напряжению на 90 электрических градусов.This goal is achieved by the fact that the AC drive contains a three-phase asynchronous motor, in the grooves of the stator magnetic core of which there are half-winding groups, while the half-windings are three equally executed groups, the half-windings belonging to one group are located in the same grooves and are connected through transistor switches : one pair of counter-parallel connected half-windings to the phase voltage of the power source, another pair of counter-parallel connected half-windings having Lo turns in

times the number of turns of the first pair, to the linear voltage of the power source having a phase shift with respect to the phase voltage of 90 electrical degrees.

 Comparative analysis with the prototype shows that the inventive device is distinguished by the presence of transistor switches and that there are four half-windings for each pole and phase. Thus, the claimed device meets the criterion of "novelty."

 Comparison of the proposed solution with other technical devices shows that it is known to use four windings on the stator that are connected in parallel to the power source [2], however, the introduction of transistor switches, in this connection, with the semi-windings of the electric motor stator in the inventive electric drive allows the formation of the resulting EMF of quadruple frequency in relation to the frequency of the power source, which allows us to conclude that the technical solution meets the criterion of "significant differences".

 Figure 1 shows the end circuit of the stator winding of the electric motor. Figure 2 shows a schematic diagram of the described electric drive, and figure 3 is a timing diagram of voltages and magnetic fluxes explaining the principle of operation of the electric drive.

раз больше, чем у полуобмоток 1-6.The AC electric drive (Fig. 2) contains an asynchronous motor with a short-circuited rotor, in the grooves of the stator of which there are twelve half-windings (1-12) in the form of three groups of half-windings. The first group of half-windings includes 1, 2, 7 and 8 half-windings, the second group includes half-windings 3, 4, 9 and 10, the third group - half-windings 5, 6, 11 and 12. The groups of half-windings are shifted relative to each other by one hundred and twenty electrical degrees. Half windings 1, 2 are connected through transistor switches 13 and 14 to phase voltage U _A , half windings 3, 4 are connected through transistor switches 15 and 16 to phase voltage U _B , half windings 5, 6 are connected through transistor switches 17 and 18 to phase voltage U _C . Half-windings 7, 8; 9, 10; 11, 12 are connected through transistor switches 19, 20; 21, 22; 23, 24 to the line voltages U _BC , U _CA , U _AB, respectively. The number of turns of semi-windings 7-12 in

times more than semi-windings 1-6.

 The principle of operation of the electric drive can be considered by the example of the operation of one group of half-windings containing half-windings 1, 2, 7, 9 and transistor switches 13, 14, 19, 20 (Fig. 3).

In the time interval 0 - t _{1, the} control voltage U _upr13 is supplied to the transistor switch 13, the transistor is open and a current flows through the half-winding 1. At time t _{1, the} transistor in the transistor switch 13 closes, the control voltage U control ₁₉ is supplied to the transistor switch 19 and the current in the interval t ₁ - t ₂ flows through the semi-winding 7. At time t _{2 the} transistor switch 19 closes, the control voltage U control ₁₄ opens transistor switch 14, in the time interval t ₂ - t _{3, the} current flows through the semi-winding 2, but the magnetic flux generated by the semi-winding 2 is directed counter to the magnetic flux created by the semi-winding 1. At time t _{3, the} transistor switch 14 is closed and the voltage m U _upr20 opens the transistor switch 20, the current in the time interval t ₃ - t ₄ flows through the semi-winding 8, the magnetic flux is directed counter to the magnetic flux of the semi-winding 7. At time t _{4 the} transistor switch 20 closes and the voltage U _upr13 opens the transistor switch 13, current flows through the semi-winding 1. The process then repeats.

 The resulting magnetic flux f in the magnetic circuit has a frequency of 200 Hz. When executing a stator of an induction motor with one pair of poles, we obtain a rotor speed of up to 12,000 rpm.

 The advantages of the invention in comparison with the prototype are: an increase in the rotor speed to 12000 rpm, an increase in power factor due to the use of the initial and final parts of the sinusoid of the supply voltage.

Sources of information
1. A.S. USSR 1069095, class H 02 M 5/16, 1984.

 2. Pat. RF 2111606, class H 02 P 5/40, 1998.

 3. Application for invention 2000102959/09 (002868), Н 02 Р 5/40, Н 02 К 47/22, 2000 / prototype /.

Claims (1)

An AC drive containing a three-phase asynchronous motor, in the grooves of the stator magnetic circuit of which there are half-winding groups, characterized in that the half-windings are three equally executed groups and half-windings belonging to the same group, are located in the same grooves and are connected through transistor switches: one pair counter-parallel connected semi-windings to the phase voltage of the power source, another pair of counter-parallel connected semi-windings having a number of turns in

times the number of turns of the first pair, to the linear voltage of the power source having a phase shift with respect to the phase voltage of 90 electrical degrees.

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