RU2035838C1 - A c electric motor drive - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: stator winding of asynchronous motor is star-connected. Starts of two phases are provided with clamps for connection of power supply source, autotransformer is linked to third phase of power supply source, mobile contact is coupled to start of third phase of stator winding. Common point of star of stator winding and finish of autotransformer winding are connected to zero lead of power supply source. EFFECT: enhanced control over mechanical characteristics. 4 dwg

Description

 The invention relates to electrical engineering and can be used in light industry.

 Known devices for controlling speed.

 In the device [1] comprising a bridge converter circuit with a step harmonic voltage filter for each of the phases, voltage regulation for controlling the speeds and the moment during operation of the consumer is performed using amplitude and pulse-width modulation with a high-frequency converter.

 The disadvantage of this device is its complexity and, as a result, low reliability.

 The closest in technical essence to the claimed device is the selected as a prototype AC drive [2] containing a three-phase asynchronous motor, the stator winding of which is connected according to the "star" scheme, and the beginnings of two phases of the stator winding are equipped with clamps for connecting to two phases of the power source, the movable contact of the transformer winding is connected to the beginning of the third phase of the stator winding.

 The disadvantages of the electric drive are the inability to smoothly control the moment, the inability to create an asymmetric mode.

 The purpose of the invention is the expansion of functionality and improvement of reliability indicators of the electric drive.

 The goal is achieved in that an alternating current drive containing a three-phase asynchronous electric motor, the stator winding of which is connected according to the "star" scheme, and the beginnings of two phases of the stator winding are equipped with clamps for connecting to two phases of the power supply, an autotransformer is introduced, one winding of which is equipped with a clamp for connecting to the third phase of the power source, while the movable contact of the autotransformer winding is connected to the beginning of the third phase of the stator winding, the common point of the "star" of the stator winding autotransformer winding end connected to a zero terminal power source.

 Figure 1 shows the structural diagram of the machine; figure 2 wiring diagram of the electric motor; figure 3 is a vector diagram for various modes of operation (i.e., at different positions of the movable contact of the autotransformer); figure 4 shows the mechanical characteristics of the electric drive.

 The device comprises an electric motor 1, a node 2 for coupling the actuator 3 (Fig. 1). The electric motor 1 contains three windings 4, 5, 6 connected according to the "star" scheme, i.e. the beginning of two of them are connected to phases A, B, the beginning of the third to the movable contact 7 of the autotransformer, the terminals of which are connected to phase C and the "zero" point formed by the connection of the windings 4, 5, 6.

 The device operates as follows.

QR_cp, где μ- коэффициент трения, зависящий от материала дисков; Q усилие нажатия; R_ср (R_м + R_m)/2 средний радиус рабочей поверхности дисков, где R_м и R_m максимальное и минимальное значения этого радиуса.Node 2, for example, a friction gear or slip clutch containing a driven and driving discs, makes it possible to adjust the speed of rotation of the working shaft of the sewing machine, acting on the actuator drive. The transmission of torque from the master to the driven disk is carried out by means of the friction moment M _Tr under the influence of force Q, which presses the disks of unit 2 to each other. The clutch is switched on in the device by pressing contact surfaces, the mating parts of the friction clutch from the foot linkage (pedal) to each other. By changing the adhesion force (pedal pressing force) of the rubbing surfaces, the friction force is regulated and the output shaft is started and continuously controlled at a constant speed of rotation of the electric motor. It can be shown that the rotation speed of the driven shaft is defined as V _cc V _dv (1 S), where V _{dv is the} speed of rotation of the electric motor; S is the amount of slip. Similarly, the moment of friction transmitted by a pair of disks, M _Tr =

QR _cp , where μ is the coefficient of friction, depending on the material of the disks; Q force of pressing; R _cf (R _m + R _m ) / 2 is the average radius of the working surface of the disks, where R _m and R _{m are the} maximum and minimum values of this radius.

Based on the general equation of the drive device (M _d M _Tr + Δ M _Tr M _s + Δ M _Tr , where Δ M _Tr loss of torque in the slip mode; M _dv motor torque; M _s moment of static resistance, determined by the value of the load of the actuator 3), we can construct vector diagrams of windings 4, 5, 6 depending on the position of the movable contact 7 of the node (Fig. 3), as well as the characteristics nf (M), where n is the rotation speed (Fig. 4), or equivalent characteristics ΔM _tr = f (S) ; M _dv f (S), from which it follows that in order to obtain the same speed V _cc, it is necessary to reduce the force of pressing the disks Q (the force on the foot pedal).

m₁I $\genfrac{}{}{0ex}{}{\text{2}}{\text{1}}$ N

-P

t, где Р_мх механическая прочность, развиваемая электродвигателем на ведущем валу; Р_н полезная мощность нагрузки; m₁ число фаз двигателя; I₁ величина тока, потребляемого фазами статора; r₂' активное сопротивление ротора; t время работы.The amount of wear of the disks can be determined by the amount of friction loss ΔA _Tr = (P _mx -P _n ) t

m ₁ I $\genfrac{}{}{0ex}{}{\text{2}}{\text{1}}$ N

-P

t, where P _{mx is the} mechanical strength developed by the electric motor on the drive shaft; R _n net load power; m _{1 the} number of phases of the engine; I _{1 the} magnitude of the current consumed by the phases of the stator; r ₂ 'the active resistance of the rotor; t working time.

The proposed device reduces M _dv , which leads to a decrease in ΔM _Tr , at the same time decreases the current consumed by the phase into which the node is included, which leads to a decrease in ΔP _Tr spent on disk wear.

- эквивалентное сопротивление двигателя, можно определить ΔР_тр', т. е. величину потерь в предложенном режиме работы и величину потерь ΔР_тр в симметричном режиме, т.е. в режиме прототипа. Расчет показывает, что K

0,7 и N_p (1/K) ˙N_н ресурс муфт сцепления по отношению к нормативному ресурсу N_н увеличивается примерно на 30% а ток в фазе С уменьшается на 55% при сохранении тока в двух фазах, что уменьшает и потребляемую мощность, кроме того, обеспечивается более плавная регулировка скорости ведомого вала и исполнительного механизма.Based on the fact that ΔР _tr mI ² r _e where m is the number of phases; II _n , i.e. load current; r _e = r

is the equivalent resistance of the engine, it is possible to determine ΔР _Tr ', i.e., the value of losses in the proposed operation mode and the value of losses ΔР _Tr in the symmetric mode, i.e. in prototype mode. The calculation shows that K

0.7 and N _p (1 / K) ˙ _{N n the} clutch resource in relation to the standard resource N _n increases by about 30% and the current in phase C decreases by 55% while maintaining the current in two phases, which reduces the power consumption In addition, a smoother adjustment of the speed of the driven shaft and actuator is provided.

 Thus, the proposed device has improved reliability characteristics and can provide, for example, the use of sewing machines with direct stitching for manual artistic embroidery.

Claims (1)

 An AC electric drive containing a three-phase asynchronous electric motor, the stator winding of which is connected according to the star circuit, the beginnings of two phases of the stator winding are equipped with clamps for connecting to two phases of the power supply, an autotransformer, one winding of which is equipped with a clamp for connecting to the third phase of the power supply, a movable contact the autotransformer winding is connected to the beginning of the third phase of the stator winding, characterized in that the common point of the stator winding star and the end of the autotransformer winding tori connected to the zero output of the power source.

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