RU2121206C1 - Stator of reversing induction motor - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: stator core of multiphase reversing induction motor has yoke with teeth carrying stator winding phase coils. Each tooth has body and pole shoe. All teeth have equal size over stator bore with equal air gap between tooth pole shoe and rotor stack. Core is assembled along axial length of at least two equal-length stacks with nonmagnetic spacers placed between them. Each phase coil is wound on one tooth on each stack over stator length. Center lines of tooth body in different stacks with one coil wound on it are parallel to motor axis of revolution and are in coincidence; tooth pole shoes of different stacks are displaced relative to tooth bodies in opposite directions. EFFECT: reduced amplitude of stray torques in induction motor. 8 dwg

Description

 The invention relates to the field of electrical engineering and can be used in the production of asynchronous low power motors.

 Traditionally, the anchor of a multiphase induction motor is made from the yoke and the tooth zone, in the grooves of which an anchor winding is placed. In order to reduce spurious moments from the higher harmonics of the magnetic field, the armature winding is made with distribution and shortening. The tooth zone is performed with teeth that have the same geometric dimensions along the stator bore and along the length of the machine.

 The grooves are open, half-closed and closed [1], p. 75, Fig. 4-27. The teeth for the loose windings of half-closed and closed grooves are made with a symmetrical tooth crown. The teeth for windings with rigid sections and half-closed grooves are made with an asymmetric tooth crown. The purpose of the asymmetry of the tooth crown is to simplify the technology of laying coils of the hard winding [1], p. 74, Fig. 4-24. Relative to the axial length of the machine, the tooth is symmetrical.

 Asynchronous power motors with an asymmetric stator are known. According to the principle of operation and design, motors of this type are similar to motors with shielded poles, but they do not have short-circuited turns at the poles [2]. In fig. 28.2 p. 638 of the literature [2] shows the design of the stator sheet of such an engine. When starting, a shift in magnetic flux is created as a result of saturation of the stator back sections of a small cross section. To improve starting performance, magnetic shunts are used between the pole piece and the small additional pole. The air gap under the pole is uneven to reduce spurious moments from the higher harmonics of the field. The disadvantages of such engines include the lack of reversal, low starting torque and low-tech manufacturing of shunts. Note that the magnetic asymmetry of the pole tip is designed to create a starting moment by creating an additional flow passing through the additional pole and the stator yoke with a reduced cross section. The pole is magnetically symmetrical along the length of the machine.

The closest analogue is the solution known from A. with. USSR N 169664, H 02 K 17/10, 1965, where the induction motor with two pairs of explicit pole poles with short-circuited turns and concentrated coils, and one pair of poles is displaced circumferentially to the other pair by 90 ^o and in the axial direction by an amount approximately equal the width of the pole. The mechanical air gap between the poles and the rotor is uniform. Since the air gap is uniform and the anchor winding is with concentrated coils, the drawback of this solution is the fact that the device has not taken special measures to reduce the amplitudes of stray moments, which makes it difficult to start the induction motor. The fifth and seventh harmonics of the field of the armature of an induction motor reduce the maximum electromagnetic moment and increase the losses in the rotor and stator in the nominal mode, which ultimately leads to a decrease in the efficiency of the device.

 The goal is achieved by the fact that the stator of a reversible multiphase asynchronous motor, the core of which consists of yoke and teeth with coils of the phases of the stator winding, each tooth has a body and a pole tip, all teeth along the stator bore have equal geometric dimensions with a uniform gap between the tooth tip and the rotor iron moreover, the core along the axial length consists of at least two packets equal in length, non-magnetic gaskets are placed between the core packets, each phase coil spans along the length of the stator along one tooth of each package, while the geometric axis of symmetry of the body of the teeth of different packages covered by one coil are parallel to the axis of rotation of the engine and coincide, and relative to the bodies of the teeth, the tooth tips of different packages are shifted in opposite directions.

 In FIG. 1 shows an axial section of a stator of a reversible induction motor; in FIG. 2a, 2b show two transverse sections of the stator of a reversible induction motor; in FIG. 3 shows in plan terms the teeth of packets A and B and the stator winding coil from the yoke side of the stator HELL; in FIG. 4 shows sections A and B of the magnetic circuit of the tooth zone and plots of the distribution of inductions on one pole division; in FIG. 5 is a vector diagram of the EMF in the shaft of a squirrel-cage rotor.

 In FIG. 1 shows, by way of example, an axial section through a stator of a reversible multiphase induction motor, the core of which in length consists of two equal lengths of packets A and B. FIG. 1 shows sections of the yoke 1 and the dentic zones of the stator core.

 Between packets A and B, non-magnetic gaskets are placed in the tooth zone 3 and in the yoke 4. Each phase coil 5 of the stator winding spans one tooth of each packet along the length of the stator.

 In FIG. 2 shows cross sections of the stator A-A and B-B, made in the area of each of the packets A and B (see Fig. 1). The stator core of a bipolar reversible multiphase induction motor has six teeth. Each tooth has a tooth body (2a, 2b) and a serrated tip (6a, 6b). The teeth are fixed in the yoke of 1 stator core, one tooth of each package. The installation of coils 5 on the teeth 2 is carried out before they are pressed into the stator yoke.

 The serrated tips 6a of each tooth of the packet A are offset relative to the body of the tooth 2a in one of the sides (for example, counterclockwise, as in Fig. 2a). The tooth tips 6b of each tooth of the package B are offset relative to the body of the tooth 2b (Fig. 2, b).

 Between the teeth of each package there are slotted slots 7a and 7b. Instead of splined slots, bridges can be made for mechanical connection of the teeth in order to create a more rigid structure of the tooth zone of the engine. With another method of mechanical articulation of the teeth, the bridges can be made non-magnetic.

In FIG. 3 in the plan from the side of the coil shows one tooth (2A) of package A and tooth (2B) of package B, separated by a non-magnetic layer 3 with an axial length l _δ . The serrated tips of packets A and B (3A and 3B) show splined slots (7A, 7B), shifted together around the circumference of the stator by an angle β _m .
Anchor coil 5 covers the cores of teeth 2A and 2B of both packages. The geometric axis of symmetry (a, b) of the body of the teeth 2A and 2B belonging to different packages coincide.

In FIG. 4a are shown on one pole division τ ₁ unfolded in a section line of three teeth (2A) with coils 5 belonging to phases: A, C, B. For a point in time when the sinusoidal current value in phase C is equal to the maximum, and in phases A and B, respectively, by −0.5 of the current amplitude in phase C, in FIG. 4b shows the following graphs of curves:
B _6A is a graph of the distribution of the induction distribution curve on the surface of the rotor of an induction motor, provided that the gap height: δ = 0 and μ _st = ∞;
B _1A , B _5A are graphs of the curves of the first and fifth harmonics of induction, respectively, when the curve B _{δA is expanded} in a Fourier series.

In FIG. 4c and 4d shows the same, but for packet B. As can be seen from the graphs of FIG. 4b and 4d, the first harmonics of the induction are shifted by an angle β _m .
In FIG. 5a, b, c show the EMF vectors induced in the rods of the short-circuited cell of the AD rotor, the first (Fig. 5a), the fifth (Fig. 5b), and the seventh (Fig. 5c) harmonics of induction of packets A and B .

The device operates as follows. The fields of packets A and B in each rod of the short-circuited winding, made, for example, without beveling the grooves, induce an EMF with amplitudes proportional to the amplitudes of the first and higher harmonics of induction in the gap. Because packages A and B according to the application of equal length, the EMF amplitudes in the rods from packages A and B from each harmonic are equal. The initial phases of the EMF in the rotor rods from the magnetic fluxes created by packets A and B depend on the shear angle β _{m of the} packets.

Consider an example. Let the stator be made with the number of pole pairs 2P ₁ = 2, and β _m = 36 geometric degrees. Then the initial phase of the EMF from the field of the first harmonic A e _1A will be shifted relative to the initial phase of the EMF from the harmonic field of the packet e _1B by an electric angle equal to β ₁ = β _m • P ₁ , and will be β ₁ = 36 x 1 = 36 el. . (4A). The resulting EMF E ₁ in the rotor shaft from the fields of the first harmonics of packets A and B can be represented as the sum of two vectors shifted by an angle β ₁ = 36 electric degrees, i.e.

E ₁ = 2E _1A • cos (β _1/2 ) = 2E _1A • cos18 ^° = 2E _1A • 0.95.
The resulting EMF from the fifth harmonic fields E _{5 of} packets A and B shifted by an angle: β ₅ = β _m • 5P ₁ = 36 • 5 • 1 = 180 el. ₅ is E = 2E _5A • cos (β _5/2) = 0.
Therefore, in the rotor winding currents in each rod from the fifth-harmonic EMF will not flow, because E ₅ is equal to zero, and therefore, the moment from the interaction of the armature field and the current of the fifth harmonic of the rotor is zero (Fig. 5b).

 Find the EMF in the rotor rod from the seventh harmonic field (Fig. 5, c).

Электромагнитный момент от седьмой гармоники поля будет составлять 34,6% = (0,587² • 100%) от случая, если бы сдвиг отсутствовал, т.е. β_m = 0. Если выполнить значение β_m = 180/7 геометрических градусов, то можно уничтожить электромагнитный паразитный момент от седьмой гармоники поля.We get:

The electromagnetic moment from the seventh harmonic of the field will be 34.6% = (0.587 ² • 100%) from the case if there was no shift, i.e. β _m = 0. If the value β _m = 180/7 geometric degrees is fulfilled, then the electromagnetic spurious moment can be destroyed from the seventh harmonic of the field.

Thus, by shifting the stator packets A and B of the induction motor by an angle β _m , it is possible to reduce the amplitude of spurious moments in the resulting electromagnetic moment. Between packets A and B, a non-magnetic gasket of thickness l _δ is placed (Fig. 2) in order to reduce the scattering fluxes between packets A and B and increase the working flux, thereby the electromagnetic moment from the first harmonic, and, as a result, the device efficiency.

Literature
1. Sergeev P.S., Vinogradov N.V., Goryainov F.A. Design of electrical machines. - M.: Energy, 1969.

 2. Handbook of electric machines: In 2 t. T. 2, p. 74. Under the general ed. Kopylova I.P., Klokova V.K. - M .: Energoamtoizdat, 1989, 688, p., Ill.

Claims (1)

 The stator of a reversible multiphase asynchronous motor, the core of which consists of yoke and teeth with coils of the phases of the stator winding, each tooth has a body and a pole tip, all the teeth along the stator bore have equal geometric dimensions with a uniform gap between the tooth tip and the rotor iron, with the core along the axial length consists of at least two equal length packages, characterized in that non-magnetic gaskets are placed between the core packages, each phase coil covers one stator length the tooth of each package, while the geometric axis of symmetry of the body of the teeth of different packages covered by one coil are parallel to the axis of rotation of the engine and coincide, and relative to the bodies of the teeth, the tooth tips of different packages are shifted in opposite directions.

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