Multi-phase ac electric motor for driving an electric vehicle

Abstract

The invention is directed toward expanding the available assortment of AC electric motors for driving electric vehicles. The technical result is a reduction in the size and weight parameters of an AC electric motor. The essential features of the invention are an electric motor stator, a stator winding, a synchronous or asynchronous rotor, a rotor shaft, and an electric motor housing. The desired technical result is achieved in that the stator winding of the electric motor is comprised of separate single-section phase coils, each of which occupies two grooves of the stator with a span equal to one pole pitch. The phase coils, arranged with an offset of 120 degrees, form three-phase groups, the phases of which are offset at an angle equal to the angle between adjacent stator grooves. The total number of phases is a multiple of three (6, 9, 12, 15, etc.).

Description

[0001] Multiphase alternating current electric motor for driving electric vehicles

[0002] Description of the invention.

[0003] The field of technology to which the invention relates.

[0004] The invention relates to electrical engineering, in particular to AC electric motors used in electric drives with semiconductor voltage converters.

[0005] State of the art.

[0006] A well-known device for a similar purpose is a two-phase asynchronous electric motor, which has a stator with a phase and starting winding positioned 90 degrees apart. The design of such asynchronous electric motors is described in [1]. Two-phase asynchronous electric motors have inferior characteristics compared to three-phase motors and are used in low-power drives due to their ability to be connected to a single-phase network. The starting winding is connected via a phase-shifting capacitor.

[0007] The closest analogue of the claimed invention is a three-phase electric motor of an asynchronous or synchronous type, which is currently the most widely used. A three-phase electric motor has a stator with three phase windings, arranged with a 120-degree shift and connected in a star or delta configuration. The design of such asynchronous and synchronous electric motors is described in [2]. An important requirement for the design of the windings of any three-phase electric motor is the formation of a rotating sinusoidal magnetic field in the stator. A non-sinusoidal magnetic field contains harmonics that do not produce useful work and cause additional energy losses in the electric motor. The third harmonic, which has a significant amplitude and creates a rotating magnetic field of negative sequence, has the greatest influence.This leads to the creation of a reverse torque, which causes a decrease in the electric motor power and additional heating of the electric motor. To reduce higher harmonics in the form of a magnetic field, a two-layer winding with a shortened pitch is used [3]. In this case, the phase windings are designed in such a way that parts of the windings of adjacent phases are located in the same slot. This makes it possible to reduce the value of the third harmonic and almost completely eliminate the fifth harmonic. The disadvantage of such a combination of parts of the windings of different phases in one slot is the presence of useless energy expenditure when currents of different phases flow in opposite directions at certain points in time, as shown in Fig. 1. The presented diagram of phase currents IA, IB, IC shows the time sections when the currents in the parts of the windings located in the same slot flow in opposite directions and compensate each other (shaded areas).However, ohmic losses from current flow in these sections of the windings exist, but no useful work is performed. Maximum compensation of opposing currents occurs at 1 m. Another significant drawback of a two-layer winding with a shortened pitch is the need to increase the number of turns in the slot and, consequently, reduce the wire cross-section, which leads to a reduction in electric motor power. Due to additional losses due to counter-currents in the combined sections of the windings, as well as the increased number of turns in the slot, the electric motor has increased dimensions and weight. This drawback is particularly noticeable when using the electric motor to drive electric vehicles, where weight and size are crucial. Summary of the invention.

[0008] The objective of the claimed invention is to expand the range of AC electric motors for driving electric vehicles.

[0009] The AC electric motor is the most important component of an electric vehicle, requiring high demands for efficiency and reduced weight and dimensions. The motor is powered by a voltage converter, enabling operation in various dynamic modes at varying speeds.

[0010] The technical result of the claimed invention is a reduction in the weight and size of an AC electric motor.

[0011] The essential features of the claimed invention are: an electric motor stator, a stator winding, a synchronous or asynchronous rotor, a rotor shaft, and an electric motor housing.

[0012] A significant distinguishing feature of the claimed invention, which enables the technical result to be achieved, is that the stator winding of the electric motor is made up of separate single-section phase coils, each of which occupies two stator slots with a diametrical pitch equal to one pole division. The phase coils, arranged with a 120-degree shift, form three-phase groups. Thus, the stator winding of the electric motor consists of several three-phase groups, the phases of which are shifted by an angle equal to the angle between adjacent stator slots. The number of stator winding phases is determined by the number of slots and the number of pole pairs. The total number of phases is a multiple of three (6, 9, 12, 15, etc.). To obtain a stator magnetic field shape close to sinusoidal, the number of phases must be at least nine. The electric motor is powered by a multiphase voltage converter with an appropriate number of phases. A large number of phases ensures a sinusoidal shape of the generated magnetic field.Each stator winding section, which is a separate phase, is individually powered from the corresponding phase of the voltage converter. This eliminates the drawbacks of short-pitch double-layer windings and single-layer windings. Furthermore, the individual power supply to each stator winding section compensates for the nonlinearity of the magnetic induction curve at values ​​close to saturation, which also ensures a sinusoidal magnetic field at maximum magnetic induction values.

[0013] The listed set of features ensures the achievement of the specified technical result.

[0014] A comparative analysis with the prior art shows that the claimed device is distinguished by the presence of new elements and their relationships with other elements. Therefore, the invention is novel. A comparison of the claimed solution with other technical solutions in related fields of technology allows us to conclude that they lack the essential distinguishing features of the claimed invention.

[0015] List of drawing figures and other materials.

[0016] Fig. 1 shows a diagram of a three-phase current, which shows the currents in the combined parts of the three-phase windings, which have opposite directions and compensate each other.

[0017] Fig. 2 shows the arrangement of windings of a nine-phase electric motor with the number of pole pairs p=1.

[0018] Fig. 3 shows a vector diagram of phase voltages for a nine-phase electric motor.

[0019] Fig. 4 shows a vector diagram of phase voltages for a twelve-phase electric motor.

[0020] Information confirming the possibility of implementing the invention.

[0021] The winding arrangement diagram of a nine-phase electric motor with the number of pole pairs q= l is shown in Fig. 2. The diagram shows: stator 10, slots for stator windings 11, winding of the first phase of the first three-phase group 1, winding of the second phase of the first three-phase group 2, winding of the third phase of the first three-phase group 3, winding of the first phase of the second three-phase group 4, winding of the second phase of the second three-phase group 5, winding of the third phase of the second three-phase group 6, winding of the first phase of the third three-phase group 7, winding of the second phase of the third three-phase group 8, winding of the third phase of the third three-phase group 9.

[0022] The number of stator slots z=l 8. The phase windings of the three-phase groups have a phase shift of 120 degrees between them and are connected in a star or a delta. The phase shift between the first phases of the three-phase groups for a nine-phase electric motor is 20 degrees. The vector diagram of phase voltages for a nine-phase electric motor is shown in Fig. 3. The diagram shows: the voltage vector of the first phase of the first three-phase group 1, the voltage vector of the second phase of the first three-phase group 2, the voltage vector of the third phase of the first three-phase group 3, the voltage vector of the first phase of the second three-phase group 4, the voltage vector of the second phase of the second three-phase group 5, the voltage vector of the third phase of the second three-phase group 6, the voltage vector of the first phase of the third three-phase group 7, the voltage vector of the second phase of the third three-phase group 8, the voltage vector of the third phase of the third three-phase group 9.

[0023] In a twelve-phase electric motor with one pole pair, the number of stator slots is z = 24. The phase shift between the first phases of the three-phase groups for a twelve-phase electric motor is 15 degrees. The phase voltage vector diagram for a twelve-phase electric motor is shown in Fig. 4.The diagram shows: the voltage vector of the first phase of the first three-phase group 1, the voltage vector of the second phase of the first three-phase group 2, the voltage vector of the third phase of the first three-phase group 3, the voltage vector of the first phase of the second three-phase group 4, the voltage vector of the second phase of the second three-phase group 5, the voltage vector of the third phase of the second three-phase group 6, the voltage vector of the first phase of the third three-phase group 7, the voltage vector of the second phase of the third three-phase group 8, the voltage vector of the third phase of the third three-phase group 9, the voltage vector of the first phase of the fourth three-phase group 10, the voltage vector of the second phase of the fourth three-phase group 11, the voltage vector of the third phase of the fourth three-phase group 12.

[0024] As the number of pole pairs increases, the number of stator slots increases proportionally. Phase windings can be either wave or loop windings.

[0025] The device operates as follows. When the phase windings are connected to a multiphase voltage converter with the appropriate number of phases and phase shift, a rotating sinusoidal magnetic field is generated. The rotating magnetic field of the stator interacts with the magnetic field of the rotor, causing the rotor to rotate. The electric motor rotor can be synchronous or asynchronous.

[0026] Bibliographic data.

[0027] 1. Aminova A.O., Vasiliev V.F., Korolev V.I. Asynchronous capacitor motors: a tutorial / VShTE SPbGUPTD. - St. Petersburg, 2018. Part 1.- 24 p., p.4. 2. Bespalov V. Ya. Electric machines: a tutorial, a manual for students of higher educational institutions / V. Ya. Bespalov, N.F. Kotelenets, - Moscow: Publishing Center "Academy", 2006, p. 85, p. 173.

[0028] 3. Kopylov I.P. Design of electrical machines: textbook for universities / edited by I. P. Kopylov. - 4th ed., corrected. and additional - M.: Vysshaya shkola, 2005, p. 118.

Claims

Invention formula. A multiphase alternating current electric motor for driving electric transport, comprising a stator of the electric motor, a stator winding, a rotor of a synchronous or asynchronous type, a rotor shaft, a housing of the electric motor, characterized in that the stator winding of the electric motor is made of separate single-section phase coils, each of which occupies two slots of the stator with a diametrical pitch per pole division, wherein the phase coils, located with a shift of 120 degrees, form three-phase groups in such a way that the stator winding of the electric motor consists of several three-phase groups, the phases of which are shifted by an angle equal to the angle between adjacent slots of the stator, wherein the number of slots of the stator is determined by the number of phases of the stator winding and the number of pairs of poles, while the total number of phases is a multiple of three. SUBSTITUTE SHEET (RULE 26)

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