BG112641A - A synchronous reactive induction motor - Google Patents

Abstract

The synchronous reactive induction motor with non-salient poles has is with rotor without winding and without compound from composition metal. The rotor is made of sheet soft-magnetic steel, as the rotor sheet has two or more slits, as well as the slit, that is closest to the opening for the shaft is of a special shape so that it is formed a large tooth with parallel walls. Between the other slits are arranged arched magneto-conductive bridges with parallel walls. By suitable ratio of the width of the magnetic-conductive bridges to the width of the slits, it is obtained a maximum difference in the magnetic conductivities on the magnetic axes, respectively maximum torque and useful power of the engine at the set dimensions and speed of rotation.

Description

TECHNICAL FIELD

The present invention relates generally to a synchronous reluctance induction motor (electric motor). More particularly, the invention relates to a synchronous reluctance induction motor with salient poles.

PRIOR ART

A synchronous reactive induction motor (electric motor) with a rotor is known, in which the maximum difference in magnetic conductivity along the two magnetic axes is ensured. This is achieved by using rotors with salient poles and aluminum alloy coating. This type of rotors is used in low-power motors and does not provide high energy efficiency of the motor.

A synchronous reactive induction motor (electric motor) is also known, including a stator with a winding, a control unit and a rotor with slots at each pole, with the rotor having implicitly expressed poles and an aluminum alloy coating. This type of electric motor spins like an asynchronous induction motor and then switches to synchronous mode after reaching synchronous speed. This starting design also requires the presence of windings and the use of aluminum, which does not significantly facilitate the production process in the manufacture of such motors. Similar designs are described in "Electrical Machines Part II", authors Prof. A. Angelov and Prof. D. Dimitrov, DI Tekhnika, Sofia, 1988. pp. 203-205.

The growing need to increase energy efficiency in use, combined with economic efficiency in the production of electric motors, is increasingly felt. This requires the development of new models of highly efficient and easily manufactured electric motors that can successfully and economically replace known solutions.

TECHNICAL ESSENCE

The present invention is a synchronous reactive induction motor with a rotor with implicitly expressed poles, the motor including a stator with a winding, a control unit and a rotor with slots at each pole, the rotor being without windings and without filling is a metal alloy, but the motor has an increased efficiency (EFI), which satisfies the above-mentioned needs. The rotor, the subject of the present invention, is made of sheet magnetic soft steel with a specified, optimized and precise cross-section. Magnetic-conductive bridges are formed between the slots. The increased efficiency is achieved by an optimal ratio of the total width of the magnetic-conductive bridges to the total width of the slots, as well as optimal ratios of the width of each magnetic-conductive bridge to the width of its corresponding adjacent slot.

This type of construction is very technological, fast and easy to manufacture and economically justified, as it does not require the use of a metal alloy for pouring, including the expensive equipment and electricity consumption accompanying pouring. This construction allows to achieve high energy efficiency. The level of energy efficiency is determined by the design of the rotor.

EXPLANATION OF THE APPENDIX FIGURES

Fig. 1 is a diagram of a rotor blade of a synchronous reactive induction motor with implicit poles and without metal alloy coating with parameters for clarification of the analytical justification.

Fig. 2 is a diagram of a rotor blade of a synchronous reactive induction motor with implicitly expressed poles and without metal alloy coating with the parametric values of the patent claims.

EXAMPLES OF IMPLEMENTATION

The invention is a synchronous reactive induction motor (electric motor) with implicitly expressed poles, with a rotor without windings and without pouring with a metal alloy. Fig. 1 shows a diagram of a rotor blade of such a synchronous reactive induction motor with implicitly expressed poles without pouring with a metal alloy. The most suitable is the design with a number of poles equal to 4, as shown in Fig. 1, and it is possible to use a design with a different number of poles. In practice, the number of poles is most often used from 2 to 8 (1 to 4 pairs of poles), but it is also possible to implement designs with a larger number of poles, which is known to the specialist in the field. The rotor blade has slots (channels) 10, 20, 30, 40 at each pole, with the slots 10, which are closest to the shaft hole, having a special shape. The slots 10 have an additional extension, which is illustrated by the radius R _x and thus between every two slots 10 a large magnetically conductive bridge-tooth with parallel walls is formed. Between the remaining adjacent slots 10, 20, 30, 40 arcuate magnetically conductive bridges are formed with parallel walls. In the center of the rotor sheet is the hole for the shaft with a keyway. The number of slots at each pole can be one or more. The rotor, in a preferred embodiment, is made of sheet magnetic soft steel. It is known to the person skilled in the art that for the manufacture of such a rotor it is possible to use other materials that have similar characteristics to magnetic soft steel.

The largest reactive moment, other things being equal, is obtained when assuming approximately equal width of the ferromagnetic and non-magnetic (air) sections along the q axis of the rotor. The most favorable in terms of implementation of the design is to work with a number of poles equal to 4. Since the motor is designed to work together with an inverter with a wide range of output frequency adjustment, this is not an obstacle to implementing a drive in a wide range of rotation speed. Based on the described considerations and taking into account the requirements for mechanical strength of the rotor, the rotor blade design shown in Fig. 1 is adopted. The rotor diameter D ₂ and the shaft diameter D _B are determined by the nominal values of the power and rotation speed of the motor. The determination of the dimensions of the rotor blade can be carried out on the basis of a sizing methodology, in which the angle CQ is determined so as to obtain an optimal ratio of the magnetic conductivities along the d and q axes, and the thickness of the slot b is determined from mechanical considerations so as to withstand the centrifugal forces of the rotor parts at maximum rotation speed. The radius of curvature R _x is determined by the requirement to reduce the concentration of mechanical stresses at the base of the large magnetically conductive bridge-tooth and the requirement to increase the magnetic resistance along the q axis of the rotor.

Below is a methodology for sizing (calculating and placing the slots) of the rotor blade:

₌ _α _ί _πθ ₂ ¹ 360 2 ^ms '

D ₂ Ro — b;

3πϋ ₂

D _B ^{R1 _} 2 ⁺ 360 4

D ₂ + D _B di

_R2 =AOi-y;

From the triangle ABO it follows:

π angleАОВ = ——«·,= 45 — cg;

AO — R _o ;

AB = R _o sin(45° - cg);

BO = R ₀ cos(45° — a _x );

From the triangle ABOi it follows:

Do 4 Dr

BOi = h _t - BO = - R ₀ cos(45° - a _t );

AO _t

AB ² + BO _X = r ₂ ^R 3 ^R s = ^R 7

RoSin ² (45°

RoSin ² (45° - a _x

D ₂ + D _B

D ₂ + D _{B 2} - R ₀ cos(45° ₂ - R ₀ cos(45° - aj rD ₂ + D _B

Rosin ² (45° - a ₂ ) + ₂ - R ₀ cos(45° a ₂ = 2(a _x + γ ₂ );

RoSin ² (45° - a ₃ ) +

Do + Dr

- R ₀ cos(45° - a ₃ ) + ^R 6 ^{— R} 5 dj;

Rosin ² (45° - a ₄ ) + i ²

- «1) ;

D ₂ + D _B ] ²

- R ₀ cos(45° - a ₄ ) + a ₄ = 4(a _x + y ₄ );

R ₈ — R7 d,;

D ₂ h ₂ - — + D _B ;

Where dj is the diameter of the rounding of the slots 10, 20, 30, 40, etc.;

(X] is the angle of distance of the center of the roundness of the slot 10 with diameter dj from axis d;

CL\ is the angle of separation of the center of the roundness of the slots 10, 20, 30, 40, etc. with diameter dj from axis d;

γ, (i > 2) is a correction angle for determining the value of 0C (at i > 1), the values of the correction angle depend on the type of motor, its purpose and the height of the axis of rotation, and vary from 1% to 80% of the value of the angle 0C;

D ₂ is the diameter of the rotor (rotor blade);

K _ms is a correction imperial coefficient taking into account the type of motor, its purpose and the height of the axis of rotation - (K _ms = 0.2 h- 2.8);

R _o is the radius of the circle on which the centers of rounding of the slots 10, 20, 30, 40 lie, the pitch circle;

Ri h- R ₈ are radii defining the arcs of the slots 10, 20, 30, 40;

b is the thickness of the slot closing the rotor surface;

D _B is the shaft diameter;

hi is the distance from the center O of the rotor blade with diameter D ₂ to the point Οι, lying on the axis q, which is the center of concentric circles defining the configuration of the slots (10, 20, 30) with radii R ₂ + R^;

AOi is the distance from the center of curvature (with diameter dj) of slot 10 to point Οι;

Angle AOB is the angle between the axis q and the line OA, with point A being the center of curvature (e.g. diameter dj) of slot 10, and point B being the perpendicular projection of point A onto the axis q;

AO = Ro is the radius of the circle on which the centers of roundness of the slots 10, 20, 30,40 lie, the size of which is determined by the requirement for mechanical strength of the section connecting two adjacent conductive bridges, which has a thickness of b = Da/2 - Ro - dj/2.

The triangles ABO and ΑΒΟΙ are auxiliary constructions used to derive the relationships between the dimensions of the rotor slots. The sides of these triangles are determined by the expressions:

AB is determined by the trigonometric function R _o sin(45° — y);

BO is determined by the trigonometric function R ₀ cos(45° — α^); BOi=hi-BO.

112 is the distance from the center of the rotor O to the center of concentric circles defining the configuration of the slot 40 with radii R? + Rs, lying on the axis q of the rotor. As a rule, 112 > hi, which causes an uneven thickness of the magnetic-conductive bridge between radii Re and R? and is favorable for improving the characteristics of the rotor;

In the considered methodology, all parameters and quantities are clearly recognizable in Fig. 1, with only the empirical coefficient K _ms being determined depending on the type of motor, its purpose and the height of the axis of rotation. The values of K _ms vary from 0.2 to 2.8.

The values of the correction angle γΐ (here specifically i > 2) also depend on the type of engine, its purpose and the height of the axis of rotation. The values vary from 1% to 80% of the value of the angle Ψ.

Based on the considered methodology for sizing the rotor blade of a synchronous reactive induction motor (electric motor) with a rotor with implicitly expressed poles, an embodiment has been developed with a ratio of the sizes of the slots and teeth, determined by obtaining the maximum difference in the magnetic conductivities along the d and q axes, respectively the maximum torque and useful power of the motor at given dimensions and rotation speed. A reactive rotor for a three-phase asynchronous motor has been sized using the described methodology. After replacing the asynchronous rotor with the reactive one, a study of the magnitude of the static torque of the motor has been carried out. The obtained results show that the maximum static torque of the reactive motor under equal conditions (nominal stator current) is equal to the nominal torque of the asynchronous motor. Considering that the synchronous reactive induction motor normally operates when powered by an inverter with vector control, in nominal mode the synchronous reactive induction motor has the same power as the asynchronous one, but since there are no losses in the rotor, it has a higher efficiency.

The engine subject to the above-described study has the following data:

U = 380/220 V, Υ/Δ; I = 0.87/1.51 A Y/Δ; P = 250 W; coscp = 0.68; η = 1370 min' ¹ , M=1.74Nm.

Basic rotor data:

Rotor diameter D2 = 65 mm;

Rotor shaft diameter Db = 16 mm;

Number of poles 2p = 4;

Nominal frequency f _H = 50 Hz.

Measured maximum static torque 1.76Nm.

Fig. 2 shows a diagram of a rotor blade of a synchronous reactive induction motor with implicitly expressed poles without metal alloy coating with the parametric values of the patent claims.

The rotor 100 is made of sheet magnetic soft steel with a cross-section as shown in Fig. 2. The most suitable design is with a number of poles equal to 4, and it is possible to use another number of poles. In the center of the rotor sheet is the hole 200 for a shaft with a keyway. The rotor sheet has slots 10, 20, 30 and 40 at each pole with a width of 2n, 2G2, respectively.

2Г3, 2Г4, where Π, Г2, Г3, Г4 are the radii of rounding of the slots 10, 20, 30 and 40. The slots 10, which are closest to the shaft hole 200, are 2Г1 wide and have a special shape. They have an additional extension, which is illustrated by the radius R _x , so that between every two slots 10 a large magnetically conductive bridge-tooth with parallel walls with a bridge width Λ1 is formed. Between the remaining adjacent slots 10, 20, 30, 40 arc-shaped magnetically conductive bridges with parallel walls and bridge widths Λ2, Λ3 and Λ4, respectively, are formed. The number of slots at each pole can be one or more. The rotor, in a preferred embodiment, is made of sheet magnetic soft steel. It is known to the person skilled in the art that it is possible to use other materials that have similar characteristics, such as magnetic soft steel, to make such a rotor.

The subject of the present invention is a synchronous reactive induction motor including a stator with a winding, a control unit and a rotor with implicitly expressed poles, the rotor being assembled from sheets of magnetic soft steel or a material with similar characteristics, and having slots according to Fig. 2, described in the previous paragraph, characterized in that the ratio of the total width of the magnetic-conducting bridges fli + di + Lz + ... + tti to the total width of the slots 2G1 + 2G2 + 2Gz + . .. +2P (i is the number of slots) is in the range from 0.8 to 1.4, and the ratio of the width of each of the magnetic-conducting bridges to the width of its corresponding adjacent slot d\ / 2η (ί>1 according to the number of slots) is in the range from 0.8 to 2.5.

In a preferred embodiment, the optimal ratio of the total width of the magnetic-conductive bridges di + di + az + ... + di to the total width of the slots 2Γι + 2Γr + 2Γz + ... +2Γΐ (i is the number of slots) is 1.

In another preferred embodiment, the ratio of the width of the magnetically conductive bridge-tooth di to the width of its corresponding adjacent slot 2G1 is in the range from 1.8 to 2.5, and the ratio of the width of each of the arcuate magnetically conductive bridges to the width of its corresponding adjacent slot Ui / 2l*i (i>2 according to the number of slots) is in the range from 0.8 to 1.4. The advantage of the proposed rotor design is obtaining a maximum difference in magnetic conductivity along the two magnetic axes d and q, which ensures high energy efficiency with the indicated simplicity of the design and high manufacturability of the rotor.

In one embodiment, the rotor has a cylindrical surface. In another embodiment, the rotor shape has a conical surface.

It is obvious to those skilled in the art that embodiments are possible in which the slots are modified compared to the preferred embodiment shown in Fig. 1 and Fig. 2, but the rotor structure would still have the desired characteristics. For example, the slots could be either concentrically or non-concentrically (but symmetrically) arranged, could have the same (in mm) or different widths along their length, and the profile of the slots could be formed by parts of a circle (Fig. 1 and Fig. 2), or by parts of other geometric shapes or an arbitrary broken line.

ANNEX

With the described rotor design, it is possible to replace the rotor of an asynchronous motor (rotor with aluminum or copper winding) with a reactive rotor without a winding and obtain a higher efficiency while maintaining the rated power. The advantages of the electric drive with a synchronous reactive induction motor (SRIM) over an electric drive with the same functional capabilities implemented with an asynchronous induction motor (AD) arise mainly from the operating principle and design of the SRIM.

In the asynchronous motor there are electrical losses in the stator (P _e l1 ⁼ ^L ² G1) ^and rotor (P _e l.2 = ^v) windings, while in the SRIM the electrical losses in the stator winding (P<^\=mli g,) are the same, but due to the absence of a current-carrying loop (rotor winding) in the rotor, including an excitation winding in the rotor, the losses there are absent (P _el .2 = 0). The reduction in energy losses for this reason can reach up to 40% in powerful machines compared to those in AD, and this in turn leads to:

- improving the technical and economic indicators of SRIM (compared to AD) in its production;

- increase in efficiency of SRIM compared to the same capacity AD;

- reduction of the time required to purchase the drive based on the saved electricity.

It is known that losses in the rotor winding are difficult to “remove”, this is done mostly through the stator of the traditional asynchronous machine and therefore, they “contribute” to the heating of the stator winding. This leads to a limitation of its permissible current loads. In SRIM they are absent, which leads to:

- thermal unloading of both the rotor and the stator;

- current load on the stator winding;

- the unloading of the stator in terms of heat (and hence in terms of current) leads to the possibility, if necessary, to obtain greater power than the corresponding gauge;

- the unloading of the stator in terms of heat (and hence in terms of current) leads to the possibility, if necessary, to reduce the size for the respective power;

- reducing the size leads to a reduction in total weight, and hence to optimizing material costs and reducing the cost of production.

The absence of a serious heat source in the rotor makes it possible to:

- optimization of bearing assemblies and selection of bearings;

- operation of the bearings in optimal temperature conditions;

- prolonging the trouble-free operation of the bearings;

- reduction of bearing noise.

The “Stator with winding” assembly of SRIM is identical to that of the widely used alternating current machines, and its rotor contains only punched (or cut by any of the known methods - laser, gas flame, etc.) sheets of electrical steel (without winding), which is a prerequisite for;

- optimization of the technological process in terms of energy consumption by eliminating the “Rotor filling” operation;

- optimization of the production process in terms of time as a whole;

- reduction of production costs (lack of aluminum or metal alloy, expensive equipment for pouring rotors and last but not least, reduction of electricity consumption);

- the slots in the rotor reduce its weight and moment of inertia.

The use of an electronic control unit and the design solutions of SRIM allow for:

- working with the same prototype at all standard and non-standard speeds with optimal efficiency;

- ability to maintain maximum torque (M _max ) when operating at different rotation speeds;

- possibility of operating with optimal power (Р _οπτ ) at different operating rotation speeds - operation in "Electricity saving"mode;

- possibility of implementing a "soft start";

- possibility of stable operation with continuous speed changes without increasing heating.

Experiments have been conducted to prove the possibility of replacing the rotor with a rotor winding with a reactive rotor. The success of the experiments is a real prerequisite for implementing future optimizations in existing old drives and increasing their electrical efficiency.

Claims (5)

1 / Synchronous reactive induction motor including: stator with winding; control unit; and a rotor (100), the rotor (100) comprising at least one slot (10, 20, 30, 40) at each pole, characterized in that the slots (10) which are closest to the opening (200) for the rotor shafts (100) have an additional expansion, so that between them is formed a magnetically conductive bridge-tooth with parallel walls with a width of the bridge (6C), and between the other slots are formed arcuate magnetically conductive bridges with parallel walls and the ratio of the total width of the magnetically conductive bridges (6Ζ ι + / ¾ ⁺ ^ 3 ^{+ +} ^ i) ^{to the} total width of the slots (2D] + 2D ₂ + 2D ₃ +... + 2η) is in the range from 0.8 to 1 , 4, and the ratio of the width of each magnetically conductive bridge to the width of its respective adjacent slot (<2j / 2C) is in the range from 0.8 to 2.5. Synchronous reactive induction motor according to claim 1, characterized in that the ratio of the total width of the magnetically conductive bridges (i / j + D ₂ + ίΖ ₃ + ... + Af) to the total width of the slots (2D ₃ + 2d ₂ + 2D ₃ +... + 2D,) is 1. Synchronous reactive induction motor according to Claim 1 or 2, characterized in that the ratio of the width of the magnetically conductive bridge-tooth (<? 1) to the width of its respective adjacent slot (2C) is in the range from 1.8 to 2 , 5, and the ratio of the width of each of the arcuate magnetically conductive bridges to the width of its respective adjacent slot (bZC / 2η, i> 2) is in the range from 0.8 to 1.4. Synchronous reactive induction motor according to any one of the preceding claims, characterized in that the rotor is made of sheet magnetic soft steel. Synchronous reactive induction motor according to any one of the preceding claims, characterized in that the rotor has a cylindrical or conical surface.