KR20080044706A - Interior permanent magnet motor for reducing cogging torque - Google Patents

Abstract

An interior permanent magnet motor for reducing cogging torque is provided to allow unnecessary cogging torque to be cut about half by forming an external cross-section of a rotor in a shape of wave. An interior permanent magnet motor(200) for reducing cogging torque includes a stator(210) and a rotor(220) inserted into the stator. The stator is an armature and the rotor is a permanent magnet. A plurality of plate permanent magnets(226) are buried in a plurality of burying grooves(225) formed at outside of a rotor yoke(224) along a circumferential direction with respect to a rotational axis(221). An external cross-section of the rotor is formed in a shape of wave having a plurality of ridges.

Description

Interior permanent magnet motor for reducing cogging torque

1 is a cross-sectional view of a conventional embedded permanent magnet electric motor.

2 is a quarter cross-sectional view of the embedded permanent magnet motor according to the preferred embodiment of the present invention.

3 is an outer sectional view of a quarter rotor showing an example in which a motor having a rotor structure according to the present invention is actually designed.

4 and 5 show torque test results of a conventional motor having a uniform pore structure and a motor proposed according to the present invention having a nonuniform pore structure.

<Description of Major Symbols in Drawing>

110, 210: Stator

113, 213: slot

114, 214: stator tooth

117, 217: voids

210, 220: rotor

121, 221: rotation axis

125, 225: Insertion groove

126, 226: permanent magnet

222 goals

223 mountains

The present invention relates to a motor, and more particularly, to a permanent magnet motor capable of selectively reducing unnecessary cogging torque components without degrading the basic performance such as efficiency, torque, speed of the permanent magnet motor.

Recently, due to the advanced and multifunctional motor specifications, the permanent magnet motor with excellent efficiency and easy control is widely used in home and industrial applications.

Such permanent magnet motors can be broadly classified into surface-mounted permanent magnet motors in which magnets are attached to the rotor surface, and embedded permanent magnet motors in which magnets are embedded in the rotor iron core.

1 is a cross-sectional view of a conventional embedded permanent magnet electric motor 100.

As shown in FIG. 1, the conventional embedded permanent magnet electric motor 100 includes a stator 110 and a rotor 120 inserted into the stator 110, wherein the stator 110 is an armature. The rotor 120 is composed of permanent magnets, respectively. The rotor 120 has a structure in which a plurality of plate-shaped permanent magnets 126 are embedded in a plurality of buried grooves 125 formed along the circumferential direction on the outside of the rotor yoke 124 with respect to the rotation shaft 121. In addition, the rotor yoke 124 may be formed by punching and forming an iron-based yoke material (a silicon steel sheet and a thin iron sheet) using a press.

The stator 110 includes a plurality of stator teeth 114 in which coils are wound, and a plurality of slots 113, which are spaces for the coil windings, surround the rotor 120 to form radial rays. It is composed.

In the conventional embedded permanent magnet electric motor 100 configured as described above, an air gap 117 is formed between the stator 110 and the rotor 120 inserted into the stator 110 and rotating along the rotation shaft 121. do. At this time, due to the characteristic of the structure of the stator 110 having a radial structure, the difference in the magnetic resistance occurs in the air gap 117, thereby causing the motor 110 to inevitably generate cogging torque.

There have been studies to reduce the unnecessary cogging torque generated by such permanent magnet motors. Existing studies are mainly limited to surface-attached permanent magnet motors. I was hugging. For example, representative examples of the basic methods are as follows.

First, a method of adjusting the dimensions and shape of the permanent magnet 126 used in the rotor 120, which is the magnetization direction is changed when the permanent magnet 126 is magnetized and the amount of magnet used is reduced, resulting in a decrease in motor performance do.

Second, a method of reducing the difference in magnetoresistance in the air gap 117 by having the stator tooth 114 inclined with respect to the radial direction, which has various problems in winding the stator coils using an automatic winding machine. .

Third, there has been an attempt to reduce cogging torque through voltage / current control in the motor control circuit unit, but this has a problem in that a control circuit and a control algorithm need to be additionally developed.

The present invention has been made to solve the above problems, to provide a permanent magnet motor that can selectively reduce unnecessary cogging torque components without degrading the basic performance, such as efficiency, torque, speed of the permanent magnet motor For the purpose of

In order to achieve the above object, the electric motor according to the present invention is characterized in that in the electric motor having a stator and a rotor inserted into the stator, the outer circumferential cross section of the rotor is a wave form having a peak and a valley.

In addition, a plurality of recessed grooves are formed in the rotor and a plurality of permanent magnets are inserted into the recessed grooves.

In addition, the starting point and the end point of the outer diameter of the rotor is characterized in that it is located between the two grooves made by the embedding grooves on both sides and the outer rotor.

In addition, the number of valleys existing between the two bridges is the same as the number of stator teeth existing in the angle between the bridge, the number of mountains is characterized in that the number of the bones plus one is determined.

In addition, the depth of the peaks and valleys is characterized in that determined by the following equation (1), (2). That is, the radius of the location of the mountain = the existing rotor radius-within 15% of the void length ... (1), the radius of the location of the valley = the existing rotor radius-within the void length of 26% ... (2) Is preferably.

In addition, the peak and the valley is characterized in that to form the wave shape using a spline curve.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, and in the following description with reference to the accompanying drawings, the same or corresponding components are denoted by the same reference numerals, regardless of the reference numerals. Duplicate explanations will be omitted.

2 is a quarter cross-sectional view of the embedded permanent magnet motor according to the preferred embodiment of the present invention.

As shown in FIG. 2, the permanent magnet electric motor 200 according to the present invention includes a stator 210 and a rotor 220 inserted into the stator 210, wherein the stator 210 is an armature. The rotor 220 is composed of a permanent magnet, respectively. The rotor 220 has a structure in which a plurality of plate-shaped permanent magnets 226 are embedded in a plurality of buried grooves 225 formed along the circumferential direction on the outside of the rotor yoke 224 with respect to the rotation shaft 221. In addition, the rotor yoke 224 may be made by laminating the iron-based yoke material (silicon steel sheet and thin iron sheet) using a press and then laminating.

The stator 210 includes a plurality of stator teeth 214, in which coils are wound, and a plurality of slots 213, which are spaces in which the coils are formed, surrounding the rotor 220 to form radial rays. It is composed.

In addition, a gap 217 is formed between the stator 210 and the rotor 220 that is inserted into the stator 210 and rotates along the rotation shaft 221.

In particular, the present invention has a wave form 227 in which the outer circumferential cross section of the rotor 220 has a certain number of peaks 223 and valleys 222, as shown in FIG. 2. While the air gap 117 of the conventional permanent magnet motor 100 shown in FIG. 1 has a structure having an inner radius of the stator 110 and an outer radius 228 of the rotor 120, The outer radius 227 of the rotor 220, as shown in Figure 2, has a wave shape.

In addition, the position of the start point and the end point of the outer diameter of the rotor 220 is located between the two recesses 229 made by the outer grooves 225 and the rotor 220 on both sides in which the permanent magnet 226 is embedded. do. The two bridges 229 correspond to a 0 to 10 ° position section and an 80 to 90 ° position section in a counterclockwise direction in a cross section of the quarter rotor 220, and the starting point of the rotor 220 is a counter clock. The end point corresponds to the 80 ° position in the 10 ° direction. In addition, the bridge 229 is formed to block the path of the permanent magnet 226 inside the rotor yoke 224.

In addition, the number of valleys (concave portions of the curve) 222 existing between the two bridges 229 is equal to the number of stator teeth 214 existing between the bridges, and the mountain (convex portions of the curves) 223 is present. ) Is preferably determined by adding 1 to the number of the bones 222. This is the optimal number to prevent cogging torque from occurring as the rotor 220 rotates.

In addition, the depth of the peaks 223 and valleys 222 is related to the torque performance of the motor. When the peaks and valleys are smaller in depth, the cogging torque control performance is lowered. Since the torque performance of is lower, the following length equations (1) and (2) are each within a preferred range.

(1) Radius of where the mountain 223 is located = Conventional rotor radius 228-Air gap 217 within 15% of length

(2) Radius of where the valley 222 is located = Conventional rotor radius 228-Air gap 217 within 26% of length

In addition, the shape of the curve between the peak 223 and the valley 223 can be formed using a spline curve in computer graphics.

As described above, since the outer portion of the rotor 220 has a wave shape, as the rotor 220 rotates, the length of the air gap 217 also changes into a wave shape to have a nonuniform pore structure.

Therefore, the motor according to the present invention has a non-uniform void structure as the rotor 220 rotates, thereby alleviating the value of the magnetic resistance of the existing motor generated in the stator teeth 214 and the slot opening 215 By doing so, it is possible to effectively reduce the value of the cogging torque generated in the rotor 220 without deteriorating the general performance of the motor.

3 is an outer sectional view of a quarter rotor showing an example in which a motor having a rotor structure according to the present invention is actually designed.

In addition, Figure 3 is a comparison with the rotor outer 227 of the electric motor according to the present invention having a rotor outer 228, a mountain 223 and a valley 222 of the existing electric motor, the rotor according to the present invention The outside of the shape between the mountain 223 and the valleys 223 has a spline (spline) curved shape, as a whole has a wave shape.

The rotor structure according to the present invention described in Figures 2 and 3 are assembled using two wire-cutting machine, and inserted into the same stator of the existing motor, various performance tests were performed under the same conditions as the existing motor, The result is as follows.

4 and 5 show torque test results of a conventional motor having a uniform pore structure and a motor proposed according to the present invention having a nonuniform pore structure.

The proposed motor of the present invention has the depths of the peaks and valleys of the above formulas (1) and (2), respectively, (1) the radius of the position where the peak is located = the existing rotor radius-the void length is within 15%, (2) Radius of the location of the valley = existing rotor radius-formed within 26% of void length. In addition, the number of bones is equal to the number of stator teeth existing between the two bridges, and the number of hills is formed at the number of bones plus two.

The cogging torque waveform test results of the motor and the existing motor having such a rotor shape of the wave is as follows.

That is, as shown in FIG. 4, the test result shows that the cogging torque (peak voltage value 151 mV) generated in the proposed motor is reduced by 50% compared to the cogging torque (peak voltage 314 mV) generated in the existing motor. have.

5A and 5B are graphs showing the back EMF waveforms of the conventional motor and the proposed motor, respectively, and it can be seen that the back EMF waveforms generated by the two motors are almost unchanged.

Table 1 shows a comparison between the conventional motor and the proposed motor with respect to the basic performance of the motor with reference to the test results of FIGS. 4 and 5.

division efficiency Rated speed Rated torque Cogging Talk Conventional electric motor 80% 500 rpm 15 kgcm 0.3 kgcm Electric motor of the present invention 79.9% 499 rpm 14.98 kgcm 0.145 kgcm

As can be seen from Table 1, the proposed motor can reduce the unnecessary cogging torque by 50% while almost maintaining the basic performance (efficiency, rated speed, rated torque) of the basic motor.

In the above, the rotor structure of the embedded permanent magnet motor has been described, but the present invention is not limited thereto and may be applicable to various types of rotor structures of the motor.

Therefore, the present invention is not limited to the above-described embodiments, and a person having ordinary skill in the art may change the design or avoid the design without departing from the scope of the technical idea of the present invention. Will be in range.

As described above, the motor according to the present invention can selectively reduce unnecessary cogging torque components without degrading the basic performance such as efficiency, torque, speed of the permanent magnet motor.

Claims (6)

In a motor having a stator and a rotor inserted into the stator, An electric motor, characterized in that the outer circumferential cross section of the rotor has a wave shape having a peak and a valley. The method of claim 1, And a plurality of embedding grooves formed in the rotor, and a plurality of permanent magnets inserted into the embedding grooves. The method of claim 2, The start point and the end point of the 1/4 outer diameter of the rotor, characterized in that located between the buried grooves on both sides and the two bridges made by the outer rotor. The method of claim 3, The number of valleys existing between the two bridges is equal to the number of stator teeth existing in the angle between the bridges, the number of the mountain is characterized in that the number of the bones is determined by adding 1 to the number. The method of claim 1, The depth of the peaks and valleys is determined by the following equations (1) and (2). Radius of the location where the mountain is = existing rotor radius-within 15% of pore length ... (1) Radius of the location of the valley = existing rotor radius-void length less than 26% ... (2) The method of claim 1, The electric motor between the peak and the valley to form the wave shape using a spline curve.

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