ROTOR FOR MOTOR WITH WOUND ROTOR AND MOTOR WITH WOUND ROTOR INCLUDING THE SAME

Abstract

Rotor (3, 103) for a motor (1) with a wound rotor, which comprises: a rotor core (10) including a cavity (12) formed in a central region thereof and coupled to a shaft; a tooth portion (20) formed radially on an outer side surface of the rotor (3, 103); and a pole piece (30) formed to extend from an end portion of the tooth portion (20) in one direction and including a part of a cross section of an outer side surface formed in an arc shape of a first imaginary circle (C1) having a first radius (r1) which is a distance from a center point (CP1) of the cavity (12) to an outermost position (P1) thereof, wherein the tooth area (20) and the pole piece (30) contain n tooth areas (21 - 28) and n pole pieces (31 - 38), the n tooth regions (21 - 28) are arranged on an outer peripheral surface of the rotor core (10) in a circumferential direction so that they have a mutual distance of 360 / n degrees, and Winding areas (S) in which coils are wound are formed between the n tooth areas (21 - 28), wherein, when an outer side surface (39a, 139a) of each of the n pole pieces (31-38) extends from one end position (al, ar) to the other end position (al, ar) of the pole piece (30) at a first angle of rotation (θ1) in a direction in which the rotor (3, 103) rotates, the first angle of rotation (θ1) is in the range of 18° to 45°, wherein a part of a cross-section of the outer side surface (39a, 139a) of the pole piece (30) is formed in an arc shape of a second imaginary circle (C2) with a second center point (CP2) and a second radius (r2), the second imaginary circle (C2) internally touches the first imaginary circle (C1) at a first point of contact and the second center point (CP2) is away from a center point (CP1) of the first imaginary circle by a difference between the first radius (r1) and the second radius (r2), characterized in that at least a part of a cross-section of the outer side surface (39a, 139a) of the pole piece (30) is formed in an arc shape of a third imaginary circle (C3) with a third center point (CP3) and a third radius (r3), the third imaginary circle (C3) externally touches the second imaginary circle at a second point of contact and the third radius (r3) is in the range from 110% of the first radius (r1) to 125% of the first radius (r1).

Description

BACKGROUND 1. Field of the invention

[0001] The present invention relates to a rotor for a wound rotor motor and a wound rotor motor incorporating the same. 2. Discussion of the state of the art

[0002] Generally, vehicles include starter motors configured to start an engine and alternators configured to generate electricity using engine rotational power. When a driver starts a vehicle, an ignition switch is connected to a power source of a battery by a driver's operation. Driving force generated by an energized starter motor rotates an engine, and the vehicle is started.

[0003] For comparison, an alternator connected to a driving part of an engine charges a battery with alternating current (AC) power using a rectifier or the like, wherein the AC power is generated by a rotor rotating in a state in which a magnetic field is generated by a driving force of the engine.

[0004] Since such a starter motor and such an AC generator are each formed to have a structure including a stator and a rotor, their structures can be very similar to each other, and the structures can serve as a power generator or a motor depending on whether a force or energy is supplied thereto.

[0005] Recently, a belt-driven starter generator (hereinafter referred to as a BSG) capable of serving as a starter motor and an alternator with one structure is being actively studied.

[0006] The number of coil turns or current should be increased to increase a motor's torque. However, in the case of the BSG, since the space constraint is large when the number of coil turns is increased and the current is limited, there is a problem that the increase in motor torque is limited.

[0007] In addition, in the case of a rotor containing multiple fields, when an ideal curve such as a generally known inverse cosine is applied to the rotor, there is a problem that an air gap increases exponentially and the magnitude of a back electromotive force decreases.

[0008] Rotor for a motor with a wound rotor are disclosed, among others, in US 2016 / 0 149 445 A1, CN 2 03 850 937 U. Further, motors with permanent magnet rotors and wound stators are known from EP 2 621 064 A1, EP 2 800 243 A1 and US 2011 / 0 050 022 A1. SUMMARY OF THE INVENTION

[0009] The present invention is directed to a rotor for a motor with a wound rotor for improving a non-linear total harmonic distortion (THD), while maintaining a constant size of a counter electromotive force, as well as to a motor with a wound rotor containing this. This object is achieved by a rotor according to claim 1 or a rotor according to claim 4.

[0010] According to one aspect of the present invention, there is provided a rotor for a wound rotor motor, which specifically includes: a rotor core including a cavity formed in a central portion thereof and coupled to a shaft; a tooth portion formed radially on an outer surface of the rotor; and a pole piece formed to extend from an end portion of the tooth portion in one direction and including a part of a cross section of an outer surface formed in an arc shape of a first imaginary circle (C1) having a first radius (r1) that is a distance from a center point (CP1) of the cavity to an outermost position (P1) thereof.

[0011] The tooth portion and the pole piece include n tooth portions and n pole pieces, wherein the n tooth portions are arranged on an outer peripheral surface of the rotor core in a circumferential direction so as to have a mutual distance of 360 / n degrees, and winding portions in which coils are wound may be formed between the n tooth portions.

[0012] When an outer side surface of each of the n pole pieces extends from one end position to the other end position of the pole piece with a first angle of rotation in a direction in which the rotor rotates, the first angle of rotation is in the range of 18° to 45°.

[0013] A part of a cross-section of the outer side surface of the pole piece is formed in an arc shape of a second imaginary circle (C2) having a second center point (CP2) and a second radius (r2), the second imaginary circle internally touching the first imaginary circle at a first intersection point and the second center point (CP2) being at a distance from a center point (CP1) of the first imaginary circle corresponding to a difference between the first radius and the second radius.

[0014] The second radius (r2) can range from 60% of the first radius (r1) to 80% of the first radius (r1).

[0015] The second radius (r2) can range from 50% of the first radius (r1) to 70% of the first radius (r1).

[0016] At least a part of a cross-section of the outer side surface of the pole piece is formed in an arc shape of a third imaginary circle (C3) having a third center point (CP3) and a third radius (r3), and the third imaginary circle may externally touch the second imaginary circle at a second intersection point.

[0017] The third radius (r3) can range from 110% of the first radius (r1) to 125% of the first radius (r1).

[0018] At least a portion of a cross-section of an outer side surface of the pole piece may be formed in an arc shape of a third imaginary circle (C3) having a third center point (CP3) and a third radius (r3), and the third imaginary circle may internally touch the second imaginary circle at a second intersection point.

[0019] The third radius (r3) can be in the range from 10% of the first radius (r1) to 30% of the first radius (r1).

[0020] Each of the first rotation angle, a second rotation angle and a third rotation angle may be an angle at which a first imaginary line passing through the one end position of the pole piece and the center point (CP1) is inclined in a rotation direction of the rotor.

[0021] The second center point may be positioned on a second imaginary line that is a distance corresponding to the second rotation angle from the first imaginary line in the direction of rotation of the rotor and is configured to extend away from the first center point.

[0022] The third center point may be positioned on a third imaginary line having a distance corresponding to the third rotation angle from the first imaginary line in the rotation direction of the rotor and configured to extend from the first center point.

[0023] The second angle of rotation can be in the range from 10% of the first angle of rotation (θ1) to 20% of the first angle of rotation (θ1).

[0024] The second rotation angle can be in the range from 40% of the first rotation angle (θ1) to 50% of the first rotation angle (θ1).

[0025] The third rotation angle can be in the range from 80% of the first rotation angle (θ1) to 90% of the first rotation angle (θ1).

[0026] The third rotation angle can be in the range from 60% of the first rotation angle (θ1) to 70% of the first rotation angle (θ1).

[0027] A cross section from one end position of the pole piece to the first crossing point (m1) of the outer side surface of the pole piece may be formed in the arc shape of the first imaginary circle (C1), a cross section from the first crossing point (m1) to the second crossing point (m2) may be formed in the arc shape of the second imaginary circle (C2), and a cross section from the second crossing point (m2) to the other end position of the pole piece may be formed in the arc shape of the third imaginary circle (C3).

[0028] A cross section from one end position of the pole piece to an outermost position of the pole piece may be formed in the arc shape of the first imaginary circle (C1), a cross section from the outermost position of the pole piece to the second crossing point (m2) may be formed in the arc shape of the second imaginary circle (C2), and a cross section from the second crossing point (m2) to the other end position of the pole piece may be formed in the arc shape of the third imaginary circle (C3).

[0029] According to another aspect of the present invention, there is provided the above-described wound rotor motor, including a rotor for a wound rotor motor and a stator formed to cover an outer peripheral surface of the rotor and arranged to have a distance from the outer peripheral surface of the rotor. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and other objects, features and advantages of the present invention will become more apparent to those skilled in the art by describing in detail embodiments thereof with reference to the accompanying drawings in which: Fig. 1 is a plan view illustrating a wound rotor motor having a rotor for a wound rotor motor according to an embodiment of the present invention; Fig. 2 is a plan view illustrating the rotor for a wound rotor motor according to an embodiment of the present invention; Fig. 3 is an enlarged view showing a portion of Fig. 2 illustrated; Fig. 4 is a plan view illustrating a modified example of the rotor for a wound rotor motor according to an embodiment of the present invention; Fig. 5 is an enlarged view showing a portion of Fig. 4 illustrated; Fig. 6 is a graph showing the magnitude of a back electromotive force based on a rotor set ratio for a wound rotor motor according to an embodiment of the present invention; and Fig. 7 is a graph showing a total nonlinear distortion (THD) value based on the rotor set ratio for a wound rotor motor according to an embodiment of the present invention. DETAILED DESCRIPTION OF EMBODIMENTS

[0031] Hereinafter, embodiments that can be easily carried out by a person skilled in the art will be described in detail with reference to the accompanying drawings. The present invention can be implemented in a variety of different forms and is not limited to the embodiments described herein. Parts not relevant to the description are omitted from the drawings in order to clearly describe the embodiment of the present invention. The same or similar parts are designated by the same reference numerals throughout this description.

[0032] It should be noted that the terms "comprise," "having," "include," and / or "containing," when used herein, specify the presence of stated features, numbers, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, and / or groups thereof. Additionally, it should be noted that when a component, such as a layer, film, region, or plate, is referred to as being "on" another component, the component may be directly on the other component or intervening components may be present thereon.In contrast, it should also be noted that when a component such as a layer, film, region or plate is referred to as being “under” another component, the component may be directly under the other component or there may be intermediate components underneath.

[0033] Fig. 1 is a plan view illustrating a wound rotor motor having a rotor for a wound rotor motor according to an embodiment of the present invention.

[0034] According to Fig. 1, in one embodiment of the present invention, a wound rotor motor including a rotor 3 for a wound rotor motor, the rotor 3 for a wound rotor motor and a stator 5 may be used.

[0035] In one embodiment of the present invention, the rotor 3 may be located within the stator 5, and an inner side surface of the stator 5 may be arranged to be spaced apart from an outer peripheral surface of the rotor 3.

[0036] In addition, a plurality of slots may be formed in an inner peripheral surface of the stator 5. Here, stator coils may be wound in the plurality of slots (not shown), and when electric power is supplied to the stator 5, an armature current may flow through the stator coils wound in the slots, and the stator 5 may serve as an electromagnet, and thus an N-pole or S-pole may be formed.

[0037] According to Fig. 1, the rotor 3 according to an embodiment of the present invention may be arranged in the stator 5 so as to have a predetermined distance therefrom and to include a rotor core 10, tooth regions 20, field coils (not shown) and pole pieces 30.

[0038] In one embodiment of the present invention, the rotor core 10 may have a cylindrical shape and a central portion with a cavity 12 coupled to a shaft (not shown) so that the rotor is rotatable. Additionally, in one embodiment of the present invention, the tooth portions 20 may be formed in a bar shape on an outer peripheral surface of the rotor core 10 so as to protrude outward in a radial direction.

[0039] In one embodiment of the present invention, a plurality of tooth regions 20 may be formed. Here, as shown in Fig. 1, the plurality of tooth regions 20 may include eight tooth regions 20 such as the first to eighth tooth regions 21 to 28, but the plurality of tooth regions 20 are not limited thereto.

[0040] According to Fig. 1, in one embodiment of the present invention, the first to eighth tooth portions 21 to 28 may be arranged on the outer peripheral surface of the rotor core 10 so as to have a constant mutual distance.

[0041] Here, an output value of the rotor 3 can be adjusted by a field current generated when power is supplied to field coils (not shown) wound around the first to eighth tooth portions 21 to 28 and an armature current generated by the stator coil.

[0042] In one embodiment of the present invention, eight winding regions S in which the field coils can be wound around the tooth regions 20 may be formed between the first to eighth tooth regions 21 to 28. Here, the winding regions S may be spaces through which the tooth regions 20 are spaced apart from each other when the plurality of tooth regions 20 are arranged in a circumferential direction on the outer peripheral surface of the rotor core 10.

[0043] That is, according to Fig. 1, the eight winding regions S in which the field coils can be wound can be formed between the first tooth region 21 and the second tooth region 22, between the second tooth region 22 and the third tooth region 23, between the third tooth region 23 and the fourth tooth region 24, between the fourth tooth region 24 and the fifth tooth region 25, between the fifth tooth region 25 and the sixth tooth region 26, between the sixth tooth region 26 and the seventh tooth region 27, between the seventh tooth region 27 and the eighth tooth region 28 and between the eighth tooth region 28 and the first tooth region 21.

[0044] In one embodiment of the present invention, the pole pieces 30 may be formed at end portions of the tooth portions 20. Here, in one embodiment of the present invention, a plurality of pole pieces 30 may be formed at the plurality of tooth portions 20.

[0045] Additionally, in one embodiment of the present invention, the pole pieces 30 may have a curved shape, and both end portions of the pole pieces 30 may extend toward the outside of both side surfaces of the tooth portions 20. Here, the pole pieces 30 may be formed integrally with the tooth portions 20, but are not limited thereto.

[0046] In one embodiment of the present invention, the pole pieces 30 may have a structure capable of influencing output torque and torque ripple, that is, increasing torque while decreasing torque ripple by using a sine wave current distribution characteristic.

[0047] According to the Fig. 2 and Fig. 3, in one embodiment of the present invention, the pole pieces 30 may include pole piece outer surfaces 39a and pole piece inner surfaces 39b. Here, in one embodiment of the present invention, cross sections of pole piece outer surfaces 39a may have an arc shape and may be arranged to face and be spaced from the inner peripheral surface of the stator 5. Additionally, cross sections of the pole piece inner surfaces 39b may have a straight line shape and connect the tooth portions 20 and the pole piece outer surfaces 39a.

[0048] The plurality of tooth portions 20 may have the pole pieces including the same pole piece outer side surfaces 39a and the same pole piece inner side surfaces 39b, but are not limited thereto, and curvatures of the pole piece outer side surfaces may be different according to positions of the pole pieces in order to improve the sine wave current distribution characteristic.

[0049] According to Fig. 1, in one embodiment of the present invention, a pole piece 30 may form a first air gap G1 through an outermost position P1 of the pole piece and the inner side surface of the stator 5, which are spaced apart by a distance D. In addition, the pole piece 30 may form a second air gap G2 through both pole piece end positions al and ar and the inner side surface of the stator 5, which are spaced apart by a distance Q.

[0050] In one embodiment of the present invention, the first air gap G1 may be smaller than the second air gap G2. That is, in one embodiment of the present invention, a distance from the pole piece outer side surfaces 39a to the inner side surface of the stator 5 may be greater than the distance D and smaller than the distance Q.

[0051] In one embodiment of the present invention, the distance from the pole piece outer surface 39a to the inner surface of the stator 5 can vary according to the curvature of the pole piece outer surface. Accordingly, torque ripple can be reduced by adjusting the air gap, which is the distance from the pole piece outer surface 39a to the inner surface of the stator 5.

[0052] According to Fig. 1, in one embodiment of the present invention, the plurality of tooth portions 20 may be the first to eighth tooth portions 21 to 28, but are not limited thereto. However, in one embodiment of the present invention, eight tooth portions are described below to describe a configuration of an outer side surface of the pole piece.

[0053] In one embodiment of the present invention, the eight tooth portions 20 may include a first tooth portion 21, a second tooth portion 22, a third tooth portion 23, a fourth tooth portion 24, a fifth tooth portion 25, a sixth tooth portion 26, a seventh tooth portion 27, and an eighth tooth portion 28. Here, the eight tooth portions 20, which are the tooth portions 21 to 28, may be arranged to have a mutual distance of 45°, where 45° is calculated by dividing 360° by eight.

[0054] That is, in one embodiment of the present invention, n tooth regions 20 may be arranged to have a mutual spacing of 360 / n degrees.

[0055] In one embodiment of the present invention, winding regions may be formed in a space between a left end position al1 of a first pole piece and a right end position ar8 of an eighth pole piece and a space between a right end position ar1 of the first pole piece and a left end position al2 of a second pole piece.

[0056] The rotor 3 for a wound rotor motor according to an embodiment of the present invention can reduce a torque ripple while not increasing an overall size of the motor and not decreasing a torque by designing the pole piece outer surface 39a according to an embodiment of the present invention.

[0057] According to the Fig. 2 and Fig. 3, in one embodiment of the present invention, a vertical line y may be an imaginary extension line connecting a center point CP1 of the cavity 12 of the rotor core 10 and a center of the winding region S, and a horizontal line x may be an imaginary extension line formed perpendicular to the vertical line y and configured to pass through the center point CP1.

[0058] A first rotation angle θ1 can be a rotation angle from the left end position al1 of the first pole piece to the right end position ar1 of the first pole piece. That is, a first rotation angle θ1 can be an angle between the two end positions of the first pole piece and can be in the range of 18° to 45°.

[0059] Accordingly, when the first rotation angle θ1 is 45°, the left end position al1 of the first pole piece may be connected to the right end position ar8 of the eighth pole piece, and the right end position ar1 of the first pole piece may be connected to the left end position al2 of the second pole piece. That is, end portions of the first to eighth pole pieces 31 to 38 may be connected.

[0060] In addition, when the first rotation angle θ1 is 18°, the left end position al1 of the first pole piece may be arranged to be spaced from the right end position ar8 of the eighth pole piece, and the right end position ar1 of the first pole piece may be spaced from the left end position al2 of the second pole piece. That is, the end positions of the first to eighth pole pieces 31 to 38 may be spaced from each other.

[0061] According to the Fig. 2 and Fig. 3, in one embodiment of the present invention, a first imaginary circle C1 may be an imaginary circle having a first radius r1, which is a distance from the first center point CP1 to the outermost position P1 of the first pole piece.

[0062] In one embodiment of the present invention, a second rotation angle θ2 may be an angle by which the vertical line y is rotated in a rightward direction. Here, the second rotation angle θ2 may be in the range of 10% of the first rotation angle θ1 to 20% of the first rotation angle.

[0063] Additionally, a second imaginary line L2 may be an imaginary extension line rotated by the second rotation angle θ2 from the vertical line y around the first center point CP1 of the first imaginary circle C1. A second center point CP2 of a second imaginary circle C2 is located on the second imaginary line L2, and a second radius r2 may be in the range from 60% of the first radius r1 to 80% of the first radius r1.

[0064] The second imaginary circle C2 may internally touch the first imaginary circle C1 at a first intersection or contact point m1. The second radius r2 of the second imaginary circle C2, which is a distance from the first contact point m1 to the second center point CP2, may range from 60% of the first radius r1 to 80% of the first radius r1.

[0065] Additionally, a distance from the second center point CP2 of the second imaginary circle C2 to the first center point CP1 of the first imaginary circle C1 may be the same as a difference between the first radius r1 of the first imaginary circle and the second radius r2 of the second imaginary circle. The second center point CP2 of the second imaginary circle C2 may be positioned on the second imaginary line L2.

[0066] According to the Fig. 2 and Fig. 3, in one embodiment of the present invention, a third rotation angle θ3 may be an angle by which the vertical line y is rotated in the right direction. Here, the third rotation angle θ3 may be in the range of 80% of the first rotation angle θ1 to 90% of the first rotation angle θ1.

[0067] Additionally, a third imaginary line L3 may be an imaginary extension line rotated and extending from the vertical line y by the third rotation angle θ3 around the first center point CP1. A third center point CP3 of a third imaginary circle C3 may be positioned on the third imaginary line L3, and a third radius r3 may be in the range from 110% of the first radius r1 to 125% of the first radius r1.

[0068] The third imaginary circle C3 may externally touch the second imaginary circle C2 at a second contact point m2. Additionally, the third radius r3 of the third imaginary circle C3, which is a distance from the right end position ar1 of the first pole piece to the third center point CP3, may be in the range from 110% of the first radius r1 to 125% of the first radius r1.

[0069] A cross-sectional area from the left end position al1 of the first pole piece to the first contact point m1 of the outer side surface 39a of the first pole piece of the rotor 3 for a wound rotor motor according to an embodiment of the present invention may be formed along the first imaginary circle C1, a cross-sectional area from the first contact point m1 to the second contact point m2 thereof may be formed along the second imaginary circle C2, and a cross-sectional area from the second contact point m2 to the right end position ar1 of the first pole piece may be formed along the third imaginary circle C3.

[0070] In addition, in a first modified embodiment of a rotor 3 for a wound rotor motor according to an embodiment of the present invention, a cross-sectional area from a left end position al1 of the first pole piece to an outermost position P1 of the first pole piece of an outer side surface 39a of the first pole piece may be formed along a first imaginary circle C1, a cross-sectional area from the outer position P1 of the first pole piece to a second contact point m2 may be formed along a second imaginary circle C2, and a cross-sectional area from the second contact point m2 to a right end position ar2 of the first pole piece may be formed along a third imaginary circle C3.

[0071] According to the Fig. 4 and Fig. 5, in a modified embodiment of the present invention, a rotor 103 for a wound rotor motor can reduce torque ripple while not increasing an overall size of the motor and not decreasing torque by designing an outer side surface 139a of the first pole piece.

[0072] In one embodiment of the present invention, a fourth imaginary circle C4 may be an imaginary circle having a fourth radius r4, which is a distance from a fourth center point CP4 to the outermost position P1 of the first pole piece.

[0073] A fourth rotation angle θ4 can be a rotation angle from the left end position al1 of the first pole piece to the right end position ar1 of the first pole piece. That is, the fourth rotation angle θ4 can be an angle between the two end positions of the first pole piece and can be in the range of 18° to 45°.

[0074] Accordingly, when the fourth rotation angle θ4 is 45°, the left end position al1 of the first pole piece is connected to the right end position ar8 of the eighth pole piece, and the right end position ar1 of the first pole piece may be connected to the end position al2 of the second pole piece. That is, the end portions of the first to eighth pole pieces 31 to 38 may be connected.

[0075] In addition, when the fourth rotation angle θ4 is 18°, the left end position al1 of the first pole piece is arranged to be spaced from the right end position ar8 of the eighth pole piece, and the right end position ar1 of the first pole piece may be arranged to be spaced from the left end position al2 of the second pole piece. That is, the end portions of the first to eighth pole pieces 31 to 38 may be arranged to be spaced from each other.

[0076] In one embodiment of the present invention, a fifth rotation angle θ5 may be an angle by which the vertical line y is rotated in the right direction. The fifth rotation angle θ5 may be in the range of 40% of the fourth rotation angle θ4 to 50% of the fourth rotation angle θ4.

[0077] Additionally, a fourth imaginary line L4 may be an imaginary extension line that is rotated and extends around the fourth center point CP4 of the fourth imaginary circle C4 by the fifth rotation angle θ5 relative to the vertical line y. Here, a fifth center point CP5 of a fifth imaginary circle C5 may be positioned on a fifth imaginary line L5, and a fifth radius r5 may be in the range of 50% of the fourth radius r4 to 70% of the fourth radius r4.

[0078] The fifth imaginary circle C5 may internally touch the fourth imaginary circle C4 at a third contact point m3. Here, the fifth radius r5 of the fifth imaginary circle C5, which is a distance from the third contact point m3 to the fifth center point CP5, is 50% of the fourth radius r4 to 70% of the fourth radius r4.

[0079] Additionally, a distance from the fifth center point CP5 of the fifth imaginary circle C5 to the fourth center point CP4 of the fourth imaginary circle C4 may be equal to the difference between the fourth radius r4 of the fourth imaginary circle and the fifth radius r5 of the fifth imaginary circle. Here, the fifth center point CP5 of the fifth imaginary circle C5 may be positioned on the fifth imaginary line L5.

[0080] According to the Fig. 2 and Fig. 3, in one embodiment of the present invention, a sixth rotation angle θ6 may be an angle at which the vertical line y is rotated in the right direction. Here, the sixth rotation angle θ6 may be in the range of 60% of the fourth rotation angle θ4 to 70% of the fourth rotation angle θ4.

[0081] Additionally, a sixth imaginary line L6 may be an imaginary extension line rotated and extending by the sixth rotation angle θ6 around the fourth center point CP4 of the fourth imaginary circle C4 relative to the vertical line y. A sixth center point CP6 of the sixth imaginary circle C6 is positioned on the sixth imaginary line L6, and the sixth radius r6 may be in the range of 10% of the fourth radius r4 to 30% of the fourth radius r4.

[0082] The sixth imaginary circle C6 may internally touch the fifth imaginary circle C5 at a fourth contact point m4. Additionally, a sixth radius r6 of the sixth imaginary circle C6, which is a distance from the right end position ar1 of the first pole piece to the sixth center point CP6, may be in the range of 10% of the fourth radius r4 to 30% of the fourth radius r4.

[0083] A cross-sectional area from a left end position al1 of the first pole piece to the third contact point m3 of the outer side surface 139a of the first pole piece of the rotor 103 for a wound rotor motor according to an embodiment of the present invention may be formed along the fourth imaginary circle C4, a cross-sectional area from the third contact point m3 to the fourth contact point m4 thereof may be formed along the fifth imaginary circle C5, and a cross-sectional area from the fourth contact point m4 to the right end position ar1 of the first pole piece thereof may be formed along the sixth imaginary circle C6.

[0084] A cross-sectional area from the left end position al1 of the first pole piece to an outermost position p1 of the first pole piece of the outer side surface 139a of the first pole piece of the rotor 103 for a wound rotor motor according to an embodiment of the present invention may be formed along the fourth imaginary circle C4, a cross-sectional area from the outermost position P1 of the first pole piece to the fourth contact point m4 thereof may be formed along the fifth imaginary circle C5, and a cross-sectional area from the fourth contact point m4 to a right end position ar1 of the first pole piece thereof may be formed along the sixth imaginary circle C6.

[0085] In an embodiment of the present invention, since a gap between an end portion of the outer side surface 39a of the pole piece of the pole pieces 30 and the inner side surface of the stator 5 is not formed to be excessively wide, a torque ripple can decrease while preventing an increase in the size of the wound rotor motor 1.

[0086] Fig. 6 is a graph showing a magnitude of a counter electromotive force based on a set ratio of the rotor for a wound rotor motor according to an embodiment of the present invention, and Fig. 7 is a graph showing a total nonlinear distortion (THD) value based on the rotor set ratio for a wound rotor motor according to an embodiment of the present invention.

[0087] In one embodiment of the present invention, an analysis of how harmonic waves are mixed into a pure sine wave is referred to as a THD analysis. When a harmonic wave is mixed into a pure sine wave, a waveform may be distorted. When the pure sine wave is assumed to be a fundamental frequency, a distortion degree of a waveform can be seen by a quantity calculated by dividing a sum of harmonic waves by the fundamental frequency. That is, when a THD value decreases, a waveform is close to a sine wave, and thus, an output of a motor is improved.

[0088] According to the Fig. 6 and Fig.7, in an example of the present invention, in the case where the third imaginary circle C3 externally contacts the first imaginary circle C1, it is seen that a THD of the rotor 3 for a wound rotor motor is 2%, which is the smallest THD, while maintaining a back electromotive force thereof similar to that of a comparative example.

[0089] In an example of the present invention, in the case where the sixth imaginary circle C6 internally contacts the fourth imaginary circle C4, it can be seen that a THD of the rotor 103 for a wound rotor motor is in the range of 4 to 12%, which is lower than that of the comparative example, while maintaining a back electromotive force similar to that of the comparative example.

[0090] Accordingly, since a THD value of the rotor 3 or 103 for a wound rotor motor according to an embodiment of the present invention is low while a back electromotive force is kept constant, an output of a motor can be improved compared with that of the comparative example.

[0091] As described above, a rotor for a wound rotor motor and a wound rotor motor including the same according to an embodiment of the present invention can maintain the magnitude of a back electromotive force at a predetermined level or greater and reduce a THD by designing an external shape of a pole piece according to an embodiment of the present invention.

[0092] A rotor for a wound rotor motor and a wound rotor motor incorporating the same according to an embodiment of the present invention can prevent an increase in the overall size of a wound rotor motor while reducing a torque ripple and increasing a torque by designing an external shape of a pole piece according to an embodiment of the present invention.

[0093] While an embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiments described herein, and those skilled in the art can easily propose different embodiments by adding, modifying, removing and supplementing components and the like within the same intellectual field, and these also fall within the spirit of the present invention. [Reference numbers] 1 ENGINE 3, 103 ROTOR 5 STATOR 10 ROTOR CORE 12 CAVITY 20 dental areas 21 to 28 FIRST TO EIGHTH TOOTH AREAS 30 POLE SHOES 31 to 38 FIRST TO EIGHTH POLE SHOES 39a, 139a POLE SHOE OUTSIDE SURFACE 39b, 139b POLE SHOE INNER SIDE SURFACE

Claims

[1] Rotor (3, 103) for a motor (1) with a wound rotor, which comprises: a rotor core (10) including a cavity (12) formed in a central region thereof and coupled to a shaft; a tooth portion (20) formed radially on an outer side surface of the rotor (3, 103); and a pole piece (30) formed to extend from an end portion of the tooth portion (20) in one direction and including a part of a cross section of an outer side surface formed in an arc shape of a first imaginary circle (C1) having a first radius (r1) which is a distance from a center point (CP1) of the cavity (12) to an outermost position (P1) thereof, wherein the tooth area (20) and the pole piece (30) contain n tooth areas (21 - 28) and n pole pieces (31 - 38), the n tooth regions (21 - 28) are arranged on an outer peripheral surface of the rotor core (10) in a circumferential direction so that they have a mutual distance of 360 / n degrees, and Winding areas (S) in which coils are wound are formed between the n tooth areas (21 - 28), wherein, when an outer side surface (39a, 139a) of each of the n pole pieces (31-38) extends from one end position (al, ar) to the other end position (al, ar) of the pole piece (30) at a first angle of rotation (θ1) in a direction in which the rotor (3, 103) rotates, the first angle of rotation (θ1) is in the range of 18° to 45°, wherein a part of a cross-section of the outer side surface (39a, 139a) of the pole piece (30) is formed in an arc shape of a second imaginary circle (C2) with a second center point (CP2) and a second radius (r2), the second imaginary circle (C2) internally touches the first imaginary circle (C1) at a first point of contact and the second center point (CP2) is away from a center point (CP1) of the first imaginary circle by a difference between the first radius (r1) and the second radius (r2), characterized by that at least part of a cross-section of the outer side surface (39a, 139a) of the pole piece (30) is formed in an arc shape of a third imaginary circle (C3) with a third center point (CP3) and a third radius (r3), the third imaginary circle (C3) externally touches the second imaginary circle at a second point of contact and the third radius (r3) is in the range from 110% of the first radius (r1) to 125% of the first radius (r1). [2] Rotor (3, 103) for a motor (1) with a wound rotor according to claim 1, wherein the second radius (r2) is in the range of 60% of the first radius (r1) to 80% of the first radius (r1). [3] Rotor (3, 103) for a motor (1) with a wound rotor according to claim 1, wherein the second radius (r2) is in the range of 50% of the first radius (r1) to 70% of the first radius (r1). [4] Rotor (3, 103) for a motor (1) with a wound rotor, which comprises: a rotor core (10) including a cavity (12) formed in a central region thereof and coupled to a shaft; a tooth portion (20) formed radially on an outer side surface of the rotor (3, 103); and a pole piece (30) formed to extend from an end portion of the tooth portion (20) in one direction and including a part of a cross section of an outer side surface formed in an arc shape of a first imaginary circle (C4) having a first radius (r4) which is a distance from a center point (CP4) of the cavity (12) to an outermost position (P1) thereof, wherein the tooth area (20) and the pole piece (30) contain n tooth areas (21 - 28) and n pole pieces (31 - 38), the n tooth regions (21 - 28) are arranged on an outer peripheral surface of the rotor core (10) in a circumferential direction so that they have a mutual distance of 360 / n degrees, and Winding areas (S) in which coils are wound are formed between the n tooth areas (21 - 28), wherein, when an outer side surface (39a, 139a) of each of the n pole pieces (31-38) extends from one end position (al, ar) to the other end position (al, ar) of the pole piece (30) at a first angle of rotation (θ4) in a direction in which the rotor (3, 103) rotates, the first angle of rotation (θ4) is in the range of 18° to 45°, wherein a part of a cross-section of the outer side surface (39a, 139a) of the pole piece (30) is formed in an arc shape of a second imaginary circle (C5) with a second center point (CP5) and a second radius (r5), the second imaginary circle (C5) internally touches the first imaginary circle (C4) at a first point of contact and the second center point (CP5) is away from a center point (CP4) of the first imaginary circle by a difference between the first radius (r4) and the second radius (r5), characterized bythat at least part of a cross-section of the outer side surface (39a, 139a) of the pole piece (30) is formed in an arc shape of a third imaginary circle (C6) with a third center point (CP6) and a third radius (r6), the third imaginary circle (C6) internally touches the second imaginary circle (C4) at a second point of contact (m4) and the third radius (r6) is in the range from 10% of the first radius (r4) to 30% of the first radius (r4). [5] A rotor (3, 103) for a wound rotor motor (1) according to claim 1 or 4, wherein each of the first rotation angle (θ1, θ4), a second rotation angle (θ2, θ5), and a third rotation angle (θ3, θ6) is an angle at which a first imaginary line passing through the one end position (al, ar) of the pole piece (30) and the center point (CP1, CP4) is inclined in a rotation direction of the rotor, the second center point (CP2, CP5) being positioned on a second imaginary line (L2, L5) which is spaced by the second rotation angle (θ2, θ5) from the first imaginary line in the rotation direction of the rotor (3, 103) and configured to extend from the first center point (CP1, CP4). [6] A rotor (3, 103) for a wound rotor motor (1) according to claim 5, wherein the third center point (CP3, CP6) is positioned on a third imaginary line which is spaced apart by the third rotation angle (θ3, θ6) from the first imaginary line in the rotation direction of the rotor (3, 103) and is configured to extend from the first center point (CP1, CP4). [7] Rotor (3, 103) for a motor (1) with a wound rotor according to one of claims 5 or 6, wherein the second rotation angle (θ2, θ5) is in the range of 10% of the first rotation angle (θ1, θ4) to 20% of the first rotation angle (θ1, θ4). [8] Rotor (3, 103) for a motor (1) with a wound rotor according to one of claims 5 or 6, wherein the second rotation angle (θ2, θ5) is in the range of 40% of the first rotation angle (θ1, θ4) to 50% of the first rotation angle (θ1, θ4). [9] Rotor (3, 103) for a motor (1) with a wound rotor according to one of claims 5 to 8, wherein the third rotation angle (θ3, θ6) is in the range of 80% of the first rotation angle (θ1, θ4) to 90% of the first rotation angle (θ1, θ4). [10] Rotor (3, 103) for a motor (1) with a wound rotor according to one of claims 5 to 8, wherein the third rotation angle (θ3, θ6) is in the range of 60% of the first rotation angle (θ1, θ4) to 70% of the first rotation angle (θ1, θ4). [11] Rotor (3, 103) for a motor (1) with a wound rotor according to one of claims 6 to 10, in which: a cross section from the one end position (al, ar) of the pole piece (30) to the first contact point (m1, m3) of the outer side surface (39a, 139a) of the pole piece (30) is formed in the arc shape of the second imaginary circle (C2, C5); a cross section from the first contact point (m1, m3) to the second contact point (m2, m4) is formed in the arc shape of the first imaginary circle (C1, C4); and a cross section from the second contact point (m2, m4) to the other end position (al, ar) of the pole piece (30) is formed in the arc shape of the third imaginary circle (C3, C6). [12] Rotor (3, 103) for a motor (1) with a wound rotor according to one of claims 6 to 10, in which: a cross section from one end position (al, ar) of the pole piece (30) to an outermost position of the pole piece (30) is formed in the arc shape of the second imaginary circle (C2, C5); a cross-section from the outermost position of the pole piece to the second contact point (m2, m4) is formed in the arc shape of the first imaginary circle (C1, C4); and a cross section from the second contact point (m2, m4) to the other end position (al, ar) of the pole piece (30) is formed in the arc shape of the third imaginary circle (C3, C6). [13] Motor (1) with wound rotor, which comprises: the rotor (3, 103) for a motor (1) with a wound rotor according to one of claims 1 to 12; and a stator (5) formed to cover an outer peripheral surface of the rotor (3, 103) and arranged to be spaced apart from the outer peripheral surface of the rotor (3, 103).

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