3-phase induction motor

Abstract

To provide a three-phase induction motor capable of realizing a low-speed region requiring large torque in six-pole operation and realizing a high-speed region requiring a high rotational number by two-pole operation.SOLUTION: In a three-phase induction motor 10, a three-phase coil includes: a first coil unit 20f and a second coil unit 20s that are arranged so as to be symmetric at 180 degrees. Each of the coil units 20f and 20s includes: a first coil 22; and a second coil 24. The first coil 22 is constructed so that winding is wound by one round within a range of 180 degrees at an electric angle at the time of two-pole operation. The second coil 24 is constructed so that the winding is wound so that a current flows to an inverse direction of the first coil 22 by two rounds within a range of 1 / 3 of a middle when dividing the first coil 22 into three parts equally, in a peripheral direction. By conducting power to both of the first coil 22 and the second coil 24, it is operated by a six-pole, and is operated by the two-pole by conducting the power only to the first coil 22.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This specification discloses a three-phase induction motor in which three-phase coils are wound in a plurality of slots provided in the inner periphery of a stator core. [Background technology]

[0002] In machine tools that process press dies and resin molding dies, small-diameter ball end mills with tool diameters of a few millimeters or less are used to process curved surfaces during the finishing process of the dies. Because of their small diameters, high rotation speeds of tens of thousands of rpm or more are required to obtain appropriate peripheral speeds and to shorten processing times. To achieve such high rotation speeds, a built-in motor structure is used, in which the rotor of an electric motor is mounted directly on the spindle.

[0003] Furthermore, since the free-form surface of the mold is machined using small diameter tools, the motor must operate continuously for long periods of time, so heat generation from the motor's windings must be kept to a minimum. At high speeds in particular, heat generation from iron loss in the stator and heat generation from the spindle bearings inevitably increases, so heat generation from the motor's windings must be kept as low as possible. Furthermore, due to the characteristics of the built-in motor structure, if heat generation is high, the spindle's thermal displacement increases, deteriorating machining accuracy.

[0004] Meanwhile, holes must be drilled to secure the mold to the press or injection molding machine, and to perform high-precision press work or injection molding, it is desirable to drill these fixing holes on the same machine as the above-mentioned finish work. These holes are generally drilled using a drill of about a few tens of millimeters, which, unlike the above-mentioned finish work, requires high torque at low speeds. Figure 2 shows the spindle speed and torque required for mold machining. In other words, high torque is required in the low-speed range, while finish work requires a high-speed range with high rotation speeds.

[0005] Conventionally, a commonly used technique for expanding the low- and high-speed range is to use Y-Δ switching, which switches the windings of a three-phase induction motor between star and delta connections. However, with Y-Δ switching, the rotation speed ratio of the delta connection to the star connection is theoretically 1.73 times (√3 times), which means that a sufficient speed range cannot be ensured.

[0006] Another technology to expand the speed range is pole number switching. Generally, this involves switching between 2 and 4 poles, or 4 and 8 poles, but the rotation speed ratio is doubled, which is still not sufficient.

[0007] Patent Document 1 shows a technology that switches between two and six poles to achieve a three times rotation speed ratio. This technology has six dispersedly arranged winding coils per phase, and when used with two poles, the current direction in all six coils is the same, and when used with six poles, the current in four of the six coils is reversed.

[0008] Patent Document 2 shows a technology that switches between two and six poles to achieve a three times rotation speed ratio. This technology has six winding coils per phase, just like the above-mentioned 1980-22857, but differs in that it is configured with six coils arranged separately for each of the six poles. When used with six poles, the current direction in adjacent coils is opposite, and when used with two poles, the current direction in adjacent three of the six coils is the same.

[0009] Patent Document 3 discloses a technology that switches between two and eight poles to achieve a fourfold rotation speed ratio. Similar to Patent Document 1, this technology has six dispersedly arranged winding coils per phase, and when used with two poles, the current direction in all six coils is the same, while when used with six poles, the current in four of the six coils is opposite. The six coils are arranged in groups of three at two locations on the inner circumference of the motor stator, which is divided into four equal parts. By not placing any winding coils in the remaining two locations, the six coils form eight poles. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Jikko No. 55-22857 [Patent Document 2] Japanese Patent Application Publication No. 55-37877 [Patent Document 3] Japanese Patent Application Publication No. 57-43547 Summary of the Invention [Problem to be solved by the invention]

[0011] In the technology disclosed in Patent Document 1, the coils that make up the six poles are positioned apart from one another, so when used with six poles, there are many areas where no magnetomotive force is generated, and approximately 50% of the stator core is not used effectively, which poses the problem of not being able to output sufficient torque required in the low-speed range.

[0012] In the technology shown in Patent Document 2, even when used with two poles, current flows through all six coils, and four of the six coils do not generate magnetic flux even when current flows through them, meaning they generate heat unnecessarily. This causes the problem of a large temperature rise in the motor in the high-speed rotation range required for two poles.

[0013] In the technology shown in Patent Document 3, the six coils are arranged at a distance from each other, so when used with eight poles, there are many areas where no magnetomotive force is generated, and approximately 50% of the stator core is not used effectively, which poses the problem of not being able to output sufficient torque required in the low-speed range. [Means for solving the problem]

[0014] The three-phase induction motor disclosed in this specification is a three-phase induction motor in which three-phase coils are wound in a plurality of slots provided on the inner circumference of a stator core, and each of the three-phase coils has one or more unit pairs consisting of a first coil unit and a second coil unit, and the first coil unit and the second coil unit are arranged symmetrically at an electrical angle of 180 degrees when operating in 2×n poles, and each coil unit has a first coil and a second coil, and the first coil is configured by winding a wire m times within a range of an electrical angle of 180 degrees when operating in 2×n poles, and the second coil is configured by winding the wire 2×m times within a range of the middle third of the first coil when the first coil is divided into thirds in the circumferential direction, so that current flows in the opposite direction to that of the first coil, and the motor operates with 6×n poles by passing current through both the first coil and the second coil, and operates with 2×n poles by passing current through only the first coil, and both m and n are natural numbers.

[0015] In this case, the first coil of the first coil unit and the first coil of the second coil unit are connected in series, and the second coil of the first coil unit and the second coil of the second coil unit are connected in series, and the first coil and the second coil do not have to be connected to each other.

[0016] The stator core has 36 of the slots, and the first coil of U phase includes a coil wound from the 1st slot to the 18th slot and a coil wound from the 36th slot to the 19th slot, the first coil of V phase includes a coil wound from the 22nd slot to the 6th slot and a coil wound from the 24th slot to the 36th slot via the 4th slot, the first coil of W phase includes a coil wound from the 15th slot to the 31st slot and a coil wound from the 13th slot to the 1st slot via the 33rd slot, and the second coil of U phase includes a coil wound from the 12th slot to the 7th slot and a coil wound from the 14th slot to the 5th slot. the V-phase second coil may include a coil wound from the 10th slot to the 17th slot, a coil wound from the 11th slot to the 16th slot, a coil wound from the 35th slot to the 28th slot, and a coil wound from the 34th slot to the 29th slot; and the W-phase second coil may include a coil wound from the 2nd slot to the 9th slot, a coil wound from the 3rd slot to the 8th slot, a coil wound from the 27th slot to the 20th slot, and a coil wound from the 26th slot to the 21st slot.

[0017] Another three-phase induction motor disclosed in this specification is a three-phase induction motor in which three-phase coils are wound in a plurality of slots provided on the inner periphery of a stator core, and each of the three-phase coils has one or more unit pairs each consisting of a first coil unit and a second coil unit, and the first coil unit and the second coil unit are arranged symmetrically at 180 degrees in electrical angle during 2×n pole operation, and each coil unit has a first coil and a second coil, and the first coil is a coil that is wound around a plurality of slots provided on the inner periphery of a stator core. The second coil is configured by winding the wire 2×m times in the central third of the range when the first coil is divided into thirds in the circumferential direction, so that current flows in the opposite direction to that of the first coil, and operates with 6×n poles by energizing both the first coil and all the second coils, and operates with 2×n poles by energizing only the first coil of the first coil unit, where m and n are both natural numbers.

[0018] In this case, the first coil of the first coil unit may be connected to neither the second coil nor the first coil of the second coil unit, and the second coil of the first coil unit, the second coil of the second coil unit, and the first coil of the second coil unit may be connected to each other.

[0019] The stator core has 36 of the slots, and the first coil of U phase includes a coil wound from the 1st slot to the 19th slot and a coil wound from the 36th slot to the 18th slot, the first coil of V phase includes a coil wound from the 6th slot to the 24th slot and a coil wound from the 4th slot via the 1st slot to the 22nd slot, the first coil of W phase includes a coil wound from the 13th slot to the 31st slot and a coil wound from the 15th slot to the 33rd slot, and the second coil of U phase includes a coil wound from the 12th slot to the 7th slot and a coil wound from the 14th slot to the 5th slot. the V-phase second coil may include a coil wound from the 17th slot to the 10th slot, a coil wound from the 16th slot to the 11th slot, a coil wound from the 28th slot to the 35th slot, and a coil wound from the 29th slot to the 34th slot; and the W-phase second coil may include a coil wound from the 27th slot to the 20th slot, a coil wound from the 26th slot to the 21st slot, a coil wound from the 2nd slot to the 9th slot, and a coil wound from the 3rd slot to the 8th slot. [Effects of the Invention]

[0020] According to the three-phase induction motor disclosed in this specification, when it is operated with 6xn poles, there are few parts of the stator that do not generate magnetomotive force, and the utilization rate of the iron core is high, so it is possible to increase the torque per motor volume and generate large torque.Furthermore, when it is operated with 2xn poles, there is no need for unnecessary current to generate a magnetic field, so heat generation is low and it is possible to suppress the temperature rise of the motor even at high speeds. [Brief explanation of the drawings]

[0021] [Figure 1]This is a cross-sectional view of a three-phase induction motor showing the windings for one phase, as well as the current direction and magnetic flux direction during two-pole operation and six-pole operation. [Figure 2] FIG. 1 is a diagram showing the rotation speed-torque characteristics of a machine tool spindle. [Figure 3] FIG. 1 is a diagram showing three phase windings in a cross section of a three-phase induction motor. [Figure 4] This is a winding diagram of a three-phase induction motor. [Figure 5] FIG. 5 is a diagram showing the magnetomotive force distribution on the inner circumference of the stator during two-pole operation when the winding diagram of FIG. 4 is used. [Figure 6] FIG. 5 is a diagram showing the magnetomotive force distribution on the inner circumference of the stator during six-pole operation when the winding diagram of FIG. 4 is used. [Figure 7] FIG. 10 is a winding diagram of another example of a three-phase induction motor. [Figure 8] FIG. 8 is a diagram showing the magnetomotive force distribution on the inner circumference of the stator during two-pole operation when the winding diagram of FIG. 7 is used. [Figure 9] FIG. 10 is a cross-sectional view of another example of a three-phase induction motor, showing one phase of windings, and the current direction and magnetic flux direction during four-pole operation and twelve-pole operation. DETAILED DESCRIPTION OF THE INVENTION

[0022] FIG. 1 shows the cross-sectional structure of a three-phase induction motor 10, the windings for one phase, and the operating principle. A stator 12 (stator core) has 36 slots 16, each of which accommodates a winding coil. FIG. 1 illustrates only one phase of the winding. Each phase coil includes a first coil unit 20f and a second coil unit 20s. The first coil unit 20f and the second coil unit 20s are arranged symmetrically across an electrical angle of 180 degrees during two-pole operation. Each of the coil units 20f and 20s includes a first coil 22 and a second coil 24. The first coil 22 is wound over a range of approximately 180 electrical degrees during two-pole operation. The second coil 24 is wound twice as many times as the first coil 22 in a range approximately one-third of the circumference of the first coil 22, so that current flows in the opposite direction to that of the first coil 22. Although the rotor 14 will not be described here, it is equipped with a typical cage-type induction winding.

[0023] Fig. 1(A) shows the operation during two-pole operation, where current is passed through only the first coil 22, resulting in the generation of two-pole magnetic flux as indicated by the thick arrows. Fig. 1(B) shows the operation during six-pole operation, where current is passed through both the first coil 22 and the second coil 24, resulting in the generation of six-pole magnetic flux as indicated by the thick arrows.

[0024] FIG. 3 illustrates the layout of each of the three-phase windings. FIG. 4 shows the connections of the three-phase windings and their insertion positions into the slots. U1 indicates the connection terminal of the U-phase first coil, V1 indicates the connection terminal of the V-phase first coil, and W1 indicates the connection terminal of the W-phase first coil. In the example shown in this figure, the first coils 22 of each phase are star-connected, with the other end of each coil connected to the neutral point. Note that although the example shown in this figure is star-connected, a delta connection can be achieved by pulling the other end of each coil externally and providing a connection terminal. U2 and U3 are connection terminals of the U-phase second coil, V2 and V3 are connection terminals of the V-phase second coil, and W2 and W3 are connection terminals of the W-phase second coil.

[0025] 4, the U-phase first coil 22 includes a coil wound in the first slot through the eighteenth slot and a coil wound in the thirty-sixth slot through the nineteenth slot, these two coils being connected in series. The U-phase second coil 24 includes a coil wound in the twelfth slot through the seventh slot, a coil wound in the fourteenth slot through the fifth slot, a coil wound in the twenty-third slot through the thirty-second slot, and a coil wound in the twenty-fifth slot through the thirty-first slot, these four coils being connected in series.

[0026] The V-phase first coil 22 includes a coil wound from the 22nd slot to the 6th slot and a coil wound from the 24th slot to the 36th slot and then to the 4th slot, these two coils being connected in series. The V-phase second coil 24 includes a coil wound from the 10th slot to the 17th slot, a coil wound from the 11th slot to the 16th slot, a coil wound from the 35th slot to the 28th slot, and a coil wound from the 34th slot to the 29th slot, these four coils being connected in series.

[0027] The W-phase first coil 22 includes a coil wound from the 15th slot to the 31st slot and a coil wound from the 13th slot via the 1st slot to the 33rd slot, these two coils being connected in series. The W-phase second coil 24 includes a coil wound from the 2nd slot to the 9th slot, a coil wound from the 3rd slot to the 8th slot, a coil wound from the 27th slot to the 20th slot, and a coil wound from the 26th slot to the 21st slot, these four coils being connected in series.

[0028] Figure 5 shows the magnetomotive force distribution when three-phase induction motor 10 employing the winding diagram of Figure 4 is operated with two poles, with the horizontal axis representing the electrical angle and the vertical axis representing the magnetomotive force. Figure 6 shows the magnetomotive force distribution when three-phase induction motor 10 employing the winding diagram of Figure 4 is operated with six poles.

[0029] FIG. 7 is a diagram showing another example of a three-phase induction motor 10. When using two poles with the winding connections shown in FIG. 4, the three-phase phase difference of the magnetomotive force has an error with respect to an electrical angle of 120 degrees. Therefore, in the three-phase induction motor 10 shown in FIG. 7, the first coil 22 of the first coil unit 20f is not connected to the first coil 22 of the second coil unit 20s but is independent. More specifically, the first coil 22 of the U-phase first coil unit 20f has a coil wound in slots 1 through 19. This coil is not connected to other coils belonging to the same phase. The first coil 22 of the U-phase second coil unit 20s has a coil wound in slots 36 through 18. This coil is connected in series with the U-phase second coil 24. The U-phase second coil 24 includes a coil wound from the 12th slot to the 7th slot, a coil wound from the 14th slot to the 5th slot, a coil wound from the 23rd slot to the 32nd slot, and a coil wound from the 25th slot to the 30th slot, and these four coils are connected in series.

[0030] The first coil 22 of the V-phase first coil unit 20f has a coil wound in the sixth slot through the twenty-fourth slot. This coil is not connected to other coils belonging to the same phase. The first coil 22 of the V-phase second coil unit 20s includes a coil wound from the fourth slot through the first slot to the twenty-second slot. This coil is connected in series with the V-phase second coil 24. The V-phase second coil 24 includes a coil wound in the seventeenth slot through the tenth slot, a coil wound in the sixteenth slot through the eleventh slot, a coil wound in the twenty-eighth slot through the thirty-fifth slot, and a coil wound in the twenty-ninth slot through the thirty-fourth slot, and these four coils are connected in series.

[0031] The first coil 22 of the W-phase first coil unit 20f includes a coil wound in the 13th slot through the 31st slot. This coil is not connected to other coils belonging to the same phase. The first coil 22 of the W-phase second coil unit 20s includes a coil wound in the 15th slot through the 33rd slot. This coil is connected in series with the W-phase second coil 24. The W-phase second coil 24 includes a coil wound in the 27th slot through the 20th slot, a coil wound in the 26th slot through the 21st slot, a coil wound in the 2nd slot through the 9th slot, and a coil wound in the 3rd slot through the 8th slot, and these four coils are connected in series.

[0032] When used in a two-pole configuration, current is only applied to the first coil 22 of the first coil unit 20f. The first coil 22 of the second coil unit 20s is connected in series with the second coil 24 and is applied when used in a six-pole configuration. In this case, the amount of winding is halved compared to when used in a two-pole configuration, which creates the issue of insufficient torque output when used in a two-pole configuration. However, because two-pole configurations require stable control at high speeds, accurate three-phase phase difference is a major advantage.

[0033] Fig. 8 shows the magnetomotive force distribution when three-phase induction motor 10 employing the winding diagram of Fig. 7 is operated with two poles. As is clear from a comparison of Fig. 5 and Fig. 8, the winding diagram of Fig. 7 makes it possible to bring the three-phase phase difference in the magnetomotive force distribution closer to 120 degrees.

[0034] FIG. 9 shows the cross-sectional structure of a half-circle and the winding arrangement for one phase of another three-phase induction motor 10. The three-phase induction motor 10 of FIG. 9 is switchable between four poles and twelve poles. In this case, 72 slots 16 are provided in the stator 12, and the winding arrangement of the first through 36th slots is the same as that of the three-phase induction motor 10 shown in FIG. 1, which switches between two and six poles. The 37th through 72nd slots (not shown) have a symmetrical structure and arrangement to the first through 36th slots. The winding arrangement shown in FIG. 9 shows the U-phase winding. For the V- and W-phases (not shown), the winding arrangement for the 36 slots of the V- and W-phases shown in FIG. 3 is expanded to two circumferential windings, resulting in 72 slots. In other words, in the three-phase induction motor 10 of FIG. 9, each phase coil has two unit pairs, each consisting of a first coil unit 20f and a second coil unit 20s.

[0035] Furthermore, the above description is merely an example, and each phase coil may have three or more pairs of units each consisting of a first coil unit 20f and a second coil unit 20s. Furthermore, up until now, the number of turns of the second coil 24 in one coil unit has not been particularly limited, as long as it is twice the number of turns of the first coil 22. [Explanation of symbols]

[0036] 10 three-phase induction motor, 12 stator, 14 rotor, 16 slot, 20f first coil unit, 20s second coil unit, 22 first coil, 24 second coil.

Claims

1. A three-phase induction motor in which three-phase coils are wound in a plurality of slots provided on the inner periphery of a stator core, Each of the three-phase coils has one or more unit pairs each composed of a first coil unit and a second coil unit, the first coil unit and the second coil unit are arranged symmetrically at 180 degrees in electrical angle during 2×n-pole operation, Each coil unit has a first coil and a second coil, The first coil is configured by winding a wire m times over a range of 180 electrical degrees during 2×n-pole operation, The second coil is configured by winding the wire 2×m times in a central third of the range when the first coil is divided into three equal parts in the circumferential direction, so that a current flows in the opposite direction to that of the first coil, By energizing both the first coil and the second coil, it operates with 6×n poles, and by energizing only the first coil, it operates with 2×n poles; Both m and n are natural numbers, the first coil of the first coil unit and the first coil of the second coil unit are connected in series, the second coil of the first coil unit and the second coil of the second coil unit are connected in series, The first coil and the second coil are not connected to each other. A three-phase induction motor.

2. 2. The three-phase induction motor according to claim 1, The stator core has 36 of the slots, the first coil of U-phase includes a coil wound in the 1st slot to the 18th slot and a coil wound in the 36th slot to the 19th slot, the first coil of V-phase includes a coil wound from the 22nd slot to the 6th slot and a coil wound from the 24th slot to the 36th slot via the 4th slot, the first coil of the W phase includes a coil wound from the 15th slot to the 31st slot, and a coil wound from the 13th slot via the first slot to the 33rd slot, the second coil of U-phase includes a coil wound in the twelfth slot to the seventh slot, a coil wound in the fourteenth slot to the fifth slot, a coil wound in the twenty-third slot to the thirty-second slot, and a coil wound in the twenty-fifth slot to the thirty-first slot, the second coil of V-phase includes a coil wound in the 10th slot to the 17th slot, a coil wound in the 11th slot to the 16th slot, a coil wound in the 35th slot to the 28th slot, and a coil wound in the 34th slot to the 29th slot, The second coil of the W phase includes a coil wound from the second slot to the ninth slot, a coil wound from the third slot to the eighth slot, a coil wound from the twenty-seventh slot to the twentieth slot, and a coil wound from the twenty-sixth slot to the twenty-first slot. A three-phase induction motor.

3. A three-phase induction motor in which three-phase coils are wound in a plurality of slots provided on the inner periphery of a stator core, Each of the three-phase coils has one or more unit pairs each composed of a first coil unit and a second coil unit, the first coil unit and the second coil unit are arranged symmetrically at 180 degrees in electrical angle during 2×n-pole operation, Each coil unit has a first coil and a second coil, The first coil is configured by winding a wire m times over a range of 180 electrical degrees during 2×n-pole operation, The second coil is configured by winding the wire 2×m times in a central third of the range when the first coil is divided into three equal parts in the circumferential direction, so that a current flows in the opposite direction to that of the first coil, By energizing both all of the first coils and the second coils, it operates with 6×n poles, and by energizing only the first coil of the first coil unit, it operates with 2×n poles; Both m and n are natural numbers, the first coil of the first coil unit is not connected to either the second coil or the first coil of the second coil unit; the second coil of the first coil unit, the second coil of the second coil unit, and the first coil of the second coil unit are connected to each other; A three-phase induction motor.

4. 4. The three-phase induction motor according to claim 3, The stator core has 36 of the slots, the first coil of U phase includes a coil wound in the 1st slot to the 19th slot and a coil wound in the 36th slot to the 18th slot, the first coil of V-phase includes a coil wound from the sixth slot to the twenty-fourth slot, and a coil wound from the fourth slot to the twenty-second slot via the first slot, the first coil of the W phase includes a coil wound in the thirteenth slot to the thirty-first slot and a coil wound in the fifteenth slot to the thirty-third slot, the second coil of U-phase includes a coil wound in the twelfth slot to the seventh slot, a coil wound in the fourteenth slot to the fifth slot, a coil wound in the twenty-third slot to the thirty-second slot, and a coil wound in the twenty-fifth slot to the thirty-first slot, the second coil of V-phase includes a coil wound from the 17th slot to the 10th slot, a coil wound from the 16th slot to the 11th slot, a coil wound from the 28th slot to the 35th slot, and a coil wound from the 29th slot to the 34th slot, The second coil of W phase includes a coil wound from the 27th slot to the 20th slot, a coil wound from the 26th slot to the 21st slot, a coil wound from the 2nd slot to the 9th slot, and a coil wound from the 3rd slot to the 8th slot. A three-phase induction motor.

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