JP4056514B2 - Permanent magnet type three-phase rotating electric machine - Google Patents

Description

  The present invention relates to a rotary electric machine such as a brushless DC motor or a stepping motor with low vibration and low noise.

1) Brushless motors for three-phase permanent magnet type rotating electrical machines are widely used in office automation equipment, but if the cogging torque, which is the torque generated only by the permanent magnet when no current is passed through the coil, is large, vibration and noise will increase. In addition, there is a problem that iron loss becomes large.
2) For example, as a conventional technique, the stator is driven with 8 slots or 16 poles with 6 slots (same motor for 6 salient poles) and the rotor with 4 poles or 12 slots (12 salient poles). .
3) For applications that require even lower vibrations, 10 or 14 pole products with 12 slots (12 salient poles) are used.

Japanese Patent Publication No.49-8568

1) In the above-mentioned prior art disclosed in Japanese Patent Publication No. 49-8568, the demand for low vibration and low noise is not always satisfactory.
2) For applications requiring high torque and low vibration, increasing the torque tended to increase vibration noise.

"Means 1"
When 12 salient poles are sequentially numbered from an arbitrary salient pole 1 with a stator made of a magnetic body in which 12 salient poles are equally provided from a substantially annular body, the salient poles 1, 2, 7 and 8 form a one-phase winding, and the direct current excitation current causes the salient pole 1 and the adjacent salient pole 2 to have the same polarity, and the salient pole 7 and the adjacent salient pole 8 correspond to the salient pole 1 and the salient pole 2. Are magnetized in different polarities, and the second phase winding is similarly provided on the salient poles 3, 4, 9, 10 and the remaining salient poles 5, 6, 11, 12 are provided with the third phase winding. A three-phase machine with a star connection in which the winding end of each phase is short-circuited, or a delta connection in which the winding end and the winding start of the next phase are sequentially coupled, and the N poles via the tips of the 12 salient poles and the air gap A cylindrical permanent magnet rotor in which S poles are alternately magnetized to a total of 2p poles, and an internal or external rotation type rotating electrical machine that is rotatably opposed to any stator protrusion And when the rotor poles are opposed, that P is 11 in a rotary electric machine which satisfies the following equation.
"Means 2"
Each of the six salient poles is further provided with two inductors, each of which has two inductors, and each of the six stators has an arbitrary shape. When numbering the six salient poles sequentially from the salient pole 1, the salient poles 1 and 4 constitute a one-phase winding, and the salient pole 1 and the salient pole 4 are magnetized to different polarities by the DC excitation current. A star connection in which the second phase winding is similarly connected to salient poles 3 and 5 and the remaining salient poles 3 and 6 are similarly provided with third phase windings, and the winding ends of each phase are short-circuited. Alternatively, it is a delta connection in which the winding end and the winding start of the next phase are sequentially coupled, and the N pole and S pole are alternately magnetized to a total of 2p poles via the inductor and air gap at the tip of the 6 salient poles. An internal or external rotating electrical machine that is rotatably opposed to the cylindrical permanent magnet rotor, and that satisfies the following formula when any inductor and rotor pole face each other An electric machine in which P is 11 .
"Means 3"
In the case where 9 salient poles are numbered sequentially from any salient pole 1 with a stator made of a magnetic material in which 9 salient poles are equally provided in an abundant form from a substantially annular body, salient poles 1, 4, 7 and 1 constitute a one-phase winding, and the direct current excitation current causes the salient pole 1 and the salient poles 4 and 7 to be wound with different polarities, and the second phase winding is similarly salient pole 2. , And salient poles 5 and 8 are different from each other, and the third phase winding is a three-phase machine provided so that the remaining salient poles 3 and salient poles 6 and 9 are different from each other. , A star connection in which the winding end of each phase is short-circuited, or a delta connection in which the winding end and the winding start of the next phase are sequentially coupled, and the N pole and the S pole are connected via the tips of the nine salient poles and the air gap. A cylindrical permanent magnet rotor that is alternately magnetized to a total of 2p poles and an internal or external rotary electric machine that is rotatably opposed to each other. When, what P is 11 in the rotary electric machine characterized by satisfying the following two expressions Equation.
"Means 4"
In the case where 9 salient poles are numbered sequentially from any salient pole 1 with a stator made of a magnetic material in which 9 salient poles are equally provided in an abundant form from a substantially annular body, salient poles 1, 5, 6 constitutes a one-phase winding, and DC exciting current is wound so that salient poles 1, 5 and 6 have the same polarity, and the second phase winding is similarly salient poles 7, 2 and 3 The three-phase machine has all the same polarity, and the third phase winding is the same salient polarity with the remaining salient poles 4, 8, and 9. A shorted star connection or a delta connection in which the end of winding and the beginning of the next phase are sequentially coupled, and the N and S poles are alternately magnetized to a total of 2p poles via the tip of the nine salient poles and the air gap. An inner or outer rotary electric machine that is rotatably opposed to the cylindrical permanent magnet rotor, and an arbitrary inductor and rotor pole face each other. Those p is 7 in a rotary electric machine characterized by satisfying the following two expressions.
"Means 5"
Cylindrical permanent magnet in which N poles and S poles are alternately magnetized to a total of 2p poles by means of means 1 to 4 through a stator having a unipolar winding with two windings of the salient poles and an air gap. A three-phase rotary electric machine that is driven by a unipolar winding with a current that is 180 degrees out of phase with an inner or outer rotary electric machine that is rotatably opposed to a magnet rotor.

"Means 6"
The rotating electric machine according to any one of means 1 to 4, wherein the rotor has a back yoke made of a magnetic material on the side opposite to the air gap of the cylindrical permanent magnet of the rotor.

The present invention is realized by the following means.
1) It is known to use a permanent magnet for the rotor to make a high-efficiency motor. However, the cogging torque in the non-energized state is determined by the total number of poles of the N and S poles of the permanent magnet and the number of stator slots (the same number as the number of stator poles or salient poles around which the coil is wound). Since the cogging torque is superimposed on the torque generated by the rotating magnetic field, torque fluctuation occurs, causing various problems for applications that require precise constant speed rotation. An effective means for reducing the cogging torque is to increase the number of pulsations of the cogging torque during one rotation of the rotor as much as possible. Then, since the torque waveform is almost a sine wave, the amplitude can be reduced accordingly.
2) The present invention provides a configuration in which the sixth-order harmonic component of the cogging torque is eliminated to obtain a twelfth-order harmonic or an eighteenth-order harmonic component, thereby increasing the number of cogging torque pulsations.
3) The means can be realized by combining the number of stator salient poles described above and the number of rotor poles satisfying the above-described formula, and specifically, the means 1 to 6 described above.

In the configuration as described above, the problem can be solved for the following reason.
Three-phase permanent magnet motors have low vibration and low rotation unevenness because the cogging torque is generally composed of a fourth-order harmonic component compared to a two-phase machine. This is because the fourth harmonic component disappears and is composed of the sixth harmonic component. However, the cogging torque of the 6th-order component is not sufficient depending on the application, and there are many demands for a rotating electrical machine with a further low cogging torque in a three-phase machine. Therefore, the present invention eliminates the 6th-order component of the cogging torque to obtain a 12th-order or higher-order cogging torque component. Focusing on the fact that the cogging torque of a three-phase machine is composed of the sum of a sixth-order component and its positive multiple component, the key point of the present invention is to use this property. Concerning that it is composed of the sum of the 6th order component and its positive multiple, “PCIM2001, INTELLIGENT MOTION 38 ^th Proceeding, pp139-141, June 19-21,2001, Nurnberg, Germany, Cogging Torque Comarison between 2
and 3 phase HB type stepping motor. Masafumi Sakamoto. ”, description thereof is omitted. That is, the cogging torque is composed of the 12th order component or more if the 6th order component is successfully eliminated, and the 18th order component or more if the 6th and 12th order components are eliminated. In that case, the existing low-order component (12th or 18th order in the above) is the main dominant component. This is because the higher the order, the smaller the amplitude, and the lower the order becomes negligible.

1) Since the cogging torque in the 12-slot or 9-slot configuration of the present invention has a pulsation number several times that of conventional motors, an extremely small low cogging torque motor can be provided.
2) 6-slot inductors with lower vibration and higher torque.
3) Unipolar type capable of high-speed rotation.
4) In addition to closed-loop three-phase brushless DC motors, it can also be used for open-loop three-phase permanent magnet stepping motors.
5) It can be realized.
6) Since the outer diameter of the rotor can be increased by using the outer rotation type, the inertia can be increased, the rotation unevenness can be reduced in a constant speed application, or suitable for an application requiring a large torque at a low speed.

FIG. 1 shows an example of a rotating electrical machine according to the first aspect of the present invention. As shown in the figure, twelve salient poles 1-1 to 1-12, which are equally arranged in a divergent form from a single annular stator, have three-phase windings of U, V, and W phases. The winding ends of each phase are short-circuited and star-connected. Therefore, bipolar driving is performed with an inversion current by an inverter or the like shown in FIG. For example, in the U phase, if the salient poles 1-1 and 1-2 are N poles, 1-7 and 1-8, which are 180 degrees opposite to each other, are wound so that they are magnetized to S poles. . This winding method for creating a winding polarity with N, N, S, S is one of the features of the present invention. For this reason, the 22-pole rotor magnet 2 faces as shown in the figure, and the magnetic flux indicated by the dotted line and the arrow from the N-pole of the permanent magnet enters the S-pole stators 1-7 and 1-8. Returning from the N poles of 1-1 and 1-2 to the S pole of the rotor, a magnetic path is connected via the back yoke. For this reason, a back yoke is required. On the other hand, the rotating electric machine having the conventional structure connects the magnetic path by the N pole, the S pole and the stator salient pole adjacent to the rotor, so that the back yoke is not necessary.
FIG. 4 is a cross-sectional view including the shaft of the rotating electrical machine according to the present invention. 1 is a stator iron core, 2 is a rotor cylindrical permanent magnet, 3 is a coil, 4 is a back yoke provided on the side opposite to the air gap of the rotor cylindrical permanent magnet, and is made of a magnetic material. Reference numeral 6 denotes a rotating shaft, which is fixedly supported on the stator core 1 so as to be rotatable by a bearing (not shown). Reference numeral 2 denotes a cylindrical permanent magnet of the rotor. In general, a rotor of this type of structure is called a surface magnet type rotor.

Next, the prior art will be described. FIG. 8 shows the prior art. In the subsequent drawings, parts having the same name or similar shape have the same numbers. Reference numeral 1 denotes a stator in which twelve coil winding portions (referred to as main poles) forming a stator pole are arranged at an equal pitch. Since the number of rotor poles (referred to as magnetic poles) is eight, when the main pole at the upper center and the N pole of the rotor coincide, the adjacent main pole and the closest magnetic pole ( In the figure, if the deflection angle with the S pole is δ, similarly, the deflection angle between the next main pole and the next magnetic pole is 2δ, and then sequentially becomes 3δ, 4δ, 5δ, Since the same relationship is repeated with the magnetic pole, the sixth-order component of permeance of the main pole viewed from the magnetic pole is as follows. The fact that the permeance component coincides with the cogging torque component is, for example, the Journal of the Institute of Electrical Engineers of Japan, Vol. The description is omitted here.

δ = 4 × 2π {(1/8)-(1/12)} = π / 3
From (electrical angle), the following equation is calculated.

P ₆ = 2 {cos0 + cos6 × 1 (π / 3) + cos6 × 2 (π / 3) + cos6 × 3 (π / 3) + cos6 × 4 (π / 3) +

cos6 × 5 (π / 3)}

Here, p is the number of pole pairs, and since the number of pole poles is 8, p = 4, and Equation (4) is 12 instead of 0. Since the angle of the cosine in [] in [4] is a series of 6th harmonics, it is always equal to the expression (1), so that this conventional technique cannot establish the expression (1). Become. Since P ₆ is a sixth-order component of permeance, it is also a sixth-order component of cogging torque. Accordingly, the cogging torque of the 12 main poles and 8 poles has a 6th order component, and the pulsation number Nc during one rotation of the rotor pulsates in 6 cycles to an electrical angle of 2π. Therefore, in one rotation (mechanical angle, 2π) It becomes p times and becomes the following.
Nc = 6p = 6 × 4 = 24
Empirically, in order to obtain low rotation unevenness at the time of rotation of about 100 rpm, this Nc needs to be 60 or more and the value of 24 is small, and this conventional technology makes the cogging torque too large and inappropriate.

FIG. 9 is also an example of the prior art. The number of stator main poles is 6, and the number of rotor poles is 4. Similarly, the sixth component of permeance is calculated as follows.

From δ = 2 × 2π {(1/4) − (1/6)} = π / 3 (electrical angle), the following equation is calculated.

P ₆ = 2 {cos0 + cos6 × 1 (π / 3) + cos6 × 2 (π / 3)}
= 6
Nc = 2 × 6 = 12
Therefore, this is also inappropriate because the cogging torque is composed of the 6th order component and the value becomes large.
In general, the value of Nc is larger when the number of stator main poles is larger and when the number of rotor poles is larger.
Nc = (number of pole pairs) × (existing cogging torque harmonics)
It can be understood from. Since the number of main poles is a multiple of 3 in a three-phase machine, a low cogging torque motor has an unsuitable number of main poles of 6 and is 9 or more. However, if the number is 18 or more, there are too many coils, which increases the price. Therefore, a practical low cogging torque motor has 9 or 12 main poles.

FIG. 1 is an example of 12 main poles and 22 rotor poles according to the present invention, and when the salient pole 1-1 and the S pole of the rotor face each other, the salient pole 1-2 and the following Since the angle δ formed with the rotor S pole is δ = {(p / 6) −2} π, if p = 11 is substituted, it becomes π / 6 as shown in the figure, and the permeance sixth order is obtained from the equation (4). When the component P ₆ is calculated, it is as follows.
= 0
That is, equation (1) can be established.
Since the harmonic number of the cogging torque of the three-phase machine is an integer multiple of 6, the 12-th harmonic component P ₁₂ of the permeance is confirmed.
= 12
That is, since the cogging torque is zero in the 6th order component and more than the 12th order component, the cogging torque is greatly reduced as compared with the prior art example.
Therefore, Nc = 12 × 11 = 132
Thus, since it greatly exceeds 60, it is suitable as a low cogging torque motor. This technique corresponds to claim 1 and means 1, and 22 rotor poles is an example satisfying the expression (1). The winding is shown as an example of star connection, but delta connection is also possible.

FIG. 2 shows another example of the present invention, which corresponds to claim 2 and means 2. The stator has a structure in which six main poles are provided at an equal angle of 60 degrees from the annular body 5 in a letter of appreciation, and two inductors are further provided from each main pole. If the pitch of each of these two inductors is 30 degrees, the permeance seen from the rotor will be the same as that of the 12 main poles in FIG. 1, the cogging torque component will be the same, the 6th order will disappear, and the 12th order component and Become. Therefore, the expression (1) can be satisfied. The rotor pole number of 22 is an example that satisfies the formula (1). The winding is shown as an example of star connection, but delta connection is also possible. In this case, the back yoke 4 is also necessary.
Comparing the configurations of FIG. 2 and FIG. 1, the cogging torque is similarly reduced as described above, but the configuration of FIG. 2 has a feature that a larger torque can be output at a lower speed than the configuration of FIG. The torque is determined by the product of electric load and magnetic load. Generally, even with the same rotor, the smaller the number of main poles, the larger the product can be and the higher torque can be produced. As a disadvantage, the coil end is larger in the 6 main poles than in the 12 main poles, which is not suitable for a thin product. In general, when the torque is increased in the prior art, the vibration increases. However, in this configuration, the vibration is low because the cogging torque is small, and there is an advantage that the torque can be increased.

Next, an example of the present invention when the number of main poles is 9 will be shown. FIG. 3 embodies claim 3 and means 3. The number of rotor poles is the same 22 pole example as in FIG. When the salient pole 1-1 and the S pole of the rotor face each other, the angle δ formed by the salient pole 1-2 and the next rotor S pole is δ = {(2p / 9) -2} π. If 11 is substituted, 4π / 9 is obtained as shown in the figure, and referring to FIG. 3, when the number of poles of the rotor is set to 22, the above-described equations (2) and (3) are changed as follows. By setting it to zero, the 6th and 12th harmonics disappear, and the 18th harmonic exists.
Further, the permeance 18th-order component P ₁₈ is calculated.
That is, since P ₁₈ ≠ 0, there is an 18th-order harmonic, and Nc = 18 × 11 = 198
Thus, it becomes suitable as a low cogging torque motor.
It should be noted that since the motor is a low cogging torque motor even at the 12th harmonic or higher, it is sufficient if the formula (2) is satisfied. Get closer to. As shown in the figure, the winding is composed of salient poles whose phase is 120 degrees apart from 1-1, 1-4, 1-7, and two poles with one pole and one pole with different polarity. It becomes a road and 4 back yokes are required. The winding is shown for only one phase. Each part number is the same as FIG.

Next, another example of the present invention when the number of main poles is 9 will be shown. Referring to FIG. 7, when the number of poles of the rotor is 14, the above-described equations (2) and (3) are set to zero, so that the 6th and 12th harmonics are respectively obtained. It disappears and there will be an 18th harmonic.
Further, the permeance 18th-order component P ₁₈ is calculated.
That is, since P ₁₈ ≠ 0, there is an 18th-order harmonic, and Nc = 18 × 7 = 126
Thus, it becomes suitable as a low cogging torque motor.
Unlike the case of FIG. 3, the winding in this case is composed of salient poles having U-phase portions of 1-1, 1-5, and 1-6, as shown in the figure, and all three pieces have the same polarity. In the V phase and W phase, the three salient poles in the phase are the same. FIG. 7 is an example of star connection, and the winding ends of the U, V, and W phases are short-circuited. Here, if a voltage is applied between the two UV terminals, two-phase excitation occurs, and if the U-phase becomes the S pole shown in the figure, the V-phase becomes an N-pole with a different polarity because the current comes from the winding end side. In this case, the ratio of the magnetic flux magnetic path of the rotor permanent magnet between the adjacent rotor magnetic poles is large, so that the necessity for the back yoke is less than in the previous examples.

As described above, in the case of the three-phase 12 main pole and the six-main pole structure with an inductor of the present invention, the number of pole pairs satisfying the expression (1), and in the case of the nine main poles, the number of pole pairs satisfying the expressions (2) and (3) As a permanent magnet rotor structure of p, smooth load driving with extremely low rotation unevenness is realized. Although the explanatory diagram shows the inner rotation type (inner rotor type), the same holds true for the outer rotation type (outer rotor type). The outer rotation type can increase the rotor inertia, so there is a merit that the rotation unevenness can be reduced in the application of constant speed driving. On the other hand, the adduction type is suitable for variable speed and the like.
The most suitable drive system is a closed-loop brushless DC motor that detects the rotor magnetic pole with a hall element and excites the stator main pole at the optimal timing (usually the coil current axis and the rotor magnetic pole axis are orthogonal). However, an open loop drive stepping motor may be used. In the case of a brushless DC motor that detects a rotor magnetic pole with a Hall element or the like, if the motor size is about 60 mm in diameter and p exceeds 11 or about 22 poles, it is difficult to detect the magnetic pole with little variation on a mass production basis. The practical number of pole pairs p is naturally limited.
Although the above description has been given for the surface magnet type rotor described above, if the number of pole pairs p is p satisfying the formula (1), or (2) and (3), the illustration is omitted, but the segment formula The same effect can be obtained by using either a surface magnet type rotor or an embedded magnet type.

  The rotating electric machine of the present invention described above is a three-terminal U, V, W phase by star or delta connection, and is bipolar driven by an inversion current from an inverter or the like, and driven by the drive circuit of FIG. For example, if the transistors T1 and T4 are turned on by the output of the Hall element, two-phase excitation of the U phase and the V phase is performed, and (T4, T5), (T5, T2), (T2, T3), (T3, T6) ), Turn on by turning on (T6, T1).

  The rotating electrical machine according to claims 1 to 4 of the present invention has a unipolar winding in which two windings of salient poles are wound, and a total of 2p poles with N poles and S poles alternately via a stator and an air gap. It is also possible to make an inner or outer rotary electric machine that is rotatably opposed to a cylindrical permanent magnet rotor magnetized in the same manner. The unipolar winding is a three-phase rotating electric machine that is driven by a current that is 180 degrees in phase with a one-way current, and can be driven by the drive circuit of FIG. A unidirectional current having a phase difference of 180 degrees is driven so that, for example, one of the transistors T1 and T2 is turned off when one is turned on. When rotating at high speed, this unipolar drive is more suitable than the bipolar drive of FIG. 5 because the winding inductance is smaller.

Schematic diagram of rotating electrical machine according to the present invention Illustration of another rotating electrical machine according to the present invention Illustration of another rotating electrical machine according to the present invention Common sectional view related to the present invention Diagram of drive circuit according to the present invention Diagram of another drive circuit according to the present invention Illustration of another rotating electrical machine according to the present invention Prior art diagram Another prior art diagram

Explanation of symbols

1: Stator,
2: Rotor permanent magnet,
3: Coil,
4: Back yoke,
5: Stator with inductor,
6: Rotating shaft

Claims (6)

When 12 salient poles are sequentially numbered from an arbitrary salient pole 1 with a stator made of a magnetic body in which 12 salient poles are equally provided from a substantially annular body, the salient poles 1, 2, 7 and 8 form a one-phase winding, and the direct current excitation current causes the salient pole 1 and the adjacent salient pole 2 to have the same polarity, and the salient pole 7 and the adjacent salient pole 8 correspond to the salient pole 1 and the salient pole 2. Are magnetized in different polarities, and the second phase winding is similarly provided on the salient poles 3, 4, 9, 10 and the remaining salient poles 5, 6, 11, 12 are provided with the third phase winding. A three-phase machine with a star connection in which the winding end of each phase is short-circuited, or a delta connection in which the winding end and the winding start of the next phase are sequentially coupled, and the N poles via the tips of the 12 salient poles and the air gap A cylindrical permanent magnet rotor in which S poles are alternately magnetized to a total of 2p poles, and an internal or external rotation type rotating electrical machine that is rotatably opposed to any stator protrusion And when the rotor poles are opposed, that P is 11 in a rotary electric machine which satisfies the following equation.
Each of the six salient poles is further provided with two inductors, each of which has two inductors, and each of the six stators has an arbitrary shape. When numbering the six salient poles sequentially from the salient pole 1, the salient poles 1 and 4 constitute a one-phase winding, and the salient pole 1 and the salient pole 4 are magnetized to different polarities by the DC excitation current. A star connection in which the second phase winding is similarly connected to salient poles 3 and 5 and the remaining salient poles 3 and 6 are similarly provided with third phase windings, and the winding ends of each phase are short-circuited. Alternatively, it is a delta connection in which the winding end and the winding start of the next phase are sequentially coupled, and the N pole and S pole are alternately magnetized to a total of 2p poles via the inductor and air gap at the tip of the 6 salient poles. An internal or external rotating electrical machine that is rotatably opposed to the cylindrical permanent magnet rotor, and that satisfies the following formula when any inductor and rotor pole face each other An electric machine in which P is 11 .
In the case where 9 salient poles are numbered sequentially from any salient pole 1 with a stator made of a magnetic material in which 9 salient poles are equally provided in an abundant form from a substantially annular body, salient poles 1, 4, 7 and 1 constitute a one-phase winding, and the direct current excitation current causes the salient pole 1 and the salient poles 4 and 7 to be wound with different polarities, and the second phase winding is similarly salient pole 2. , And salient poles 5 and 8 are different from each other, and the third phase winding is a three-phase machine provided so that the remaining salient poles 3 and salient poles 6 and 9 are different from each other. , A star connection in which the winding end of each phase is short-circuited, or a delta connection in which the winding end and the winding start of the next phase are sequentially coupled, and the N pole and the S pole are connected via the tips of the nine salient poles and the air gap. A cylindrical permanent magnet rotor that is alternately magnetized to a total of 2p poles and an internal or external rotary electric machine that is rotatably opposed to each other. When, what P is 11 in the rotary electric machine characterized by satisfying the following two expressions.
In the case where 9 salient poles are numbered sequentially from any salient pole 1 with a stator made of a magnetic material in which 9 salient poles are equally provided in an abundant form from a substantially annular body, salient poles 1, 5, 6 constitutes a one-phase winding, and DC exciting current is wound so that salient poles 1, 5 and 6 have the same polarity, and the second phase winding is similarly salient poles 7, 2 and 3 The three-phase machine has all the same polarity, and the third phase winding is the same salient polarity with the remaining salient poles 4, 8, and 9. A shorted star connection or a delta connection in which the end of winding and the beginning of the next phase are sequentially coupled, and the N and S poles are alternately magnetized to a total of 2p poles via the tip of the nine salient poles and the air gap. An inner or outer rotary electric machine that is rotatably opposed to the cylindrical permanent magnet rotor, and an arbitrary inductor and rotor pole face each other. Those P is 7 in a rotary electric machine characterized by satisfying the following two expressions.
5. The cylindrical permanent magnet according to claim 1, wherein a stator having a unipolar winding in which two windings of the salient pole are wound and an N pole and an S pole are alternately magnetized to a total of 2p poles through an air gap. A three-phase rotating electric machine that is driven by a unipolar winding with a current that is 180 degrees out of phase with an inner or outer rotating electric machine that is rotatably opposed to a magnet rotor. 5. The rotating electrical machine according to claim 1, wherein a back yoke made of a magnetic material is provided on the side opposite to the air gap of the cylindrical permanent magnet of the rotor.