Abstract:
A permanent-magnet electric rotating machine with a concentrated winding stator, including a stator having a plurality of stator magnetic poles formed so as to extend radially from an annular yoke portion of a stator iron core, and windings mounted on the stator magnetic poles; and a rotor having a permanent magnet with a plurality of magnetic poles and rotatably held so as to face the stator through an air gap; wherein each of the stator magnetic poles has a straight shape having a width which is made constant over a whole length, small grooves are formed in each of the stator magnetic poles in symmetrical positions on opposite sides and near a top end portion of the stator magnetic pole, a bottom portion of each slot portion defined by adjacent ones of the stator magnetic poles and the yoke is formed triangularly, each of the stator winding is constituted so that a winding having a predetermined number of turns and winding being formed so as to be fittable to each of the stator magnetic poles is mounted on the stator magnetic pole through an insulator, and wedges are fitted to the small grooves formed in the stator magnetic poles.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a permanent-magnet electric rotating machine, and particularly relates to a permanent-magnet electric rotating machine with a concentrated winding stator suitable to windings with thick wire. 
     2. Description of the Related Art 
     A large current of a low voltage is fed to an electric rotating machine using a battery or the like as power source. Therefore, thick wire windings are used as a stator windings wound on stator magnetic poles of such an electric rotating machine in order to reduce the resistance value of the windings. 
     A stator used in a conventional electric rotating machine of such a type will be described with reference to FIG.  19 . 
     FIG. 19 is a cross-sectional view of a stator  84  of a conventional electric rotating machine, viewed in its axial direction. Twelve stator magnetic poles  85   a   1  to  85   a   12  are formed at circumferentially equal intervals so as to radially extend from a yoke  86  toward the center of the stator. In addition, the stator magnetic poles  85   a   1  to  85   a   12  have circumferentially widened top end portions  85   b   1  to  85   b   12  respectively. The reference numeral W 0  designates a slit width between adjacent stator magnetic poles, for example,  85   a   1  and  85   a   2 , and so on. A bottom portion  87   a  of each slot  87  formed between adjacent stator magnetic poles is shaped to be an arc. 
     Generally, a permanent-magnet electric rotating machine has stator magnetic poles, and, conventionally, in such a permanent-magnet electric rotating machine, stator windings are concentratedly mounted on the magnetic poles. In such a conventional permanent-magnet electric rotating machine, it is general that the ratio of the number M of the magnetic poles of the stator to the number P of the magnetic poles of the permanent magnet is set to 3:2, that is M:P=3:2. Further, a motor winding and a generator winding are wound in one and the same slot. 
     In such a conventional electric rotating machine with a concentrated winding stator, however, there have been some problems as follows. 
     (1) In the stator of such a conventional electric rotating machine, the top end portions of the stator magnetic poles are circumferentially widen as shown in FIG.  19 . Accordingly, the slit width between adjacent stator magnetic poles is narrow. When thick-wire windings are to be wound on the respective stator magnetic poles by use of a nozzle of a winding machine, the width of the nozzle is limited because the slit width passed by the nozzle is narrow, so that it has been impossible to mount such thick-wire windings. 
     (2) In addition, if a windings in which thick wire is wound on a bobbin in advance is to be used, the slit width is too narrow to mount onto a stator magnetic pole from the radial center side of the stator. 
     (3) Further, because the bottom portion of each slot is shaped to be an arc, the slot area is small, and the total number of turns of the windings is limited. 
     (4) Moreover, because the ratio of the number M of the magnetic poles of the stator to the number P of the magnetic poles of the permanent magnet is set to M:P=3:2, cogging torque is large, and the winding factor expressing the effective utilization ratio of the winding takes a small value of 0.866. Therefore, in the electric rotating machine, the motor torque is small, and the voltage generated by a generator is low. 
     (5) Further, because the ratio of the number M of the magnetic poles of the stator to the number P of the magnetic poles of the permanent magnet is set to M:P=3:2, it is impossible to dispose motor winding sets and generator winding sets on the stator magnetic poles independently of each other. Accordingly, insulation is used in common to both the winding sets, so that the safety is inferior. 
     It is an object of the present invention to provide a permanent-magnet electric rotating machine with a concentrated winding stator in which the foregoing problems in the conventional electric rotating machine can be solved. 
     SUMMARY OF THE INVENTION 
     In order to achieve the above object, according to an aspect of the present invention, provided is a permanent-magnet electric rotating machine with a concentrated winding stator, including a stator having a plurality of stator magnetic poles formed so as to extend radially from an annular yoke portion of a stator iron core, and windings mounted on the stator magnetic poles; and a rotor having a permanent magnet with a plurality of magnetic poles and rotatably held so as to face the stator through an air gap; wherein each of the stator magnetic poles has a straight shape having a width which is made constant over a whole length, small grooves are formed in each of the stator magnetic poles in symmetrical positions on opposite sides and near a top end portion of the stator magnetic pole, a bottom portion of each slot portion defined by adjacent ones of the stator magnetic poles and the yoke is formed triangularly, each of the stator winding is constituted so that a winding having a predetermined number of turns and winding being formed so as to be fittable to each of the stator magnetic poles is mounted on the stator magnetic pole through an insulator, and wedges are fitted to the small grooves formed in the stator magnetic poles. 
     According to this configuration, each of the stator magnetic poles is formed so as to have a straight shape in which the width of the magnetic pole is made constant and the slot has a bottom portion which is formed to be triangular, as mentioned above. Accordingly, the slit width between stator magnetic poles adjacent to each other is widened. Therefore, stator windings which are bobbin-wound with thick wires in advance can be mounted on the stator magnetic poles from the radial center side of the stator iron core. 
     Further, the slot area is increased so that it is possible to increase the total number of turns of the stator windings. 
     In the above permanent-magnet electric rotating machine with a concentrated winding stator, preferably, each of the stator windings includes motor windings and generator windings, the motor windings being mounted on every two of, that is, a half of the stator magnetic poles, while the generator windings are mounted in the same manner in the rest half of the stator magnetic poles. 
     With such a configuration, insulations for the motor windings and the generator windings are separated perfectly. Accordingly, it is possible to obtain an electric rotating machine in which the safety is improved. In addition, it is possible to reduce the number of terminals of the windings to be processed. 
     In the above permanent-magnet electric rotating machine with a concentrated winding stator, preferably, the number of turns of the motor windings is made different from that of the generator windings. 
     With such a configuration, it is possible to increase the generator output voltage taking the voltage drop due to a load in the generator output into consideration in advance. 
     In the above permanent-magnet electric rotating machine with a concentrated winding stator, preferably, the relationship between the number M of the stator magnetic poles and the number P of the magnetic poles of the permanent magnet is set to satisfy conditions of (2/3)&lt;(P/M)&lt;(4/3) and P≠M. 
     With such a combination of the numbers M and P in the conditions mentioned above, it is possible to obtain the above-mentioned winding factor expressing the effective utilization ratio of the stator windings the value of which is equal to or larger than that in the conventional case. 
     In the above permanent-magnet electric rotating machine with a concentrated winding stator, preferably, the relationship between the number M of the stator magnetic poles and the number P of the magnetic poles of the permanent magnet is set to satisfy a condition of M:P=6n:(6n±2) (n being an integer not smaller than 2). 
     With such a ratio of the number M to the number P, the winding factor takes a large value of 0.933 in the case of n=2, 0.970 in the case of n=3 and 0.983 in the case of n=4. Accordingly, the electric rotating machine having a large motor torque, a high generator voltage, and a small cogging torque can be obtained. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially cutaway longitudinally sectional view illustrating an embodiment of an electric rotating machine according to the present invention; 
     FIG. 2 is a cross-sectional view of a motor generator provided with motor windings and generator windings in the electric rotating machine according to the present invention; 
     FIG. 3 is an axially sectional view of a stator iron core in the electric rotating machine according to the present invention; 
     FIG. 4 is a half sectional view of the magnetic flux distribution based on magnetic field analysis of stator magnetic poles and a permanent-magnetic rotor in the electric rotating machine according to the present invention; 
     FIG. 5 is a drawing as Table 1 showing winding factors K in combination with the number M of the magnetic poles of the stator and the number P of the magnetic poles of the permanent magnet; 
     FIG. 6 is a perspective view of a bobbin-wound winding in the electric rotating machine according to the present invention; 
     FIG. 7 is a perspective view of an insulator inserted to a stator magnetic pole in the electric rotating machine according to the present invention; 
     FIG. 8 is a perspective view of a wedge to be inserted into grooves of stator magnetic poles in the electric rotating machine according to the present invention; 
     FIG. 9 is a series-connection diagram of motor stator windings in the electric rotating machine according to the present invention; 
     FIG. 10 is a series-connection diagram of generator stator windings in the electric rotating machine according to the present invention; 
     FIG. 11 is a series-connection diagram showing another embodiment of stator windings in the electric rotating machine according to the present invention; 
     FIG. 12 is a parallel-connection diagram of motor stator windings in the electric rotating machine according to the present invention; 
     FIG. 13 is a parallel-connection diagram of generator stator windings in the electric rotating machine according to the present invention; 
     FIG. 14 is a connection diagram wherein stator windings of an independent machine for a motor and stator windings of an independent machine for a generator in the electric rotating machine according to the present invention are connected in series and in parallel to each other so as to form windings for respective phases; 
     FIG. 15 is a cross-sectional view showing a state in which a coating of synthetic resin or the like is made adhered to each of magnetic poles of a stator iron core in the electric rotating machine according to the present invention; 
     FIG. 16 is a cross-sectional view of a stator iron core in which a magnetic pole shaped straight and a magnetic pole provided with a pole shoe on its top end are disposed alternately in the electric rotating machine according to the present invention; 
     FIG. 17 is a drawing as Table 2 showing the relationship between the wire diameter and the number of turns of the motor winding and the generator winding; 
     FIG. 18 is a perspective view of a wedge in another embodiment, to be inserted into grooves of stator magnetic poles in the electric rotating machine according to the present invention; and 
     FIG. 19 is a cross-sectional view of a stator iron core in a conventional electric rotating machine. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of a permanent-magnet electric rotating machine with a concentrated winding stator according to the present invention will be described with reference to FIG.  1 . 
     FIG. 1 is a partially cutaway longitudinally sectional view illustrating an embodiment of a three-phase permanent-magnet electric rotating machine of the type mentioned above according to the present invention. 
     In FIG. 1, a permanent-magnet electric rotating machine  1  according to the present invention is constituted by a stator  2  and a rotor  3 . The stator  2  has a stator iron core  4 , stator windings  5 , insulators  6  for electrically insulating the stator windings  5 , and a connection plate  7  for connecting terminal wires (not-shown) from the stator windings  5 . A cable  10  electrically connected to an output terminal  8  of the connection plate  7  is led out through a bushing  9  fixed to a front cover  11 . 
     In addition, the stator iron core  4  is fixed on the inner circumferential surface of the front cover  11  having heat radiation fins  11   a . A rear cover  12  is fitted to the front cover  11 . The front cover  11  and the rear cover  12  are disposed on the axially opposite ends, respectively, of the permanent-magnet electric rotating machine. 
     On the other hand, in the rotor  3 , a permanent magnet  21  is fixed on a rotor iron core  22  so as to face the stator iron core  4  through a gap. The rotor iron core  22  is pressed onto a shaft  23 , or fixed to the shaft  23  by a key (not-shown). A pressing plate  24  for defining the axial position of the rotor iron core  22  is fixed to axially one end of the rotor iron core  22  by means of only a nut  25   b  screwed to the shaft  23 . In addition, a mount plate  27  to which a magnetic pole position detecting magnet  26  having the same number of magnetic poles as that of the permanent magnet  21  is fixed is disposed at the other end of the rotor iron core  22 . 
     The magnetic pole position detecting magnet  26  is disposed at a predetermined axial air-gap distance from the end surface of the permanent magnet  21 . Ball bearings  28   a  and  28   b  are provided at the opposite ends of the shaft  23 , and inserted and fitted into the recess portions of the front cover  11  and the rear cover  12 , respectively. The ball bearing  28   a  is fixed so that its inner ring is prevented from axially moving by means of a nut  25   a  and its outer ring is prevented from axially moving by means of a nut  25   c  screwed into the recess portion of the front cover. 
     Through an axial gap from the magnetic pole position detecting magnet  26 , a board  29  having magnetic pole position detectors disposed thereon for detecting the position of the permanent magnet  21  of the rotor  3  is fixed to a top end portion  11   b  of the bearing support portion of the front cover  11  facing the permanent magnet  21 . This magnet pole position detectors are generally constituted by Hall ICs, a Hall devices or the like, and three magnet pole position detectors are provided circumferentially separated at mechanical angles of 120 degrees. 
     Next, FIG. 2 shows a cross-sectional view of the permanent-magnet electric rotating machine  1  with a concentrated winding stator according to the present invention, in which motor windings and generator windings are provided as the stator windings  5 . In addition, FIG. 3 shows a cross-sectional view of the stator iron core  4  used in the permanent-magnet electric rotating machine  1  according to the present invention. 
     In FIGS. 2 and 3, the stator  2  is constituted by the stator iron core  4 , the stator winding  5 , the insulators  6  for electrically insulating the stator windings  5 , and wedges  13  having two functions to prevent the stator windings  5  from falling down and to electrically insulate the stator windings  5 . 
     Further, the structure of respective parts will be described with reference to FIGS. 2 and 3. 
     First, the stator iron core  4  is constituted by a stator iron core yoke  40  and  12  stator magnetic poles  41  which are individually referenced by the numerals  51  to  62 . 
     Next, two grooves  42   a  and  42   b  are provided on the opposite sides at the inner end portion of the stator magnetic poles  41 , as shown in FIG.  3 . The sectional shape of each stator magnetic pole  41  is formed such that the magnetic pole thickness t is made to be constant from its inner end to its outer end on the magnetic pole so as to be straight and so that the magnetic pole has the same sectional shape from its top end to its base portion. Because of such a straight shape of each stator magnetic pole  41 , slit portion size W between adjacent stator magnetic poles  41 , for example, between the magnetic poles  55  and  56 , can be formed to be wider than the conventional slit size W 0  shown in FIG.  19 . 
     In addition, the sectional shape of a radially outward bottom portion  70   a  of a slot portion  70  in which the stator winding  5  is disposed is formed not to be an arc centering the shaft center in the conventional case but formed to be a triangle connecting straight lines as shown in FIG.  3 . Therefore, as for the radial thickness of the yoke  40  of the stator iron core  4 , the thickness t2 of a center portion of the yoke  40  between the adjacent stator magnetic poles  41  is smaller than the thickness t1 of the yoke  40  at each stator magnetic pole  41 . In such a manner, the sectional area of the slot portion  70  can be increased by forming the slot bottom portion  70   a  into a triangle. 
     The rotor  3  opposite to the stator iron core  4  through an air gap is constituted by 10 magnetic poles (or 14 magnetic poles) of the permanent magnet  21  and the rotor iron core  22  constituted by a stack of thin iron plates, as shown in FIG.  2 . In either case where the number of magnetic poles of the permanent magnet  21  is 10 or 14, the same winding factor is taken when the number of the stator magnetic poles is 12, as shown in Table 1 of FIG. 5 which will be described later. 
     Each permanent magnet  21  is disposed in opposition to the stator iron core  4  through a small gap directly without providing any reinforcing ring in the outer circumferential portion of the permanent magnet  21 . 
     In addition, each permanent magnet  21  shaped into a trapezoid is inserted into an inverted-trapezoidal groove formed in the rotor iron core  22 , and fixed by a bonding agent or the like. 
     The sectional shape of each permanent magnet  21  may be formed so that its upper surface opposite to the stator iron core  4  through a gap as shown in FIG. 2 is shaped into an arc, while the lower surface contacting with the rotor iron core  22  is made flat, and the opposite side surfaces are tapered. In such a case, there are features that the magnetic flux distribution in the gap can be made approximate to a sine wave, the adhesion of each permanent magnet  21  to the rotor iron core  22  can be made firm, and each permanent magnet  21  can be manufactured at a low price. 
     The number M of the magnetic poles of the stator and the number P of the magnetic poles of the permanent magnet according to the present invention can be combined variously. When the combination of the numbers M and P is selected, the relationship between the combination of M and P and the winding factor can be calculated so as to satisfy the condition (2/3)&lt;(P/M)&lt;(4/3) and P≠M, as expressed in Table 1 shown in FIG.  5 . It is understood from Table 1 that the winding factor in any combination of M and P takes 0.866 or more. 
     Therefore, the value of the winding factor herein is equal to or higher than that of the combination of M and P in a conventional electric rotating machine because the winding factor K herein is 0.866 as mentioned above in the conventional electric rotating machine with a concentrated winding stator in which the ratio of M to P is 3:2. 
     Particularly, the combination with the affix * in the column of “the number P of magnetic poles of permanent magnet” takes the maximum value as the winding factor K. 
     The relationship of these combinations between the number M of the magnetic poles of the stator and the number P of the magnetic poles of the permanent magnet taking the maximum value as the winding factor K is expressed by: 
     M:P=6n:(6n±2) Providing n is an integer of 2 or more. 
     In addition, the combination of M and P with the affix # in the column of “the number P of magnetic poles of permanent magnet” takes the largest value as the winding factor K next to the above-mentioned combination taking the maximum value. 
     On the basis of the above discussion, in the embodiment of the present invention which will be described below, one combination in Table 1 in which the number M of the magnetic poles of the stator is 12 while the number P of the magnetic poles of the permanent magnet is 14 is adopted by way of example, and the configuration with the combination will be described hereunder. 
     FIG. 4 shows a half sectional view of magnetic flux distribution based on magnetic field analysis in the case of 12 stator magnetic poles  41  and 14 magnetic poles of permanent magnet  21  used in the embodiment of the permanent-magnet electric rotating machine  1  with a concentrated winding stator according to the present invention. Although the case where the permanent magnet  21  has 10 magnetic poles is shown in FIG. 2 for convenience of illustration, as is understood from the magnetic flux distribution view of FIG. 4 in comparison with FIG. 2, magnetic flux passes through an air gap from the stator magnetic pole  51 , and passes through the magnetic pole of a permanent magnet  21  and the rotor iron core  22 , and thereafter further passes through the magnetic pole of another permanent magnet  21  and an air gap successively, and divided into two portions which enter the stator magnetic poles  52  and  62 , and then return to the stator magnetic pole  51 . 
     Therefore, the magnetic flux has a linkage to the stator winding  5  when the stator winding  5  is mounted on the stator magnetic pole  57  in the position opposite to and shifted by 180 degrees from the stator magnetic pole  51 . Thus, one phase of winding of a three-phase motor/generator can be formed. 
     In this case, the winding factor takes a large value, 0.933. 
     It is also understood from the magnetic flux distribution view shown in FIG. 4 that there is much effective magnetic flux because the stator magnetic poles  41  are disposed in opposition to magnetic poles of the permanent magnet  21  directly through an air gap without any magnetic interposition so that there is little leakage magnetic flux between adjacent magnetic poles of the permanent magnet  21 . 
     Returning to FIG. 2, the arrangement of the stator windings  5  as another feature of the present invention will be described. The stator windings  5  are constituted by 6 stator windings  5   a  for a motor and 6 stator windings  5   b  for a generator. 
     The motor stator windings  5   a  are mounted on every two of the stator magnetic poles  41 , that is, on the magnetic poles  51 ,  53 ,  55 ,  57 ,  59  and  61 , as shown in FIG.  2 . On the other hand, the generator stator windings  5   b  are mounted on the rest of the stator magnetic poles  41 , that is, the magnetic poles  52 ,  54 ,  56 ,  58 ,  60  and  62 . 
     In FIG. 2, therefore, the motor stator windings  5   a  are individually referenced by  51   a ,  53   a ,  55   a ,  57   a ,  59   a  and  61   a , while the generator stator windings  5   b  are individually referenced by  52   a ,  54   a ,  56   a ,  58   a ,  60   a  and  62   a.    
     The respective motor stator windings  5 a and generator stator windings  5   b  are bobbin-wound in advance by use of a winding jig as shown in FIG. 6, and two terminals of the start and end of each winding are led out. 
     FIG. 7 shows a perspective view of an L-shaped insulator  6  of an insulating material attached to each stator magnetic pole  41 . Such an insulator  6  having a rectangular hole as shown in FIG. 7 is inserted onto each stator magnetic pole  41  shown in FIG. 2 so as to enclose the stator magnetic pole  41 . Further, the motor stator windings  5   a  and the generator stator windings  5   b  are inserted onto the predetermined stator magnetic poles  41  through the insulators  6  respectively. FIG. 2 shows a state after insertion of the insulators  6  onto the stator magnetic poles  41  respectively. 
     After the stator windings  5  are inserted, thin-plate wedges  13  of insulating material as shown in FIG. 8 are axially inserted into the groove portions  42  of the stator magnetic poles  41  respectively. The thin-plate wedges  13  are used for electrically insulating the stator windings  5  and for preventing the windings from falling down. 
     After the wedges  13  are inserted, the stator windings  5  are fixed by varnish or mold material. 
     FIG. 9 shows a connection diagram of the motor stator windings  5   a.    
     The motor stator windings  5   a  are formed for three phases of U, V and W in a three-phase permanent-magnetic motor. 
     As for the U-phase, a terminal U 1 (+) of the stator winding  51   a  mounted on the magnetic pole  51  of the stator magnetic poles  41  (hereinafter referred to as “stator magnetic pole  51 ”, this applies to other magnetic poles), and a terminal U 1 (−) of the stator winding  57   a  of the stator winding  5   a  (hereinafter referred to as “stator winding  57   a ”, and this applies to other magnetic poles) mounted on the stator magnetic pole  57  disposed in opposition to and shifted by 180 degrees from the stator magnetic pole  51  are connected in series so as to form a U-phase. 
     Next, as for the V-phase, a terminal V 1 (−) of the stator winding  53   a  mounted on the stator magnetic pole  53  and a terminal V 1 (+) of the stator winding  59   a  mounted on the stator magnetic pole  59  which is in opposition to and shifted by 180 degrees from the state magnetic pole  53  are connected in series so as to form a V-phase. 
     In the same manner, as for the W-phase, a terminal W 1 (+) of the stator winding  55   a  mounted on the stator magnetic pole  55  and a terminal W 1 (−) of the stator winding  61   a  mounted on the stator magnetic pole  61  which is in opposition to and shifted by 180 degrees from the stator magnetic pole  55  are connected in series so as to form a W-phase. 
     The winding end terminals of the stator windings  57   a ,  59   a  and  61   a  of the U-, V- and W-phases are connected to form a neutral points. 
     The marks (+) and (−) designate winding directions of the winding. For example, the mark (+) designates clockwise winding, while the mark (−) designates counterclockwise winding. 
     FIG. 10 shows a connection diagram of the generator stator windings  5   b.    
     The generator stator windings  5   b  are constituted by three phases of U, V and W in a three-phase permanent-magnetic generator. 
     As for the U-phase, a terminal U 2 (−) of the stator winding  52   a  mounted on the stator magnetic pole  52  and a terminal U 2 (+) of the stator winding  58   a  mounted on the stator magnetic pole  58  which is in opposition to and shifted by 180 degrees from the stator magnetic poles  52  are connected in series so as to form a U-phase. 
     Next, as for the V-phase, a terminal V 2 (+) of the stator winding  54   a  mounted on the stator magnetic pole  54  and a terminal V 2 (−) of the stator winding  60   a  mounted on the stator magnetic pole  60  which is in opposition to and shifted by 180 degrees from the stator magnetic pole  54  are connected in series so as to form a V-phase. 
     In the same manner, as for the W-phase, a terminal W 2 (−) of the stator winding  56   a  mounted on the stator magnetic pole  56  and a terminal W 2 (+) of the stator winding  62   a  mounted on the stator magnetic pole  62  which is in opposition to and shifted by 180 degrees from the stator magnetic pole  56  are connected in series so as to form a W-phase. 
     The winding end terminals of the stator windings  58   a ,  60   a  and  62   a  of the respective U-, V- and W-phases are connected to form a neutral point. 
     In the same manner as those in the motor windings  5   a , the marks (+) and (−) designate winding directions of the windings. For example, the mark (+) designates clockwise winding, while the mark (−) designates counterclockwise winding. 
     In such a manner, in the permanent-magnet electric rotating machine  1  with a concentrated winding stator according to the present invention, the motor stator windings  5   a  and the generator stator windings  5   b  are mounted on different stator magnetic poles  41  respectively each mounted on every two poles. Accordingly, the motor stator windings are separated perfectly from the generator stator windings with respect to insulation. 
     The number of turns N 1  of the motor stator windings  5   a  may be equal to the number of turns N 2  of the generator stator windings  5   b . Alternatively, the numbers N 1  and N 2  may be set to satisfy N 1 &lt;N 2  so as to increase the generated voltage taking the voltage drop in the generator output caused by a load into consideration in advance. 
     Although, in the permanent-magnet electric rotating machine  1  with a concentrated winding stator according to the present invention, the aforementioned embodiment is described about the case where the number M of the magnetic poles of a stator is 12 while the number P of the magnetic poles of permanent magnet is 14, the same winding factor 0.933 can be obtained also when M=12 and P=10 so that the condition of M:P=6n:(6n±2) is satisfied, where n is an integer of 2 or more. 
     The stator windings  51   a  and  57   a  constituting the U-phase of the motor stator windings  5   a  are bobbin-wound clockwise and counterclockwise respectively, and the winding end of the stator winding  51   a  and the winding start of the stator winding  57   a  are connected to each other to form the U-phase of the phases U 1 (+) and U 1 (−). However, when the stator windings  51   a  and  57   a  are bobbin-wound in the same direction (for example, clockwise) and the respective winding ends of the stator windings  51   a  and  57   a  are connected to each other, the phases U 1 (+) and U 1 (−) can be obtained. Similarly, as for the V- and W-phases of the motor stator windings  5   a  and the U-, V- and W-phases of the generator stator windings  5   b , necessary phases of the stator windings  5  can be obtained in the same manner. 
     Although each of the stator magnetic pole  41  is shaped straight so that its magnetic pole width is constant over the whole length as mentioned above, it may be tapered, instead, so that the magnetic pole width is made large on the yoke  40  side of the stator core while it is made smaller as a position goes toward the inner top side. In this case, the slit width between adjacent stator magnetic poles is increased, so that the bobbin-wound windings  5  can be mounted onto the magnetic poles  41  smoothly. 
     In addition, in the permanent-magnet electric rotating machine with a concentrated winding stator according to the present invention described in the above embodiment, the motor stator windings  5   a  are mounted on every two poles, that is, on half of M stator magnetic poles  41 , while the generator stator windings  5   b  are similarly mounted on the rest half to thereby constitute a motor and a generator. 
     To form an electric rotating machine as an independent motor with a concentrated winding stator, it will go well if the motor stator windings  5   a  are mounted on every two poles, that is, on half of M stator magnetic poles  41 , while other motor stator windings  5   a  are similarly mounted on the rest half. 
     In the same manner, an electric rotating machine and an independent generator with a concentrated winding stator can be formed if the generator stator windings  5   b  are mounted on every two poles, that is, on half of M stator magnetic poles  41 , while other generator stator windings  5   b  are similarly mounted on the rest half. 
     Then, the number of turns of the motor windings  5   a  and that of the generator windings  5   b  are made twice as large as that in the former case. 
     As shown in the winding connection diagram of FIG. 11, 12 stator windings  5  formed by thick-wire bobbin-wound in advance are inserted/mounted on all the 12 stator magnetic poles  41 . The U-phase is formed by the four terminals, that is, U 1 (+) of the stator winding  51   a , U 1 (−) of the stator winding  52   a , U 1 (−) of the stator winding  57   a  and U 1 (+) of the stator winding  58   a ; the V-phase is formed by the four terminals, that is, V 1 (−) of the stator winding  53   a , V 1 (+) of the stator winding  54   a , V 1 (+) of the stator winding  59   a , and V 1 (−) of the stator winding  60   a ; and the W-phase is formed by the four terminals, that is, W 1 (+) of the stator winding  55   a , W 1 (−) of the stator winding  56   a , W 1 (+) of the stator winding  61   a  and W 1 (−) of the stator winding  62   a . If each phase is formed by a series connection, it is possible to obtain an electric rotating machine with a concentrated winding stator which functions as an independent motor or an independent generator, in the same manner as described above. 
     FIGS. 9 to  11  show winding connection diagrams of the electric rotating machine with a concentrated stator windings according to the present invention, in which the windings  5  in each phase are connected in series when all the windings are formed as the motor windings  5   a  or as the generator windings  5   b  for constituting independently a motor of a generator. However, the windings  5  in each phase may be connected in parallel. 
     That is, FIG. 12 shows a connection diagram in which as the stator windings  5  used in a permanent-magnet electric rotating machine according to the present invention, the motor windings  5   a  are connected in parallel to form the respective phases. FIG. 13 shows a connection diagram in which as the stator windings  5  used in an electric rotating machine according to the present invention, the generator windings  5   b  are connected in parallel to form the respective phases. FIG. 14 shows a connection diagram in which the windings  5  connected in series are further connected in parallel to form each phase to constitute an independent motor with the motor windings  5   a  or an independent generator with the generator windings  5   b.    
     Alternatively, the windings  5  connected in parallel may be further connected in series to form each phase. 
     In the case of parallel connection, it is necessary to make the windings  5   a  or  5   b  equal in the number of turns to each other. As for the connection examples shown in FIGS. 9 to  11 ,  12  to  14 , examples of the relationship between the wire diameter and the number of turns of each winding of the motor windings  5   a  and the generator windings  5   b  are shown in Table 2 of FIG.  17 . In Table 2, φD 1  and φD 2  have the relationship expressed by the following equation (1), and φD 2  and φD 3  have the relationship expressed by the following equation (2). 
     
       
         sectional area of φD 2 =(sectional area of φD 1 )/2. . . (1) 
       
     
     
       
         sectional area of φD 3 =(sectional area of φD 2 )/2. . . (2) 
       
     
     In the structure of the stator  2  shown in FIG. 2, the insulators  6  are attached to the magnetic poles  41  of the stator iron core  4 , and the stator windings  5  are mounted on the magnetic poles  41  through these insulators  6  respectively. However, the magnetic poles  41  of the stator iron core  4  may be provided with such an insulating structure  41 G that the inner circumferential surfaces of the magnetic poles  41  are coated with synthetic resin or the like as shown in FIG.  15 . Thus, the insulators  6  may be replaced by this insulating structure  41 G. Accordingly, in the permanent-magnet electric rotating machine with a concentrated winding stator according to the present invention, it can be also considered that the insulators  6  are omitted in the magnetic poles  41  of the stator iron core  4 . 
     The thin-plate wedge  13  of insulating material as shown in FIG. 8 may be replaced by a magnetic wedge in which not insulating material as mentioned above but, for example, a mixture of synthetic resin and iron powder with a larger magnetic permeability than the air is heated and pressurized so as to be formed into a laminated plate. In this case, it is possible to reduce eddy-current loss generated in the permanent magnet caused by dropping down of the magnetic flux density in the stator magnetic pole grooves  42   a  and  42   b . It is therefore possible to reduce the temperature rising in the rotor  3 , improve the efficiency of the electric rotating machine  1 , and reduce vibrations or noise. 
     On the other hand, if the magnetic wedge is shaped not like such a thin plate as shown in FIG. 8 but like a V-block the thickness of which is reduced substantially in the center portion of width W′ as shown as a magnetic wedge  13 ′ in FIG. 18, it is possible to reduce the magnetic flux leaking between adjacent stator magnetic poles  41 . 
     The shape of the stator iron core  4  shown in FIG. 3 may be modified such that a magnetic pole having the straight shape in which the magnetic pole width is constant from its top end to its root and a magnetic pole having a pall shoe on its top end are disposed alternately as shown in FIG.  16 . In this case, windings  5  shaped in advance may be mounted on the straight magnetic poles while other windings may be mounted on the pall-shoed magnetic poles by means of a nozzle of a winding machine. 
     The thus configured permanent-magnet electric rotating machine with a concentrated winding stator according to the present invention has superior effects as follows. 
     (1) In the electric rotating machine according to the present invention, the slit width between adjacent stator magnetic poles is large so that stator windings bobbin-wound with thick wires in advance can be inserted onto stator magnetic poles from the radial center side of a stator iron core. Accordingly, the resistance of the windings can be reduced, so that it is possible to obtain an electric rotating machine having high power and low loss. 
     (2) Because a slot bottom portion is shaped to be triangular, the slot area increases so that the number of turns of the stator windings can be increased. Accordingly, it is possible to obtain a large motor torque and a high generator voltage. 
     (3) Because the ratio of the number M of the magnetic poles of a stator to the number P of the magnetic poles of the permanent magnet is set to M:P=6n:(6n±2), the winding factor increases to 0.933. Here, n is an integer of 2 or more. Accordingly, it is possible to obtain a large motor torque and a high generator voltage. In addition, it is possible to obtain an electric rotating machine having a small cogging torque. 
     (4) Because motor stator windings are mounted on a half of the number M (that is, M/2) of magnetic poles of the stator and generator stator windings are mounted on the rest half, the former windings are separated perfectly with respect to insulation from the latter windings. Accordingly, the safety is improved. In addition, because the number of terminals to be processed is reduced, it is possible to reduce the time taken for connection of the terminals to a connection plate. 
     (5) Because the stator iron core and the permanent magnet are disposed in opposition to each other directly through an air gap, the leakage magnetic flux from the permanent magnet is reduced. It is therefore possible to increase the effective magnetic flux, obtain a large motor torque, and reduce inductance. 
     (6) The number of turns of the windings can be made different between the motor windings and the generator windings, so that it is possible to increase the generator voltage in advance taking the voltage drop of the generator output caused by a load into consideration.