GB2268343A

GB2268343A - Control of synchronous machine

Info

Publication number: GB2268343A
Application number: GB9309799A
Authority: GB
Inventors: Kinshiro Naito; Tokuzou Sekiyama
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-05-13
Filing date: 1993-05-12
Publication date: 1994-01-05
Also published as: ITMI930968A0; ITMI930968A1; IT1264430B1; FR2691304A1; TW299522B; SE9301608L; DE4315939A1; CA2095669A1; NL9300832A; SE9301608D0; GB9309799D0

Description

Synchronous Machine

Background of The Invention

1. Technical Field

This invention relates to a synchronous machine, and, in particular, to a rotary or a linear synchronous motor and a synchronous generator. This invention also relates to a main spindle motor in machine tools and the like, and moreover to a synchronous motor of which rotational frequency and output value or output torque are controlled simultaneously. 2. Background Art

Conventionally, a synchronous motor in machine tools and the like has a rotor and an armature. The rotor has either permanent magnets or coils which is excited by direct current. The armature has a single-layer coil with two-poles, four- poles, six-poles or the like. A two-phases or three-phase alternating current is used for generating rotating magnetic field. 25 However, the synchronous motor for the main spindle of machine tools is required to control not only the rotational frequency but also its output value simultoneously. For a bottom milling machine used for grinding flat surfaces, for example, the end mill usually directly connected to a main spindle motor. When cutting to form fine worked surfaces, a constant peripheral velocity and cutting force are required. These are determined by the material and type of the end mill, material of the work piece and the like. Therefore, it is preferable to maintain the output value of the main spindle motor constant by either generating a low speed and a large torque, as in the case of a large diameter end mill shown in Fig. 1A or high speed and low torque, as in a small diameter end mills shown in Fig. 1B.

A main spindle motor used for rotating a main spindle of the milling machine is required to be able to supply a constant cutting force regardless of the process radius. That is to say, as shown in Fig. 2, the cutting volume or the cutting force is required to be constant even if the process radius becomes to decrease in proportion to the cutting progress. Therefore, the output value is required to be constant by increasing rotational frequency of the motor.

As mentioned above. the motor in use of a main spindle of machine tools is required to include a control method for controlling rotational frequency and torque value or rotational frequency and output value to be predetermined value at the same time. However the conventional motor used for the main spindle of machine tool has a single-layer coil in single-layer and controls phase, frequency, gain, etc. of the current therein. Therefore. it is difficult to produce predetermined load characteristics due to complication of the control method.

As mentioned above, there is a problem that the conventional synchronous motor is difficult to satisfy various characteristics required for a main spindle of machine tools due to the complication of the control method for controlling the current because the coil is a single layer winding.

Furthermore, the synchronous motor in conventional machine tools has an armature (stator) and a rotor. In order to generate a magnetic field pole, the synchronous motor has aotor with either permanent magnet or a coil which is excited by a direct current. A synchronous motor having two to eight poles is popular.

In addition, the conventional synchronous generator has an armature (stator) and a rotor as well. In order to generate a magnetic field pole, the synchronous generator has a rotor with either a permanent magnet or a coil which act as an electromagnet.

However, the structure of the generator is complicated and weakened because of a permanent magneto of the rotor or a coil wound about the rotor. Therefore, there is a problem that various troubles are caused by the deformation or the failure in case of rotation at a high speed.

There is another problem when the synchronous generator is required various characteristics such as a constant output characteristic in a wide rotational range, rotational characteristic with small torque pulsation, and a characteristic without a thermal deformation by an exoergic of the rotor.

Summary of The Invention

It is an object of the present invention to provide a synchronous machine which is suitable for a main spindle of machine tools and able to control either rotational frequency and torque value or rotational frequency and output value to predetermined value simultaneouslyat.

It is another object of the present invention to provide a synchronous machine which does not require the use of permanent magnet or coil. In order to achieve the objects mentioned above, from the first point of view, the present invention provides a synchronous motor device comprising: 30 a stator wound with a first winding and a second winding in double-layer winding; a rotor having a salient pole shape and rotatably received in'the stator; a first controller serving as a power source of te first winding and controlling rotational frequency of the motor; and a second controller serving as a power source and controlling output value or torque value of the motor.

In addition, the present invention also provides a synchronous motor device comprising:

a stator wound with a first winding and a second winding in double-layer winding; a rotor essentially consisting of magnetic anisotropic materials to provide saliency and being rotatably received in the stator; a first controller serving as a power source of the first winding and controlling rotational frequency of the motor; and a second controller serving as a power source of the second winding and controlling output value or torque value of the motor.

Moreover, the present invention provides a synchronous motor device comprising:

a stator wound with a first winding and a second winding in double-layer winding; a rotor being provided with a permanent magnet member to generate field magnetic flux and rotatably received in the stator; a first controller serving as a power source of first winding and controlling rotational frequency of the motor; and a second controller serving as a power source of the second winding and controlling output value or torque value of the motor.

Further, the present invention provides a synchronous motor device comprising:

a stator wound with a first winding and a second winding in double-layer winding; a rotor wound with at least one coil to be supplied with current and rotatably received in the stator; a first controller serving as a power source the first winding and controlling rotational frequency of the motor; and a second controller serving as a power source of the second winding and controlling output value or torque value of the motor. 5 Furthermore, the present invention provides a synchronous motor device comprising: a stator wound with a first winding and a second winding in double-layer winding; rotor made of magnetic anisotropic material and rotatably received in the stator; first controller serving as a power source of the first winding and controlling rotational frequency of the motor; and a second controller serving as a power source of the second winding and controlling output value or torque value of the motor.

In the synchronous motor device above-described, the rotational frequency of the motor is controlled by detecting the rotational frequency and the position of the rotor by the first controller to control the current supplied to the first winding. The output value or the torque value is controlled by controlling the current supplied to the second winding to change the rotating magnetic field to increasing or decreasing the magnetic force.

From the second point of view, the present invention provides a synchronous machine comprising:

an armature having a core wound with a field winding for generating a magnetic field flux and with an armature winding substantially proceeding by an angle of 900 in electrical phase from the field winding; and a rotor rotatably received in the armature and magnetized in a predetermined direction by the field magnetic flux.

In addition, the present invention also provides a synchronous machine comprising:

an armature having a core wound with a field winding and an armature winding, the field winding having three pairs of three phase windings successively shifted by a phase angle of 1200 and generating a magnetic field flux, 5 the armature windings having three pairs of three phase windings successively shifted by a phase angle of 1200 and substantially proceeds by an angle of 900 from the field winding; and a rotor rotatably received in the armature and magnetized in a predetermined direction by the field magnetic flux.

In regard to the synchronous machine mentioned above, the rotor is magnetized in a predetermined direction by the field current of the field winding, a rotating torque generated by the field magnetic flux generated by the field current and the armature current supplied to the armature winding because each phase angle between the rotor, the armature current, and the field current is controlled to be predetermined angle constantly even-if the rotor places at any place. In addition, if the rotor is rotated by an external force, induced voltage is produced so that the synchronous machine serves as a rotating-field magnetic pole type synchronous machine.

Brief Description of The Drawings

Fig. 1A is a view of the relationship between the large diameter end mill and the work piece.

Fig. IB is a view of the relationship between the small diameter end mill and the work piece.

Fig. 2 is a view of the relationship between the cutting process and the process radius of the turning machine.

Fig. 3 is a block diagram showing the controller using the reluctance synchronous motor according to the first embodiment of the present invention.

Fig. 4 is a view of the relationship between the magnetic pole direction and the rotating magnetic field of the rotor in regard to the first embodiment.

Fig. 5 is a view of the relationship between the rotating magnetic fields generated by the A-winding and the

B-winding and the composite magnetic field in regard to the first embodiment.

Fig. 6 is a view of an example of the armature core comprising doublelayer windings in regard to the first embodiment.

Fig. 7 is a view of a phase relationship between the currents of A-winding and B-winding when the phase difference between A-winding and B-winding is an angle of 900 in regard to the reluctance synchronous motor of Fig. 3.

Fig. 8 is a view of a phase relationship between the currents of A-winding and B-winding in case of three phase current in regard to the reluctance synchronous motor of Fig. 3.

Fig. 9 is a view of an example of the armature core insulated by a material which has strong magnetic reluctance for reducing the interference between A-winding and B-winding in regard to the first embodiment.

Fig. 10 is a view of an example of the synchronous motor using two-poles permanent magnets according to the present invention.

Fig. 11 is a view of an example of the synchronous motor of Fig. 10 with four poles. - Fig. 12 is a view of the structure of the armature of the three phase synchronous motor in regard to the second embodiment according to the present invention.

Fig. 13 is a view of a phase difference between the currents supplied to the field winding and the armature winding in regard to the three phase synchronous motor of

Fig. 12.

Fig. 14 is a view of a magnetic density generated by the field current in regard to the second embodiment.

Fig. 15 is a view of an example of the rotor made from a magnetic. anisotropic magnetic body in regard to the second embodiment.

Fig. 16 is a view of an example of the rotor having 5 a salient pole shape in regard to the second embodiment.

Fig. 17 is a view of an example of the rotor being a segment type in regard to the second embodiment.

Fig. 18 is a view of an example of the rotor being a hybrid type in regard to the second embodiment.

Fig. 19 is a view of an example of the rotor being in a shape of salient poles in case of four poles in regard to the second embodiment.

Fig. 20 is a block diagram showing the controller for controlling the rotational speed of the synchronous motor according to the second embodiment.

Fig. 21 is a block diagram showing the controller for controlling the position of the synchronous motor according to the second embodiment.

Fig. 22 is a block diagram showing the controller for controlling to minimize a loss of the synchronous motor according to the second embodiment. Fig. 23 is a view of an example which the phase lag of the synchronous motor produced by a reactor in regard to the second embodiment. 25 Fig. 24 is a view of an example of the synchronous motor which further comprises permanent magnets for the rotor in regard to the second embodiment. Fig. 25A is a.longitudinal sectional view of an example of the synchronous motor comprising the armature divided into two to simplify the assembly in regard to the second embodiment.

Fig. 25B is a cross-sectional view of the -synchronousmotor shown in Fig. 25A.

Fig. 26 is a view of an example formed as one body with rotor shaft of the motor and a main spindle of a machine tool in regard to the second embodiment.

Fig. 27 is a view of an example which the field winding and thearmature winding are structured respectively and placed side by side in the second embodiment.

Fig. 28A is a view of an arrangement relationship between the field winding and the magnetic winding in regard to Fig. 27.

Fig. 28B is a view of an arrangement relationship between the field winding and the magnetic winding in regard to Fig. 27.

Fig. 29 is a view of a structure of an embodiment applying the present invention to a linear motor.

Fig. 30 is a drawing for describing a principle in examples of the synchronous generator according to the present invention.

Fig. 31 is a block diagram showing an example of controller for maintaining constant current output in regard to the synchronous generator of Fig. 30.

Description of The Preferred Embodiment

First Embodiment With reference to the accompanying drawings, a synchronous motor device according to a first embodiment of the present invention will be described hereinafter.

Referring to Fig. 3, the synchronous motor device includes a reaction synchronous motor 101 and a control circuit for controlling the reaction synchronous motor 101.

The reaction synchronous motor 101 comprises a stator and a rotor. The control circuit will be described later.

Turning to Fig. 4, description will be made as regards the reaction synchronous motor 101. When the stator winding is supplied with a threephase current to generate a rotating magnetic field, the rotor is excited in a polar axis direction P in which magnetic.reluctance is the lowest. This is because the magnetic reluctance changes at various angles of the rotor. The polar axis direction P corresponds to the direction in which the rotor projects. As a result, the rotor is rotated by the rotating magnetic field and the polar axis are produced by magnetization.

In addition, although the rotor shown in Fig. 4 forms the shape of salient pole in a cross-section in order to magnetize the rotor in the predetermined direction (a polar axis direction), the rotor may form a circular shape in the case of a magnetic anisotropic magnetic body, the rotor may includes a plurality of slits extending in a polar axis direction, the rotor may be of a hybrid type, and the rotor may have two polar axes, as shown in Figs. 15 to 19.

Turning to Fig. 6, the stator of the synchronous motors 101 further comprises double-layer windings, namely, A-winding W-V-W) and B-winding (u-v-w). The rotating magnetic field is controlled by controlling a composite vector of these windings. A control block diagram for controlling the rotating magnetic field will be described below.

Returning to Fig. 3, the description will be directed to the bontrol circuit. The control circuit comprises a first controller and a second controller. The first controller is for supplying A-winding current IA to A-winding. The first controller comprises a rotational frequency command device 151, a rotational frequency detector 103 for detecting rotational frequency N of the motor 101, a position detector 105 for detecting a rotor position to produce a rotor position signal R, a first subtracter 107 for comparing rotational frequency NO of the rotational frequency command device with rotational frequency R of the iflotor to find a difference el, a first current determination circuit log for determining a current command mI, of the A-winding according to the difference el, a first inverter 113 for supplying a first predetermined current, namely, A-winding current IA to the A-winding, and a first control unit 111 deciding a first control signal M1 e.g. a pulse width modulation control signal for controlling the first inverter 113 according to the current command inl, the rotor position signal R, and a first detected current Il which will presently be described.

The first current detector 123 detects the first predetermined current to generate the-first detected current I1 that represents a first current value. When the difference el is positive, in other words when the rotational frequency N is substantially smaller than the predetermined rotational frequency N, the first current determination circuit 109 determines the current command signal ml so as to increase the A-winding current IA. In the opposite case, the first current determination circuit 109 determines the current command signal ml so as to decrease the current IA.

The first control unit 111 produces a control current value corresponding to the rotor position signal R according to the current command signal ml. Further, the first control unit 111 compares the control current value with the first current value to produce the first control signal M1 to find the difference therebetween. The first control unit ill produces a first control signal M1 e.g. a pulse width modulation control signal for controlling the first inverter 113. In a case where a three-phase current is supplied to the synchronous motors, the first control unit produces three pulse width modulation control signals which have phase differences of an angle of 1200 from one another.

The rotational frequency of the motor and the rotor position are detected by the use of a rotary encoder or a resolver In the manner known in the arts.

The description will be directed to the second controller which is for supplying a B-winding current IB to the B-winding. The second controller-comprises an output command device 153 for commanding output value for the motor, an output arithmetic circuit 121 for computing output value for the motor according to data form the rotational frequency detector 103, the position detector 105, the first current detector 123 and the second current detector 125, a second subtracter 127 for comparing the output value P commanded by the output command device with the output value computed by the output arithmetic circuit 121 to detect difference e2, a second current determination circuit 129 for generating a current command signal m2 which is for determining a current supplied to the Bwinding according to the difference e2, a second inverter 133 for supplying a second predetermined current, namely, the B-winding current to the B-winding, and a second control unit 131 outputting a second control signal M2 e.g., a pulse width modulation control signal for controlling the second inverter 133 according to the current command signal m2 the rotor position signal R and a second detected current 12 which will presently be described.

The second current.detector 125 detects the second predetermined current to produce the second detected current 12. When the difference e2 is positive, in other words when the output value computed by the output arithmetic circuit 121 is smaller than the predetermined output value P, the second current determination circuit 129 outputs the current command signal m2 to increase the current supplied to the B-winding so that the magnetic force of the composite magnetic field increases. That is to say, as shown in Fig. 4, if a direction of a magnetized magnetic pole of the rotor is designated by P and a composite direction of the rotating magnetic field which is generated by the A-winding current IA and the B-winding current IB is designated by HO, the B-winding current IB is increased so that the load angle a is increasing.

This is due to the fact that the rotating torque increases by moving the changing the direction of an alternating current, which generates a rotating magnetic field, toward a right angle with a direction of a magnetic 5 field vector by magnetic pole. Therefore, as shown in the Fig. 5, a magnetic field HB generated by the B-winding current IB is increased in a positive direction relative to a direction of the rotating magnetic field HA generated by the A-winding current IA. The composite magnetic field HO moves so that the phase moves forward. If the difference e2 is negative, the B-winding current IB is increased so that the magnetic field HB is increased in a negative direction.

The second control unit 131 produces a control current value corresponding to the rotor position signal R in accordance with the current command signal m2. In addition, the second control unit 131 compares the control current value with a second current value of the second current detector 125 to produce the second control signal M2 for the second inverter 133 according to the difference therebetween. The second control signal M2 is to regulate the B-winding current IB such that a phase angle of lead or lag of the B-winding current IB supplied to the second inverter relative to the A-winding current IA supplied to the first inverter becomes 90. In the case where three- phase current is supplied to the synchronous motor, the second control unit produces three pulse width modulation control signals which have phase differences of an angle of 1200 from one another.

The rotational frequency N and the output value P ordered by a rotational frequency command device 151 and a output commander 153, respectively, are not necessary to be constant and may change according to time and conditions.

For example, the start and the like of the motor can be controlled with programmed control or logic control.

Turning to Fig 6, the armature core has four poles fifid tWgfltY f89P slots and two windings in double-layer winding, namely, the A-winding and the B-winding supplied with three phase alternating current. In Fig. 6, the numeral 201 designates the armature core and the numeral 203 designates the rotor. The numerals 205 and 207 designate double-layer winding. In this case, A-winding is designated by a combination of coils U, V, W, W, V' and W. B-winding is designated by a combination of coils u, v, w, u', v' and w'. The windings are wound in the manner known in the art. In order to decrease interference between A-winding and B-winding, the armature may provide an insulation made of a material 211 which has strong magnetic reluctance between A-winding and B-winding.

Fig. 7 shows a phase relationship between currents supplied to the coils U and u, in the case of the current of the A- winding and the current of the B-winding have phase difference of an angle of 90 therebetween.

Fig. 8 shows a phase relationship between currents flowing through each winding to which three-phase alternating current is supplied. The rotational frequency of the motor and the pole direction of the rotor can be detected by means of a rotary encoder or resolver in the manner known in the art.

When the rotating magnetic field HA is stronger than the rotating magnetic field HB, for example, when a current value lIA: flowing through the A-winding is several times as large as current value:IBI, a direction of the magnetic pole which magnetizes the rotor is determined by the rotating magnetic field HA generated almost by the A- winding current IA, and the B-winding current Is able to be used as a current for mainly controlling the rotating magnetic field HA.

Although the phase difference between the A-winding current IA and the Bwinding current IB is 900 in the synchronous motor described above, this can be a predetermined angle a (00<a<90). It is preferable that -14 the phase difference is 900 for controlling and decreasing interference caused by armature reaction etc.

The output can be calculated with the rotational frequency of the motor, the rotor position and the currents IA and IB flowing in the windings in the manner known in the arts, or the output can be found in advance in experiments.

In the synchronous motor described above, although there is described the method for controlling the rotational frequency and the output value simultaneously, the method can be used to control the rotational frequency and the output torque at the same time.

Turning to Figs. 10 and 11, the description will be directed to synchronous motors according to modified embodiments of the present invention. Each of the synchronous motors has magnetic poles produced by permanent magnets. Fig. 10 shows a case where the number of the magnetic poles is two. Fig. 11 shows a case where the number of the magnetic poles is four.

In Fig. 10,.the numeral 231 designates a rotor.

The rotor has permanent magnets 233 and 235 secured to the exterior of the rotor. The numeral 241 designates an armature. The armature is wound with a A-winding 243 and a B-winding 245 in double-layer winding. When a current is supplied to the A-winding and the B-winding as shown in the figure, i.e. when the B-winding lags by 900 from the Awinding, a rotating magnetic field by the A-winding generates in a directfon shown by the solid line in the figure, a rotating magnetic field by the B-winding generates in a direction indicated by a dotted line.

The rotor has a magnetic pole direction determined mainly by the permanent magnets. The rotational frequency and output value of the motor are determined by the rotating magnetic field generated by the currents which are supplied to the A-winding and the B-winding. If phase difference between the A-winding current IA and the B- winding current IB is 9C, the pole direction can be controlled easily by controlling the B-winding current IB. In addition, a load angle can also be controlled easily. The current values IIA1 and 1IBI are not necessary different from each other and may have somewhat similar value.

It is possible to control the reaction of the synchronous motor with the permanent magnets in the manner which is described in Fig. 3-.

In Fig. 11, the number of the magnetic pole is four. In this case, the reaction synchronous motor can be also controlled in the manner described above as well as inthe case of Fig. 10.

Although the description is directed only to the synchronous motor of a rotary type, it is possible to apply this invention to a synchronous motor of a linear type.

As described above, the first embodiment can readily control the rotational frequency and the output value or the rotational frequency and the output torque.

Therefore, this has a high utility value as the main spindle motor in machine tools which output value is preferably constant.

Second Embodiment With reference to drawings, a rotary synchronous motor according to a second embodiment of the present invention will be described below.

Referring to Fig. 12, a three-phase synchronous motor 101 comprises an armature core 13 having twenty four slots 15. A field winding 17 and an armature winding 19 are wound about the armature core 13 in double-layer winding through each of slots 15. The armature core 13 -rotatably reCeives a rotor 21 inside thereof. The rotor 21 can be readily magnetized in the predetermined direction.

The field winding 17 comprises.first, second, third, forth, fifth and sixth field coils u, v, w, u', v', and w'. The armature winding 19comprises first, second, third, forth, fifth, and sixth armature coils U, V, W, U', W, and W. The first, the second and the third field coils u, v, w are placed at an angle of 1200 from each other. The forth, the fifth, and the sixth field coils u', v', and w' are placed at an angle of 120 from each other. The first, the second, and the third armature coils U, V, and W are placed at an angle of 120 from each other. The forth, the fifth and the sixth armature coils U', V', and W' are placed at an angle of 1200 each other. The first, the second and the third field coils u, v, and w are shifted by an angle of 90 from the first, the second, and third armature coils U, V, W, respectively. The forth, the fifth, and the sixth field coils u', v', are w' are shifted by an angle of 90 from the forth, the fifth, and sixth armature coils U', V', and W', respectively.

Referring to Fig. 13 in conjunction with Fig. 12, the description will be as follows. When the field winding currents Iu, Iv and Iw, are supplied to the field winding

17, a composite magnetic field N and S is generated. In this event, the magnetic flux distribution is a sinusoidal wave. When a maximum magnetic flux is Om with a magnetic flux center 9 being equal to zero, the magnetic flux is represented by equation (1). 25 0 = OM - cos 9 In the case where the rotor has an axis of easy magnetization, when the field winding currents are controlled in the manner that the magnetic flux center of the magnetic field is consistent with the axis of easy magnetization, the rotor is magnetized in the predetermined direction. In this event, the magnetic field has a magnetic flux density represented by an equation (2).

B = Bm. cos a (2) Three-phase currents IU, IV, and IW are supplied to the armature winding. The three-phase currents IU, IV, a nd IW lead from the field winding currents Iu, Iv, and Iw by the predetermined angle a or preferably 900 in electrical phase.

This results in generation of torque T to rotate the rotor according to Fleming's rule. Torque T will be 5 described as follow.

In the case where the phases of the armature currents IU, IV, and W are controlled so as to be consistent with the magnetic poles of the magnetized rotor, the torque T will be expressed as follows. Magnetic flux densities BU, BV, and BW at each coil of the armature coils U, V, and W are represented by equation (3).

BU = Bm. cos 9 BV = Bm. cos (9 - 1200) BW = Bm - cos (9 - 2400) (3) Because the armature currents IU, IV, IW are controlled so as to be consistent with the positions of the magnetic poles, the armature IU, IV, IW are represented by equation (4).

IU = Im - cos a IV = Im. cos (9 - 1200) IW = Im - cos (9.- 2400) (4) Therefore torque T is represented by equation (5).

T = K (BU.IU + BV.IV + BW.M = 3/2 KBm.Im (5) where Bm designates the maximum magnetic flux density, Im designating maximum value of the armature current, and 9 designates a phase angle between the center of the magnetic pole and the coil U. In addition, a magnetic flux density 0' is produced by the armature current. However, because the rotor is made of magnetic anisotropic substance and the magnetic reluctance is strong in the direction of the magnetic flux, the magnetic flux 0' is not affected.

The above mentioned relationship is schematically illustrated in Fig. 14.

Turning to Figs. 15 to 18, the description will be directed to an example of magnetic anisotropic rotor. A rotor 31 is made from an magnetic anisotropic magnetic body and the section is in a circular shape. The metal for the magnetic anisotropic magnetic body is made of a grain oriented silicon steel, a grain oriented nickel iron steel or the like. In Fig. 15, the magnetic anisotropic magnetic body is easy to be magnetized in a first direction X but difficult to be magnetized in a second direction Y which is perpendicular to the first direction X.

Turning to Fig. 16, the description will be directed to another example of the magnetic anisotropic rotor. A rotor 33 is a salient pole type and is made from an isotropic magnetic body. The rotor 33 is easy to be magnetized in the first direction X but difficult to be magnetized in the second direction Y due to cutoff.

Turning to Fig. 17, the description will be directed to another example of the magnetic anisotropic rotor. A rotor 35 is of a segment type. The rotor 35 comprises an inside and an outside section. The inside section is made of a non-magnetic body 37. The outside section is made of a magnetic body 39. The magnetic body 39 is provided with air gaps 41 in the first direction X. The air gaps 41 may be non-magnetic bodies. The rotor 35 is easy to be magnetized in the first direction X, because of its smallmagnetic resistance, but is difficult to be magnetized in the second direction Y.

Turning to Fig. 18, the description will be made in regards to another example of the magnetic anisotropic rotor. A rotor 43 is of a hybrid type. The rotor 43 is made of a magnetic body 45. The magnetic body 45 is provided with air gaps 47 in the first direction X. The air gaps 47 may be a non-magnetic body. Therefore the rotor 43 is easy to be magnetized in the first direction X but difficult to be.magnetized in the second direction Y.

Turning to Fig. 19, the description will be directed to another example of a rotor which has four magnetic poles. The rotor 49 is easy to be magnetized in X and X' directions but difficult to be magnetized in Y and Y' directions, respectively.

As described above, the rotor provides magnetic anisotropy in the predetermined direction that is perpendicular to the rotational axis direction. The armature is wound with two pair of three- phase windings. The current phases of the two windings are shifted preferably by an 90 angle from each other. Thus, a field magnetic flux generated by the field winding currents and the armature winding currents produce torque according to Fleming's rule. As a result, it is possible to achieve a complete vector control which is able to produce the most preferable torque of maximum value with the magnetic flux 0 and current I.

If the field magnetic flux is proportional to the field current, torque T is represented by equation (6).

T = K2 IA-IB (6) where IA represents the field current and IB- representes the armature current.

In the manner mentioned above, an armature reluctance magnetic flux o'.is also generated by the armature current IB. The direction of the magnetic flux 0' is perpendicular to the direction of the first mentioned magnetic flux 0. However. if the rotor is made of a magnetic isotropic material of a circular shape-in a cross section and there is a constant air gap around the rotor, the rotor cannot be rotated.

If the rotor is the magnetic anisotropic rotor which has easy magnetization axis in the direction along the magnetic flux, torque T is produced according to the equation (5) even if the rotor has the circular shape and there is constant air gap around the rotor.

Therefore, the synchronous motor according to the present invention is achieved by the rotor of a material which is easy to be magnetized In the direction of the first mentioned magnetic flux 0 and difficult to be magnetized in the direction of the second mentioned magnetic flux 0'.

Consequently, the synchronous motor according to the present invention does not need to wind a field coil about the rotor or provide a permanent magnet for the rotor as conventional synchronous machines. Also the synchronous motor according to the present invention does not also need the silicon steel plate for the rotor-nor provide slots therein and with a winding of squirrel cage type made of aluminum, copper or the like, and does not generate heat by an induced current as compared with a conventional induction motor.

The synchronous motor according to the present invention is usable as follows.

The output value P [w] of the motor in equation (5) is represented by equation (7).

P = 21rnT = 1-3 EI (7) where n designates the rotation per second [.rps] of the motor, T designating torque [NmI, E designates a back electromotive force [v] between the three-phase windings, and I designates a phase current [A]. The back electromotive force E [v] is represented by equation (8) where k designates a proportional constant, and 0 represents a magnetic flux density.

E = k. 0.n [v] (8) According to equations (7) and (8), the synchronous motor can be used as follows: a synchronous motor which makes the magnetic flux density 0 to be constant and has a constant torque characteristic from 0 to n range in the number of rotation, a synchronous motor which makes the magnetic flux density 0 variable and has a constant output value characteristic in the range from 0 to n in the number of rotation, a high effective synchronous motor which makes the product of 0.1 to be properly controlled to minimize a motor loss in various load, and the like. Therefore, the synchronous motor according to the present invention can be used in any field of this industry. Some concrete examples will be described below.

Turning to Fig. 20, description will be directed to an AC servomotor which speed is controlled by the synchronous motor 101 according to the present invention.

As shown in Fig. 12, the synchronous motor 101 has the armature winding 19 and the."ield winding 17. The armature winding 19 and the field winding 17 are supplied with an armature current Ia and a field current If. The position and rotational speed detector 143 detects a magnetic pole position and the rotational speed. The position and rotational speed detector 143 detects the rotational speed and the magnetic pole position by use of the manner known in the arts such as a rotary encoder and rotary resolver.

The armature current Ia and the field current If are controlled by the first inverter 145 and the second inverter 147 as described below. That Is, the rotational speed of the synchronous motor 101 is controlled as follows.

First, a rotational,speed amplifier 161 is supplied with a rotational speed command signal S1 which is the representative of a desirable rotational frequency. The position and revolution detector 143 detects the rotational frequency of the synchronous motor 101 to produce a rotational speed signal S2 that is supplied to the rotational speed amplifier 161. Responsive to the rotational speed command and the revolution signals S1 and S2, the rotational speed amplifier 161 produces an armature current control command signal S3.

An armature current amplifier 163 is supplied with the armature current control command signal S3 as well as an armature current command signal S5. An armature current signal S7 detected by an armature current detector 115 provided at an output side of the first Inverter 145 is feedbacked to the armature current amplifier 163. The armature current amplifier 163 is supplied with an inverter control signal S9.

While the field current amplifier 171 is supplied with the field current command signal S11, the field current signal S13 detected by a field current detector 117 which is provided by an output side of the second inverter is feedbacked to the field current amplifier 171. The field current amplifier 171 outputs an inverter control signal S15 for controlling the second inverter 147.

Furthermore, an armature and field current phases control amplifier 173 is supplied with a magnetic pole position signal S4, the armature current signal S7 and the field current signal S13. The first inverter 145 and the second inverter 147 are supplied with control signals S17 and S19 for controlling each phase and frequency of currents from the armature and field current phases control amplifier 173, respectively. -Accordingly, the synchronous motor according to the present invention serves as an AC servomotor by controlling the currents Ia and If to provide the desirable rotational speed.

Fig. 21 is a view of another example according to the present invention and shows a block diagram of an AC servomotor in which a load moving range or an angle of rotation in load is controlled. Fig. 21 has the same circuits as that of in Fig. 20 with the same numerals; therefore, descriptions are omitted.

A position deviation amplifier 251 is supplied with a position command signal S21 which represents the desirable load moving range or the angle of rotation in load. A load moving range signal S23 is detected by a load moving range detecting sensor-253. The position deviation amplifier 251 is supplied with the load moving range signal S23 and the magnetic pole position signal S25. The rotational speed amplifier 161 is supplied with a rotational speed command signal S27 produced by the position deviation amplifier 251 and thus rotating the motor and control the load moving range or the load angle of rotation.

Turning to Fig. 22, the description will be directed to another example of a high efficiency control system in the present invention. The high efficiency control system is able to minimize the loss of the synchronous motor 101. In Fig. 22. the same circuits as that of Fig. 20 are shown with same numerals; therefore descriptions are omitted.

As described above, the output value is represented by p = 2wnT as shown in equation (7), and torque T is represented by T = k2.IA.IB as shown in equation (6). Therefore, the synchronous motor can run with high efficiency if the proportion between the armature current Ia and the field current If is regulated so as to reduce a loss of the motor to a minimum according to the field magnetic flux and motor characteristics. The field magnetic flux characteristic is defined by an armature winding resistance Ra. a field winding resistance Rf, the field current If. The motor characteristics such as iron loss are defined by the frequency of the armature and field current. Desired rotational frequency and torque is controlled which---proportion accomplish the high efficient running.

With reference to Fig. 22, an example of the high efficiency control system for minimizing a copper loss of the motor will be described below.

If the armature current is designated by Ia [A], the field current is designated by If [A]. the armature resistance is designated by Ra [ú11, and the field magnetic resistance is designated by Rf [a}, the copper loss Pc [w]is represented by an equation (9) and the torque T [Nml is represented by an equation (10).

Pc WC-Ra + If2-Rf M (9) T K.1a.If [Nml (10) A load torque is found from the current Ia and If detected by the armature current detector 115 and the field current detector 115. The current Ia and If are variable not to be lower than the load torque, to decide a first control command signal Ia and a second control command signal If so as to make the copper loss Pc minimum, and thus controlling with the first and the second control command signal Ia and If. Namely, in Fig. 22, a motor loss minimum control circuit 211 is supplied with the armature current Ia detected by the armature current detector 115 and the field current If detected by the field current detector 117. The armature resistance-Ra and the field resistance Rf of the motor loss minimum control circuit 211 is set to an eigenvalue determined by the motor. The first control command signal Ia and the second control command signal If produced by the motor loss minimum control circuit 211 is supplied to the armature current amplifier 163 and the field current amplifier 171 instead of the armature current signal S7 and the field current signal S13 in Fig. 20, and thus realizing the minimization of the motor copper loss and high efficiency control.

Turning to Fig. 23, the description will be directed to another example of the synchronous motor according to the present invention. The synchronous motor comprises a rotor 227, the armature winding 19 and field winding 17. The armature winding 19 is directly connected to a three-phase alternating current source. The field winding 17 is connected to the three-phase alternating current source through a condenser 221 and an electromagnetic switch 223. The electromagnetic switch 223 is controlled by a synchronous circuit 225.

First, when the armature winding 19 is supplied with the three-phase. alternating current when the electromagnetic switch 223 is off, an induced current flows through the rotor 227, so that a rotating magnetic field generated by the armature winding 19 and the induced current produce a torque according-to Fleming's rule to rotate the motor as an induction motor. When the rotational speed of the motor approaches a synchronous speed by the induced torque, the synchronous circuit 225 is operated to switch on the electromagnetic switch 223. The field winding 17 is supplied with a current which phase difference is 90 by the condenser 221 to generate a field magnetic pole in the rotor 227. Attraction is generated between the field magnetic pole and the rotating magnetic field. The rotor is synchronized with the attraction and rotates as a synchronous motor. A coil or both a coil and a condenser may be used instead of the condenser 221. Turning to Fig. 24, the description will be directed to another example according to the present invention. The synchronous motor has a rotor 241. In this event, the rotor 241 is provided with permanent magnets 243a and 243b. A permanent magnet magnetic flux 01 is generated by the permanent magnets 243a and 243b. A field winding magnetic flux 0 is generated by the field winding' 17 (u, v, w).

The rotor 241 is provided with the magnetic pole position detector (not shown) to control the field magnetic current so that the direction of the permanent magnet magnetic flux 01 is consistent with the direction of the field windingmagnetic flux 0. In this event, if the permanent magnet magnetic flux 01 and the field winding magnetic flux 0 have the same phase, a composite field magnetic flux EO = 01 + 0 increasing the field magnetic flux. If the permanent magnetic flux 01 and the field winding magnetic flux 0 have antiphases, the composite field magnetic flux EO = 01 - 0 decreasing the field magnetic flux.

Turning to Figs. 25A and 25B, the description will be directed to an example of the synchronous motor having an armature which can be divided into two to simplify the assembly of the motor. In Figs. 25A and 25B, the divided armatures 261a and 261b has windings 263a and 263b, respectively.

Accordingly, limitations on the assembly of the motor is decreased. The divided armatures 261a and 261b can be combined by facing each other in an arrow direction shown in the figure. Therefore, a bearing 265 can be mounted on a rotary axis 267, irrespective of the assembly of the motor.

Turning to Fig. 26, the description will be directed to an example in which the main spindle of a machine tool Is integrally formed with the rotor shaft of the motor. An armature 285 is wound with an armature winding and field winding therein. In the case where the main spindle 281 is made from a magnetic body, its end portion is processed to structure a rotor according to the present invention, and arranging an armature 285 around the rotor, so that it is possible to form the machine tool and the motor as one body. A cutter 287 is mounted on a machine shop tool 289. Machine shop tool 289 is secured to the main spindle 281. The main spindle 281 is rotatably supported by bearing 291.

Turning to Figs. 27, 28A and 28B, the description will be directed to another example of the synchronous motor which is able to assembly in an axis direction. The synchronous motor comprises a field winding 301, an armature winding 303, armature cores 305 and 307, a rotary shaft 313, and a rotor 319. The armature cores 305 and 307 are wound with the field winding 301 and the armature winding 303, respectively. The armature cores 305 and 307 are arranged side by side in the axial direction. Reference axis 309 and 311 are adjusted to make the phase difference between the armature cores 305 and 307 at a 900 angle preferably. In Fig. 27, the rotor 319 is made of a magnetic body 315 and magnetic body part 317 around the rotary shaft 313. The armature cores 305 and 307 are arranged on the outside of the rotor 319. A connector magnetic body 321 for structuring azmagnetic circuit is arranged on the outside of the armature core 305 and 307, thereby providing the closed magnetic circuit shown by a dashed line. Consequently, the synchronous motor of this example shows the same performance as that of the above mentioned synchronous motor with a plurality of windings. Because the distance across the armature can be shortened with the divided armatures, the synchronous motor of this example is available for machines which require a slender motor.

Turning to Fig. 29, description will be directed to an example applying the present invention to a linear motor. The linear motor 401 comprises an armature 403 and a needle 405. The armature 403 is a three-phase armature having two poles and twenty four slots shown in Fig. 12. The needle 405 has a magnetic pole which has the segment structure shown in Fig. 8.

The armature 403 comprises an armature core 407 and a field winding 409 comprising coils u, v,.and w and an armature winding 411 comprising coils U, V, and W. The armature core 407 has a comb section and is wound with the field winding 409 and the armature winding 411 in doublelayer winding. The needle 405 comprises a plurality of magnetic poles 413 made of a magnetic body such as iron and a mounting plate 417 made of a non-magnetic body such as aluminum. The magnetic poles 413 are mounted on the mounting plate 417 with a predetermined space 415 therebetween. When the windings 409 and 411 are supplied with the three phase alternating current, a horizontal force is produced between the armature and the needle. Accordingly, if the armature is fixed, the needle moves and if the needle is fixed, the armature moves- Although this example has two poles and twenty four slots, this example is not limited to Fig. 29 and may be variously modified.

Turning to Fig. 30, description will be directed to the principle for examples of the synchronous generator according to the present invention. The generator comprises an armature core 501 and a rotor 507. The armature core 501 has a double-layer winding, namely, a field winding 503 and an armature winding 505. The rotor 507 is easy to magnetize in vertical direction in figure and difficult to magnetize in horizontal direction In figure because the rotor is a salient-pole type. The windings 503 and 505 are-three-phase windings and have two poles each. The winding 503 and 505 are arranged so that the phase difference is an preferably 90.

When the field winding 503 having coils u, v, and w is supplied with the three phase current, a field magnetic flux 509 is generated. A field winding current is controlled so as to correspond a magnetic pole central axis 511 of the field magnetic flux 509 with an axis of easy magnetization 513 of the rotor constantly. The three phase voltage is induced in the armature winding 505 having coils u', v, and w' by rotating the rotor which.is always magnetized in a constant direction. Therefore, a generator is provided.

An output voltage V and an output frequency f of the generator are represented by equations (11) and (12), respectively.

V = Ki.(D.n [v] (11) f = K2.n.p [HZ] (12) where, K1 and K2 indicate proportional constants, 0 designates a field magnetic flux [MAXWELL], and n designates a rotational frequency per second [rps]. If a field current If is proportionate to the field magnetic flux 0, equation (13) is as follows.

0 = K3-If [MAXWELL] (13) As described above, the synchronous generator according to the present invention does not necessary wind the rotor with a coil nor mount a permanent magnet on the rotor. As a result, the present invention can provide the synchronous generator with a rotor which is exceedingly simple and sturdy.

Fig. 31 shows a block diagragm of a controller for controlling output voltage to be constant against the load fluctuation in the synchronous generator according to the present invention.

In Fig. 31, the controller includes a synchronous generator 521 and a control circuit for keeping an output voltage constant against load fluctuation.

The synchronous generator 521 comprises a rotor 523 and an armature winding 505. The rotor 523 is-connected to a driving-motor 525 such as turbine, engine, and hydraulic turbine and rotates at constant speed. The armature winding 505 is connected to the load 527. The rotor 523 is provided with a magnetic pole position detector 531 such as a rotary encoder to produce a magnetic pole position signal S51. The armature 505 is provided with an instrument potential device 535 to detect output voltage and to produce the output voltage signal S52.

The control circuit includes an armature voltage amplifier 537, a field current amplifier 539, an inverter 543, a field current phase control amplifier 541, and a field current detector 542. The armature voltage amplifier

537 is supplied with a voltage command signal S53 as the desirable voltage and the output voltage signal S52 simultaneously. The field current amplifier 539 is supplied with a field current command signal S55 by the armature voltage amplifier 537 and also a field current single S57 detected by the field current detector 542.

The field current phase control amplifier 541 is supplied with a field current value command signal S59 produced by'the field current amplifier 539 and with a magnetic pole position signal S51. The inverter 543 is supplied with an inverter control signal S61 by the field current phase control amplifier 541.

If the load is not connected to the synchronous generator, namely, noload running,-the induced voltage is equal to the output voltage. If the load is connected to the synchronous generator, a current flows through the armature winding (U, V, W) and a voltage drop is caused by the impedance of the armature winding to reduce the output voltage. Accordingly, the armature voltage amplifier 537 is supplied with the output veltage signal S52 by the instrument potential device 535 for maintaing the output voltage constant by compensating for the voltage drop. The armature voltage amplifier 537 amplifies the deviation between the voltage command signal S53 and the output voltage signal S52 to supply the field current amplifier 539 with the field current command signal S55. The field current amplifier 539 amplifies the deviation between the field current command signal S55 and the field current signal S57 to supply the field current value command signal S59 to the field current phase control amplifier 541. According to the field position signal S51 and the field current value command signal S59, the field current phase control amplifier 541 produce an Inverter control signal S61 so as to correctly supply the field current to the field winding even if the rotor Is placed at a different place. The inverter 543 produces thefield current according to the inverter control signal S61 and controls value of the field current. Therefore, the output voltage is constant even if the load fluctuates.

As mentioned above. according to the second embodiment. there can be provided the synchronous machine having the rotor with a simple and sturdy structure because the rotor does not necessary have a permanent magnet and be wound with coils. At high speeds, the rotor does not -appear dameged due to its sturdy structure.

Claims

What Is Claimed Is:

1.A synchronous motor device comprising:

a stator wound with a first winding and a second winding in double-layer winding; a rotor having salient pole shape and rotatably received in said stator; a first controller serving as a power source of said first winding and controlling rotational frequency of said motor; and a second controller serving as a power source and controlling output value or torque value of said motor.

2. A synchronous motor device comprising:

a stator wound with a first winding and a second winding in double-layer winding; a rotor essentially consisting of magnetic anisotropic materials to provide saliency and being rotatably received in said stator; a first controller serving as a power source of said first winding and controlling rotational frequency of said motor; and a second controller serving as a power source of said second winding and controlling output value or torque value of said motor.

3. A synchronous motor device comprising: a stator wound with a first winding and a second winding in double-layer winding; a rotor being provided with a permanent magnet member to generate field magnetic flux and rotatably received in said stator; a first controller serving as a power source of first winding and controlling rotational frequency of said motor; and a second controller serving as a power source of said second winding and controlling output value or torque 32- value of said motor.

4. A synchronous motor device comprising: a stator wound with a first winding and a second winding in double-layer winding; a rotor wound with at least one coil to be supplied with current and rotatably received in said stator; a first controller serving as a power source said first winding and controlling rotational frequency of said motor; and a second controller serving as a power source of said second winding and controlling output value or torque value of said motor.

5. A synchronous motor device comprising: a stator wound with a first winding and a second winding in double-layer winding; a rotor made of magnetic anisotropic material and rotatably received in said stator; a first controller serving as a power source of said first winding and controlling rotational frequency of said motor; and a second controller serving as a power source of said second winding and controlling output value or torque value of said motor.

6. A synchronous motor device as claimed in any one of Claims 1, 2, 3, 4 or 5.

wherein said second controller keeps a phase difference between the current of said first winding and the current of said second winding in an angle of 900 and further Includes a circuit for controlling gain-magnitude of the current supplied to said first winding.

7. A synchronous motor device as claimed in any one of Claims 1, 2, 3, 4 or 5, wherein said first controller includes; a rotational frequency command device for producing a current command signal to command rotational frequency of said motor; a first winding current determination circuit for comparing said commanded rotational frequency with data measured rotational frequency of said motor to produce a difference therebetween and for determining and producing a first current command signal to said first winding; and a first winding current supply circuit for supplying a first predetermined current to said first winding according to said first current command signal, first current value data of said first winding and position data of said rotor; wherein said second controller includes; an output commander for commanding a commanded output value of said motor; an output arithmetic circuit for calculating,a calculated output value of said motor according to current data supplied to said first and second windings, a rotational frequency data of said motor, and a position data of said rotor; a second winding determination circuit for comparing output said calculated value with said commanded output value to produce a difference therebetween and for producing a second current command signal to said second winding according to said difference; and a second winding current supply circuit for supplying a second predetermined current to said second winding according to said second current command signal from said second winding determination circuit, said second current value data of said second winding and said position data of said rotor.

8. A synchronous machine comprising:

an armature having a core wound with a field winding for generating a field magnetic flux and with an armature winding substantially proceeding by an angle of 90' in electrical phase from said field winding; and a rotor rotatably received in said armature and magnetized in a predetermined direction by said field magnetic flux.

9. A synchronous machine comprising:

an armature having a core wound with a field winding and an armature winding, said field winding having three pairs of three phase windings successively shifted by a phase angle of 120 and generating a field magnetic flux, said armature windings having three pairs of three phase windings successively shifted by a phase angle of 1200 and substantially proceeds by an angle of 90 from said field winding; and a rotor rotatably received in said armature and magnetized in a predetermined direction by said field magnetic flux.

10. A synchronous machine as claimed in Claim 9, wherein said armature winding substantially proceeding by an angle of 900 in electrical phase from said field winding.

11. A synchronous machine as claimed in Claims 8 or 9, wherein said rotor comprises a magnetic anisotropic rotor.

12. A synchronous machine as claimed in Claim 11, wherein said magnetic anisotropic rotor comprises magnetic anisotropic magnetic body having a predetermined shape.

13. A synchronous machine as claimed in Claim 12, wherein said magnetic anisotropic magnetic body comprises a member selected from the group consisting of grain oriented silicon steel and grain oriented nickel steel.

14. A synchronous machine as claimed in Claim 11, wherein said magnetic anisotropic magnetic body is in the 5 shape of salient pole.

15. A synchronous machine as claimed in Claim 11, wherein said magnetic anisotropic magnetic body comprises a magnetic body portion on an outside and a non-magnetic body portion in an inside, said magnetic body being provided with an air gap in a slit shape or a non-magnetic member in a predetermined diameter direction.

16. A synchronous machine as claimed in Claim 11, wherein said magnetic anisotropic magnetic body has a magnetic member provided with an air gap in a slit shape or a non-magnetic member in a predetermined diameter direction.

17. A synchronous machine as claimed in Claim 11, wherein said magnetic anisotropic magnetic body is in the shape of salient pole with four poles.

18. A synchronous machine as claimed in Claim 9, wherein said rotor is integrally connected to a load axis of a machine ok a tool.

19. A synchronous.machine as claimed in Claim 9, wherein said field winding and said armature winding are supplied with two pair of three phase currents shifted each other by an electrical phase angle of 90; said synchronous machine further comprising a control means for controlling torque. rotAtional frequency, and rotation angle and shifting volume of said motor by controlling frequency and current of said three phase currents.

20. A synchronous machine as claimed in Claim 9, wherein said field winding and said armature winding are supplied with two pairs of three phase currents shifted from each other by a predetermined phase angle; said synchronous machine further comprising a control means for controlling torque, rotational frequency, and rotation angle and shifting volume of said motor by controlling frequency and current of said three phase currents.

21. A synchronous machine as claimed in Claim 9, further comprising control means for optimal controlling two pairs of three phase currents supplied to said armature to reduce a loss of said motor to a minimum in case of a predetermined rotation and a predetermined load. 15

22. A synchronous machine as claimed in Claim 9, wherein said armature winding is connected to a three phase power source so as to be rotated closely at nearly synchronous rotations by inducted current torque, while said field winding-is supplied with a three phase power source through a condenser or a reactor, said synchronous machine further comprising a synchronous circuit for providing said rotor with field magnetic pole by supplying said rotor with a current shifted by a predetermined electric phase angle to synchronize said motor.

23. A synchronous motor as claimed in Claim 22, wherein said rotor is provided with a field magnetic pole by said current shifted by an electric phase of 90.

24. A synchronous machine as claimed in Claim 9, wherein said rotor is provided with a permanent magnet member to generate a field magnetic pole as a total of a magnetic flux generated by said permanent magnet and a magnetic flux generated by a field current.

25. A synchronous machine as claimed in Claim 9, wherein said armature is formed to be divisible into two or more to assemble a stator after said rotor is mounted to a machine.

26. A synchronous machine as claimed in Claim 25, wherein said rotor is integrally formed with a shaft of a machine as one body.

27. A synchronous machine as claimed in Claim 9, wherein said core is divided into two in an axial direction, one of the divided core is wound with said field winding and the other divided core is wound with said armature winding.

28. A synchronous machine as claimed in Claim 9, wherein said synchronous machine is used for a linear motor, said armature is formed as a linear armature, and said stator comprises a needle having a plurality of 20 magnetic poles placed in an axial direction.

29. A synchronous machine as claimed in Claim 9. wherein said synchronous machine serves as a synchronous generator. 25

30. A device which comprises a stator wound with a first winding and a second winding, a rotor rotatably receivable in the stator, which rotor is magnetisable, in use, in a predetermined direction, a first controller for controlling rotational frequency of the motor and which, in use, serves as a power source for the first winding and a second controller for controlling output value or torque value of the motor and which, in use, serves as a power source for the second winding.

31. A device according to Claim 30, wherein the first winding and the second winding are arranged in a double layer.

32. A device according to Claim 30 or 31, wherein the magnetisable rotor is a permanent magnet.

33. A device according to any one of Claims 30. to 32, wherein the second controller maintains a phase difference between the current of the first winding and the current of the second winding at an angle a of 00-<a:5900.

34. A machine which comprises an armature having a core wound with a field winding for generating a field magnetic flux and with an armature winding substantially proceeding by an electrical phase angle a of 00:5a5900 from the field winding and a rotor rotatably receivable in the armature, which rotor is magnetisable, in use, in a predetermined direction.

35. A machine according to claim 34 wherein the magnetisable rotor is a permanent magnet.

36. A machine which comprises.a linear armature having a core wound with a f ield winding for generating a f ield magnetic f lux and with an armature winding substantially proceeding by an electrical phase angle a of 00<a:5900 from the f ield winding and a stator, which stator comprises a needle having a plurality of magnetic poles aligned in an axial direction.

37. A machine according to any one of Claims 34 to 36, wherein the f ield winding comprises n pairs of n phase windings successively shifted by a phase angle of -16-00 and the armature winding comprises n pairs of n p1Pase windings successively shifted by a phase angle of 3600 wherein n is an integer. n

38. A machine according to Claim 37, wherein n is 3.

39. A machine according to any one of claims 8 to 29 or 34 to 38. wherein the machine is a generator.

40. A device substantially as hereinbefore described with reference to and as shown in Figures 3, 4, 6, 9 to 12, 14, or 20 to 31 of the accompanying drawings.

41. A device having a rotor substantially as hereinbefore described with reference to and as shown in Figures 15 to 19 of the accompanying drawings.

42. A machine substantially as hereinbefore described with reference to and as shown in Figures 3, 4, 6, 9 to 12, 14, or 20 to 31 of the accompanying drawings.

43. A machine having a rotor substantially as hereinbefore described with reference to and as shown in Figures 15 to 19 of the accompanying drawings.

44. Any novel feature or combination of features described herein.