JP2003111370A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a cost, and to prolong the life by using a single-phase AC power supply, and forming a motor out of a simple drive (speed control) circuit. SOLUTION: This motor is a two-pole flat motor having air gaps in axial directions. The motor is provided with an excitation coil 5 which generates AC magnetic fluxes by the single-phase AC power supply and a pair of permanent magnets 6, 7 which generate DC magnetic fluxes, and is composed of a stator 1 which generates those magnetic fluxes in the axial direction of a shaft 3, and a disk-shaped rotor 2 on which a short-circuiting winding 10 to which diodes 11 for causing a half-wave rectified current to flow by the AC magnetic fluxes are connected in series, is wound in the circumferential direction at equal intervals. The AC magnetic fluxes generated by the excitation coil 5 of the stator 1 and the DC magnetic fluxes generated by the permanent magnets 6, 7 are generated in directions vertical to the surface of the rotor 2. A force in one direction acts on the short-circuiting winding 10 by the DC magnetic fluxes and a current which flows in the short-circuiting coil 10 by the AC magnetic fluxes, and this generates continuous torque and rotates the rotor 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor used as a power source for home electric appliances and various machines, and more particularly to an electric motor having a novel structure different from an induction motor (induction motor) or a DC motor. It is a thing.

[0002]

2. Description of the Related Art As an electric motor, an induction motor using an alternating current as a drive source and a brushless D using a direct current as a drive source
There are C motors, universal motors, etc. that can be driven by either AC or DC. An induction motor is one in which a rotating magnetic field is generated in a stator using a three-phase power source or a single-phase power source, and when the rotor is placed in the rotating magnetic field, the rotor rotates in the rotation direction of the magnetic field. Since such an AC motor has a simple structure, the manufacturing cost is low, and the driving circuit is simple, so that the cost can be reduced, and thus it is widely used in home appliances. .

A brushless DC motor comprises a stator having windings and a rotor having a permanent magnet embedded therein.
For example, in the case of a three-phase motor, while energizing the two phases of the stator, the position of the rotor is detected using the induced voltage generated in the remaining one phase, or it is placed in the main body. The position of the rotor is detected using a sensor, and the energization of the stator winding is switched based on this position detection, and the direction of the current flowing in the winding is controlled to generate a rotating magnetic field in the stator. The rotor rotates under the influence of this rotating magnetic field.

Such a DC motor is small in size and strong in power. In other words, since the torque is large and the speed control etc. can be easily performed by the electronic circuit (inverter drive circuit), it has a wide range of use, and is used in various fields including home appliances to industrial equipment. There is. Similar to a DC motor, a universal motor has a relatively small size, a high power, and a high rotation speed, and is used for electric home appliances such as electric saws and electric planes.

[0005]

Among the above electric motors, the induction motor is limited in its range of use due to the drawback of low efficiency, and the brushless DC motor requires a high-priced inverter drive circuit, so that the product is expensive. It comes at a cost. Further, the universal motor has a drawback that it has a short life due to abrasion of the brush.

The present invention has been made in view of the above problems, and an object of the present invention is to enable driving with a single-phase AC power source, speed control with a simple circuit, and cost reduction and long life. It is to provide a new electric motor that is capable of

[0007]

In order to achieve the above object, the present invention provides a stator having at least one set of an iron core, an AC excitation winding and a pair of permanent magnets, and a rotor having one set. The semiconductor device has a plurality of short-circuit windings in which semiconductor elements that flow current only in the direction are interposed in series, and an alternating current is applied to the alternating excitation winding to generate an alternating magnetic flux (alternating magnetic field). A voltage is induced in the short-circuited winding to flow a half-wave rectified current (current in only one direction).
With the magnetic flux generated by the permanent magnet, a force is exerted in one direction (clockwise or counterclockwise) on the short-circuited winding to generate continuous torque, and the rotor is continuously rotated. It is characterized by that.

The rotor is arranged inside the stator, the rotor is formed into a disk shape, and short-circuit windings including the semiconductor elements are circumferentially equidistantly arranged on the disk surface of the rotor. Provided,
When the stator is configured so that the AC magnetic flux generated by the AC excitation winding and the magnetic flux generated by the permanent magnet are generated in the disc surface direction of the rotor, and is a flat type electric motor having an air gap formed in the axial direction. Good. Thereby, the single-phase AC power is supplied to the AC excitation winding,
The flat type electric motor rotates. Moreover, the electric motor can be realized as a flat type electric motor having low cost and long life.

The rotor is arranged inside the stator,
This stator has a cylindrical shape, and the iron core, AC excitation winding, and permanent magnet are provided in the circumferential direction on the inner peripheral side of the stator to rotate the AC magnetic flux generated by the AC excitation winding and the magnetic flux generated by the permanent magnet. It is generated in the side direction of the child,
The inner rotor type motor in which the rotor has a cylindrical shape and short-circuit windings including the semiconductor element are provided on the outer peripheral side of the rotor at equal intervals in the circumferential direction, and an air gap is formed in the radial direction. Good to do. As a result, the single-phase AC power supply is supplied to the AC excitation winding, and the inner rotor type electric motor rotates. Moreover, the electric motor can be realized as an inner rotor type electric motor having a low cost and a long life.

The rotor is arranged outside the stator,
This stator has a cylindrical shape, and the AC excitation winding and the permanent magnet are provided on the outer peripheral side of the stator in the circumferential direction so that the AC magnetic flux generated by the AC excitation winding and the magnetic flux generated by the permanent magnet are generated in the rotor. In addition to generating in the circumferential surface direction, the rotor has a cylindrical shape, and short-circuit windings including the semiconductor element are provided on the inner circumferential side of the rotor at equal intervals in the circumferential direction, and an air gap is formed in the radial direction. It is preferable to use an outer rotor type electric motor in which As a result, the single-phase AC power is supplied to the AC excitation winding, and the outer rotor type electric motor rotates. Moreover, the electric motor can be realized as an outer rotor type electric motor having a low cost and a long life.

The AC excitation winding may be concentrated winding.
As a result, the cost of the electric motor can be reduced by using the concentrated winding, which is actually low in cost.

A ferrite magnet may be used as the permanent magnet. As described above, since the inexpensive ferrite magnet is used, cost reduction of the electric motor can be expected.

A rare earth magnet may be used as the permanent magnet. As described above, by using the rare earth magnet having a large magnetic force, an electric motor having a large torque can be realized.

A thyristor is connected in series to the AC exciting winding, an AC power is supplied to the series circuit to allow an AC current to flow through the AC exciting winding, and the conduction angle of the thyristor can be varied to control the phase. It should be set to. As a result, a simple and inexpensive thyristor circuit can be used without using a high-cost inverter circuit or the like, so that the cost of a device using the electric motor can be reduced.

The AC excitation winding is provided with a plurality of taps at different positions. When an AC current is passed through the AC excitation winding, the taps are switched to change the magnitude of the AC current for speed control. It should be possible. As a result, a control circuit for speed control is hardly needed, and the cost of the device using the electric motor can be further reduced.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
It will be described in detail with reference to FIGS. 2 is a schematic sectional view taken along the line A-AA in FIG. 1 and 2, an electric motor according to a first embodiment of the present invention is a two-pole flat type motor having an air gap in the axial direction, and includes one set of an iron core, an AC excitation winding, and a pair of permanent magnets. A stator is provided with a magnet to generate an AC magnetic flux generated by an AC excitation winding and a magnetic flux generated by a permanent magnet in the rotation axis direction, and a rotor 2 having a plurality of short-circuited windings for flowing only one current by the AC magnetic flux. It consists of

The stator 1 is provided with an exciting winding (AC exciting winding) 5 on a yoke portion 4 having a U-shaped cross section so as to sandwich the disc-shaped rotor 2 from the axial direction of the shaft 3. Two pairs of permanent magnets 6 and 7 are arranged adjacent to the yoke portion 4 with different poles, respectively, and the AC magnetic flux from the excitation winding 5 and the magnetic flux from the permanent magnets 6 and 7 are perpendicular to the surface of the rotor 2. It is configured to generate.

The two pairs of permanent magnets 6 and 7 are fixed to magnet yoke portions (iron) 8 and 9 each having a U-shaped cross section, and
Adjacent pairs of permanent magnets have different poles, for example, the upper permanent magnet 6a fixed to one magnet yoke portion 8 has an S pole,
When the lower permanent magnet 6b has an N pole, the upper permanent magnet 7a fixed to the other magnet yoke portion 9 has an N pole and the lower permanent magnet 7b has an S pole.

The yoke portion 4, the magnet yoke portions 8 and 9 and the permanent magnets 6a, 6b, 7a and 7b are at least the rotor 2.
Each has a fan-shaped portion in conformity with the disk shape, and the central angle of these arcs is approximately 120 degrees. Further, the yoke portion 4 has a shape in which an outer circumferential arc is linearly extended and a fan-shaped outer arc is added with a substantially rectangular shape in order to easily apply the excitation winding 5.

The excitation winding 5 may be concentrated winding in consideration of cost reduction. The permanent magnets 6a, 6b, 6
Do not use ferrite magnets or rare earth magnets as c and 6d. When a ferrite magnet is used, cost reduction of the electric motor can be expected, and when a rare earth magnet is used, high efficiency and miniaturization of the electric motor can be expected. Further, the permanent magnets 6a and 6b may be permanent magnets having a U-shaped cross section, and the permanent magnets 7a and 7b may be permanent magnets having a U-shaped cross section, and may be a pair of permanent magnets.

A plurality of short-circuit windings (closed-circuit windings) 10 are arranged on the rotor 2 at equal intervals in the circumferential direction, and a current flows through these short-circuit windings 10 in only one direction. As described above, the semiconductor elements (for example, diodes) 11 are interposed in series.

A film-shaped winding is preferably used as the short-circuit winding 10. Further, the short-circuit winding 10 may have a similar shape to the fan shape so that at least the magnetic flux generated by the fan-shaped yoke portion 4 may penetrate more, and the short-circuit winding 10 may be arranged at equal intervals (60 degree intervals) in the circumferential direction. It is good to arrange 6 pieces.
Therefore, the number of adjacent short-circuit windings 10 is 60
It will overlap again and again.

In order to drive the electric motor having the above structure, an AC voltage is applied to the excitation winding 5 and an AC current is passed through the excitation winding 5, whereby an AC magnetic flux (alternating magnetic field) is generated inside the U-shaped portion of the yoke portion 4. ) Is generated. The AC magnetic flux is generated in a direction substantially vertical to the paper surface of FIG. 1 (vertical direction of the paper surface of FIG. 2) and penetrates the inside of the short-circuit winding 10 of the rotor 2.

Induced power is generated in the short-circuit winding 10 by the AC magnetic flux. In this case, only half-wave rectified current (current in only one direction) flows through the diode 11. on the other hand,
Magnetic flux in the vertical direction is generated in the rotor 2 by the two pairs of permanent magnets 6 and 7, respectively. At this time, the DC magnetic flux is in the direction perpendicular to the short-circuit winding 10 in which the half-wave rectification current is flowing.

Therefore, due to the half-wave rectification current and the DC magnetic flux of the pair of permanent magnets 6 and 7, a force acts on the short-circuit winding 10 in the direction of the broken line arrows a and b in FIG. 1 (that is, torque is generated). ), The rotor 2 is rotated clockwise. That is, the magnetic fluxes from the permanent magnets 6a and 6b penetrate from the front side to the back side of the paper, and the magnetic fluxes from the permanent magnets 7a and 7b penetrate from the back side to the front side of the paper.

When the rotor 2 rotates by a certain angle, for example, 6
When rotated by 0 degree, torque is generated in the clockwise direction by the half-wave rectification current and the DC magnetic flux of the pair of permanent magnets 6 and 7, respectively, as described above. In this way, the rotor 2 can be continuously rotated in the clockwise direction by continuously generating the torque in synchronization with the AC voltage.

In the above embodiment, the number of short-circuit windings 10 provided on the rotor 2 is 6, but the short-circuit windings 10 are provided.
There may be three and the adjacent short-circuit windings 10 may not overlap. In this case, it is highly likely that the torque and the rotational speed (rotational speed) will not be as good as those in the above-described embodiment.

As a method of controlling the torque and the rotation speed (rotation speed) of the electric motor, for example, the drive circuit shown in FIG. 3 may be used. In FIG. 3, a thyristor 12 is connected in series to the excitation winding 5 of the AC excitation winding, and the voltage of the AC power supply 13 is supplied to this series circuit. Thyristor 12
When the energization is controlled, the voltage applied to the excitation winding 5 has the shape shown in FIG. That is, if the energization angle θ of the thyristor 12 is changed and the phase is controlled, the current of the exciting winding 5 can be changed.

When the current of the exciting winding 5 changes, the density of the AC magnetic flux generated in the yoke portion 4 naturally changes, so that the induced power generated in the short-circuit winding 10 changes and the torque generated in the rotor 2 changes. fluctuate. This fluctuation of the rotational force also affects the rotational speed of the rotor 2, and the rotational speed changes. Therefore, FIG.
As shown in, the torque and the rotational speed are controlled by the magnitude of the energization angle θ, and the speed can be controlled.

As a method of controlling the rotation speed and torque of the electric motor, for example, as shown in FIG. 6, a plurality of taps (for example, L, M, H) are drawn from the middle of the excitation winding 5 and the taps are switched. Alternatively, an AC voltage may be applied.

For example, when the tap H is switched, the resistance of the excitation winding 5 decreases, so that the current of the excitation winding 5 increases. That is, since the density of the AC magnetic flux generated inside the U-shape of the yoke portion 4 becomes high, the induced power generated in the short-circuit winding 10 becomes large and the torque related to the short-circuit winding 10 becomes large. In this way, the torque and the rotation speed can be controlled by switching the taps and changing the current of the excitation winding 5.

FIG. 7 is a schematic configuration diagram of an electric motor showing a second embodiment of the present invention. In the figure, the same parts as those in FIG. 1 and FIG. This electric motor is a four-pole inner rotor type motor with an air gap in the radial direction, and it has two pairs of permanent magnets arranged between the opposing AC excitation windings (stator windings) and these stator windings in the circumferential direction. A stator 20 that has a magnet and generates an AC magnetic flux from the stator winding and a DC magnetic flux from a permanent magnet in parallel to the paper surface; and a plurality of short-circuit windings (rotor winding Line 21) and the rotor 21.

The stator 20 has a cylindrical yoke portion 20.
Stator windings 22 and 23 that generate an AC magnetic flux are applied to the opposing teeth 20b and 20c formed in a, and the permanent magnets 24 and 25 are provided between the stator windings 22 and 23 in the circumferential direction. 26 and the permanent magnet 27, and the adjacent permanent magnets 24 and 25 and the permanent magnet 2 are arranged.
6, 27 have different polarities, and the opposing permanent magnets 24,
27 and the permanent magnets 25 and 26 have the same pole. The stator windings 22 and 23 may be reversely wound and may be concentratedly wound for the same reason as in the previous embodiment.

Twelve teeth 21a are formed on the rotor 21 at equal intervals in the circumferential direction, and two teeth are arranged every other slot.
The rotor winding 28 is applied over the two teeth 21a, 21a,
Twelve rotor windings 28 are sequentially provided in the rotor winding 28 so that a semiconductor element (for example, a diode) 29 is interposed in series so that a current flows only in one direction.

The teeth 20b, 20c of the stator 20 are also provided.
The tooth width is equal to or larger than the width of the teeth 20b and 20c at least over the teeth 21a and 21a of the rotor 21. Further, the width of the permanent magnets 24 to 27 in the circumferential direction is set so as to cover the entire two teeth 21a, 21a of the rotor 21,
The teeth 20a, 20b and the permanent magnets 24 to 27
Is 60 degrees apart.

When driving the electric motor having the above structure, an AC voltage is applied to the stator windings 22 and 23. For example, the magnetic flux from the teeth 20b is generated by the air gap, the rotor 2
1 and the tooth 20c through the air gap, and further divided into two at the yoke portion 20a and returned to the original state. Also,
The magnetic flux from the tooth 20c also returns to its original state.

At this time, as in the previous embodiment, since the magnetic flux penetrates the rotor winding 28, an induced voltage is generated in the rotor winding 28. At this time, only the half-wave rectification current flows by the diode 29, and the permanent magnets 24 to 25 generate a magnetic flux in the lateral direction with respect to the rotor 21.

Therefore, by the half-wave rectified current and the DC magnetic flux of the permanent magnets 24 to 27, the rotor winding 28
A force acts in one direction (counterclockwise direction) to rotate the rotor 21 counterclockwise. When the rotor 21 rotates by a certain angle, for example, 30 degrees, torque is generated in the counterclockwise direction due to the half-wave rectification current and the DC magnetic flux of the pair of permanent magnets 24 to 27 as described above.

In this manner, the torque is continuously generated in synchronization with the AC voltage, so that the rotor 2 continuously rotates counterclockwise. In the present embodiment, the first
The driving method and speed control described in the above embodiment are used. Further, for the same reason as in the first embodiment, the permanent magnets 24 to 27 are ferrite magnets or rare earth magnets.

FIG. 8 is a schematic configuration diagram of an electric motor showing a third embodiment of the present invention. This electric motor is a four-pole outer rotor type motor having an air gap in the radial direction, and is arranged inside and between a pair of AC excitation windings (stator windings) and the circumferential direction of these stator windings. A stator 30 that has two pairs of permanent magnets and that generates an AC magnetic flux from the stator winding and a DC magnetic flux from the permanent magnets in parallel with the plane of the paper, and a stator 30 outside the stator 30 that has only one of them. The rotor 31 is provided with a plurality of short-circuit windings (rotor windings) through which electric current flows.

The stator 30 has a cylindrical yoke portion 30.
The stator windings 32 and 33 that generate alternating magnetic flux are provided on the teeth 30b and 30c that are opposite to each other and extend to the outer peripheral side, and the permanent magnet 34 is provided between the stator windings 32 and 33 in the circumferential direction.
And the permanent magnet 35, and the permanent magnet 36 and the permanent magnet 3
7 are arranged so that the adjacent permanent magnets 34 and 35 and the permanent magnets 36 and 37 have different polarities, and the opposing permanent magnets 34 and 37 and the permanent magnets 35 and 36 have the same polarities. The stator windings 32 and 33 may be reversely wound and concentrated winding for the same reason as in the previous embodiment.

The rotor 31 is provided with 1 toward the center of rotation.
The two teeth 31a are formed at equal intervals in the circumferential direction, and the rotor winding 38 is provided over the two teeth 31a, 31a arranged at intervals of one slot. Twelve rotor windings 38 are sequentially provided with a semiconductor element (for example, a diode) 39 interposed in series so as to flow.

The teeth 30b and 30c of the stator 30 are also provided.
The tooth width of the permanent magnets 34 to 37 is about the width of the teeth 31a of the rotor 31.
b, 30c and the permanent magnets 34 to 37 are spaced by 60 degrees.

When driving the electric motor having the above structure, an AC voltage is applied to the stator windings 32 and 33. For example, the magnetic flux from the tooth 30b may cause the air gap and the rotor 2
The outer peripheral core 1 splits into two and reaches the tooth 30c through the air gap, and then returns to the original state through the yoke portion 30a. Further, the magnetic flux from the tooth 30c also returns to the original state.

At this time, since the magnetic flux penetrates the rotor winding 38 as in the previous embodiment, the rotor winding 38 is
An induced voltage is generated in. In this case, only the half-wave rectified current flows through the diode 39, and the permanent magnets 34 to 37 generate a magnetic flux in the lateral direction with respect to the rotor 31.

Therefore, as in the second embodiment, a force acts in one direction on the rotor winding 38 by the half-wave rectified current and the DC magnetic flux of the permanent magnets 34 to 37, and the rotor 31 is rotated.
Will be rotated. In this case, the direction of the magnetic flux generated by the permanent magnets 34 to 37 is opposite to that in the second embodiment, so that the rotor 31 rotates in the clockwise direction. Since the detailed description of the rotation operation of the rotor 31 is as described in the second embodiment,
Please refer to the second embodiment.

In this way, the rotor 2 is continuously rotated counterclockwise by continuously generating the torque in synchronization with the AC voltage. In this embodiment, the driving method and phase control (speed control) described in the first embodiment are used. For the same reason as in the first embodiment, the permanent magnets 34 to 37 are ferrite magnets or rare earth magnets.

[0048]

As described above, the present invention has the following effects. The motor of the present invention has at least one AC excitation winding and a pair of permanent magnets in the stator, and has at least three short-circuit windings in which a diode is interposed in series in the rotor. An alternating magnetic flux (alternating magnetic field) is generated by the windings, and a half-wave rectification current (current in only one direction) is applied to the short-circuited windings. Since a force is applied to generate continuous torque, it is possible to realize an electric motor that combines a DC motor and an AC motor with permanent magnets. Therefore, for example, the efficiency is higher than that of an induction motor, and an inexpensive inverter circuit or the like is not required by directly using the AC voltage of a single-phase AC power source, as compared with a brushless DC motor, so that cost reduction can be achieved. Can be planned. Furthermore, compared with a universal motor, it does not require a brush, so it can have a longer life. Furthermore, the drive can be speed-controlled by a simple circuit such as a thyristor, which also realizes low cost. Has a useful effect.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electric motor showing a first embodiment of the present invention.

2 is a schematic cross-sectional view of the electric motor shown in FIG.

FIG. 3 is a schematic drive circuit diagram for driving the electric motor shown in FIGS. 1 and 2.

4 is a schematic waveform diagram for explaining the operation of the drive circuit shown in FIG.

5 is a schematic graph for explaining the operation of the electric motor by the drive circuit shown in FIG.

6 is a schematic drive circuit diagram for driving the electric motor shown in FIGS. 1 and 2. FIG.

FIG. 7 is a schematic configuration diagram of an electric motor showing a second embodiment of the present invention.

FIG. 8 is a schematic configuration diagram of an electric motor showing a third embodiment of the present invention.

[Explanation of symbols]

1, 20, 30 Stator 2, 21, 31 Rotor 3 Shaft 4 Yoke part 5, 22, 23, 32, 33 Excitation winding (AC excitation winding) 6,7 Pair of permanent magnets 6a, 7b, 25, 26,35,36 Permanent magnet (S
Pole) 6b, 7a, 24, 27, 34, 37 Permanent magnet (N
Pole) 8,9 Magnet yoke part 10,28,38 Short-circuited winding (closed-circuit winding in which diodes are connected in series) 11,29,39 Semiconductor element (diode) 12 Thyristor 13 AC power supply 20a Yoke part (stator 20) 20b, 20c Teeth (of the stator 20) 30a Yoke part (of the stator 30) 30b, 30c Teeth (of the stator 30)

Claims (10)

[Claims] 1. A stator has at least one set of an iron core, an AC excitation winding, and a pair of permanent magnets, and a plurality of semiconductor elements in which a semiconductor element for flowing a current only in one direction is interposed in series in a rotor. A short-circuit winding is provided, and an AC magnetic flux (alternating magnetic field) is generated by flowing an AC current through the AC excitation winding, and a voltage is induced in the short-circuit winding by the AC magnetic flux to generate a half-wave rectification current (one Directional current), the current and the magnetic flux generated by the permanent magnet exert a force in one direction (clockwise or counterclockwise) on the short-circuited winding to generate continuous torque, An electric motor, wherein the rotor is continuously rotated. 2. The rotor is disposed inside the stator, the rotor is disc-shaped, and short-circuit windings including the semiconductor element are circumferentially arranged on the disc surface of the rotor. Provided at intervals,
The stator is configured so that the AC magnetic flux generated by the AC excitation winding and the magnetic flux generated by the permanent magnet are generated in the disc surface direction of the rotor, and is a flat type electric motor having an air gap formed in the axial direction. The electric motor according to claim 1. 3. The rotor is arranged inside the stator, the stator is formed into a cylindrical shape, and the iron core, the AC excitation winding, and the permanent magnet are provided in the circumferential direction on the inner peripheral side of the stator. And a magnetic flux generated by the permanent magnet are generated in the lateral direction of the rotor, and the rotor has a cylindrical shape, and a short-circuit winding including the semiconductor element on the outer peripheral side of the rotor. The electric motor according to claim 1, wherein the inner rotor type electric motor has a structure in which the air gaps are provided at equal intervals in the circumferential direction, and an air gap is formed in the radial direction. 4. The rotor is arranged outside the stator, the stator is formed into a columnar shape, and the AC excitation winding and the permanent magnet are provided in the circumferential direction on the outer peripheral side of the stator, and the same AC An AC magnetic flux generated by the excitation winding and a magnetic flux generated by the permanent magnet are generated in the inner peripheral surface direction of the rotor, and the rotor has a cylindrical shape, and a short-circuit winding including the semiconductor element on the inner peripheral side of the rotor. The electric motor according to claim 1, wherein the electric motor is an outer rotor type electric motor having a structure in which the air gaps are provided at equal intervals in the circumferential direction, and an air gap is formed in the radial direction. 5. The electric motor according to claim 1, 2, 3 or 4, wherein the AC excitation winding is a concentrated winding. 6. The electric motor according to claim 1, 2, 3, 4, or 5, wherein a ferrite magnet is used as the permanent magnet. 7. The electric motor according to claim 1, 2, 3, 4 or 5, wherein a rare earth magnet is used as the permanent magnet. 8. A thyristor is connected in series to the AC exciting winding, and an AC power is supplied to the series circuit to allow an AC current to flow in the AC exciting winding, while changing the conduction angle of the thyristor to change the phase. Controllable claims 1, 2, 3, 4,
The electric motor according to 5, 6, or 7. 9. The AC excitation winding is provided with a plurality of taps at different positions, and when an AC current is passed through the AC excitation winding, the taps are switched to change the magnitude of the AC current. Claims 1, 2 which enable speed control by
The electric motor according to 3, 4, 5, 6 or 7. 10. The electric motor according to claim 1, wherein a diode, a transistor, or a thyristor is used as the semiconductor element that allows a current to flow only in one direction.