JPH11252876A - Reluctance motor, apparatus and method for driving the motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly start a reluctance motor by making good use of an induced current produced in the rotor, when rotating fields are produced. SOLUTION: A rotor 3 having a salient-pole portion 2 is provided with a short-circuiting ring 6 penetrating the rotor, made of a material the conductivity which is higher than that of the material of the rotor 3. Induced currents are passed through the short-circuiting ring 6 due to rotating fields, and induced torque is developed. The torque is utilized in the start-up, and thereby asynchronous operation is performed. When the number of rotations of the rotor 3 reaches a specified value, rotating fields are produced so that a constant phase difference angle to the rotor 3 is maintained, and thus synchronous operation conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure and drive of a synchronous motor using reluctance torque.

[0002]

2. Description of the Related Art Most types of motors conventionally used are a DC motor, an induction motor and a DC brushless motor. However, in recent years, due to advances in control methods and devices, techniques for effectively utilizing reluctance torque have been improved.In general, motors that operate only with reluctance torque and motors that operate by combining reluctance torque with conventional magnet torque and the like are generally used. It is becoming. The reluctance torque is generated by a difference between the magnetic resistance when the rotor is in the position of the d-axis excitation and the magnetic resistance when the rotor is in the position of the q-axis excitation.

In a reluctance motor which is a synchronous motor using reluctance torque, it is necessary to increase the magnetic salient pole ratio by devising a rotor shape in order to effectively utilize the reluctance torque. Is a technique disclosed in Japanese Patent Application Laid-Open No. 5-316702. In the reluctance motor having this salient pole portion, by providing a plurality of non-magnetic portions along a magnetic path at the time of d-axis excitation having a cross section orthogonal to the axis of the rotating shaft of the rotor, the magnetic property at the time of d-axis excitation is increased. The difference between the resistance and the magnetic resistance during the q-axis excitation is increased to increase the magnetic salient pole ratio.

The reluctance motor can generate reluctance torque and maintain rotation in a synchronous state.
At startup, it is necessary to use some means to raise the number of rotations to the synchronous speed. For this reason, an induction motor is juxtaposed, and the operation is accelerated by performing asynchronous operation by the induction motor at the time of startup. However, this structure requires two types of motors, so that the structure is complicated and large.

Therefore, in order to drive a reluctance motor without using an induction motor, it is preferable to detect the rotor position and perform excitation so as to apply a magnetomotive force in an appropriate direction. In this case, a device must be devised when starting the motor. The starting method is disclosed in JP-A-5-316777. This starting method energizes one of the stator windings, temporarily stops the salient pole portion at a desired position, detects the position of the rotor, and then starts the stator winding at the desired position. The motor is driven by rotating the rotor in an arbitrary direction by sequentially exciting the stator windings adjacent to the direction to be rotated.

[0006]

In a rotor in which the magnetic salient pole ratio is increased by providing a plurality of non-magnetic portions along the magnetic path of the prior art, the non-magnetic portion may be a simple air gap. In view of the above, it is better to fill the non-magnetic member. At present, aluminum is the most common material for the non-magnetic member because of its strength and cost. However, since aluminum has high conductivity, an induced current and an overcurrent flow due to harmonic components, resulting in energy loss. In addition, even when asynchronous operation is performed at the time of startup, an induced current flows and energy is lost.

When the reluctance motor is started, if the rotor position is detected and then excitation is not performed so as to apply a magnetomotive force in an appropriate direction, the motor may or may not rotate in the opposite direction. Therefore, in order to utilize the reluctance torque, a highly accurate position detector is required. Further, it is necessary to provide a position detection step before the start-up, and the drive control becomes complicated.

In view of the above, it is an object of the present invention to provide a reluctance motor capable of performing a smooth start by effectively utilizing an induced current generated at the time of starting to obtain an induced torque. It is another object of the present invention to provide a reluctance motor that can be started with easy drive control without detecting the rotor position at the time of starting.

[0009]

The object of the present invention is to provide a rotor having salient poles provided with a short-circuit ring having higher conductivity than the rotor. Alternatively, a magnetic material and a non-magnetic material having higher conductivity are alternately overlapped along a plane parallel to the axial direction, so that the rotor has a magnetic salient pole structure, and the rotor has a magnetic salient pole structure. At both ends, a non-conductive coating plate with high conductivity is provided so as to cover the entire end of the rotor or only a part of the periphery, and the non-magnetic material and the coating plate are electrically connected to form a short-circuit ring Is what you do.

As a result, an induced current flows through the short-circuit ring due to the rotating magnetic field, and an induced torque is generated. By utilizing this torque at the time of starting, asynchronous operation is performed. When utilizing the reluctance torque, the synchronous operation is performed by detecting the position of a rotor having a magnetic salient pole structure and generating a rotating magnetic field so as to maintain a constant phase difference angle with the rotor. When the rotor is formed to have a shape in which the rotor is twisted along the axial direction, torque pulsation is reduced, and a highly reliable reluctance motor is obtained.

A driving device for driving the reluctance motor includes a driving circuit for generating a rotating magnetic field in the stator, a position detector for detecting the rotation speed and the position of the rotor, A control circuit for controlling a drive circuit to change the number of rotations of the rotating magnetic field based on the output signal.

When a rotating magnetic field is generated in the stator at the time of startup, the rotor starts to rotate with an induction torque generated by the induction current of the short-circuit ring, and is started as a slipping induction motor. When a predetermined number of rotations is reached, the revolving motor is driven as a reluctance motor by performing control to switch the number of rotations of the rotating magnetic field to the number of rotations for performing synchronous operation.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a reluctance motor according to the present invention will be described. First, as shown in FIG. 1, the reluctance motor of the first embodiment includes a cylindrical stator 1 for generating a rotating magnetic field, and a rotor 3 having a salient pole portion 2 inserted into the stator 1. It has a two-pole magnetic salient pole structure.

Although not shown, the stator 1 is provided with a winding having a plurality of poles. The rotor 3 is made of a magnetic material such as a silicon steel plate, and has a shape obtained by cutting off both side surfaces of a cylinder.
The rotation shaft 4 passes through the center. The portion of the arc surface is the salient pole portion 2, and the gap between the salient pole portion 2 and the stator 1 is smaller than the gap between the flat portion of the side surface and the stator 1. A position detector 5 such as an optical rotary encoder is disposed at one end of the rotor 3 and detects the number of rotations and the position from the rotation angle of the rotor 3. These constitute a synchronous reluctance motor.

A pair of nonmagnetic short-circuit rings 6 are embedded in the rotor 3, penetrate the salient pole portion 2 in the axial direction, and both ends protrude outside the rotor 3. For the short-circuit ring 6, a coil having a higher conductivity than the rotor 3, such as a copper wire or an aluminum wire, is used so that an induced current flows by a rotating magnetic field.

As described above, when the rotor 3 of the reluctance motor has a structure having magnetic salient poles, the following reluctance torque T can be obtained.

T = n / 2 · (Ld−Lq) Id · Iq (1) Id = Isin θ (2) Iq = Icos θ (3) n; number of poles Ld, Lq; d, q-axis inductance Id, Iq; d , Q-axis current θ; current phase angle of I with respect to d-axis From equations (1), (2), and (3), the current phase angle of I must be kept constant with the rotor d-axis. This means that the rotating magnetic field and the rotor d-axis need to be synchronized at a constant phase difference angle.

Further, when the rotor 3 is provided with the short-circuit ring 6, if the rotating magnetic field is generated by applying an appropriate excitation to the winding of the stator 1, the short-circuit ring 6 having a high electric conductivity is attached to the right hand of Fleming. According to the law, the following electromotive force e is induced.

E = v · B · l (4) v = r · ω (5) B; magnetic flux density l; axial length of the short-circuit ring r; distance from the axis center to the short-circuit ring ω; The angular velocity of the rotating magnetic field as seen by this induced electromotive force e, the induced current Im
Flows, the following electromagnetic force f is generated from Fleming's left hand rule.

F = Im · B · l (6) From the equations (4), (5) and (6), since the short-circuit ring 6 of the rotor 3 needs to have a certain relative speed to the rotating magnetic field. When the reluctance motor is operated by the electromagnetic force f of the formula (6), the operation is asynchronous.

As described above, the short-circuit ring 6
If a rotating magnetic field is generated by the stator 1 without detecting the position of the rotor 3, an induced current flows through the short-circuit ring 6 and the clockwise or counterclockwise rotation , An induced torque in any direction selected. That is, at the time of startup, it is driven as an induction motor using induction torque. Further, when the position of the rotor 3 is detected and a rotating magnetic field is generated while maintaining a constant phase difference angle, synchronous operation is performed and the motor is driven as a reluctance motor utilizing reluctance torque.

Although the description has been given of the case of the rotor 3 having a cylindrical shape with the side surfaces cut off, the present invention is also applicable to the rotor 3 having a magnetic salient pole structure using a gap or a barrier made of a material having a different magnetic permeability. it can.

FIG. 2 shows the structure of the reluctance motor according to the second embodiment. The rotor 3 has a cylindrical shape in which a magnetic material 7 such as a silicon steel plate and a nonmagnetic material 8 such as aluminum and copper having higher conductivity are alternately superposed in parallel along a plane parallel to the axial direction. Formed. In addition, as a method of superposing, the nonmagnetic material 8 is superposed so as to be the outermost layer. Thus, by superposing the two members 7 and 8 on each other, the magnetic salient pole ratio in the direction parallel to the axial direction can be increased, and a magnetic salient pole structure is obtained.

Both ends of the rotor 3 in the axial direction are covered with a non-magnetic covering plate 9 of high conductivity such as aluminum or copper. The cover plate 9 has a disk shape having the same diameter as the rotor 3, and the rotation shaft 4 penetrates. As a result, the non-magnetic material 8 having good conductivity and the cover plate 9 are electrically connected, and the short-circuit ring
Is configured. At this time, as long as it is covered with the non-magnetic covering plate 9,
The magnetic saliency of the rotor 3 is not impaired.

Therefore, by adopting such a structure, when the rotating magnetic field is generated by the stator 1 without detecting the position of the rotor 3 as in the structure in which the short-circuit ring 6 is provided, the non- An induction current flows from the magnetic material 8 through the coating plates 9 on both sides to generate an induction torque, and the motor can be driven as an induction motor at startup. Further, since it has a magnetic salient pole structure, when the position of the rotor 3 is detected and a rotating magnetic field is generated while maintaining a constant phase difference angle, synchronous operation is performed and the motor is driven as a reluctance motor. Moreover,
Since the cross-sectional shape of the rotor 3 is circular, air resistance is reduced when rotating, energy loss is reduced, and noise can be reduced.

Here, the induced current flowing in the vicinity of the axis of the non-magnetic material 8 hardly contributes to the torque. Therefore, the covering plate 9 corresponding to this portion may be omitted. That is, FIG.
The cover plate 11 is formed in an annular shape as shown in FIG. Then, the periphery of both ends of the rotor 3 is cut out to form a step 12, and the cover plate 11 is fitted and fixed therein. Note that the shape of the cover plate 11 is an annular shape that matches the shape of the rotor 3.

Even when the cover plate 11 is formed in such a shape, the cover plate 11 is electrically connected to the non-magnetic material 8, so that the induced torque can be effectively taken out. Moreover, the material used for the covering plate 11 can be minimized, and when the disc-shaped covering plate 9 is attached to both ends of the rotor 3, the axial length is equal to the thickness of the two covering plates 9. Although there is a slight increase, in this case, the length in the axial direction does not change, which can contribute to miniaturization and weight reduction.

FIG. 4 shows the structure of the reluctance motor according to the third embodiment. The rotor 3 has a structure in which the rotor 3 shown in the first embodiment is twisted (skewed) along the axial direction.

That is, a plurality of magnetic materials 13 such as silicon steel plates are stacked in the axial direction. At this time, several magnetic materials 1
3 as one set, the gap surfaces are shifted and fixed for each set while the rotating shafts 4 are aligned. When the short-circuit ring 6 is inserted along the short-circuit ring 6, the rotor 3 has a skew. With such a structure, torque pulsation can be reduced.

Further, as shown in FIG. 5, skew may be added to each of the reluctance motors of the second and third embodiments. In this case, since the rotor 3 is cylindrical,
The shape is shifted in the circumferential direction.

Next, a driving device for driving the reluctance motor of each embodiment will be described. As shown in FIG. 6, the driving device includes a driving circuit 20 for generating a rotating magnetic field in the stator 1, a position detector 5 for detecting a rotation speed and a position of the rotor 3, And a control circuit for controlling the drive circuit to change the number of rotations of the rotating magnetic field based on the output signal.

The drive circuit 20 includes a diode bridge 2
2. The inverter unit 24 includes a smoothing capacitor 23 and an inverter unit 24. The inverter unit 24 includes switching elements 25a to 25f of power transistors such as IGBTs and recovery diodes 26a to 26f. Control circuit 2
1 is a main control unit 27 having a microcomputer and a memory, and an inverter drive unit 2 including a PWM generation circuit and the like.
And 8.

The control circuit 21 generates a rotating magnetic field on the stator 1 at the time of start-up, and when the rotor 3 starts rotating by an induced torque generated by the induced current and reaches a predetermined rotational speed, the rotational speed of the rotating magnetic field is increased. Is switched to the number of revolutions for performing the synchronous operation.

In the above configuration, the alternating current from the power supply 29 is full-wave rectified by the diode bridge 22, smoothed by the smoothing capacitor 23, and then input to the inverter 24. Bipolar driving is performed by the inverter 24 to which the reluctance motor M is connected.

First, the main controller 2 is controlled so that three-phase alternating current flows.
At 7, the PWM switching pattern is determined, and the inverter driving unit 28 drives the respective switching elements 25a to 25f. As described above, by sequentially exciting the windings of the stator 1 to generate a rotating magnetic field, an induced current flows through the short-circuit rings 6 and 10 of the rotor 3 and an induced torque is generated. Driven as Therefore, a smooth and reliable start can be performed.

Further, since the motor is driven as an induction motor at the start of rotation, the rotation direction can be easily controlled to one of them at all times, and the generation of noise at the start of rotation can be prevented without adversely affecting the load. be able to.

During this driving, the position of the rotor 3 is detected by the position detector 5 at intervals of one degree. The main control unit is controlled by a magnetic flux vector control method so as to generate a rotating magnetic field having a constant phase difference angle with respect to the d-axis of the rotor 3 when a predetermined rotation speed at which synchronous operation is possible, for example, 300 rpm is reached. At 27, a switching pattern is determined. In order to determine this, a data table corresponding to each angle is provided in the microcomputer, and a switching pattern corresponding to the set number of revolutions is selected from this data table. Thereby, the control can be performed at high speed and simplified.

Based on the determined switching pattern, the inverter driving section 28 switches the switching elements 25a to 25a-2.
By driving 5f, the motor M is smoothly switched to synchronous operation, and is driven as a reluctance motor.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that many modifications and changes can be made to the above-described embodiment within the scope of the present invention. For example, as shown in FIGS. 7 and 8, even when the rotor 3 of the reluctance motor has a four-pole magnetic salient pole structure, the short-circuit ring 6 is provided or the magnetic material 7 and the non-magnetic material 8 are alternately combined. By configuring the short-circuit ring 10 with a different structure, the startability can be improved.

[0040]

As is apparent from the above description, according to the present invention, a short-circuit ring having higher conductivity than the rotor is provided to the rotor having the magnetic salient pole structure so that an induced current flows by the rotating magnetic field. With this, an induction torque can be obtained when a rotating magnetic field is generated. This makes it possible to use the induced current flowing during the asynchronous operation, prevent energy loss, and improve efficiency.

Therefore, the reluctance motor can be reliably started by utilizing this induced torque during low-speed rotation at which synchronous operation is not possible. That is, the motor is driven as an induction motor at the time of startup, and can be driven as a reluctance motor utilizing reluctance torque when a rotating magnetic field is generated so as to maintain a constant phase difference angle with the rotor.

By forming the rotor in a shape in which the rotor is twisted along the axial direction, torque pulsation can be reduced, and a highly reliable motor with stable output can be obtained.

[0043] Therefore, a driving method in which the advantageous portions of the respective characteristics are selectively used to perform the asynchronous operation using the induction torque at the time of starting, and to perform the synchronous operation using the reluctance torque at the time when the predetermined rotational speed is reached. By doing so, activation can be easily performed. In addition, since the motor can be driven as an induction motor, the rotation direction at the time of starting can be set arbitrarily, and it is not necessary to detect the position of the rotor before the starting, so that driving control can be simplified.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of a reluctance motor according to a first embodiment of the present invention.

FIGS. 2A and 2B show a rotor of a reluctance motor according to a second embodiment, wherein FIG. 2A is a perspective view and FIG.

FIG. 3 is an exploded perspective view of a rotor of a reluctance motor according to a modification of the second embodiment.

4A and 4B show a rotor of a reluctance motor according to a third embodiment, wherein FIG. 4A is a perspective view and FIG.

FIG. 5 is a front view of a rotor of a reluctance motor according to another embodiment.

FIG. 6 is a circuit diagram of a drive device for a reluctance motor.

FIG. 7 shows another shape of the rotor of the first embodiment,
(A) is a front view, (b) is a cross-sectional view.

FIG. 8 shows another shape of the rotor of the second embodiment,
(A) is a front view, (b) is a cross-sectional view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stator 2 Salient pole part 3 Rotor 4 Rotating shaft 5 Position detector 6 Short-circuit ring 7 Magnetic material 8 Non-magnetic material 9 Coating plate 10 Short-circuit ring 11 Ring-shaped coating plate 20 Drive circuit 21 Control circuit

Claims (7)

[Claims] A cylindrical stator for generating a rotating magnetic field;
A rotor having salient pole portions inserted into the stator, wherein the rotor is provided with a short-circuit ring having a higher conductivity than the rotor so that an induced current flows by a rotating magnetic field. Reluctance motor. 2. The reluctance motor according to claim 1, wherein the short-circuit ring comprises a coil embedded in the rotor so as to penetrate the salient pole. 3. A cylindrical stator for generating a rotating magnetic field,
A rotor having salient pole portions inserted into the stator, wherein the rotor alternately overlaps a magnetic material and a non-magnetic material having a higher conductivity along a plane parallel to the axial direction. A non-magnetic covering plate having high conductivity is provided at both ends in the axial direction of the rotor, and the non-magnetic material and the covering plate are electrically connected to each other, and a short-circuit ring through which an induced current flows by a rotating magnetic field. The reluctance motor characterized by comprising. 4. The reluctance motor according to claim 3, wherein the covering plate is formed in an annular shape and fitted around the end of the rotor. 5. The rotor according to claim 1, wherein the rotor has a shape twisted along the axial direction.
The reluctance motor according to any one of the above. 6. A cylindrical stator for generating a rotating magnetic field,
A rotor having a salient pole portion inserted into the stator, wherein the rotor generates a rotating magnetic field in a reluctance motor in which a short-circuit ring is formed so that an induced current flows by the rotating magnetic field. Circuit for detecting the number of rotations and the position of the rotor, and control for controlling the drive circuit to change the number of rotations of the rotating magnetic field based on an output signal from the position detector And a control circuit for controlling the rotational speed of the rotating magnetic field to perform a synchronous operation when the rotor starts rotating with an induced torque generated by the induced current after the start and reaches a predetermined rotational speed. A reluctance motor drive device characterized by switching to (1). 7. A cylindrical stator for generating a rotating magnetic field,
A rotor having a salient pole portion inserted into the stator, a reluctance motor in which a short-circuit ring is formed so that an induction current flows by a rotating magnetic field in the rotor. A method for driving a reluctance motor, comprising: performing asynchronous operation using induction torque generated by a flowing induction current; and performing synchronous operation using reluctance torque when a predetermined number of revolutions is reached.