JPH10248218A - Maglev motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a maglev motor, which can be controlled stably for its floating position by eliminating the influence of an induced current generated in a secondary conductor by n-pole pairs of position control magnetic fields without hindering the generation of a driving current by m-pole pairs of rotating magnetic fields, and which at the same time can be manufactured easily at a low cost. SOLUTION: In an induction motor type maglev motor which magnetically levitates a rotating magnetic pole by giving a rotational force to a rotating magnetic field, by superimposing n-pole pairs of control magnetic fields upon a driving magnetic field composed of rotating m-pole pairs in synchronism with the driving magnetic field and, at the same time, increasing/decreasing the control magnetic field from the displacement of the rotating magnetic pole detected by means of a displacement detecting means which detects the displacement of the rotating magnetic pole, the rotating magnetic pole is a cage rotor composed of a plurality of conductor bars 11 and conductor end rings 12 fixing both ends of the bars 11, and the skew angle of the conductor bars 11 are roughly set at 2π/n rad (where, n>=2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic levitation motor having both a magnetic bearing function for controlling a position of a rotor in a radial direction and a function for rotationally driving a rotor.

[0002]

2. Description of the Related Art Conventionally, a cylindrical rotor is incorporated in a cylindrical stator, and an excitation circuit is arranged on the stator to form two stators having different numbers of poles.
Various types of magnetic levitation motors have been devised in which various types of rotating magnetic fields are formed, where a rotating force is applied to a rotor and magnetically levitated and held at a predetermined position to exert a position control force. This is equipped with a winding for rotation drive and a winding for control on the stator,
By passing a three-phase alternating current through each of them, a rotating magnetic field having a different number of poles in a predetermined relationship is formed, and the magnetic attraction in the radial direction is deviated on the plane perpendicular to the rotation axis of the cylindrical rotor.

In such a magnetic levitation motor, a rotating magnetic field of an m-pole pair and a rotating magnetic field of an n-pole pair are generated by passing a current through a winding of a stator. Hereinafter, the rotating magnetic field of the m-pole pair is referred to as a driving magnetic field, and the rotating magnetic field of the n-pole pair is referred to as a position control magnetic field. The driving magnetic field is used to apply a rotational driving force to the rotor like a normal electric motor, and the position control magnetic field is superimposed on the driving magnetic field, so that a radial force can be applied to the rotor. The floating position of the rotor in the radial direction can be freely controlled. Since m and n have a relationship of n = m ± 1, the above flying position control becomes possible.

Accordingly, the rotor is magnetically attracted,
In addition to functioning as an electric motor for applying a rotating force to the rotor, the floating position and posture of the rotor can be controlled to function as a magnetic bearing capable of supporting the stator in a non-contact floating manner. For this reason, an electromagnet yoke portion and a winding corresponding to a magnetic bearing, which have been conventionally required, are not required, and the shaft length of the rotating machine can be shortened, and the limitation of high-speed rotation from shaft vibration can be reduced. Further, the size and weight of the rotating machine can be reduced. In addition, the operation equivalent to a magnetic bearing can be performed by a synergistic effect of a magnetic field generated by the current of the control winding and the current of the drive winding, so that the control force can be reduced with a much smaller current than a conventional magnetic bearing. , And significant energy savings are possible.

[0005] An induction rotor is one of the systems in which an induced current is generated in a secondary conductor of the rotor by a rotating magnetic field generated by the stator to apply a rotational driving force. There are various types of induction rotors, and a typical example is a cage rotor. In this method, a number of low-resistance metal conductor bars (secondary conductors) are arranged on the rotor as current paths substantially parallel to the rotation axis, and each metal conductor bar is fixed to a low-resistance metal conductor ring (end ring) at both ends. It was done. The number of magnetic flux linkages in the rotor secondary conductor fluctuates due to the rotating magnetic field formed by the stator winding, and an induced voltage is generated in the rotor secondary conductor due to the electromagnetic induction phenomenon, so that an induced current flows. The Lorentz force is generated by the interaction between the magnetic flux interlinked by the rotor and the induced current on the rotor, and a rotational driving force is generated in the induction rotor.

[0006]

In a magnetic levitation motor, since an m-pole pair rotation driving magnetic field and an n-pole pair position control magnetic field coexist, when an ordinary cage-type induction rotor is used, the rotation of the motor becomes impossible. The currents induced by both magnetic fields flow through the sub-current paths (conductor bars). The rotating magnetic field having the distribution of m pole pairs applies a rotational driving force to the rotor. Therefore, in principle, an induction motor cannot be realized unless an induced current flows. On the other hand, n
When an induced current due to the pole pair position control magnetic field flows through the rotor current path, a magnetic field generated by the rotor current as a disturbance occurs in addition to the magnetic field generated by the stator winding, so the position control magnetic field is fixed. It is not determined only by the magnetic field of the m-pole pair and the n-pole pair formed by the winding current of the rotor, the radial force becomes unstable, and stable floating position control of the rotor cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and does not hinder the generation of a drive current due to a rotating magnetic field of an m-pole pair, and the effect of an induced current generated in a secondary conductor due to an n-pole pair position control magnetic field. It is therefore an object of the present invention to provide a magnetic levitation motor that can perform stable levitation position control and that can be easily manufactured at low cost.

[0008]

A magnetic levitation motor according to the present invention superimposes a control magnetic field of an n-pole pair on a driving magnetic field in synchronization with a driving magnetic field of a rotating m-pole pair to apply a rotating force to the rotating magnetic pole. At the same time, in an induction motor type magnetic levitation motor in which the control magnetic field is increased or decreased from the displacement of the rotating magnetic pole detected by the displacement detecting means of the rotating magnetic pole to magnetically levitate the rotating magnetic pole, the rotating magnetic pole has a plurality of conductor bars. A magnetic levitation motor comprising: a cage-shaped rotor comprising: a conductor end ring having both ends fixed to each other; and a skew angle of the conductor bar is approximately 2π / n (radian: n = 2 or more). And

The magnetic levitation motor according to claim 1, wherein the two rotors are connected and arranged so that their skew angles are equal in magnitude and opposite in direction.

2. The magnetic levitation motor according to claim 1, wherein the rotating machine that generates the axial force is provided with the skew angle on the conductor bar of the rotor so as to oppose the axial force. And

According to the configuration of the present invention described above, the skew angle of the conductor bar of the cage induction rotor is set to approximately 2π / n (radian: n = 2 or more), thereby driving the m pole pairs in rotation. The magnetic field generates an m-pole induced voltage, but the n-pole position control magnetic field cancels out the induced voltage within one conductor bar and can be almost zero. Therefore, since only the drive current by the drive magnetic field flows through the current path of the rotor, a torque similar to that of a normal cage rotor is generated by this Lorentzka, and the rotor is rotationally driven. On the other hand, since the induced current due to the position control magnetic field does not flow through the conductor bar, the rotation drive magnetic field of the m-pole pair and the position control magnetic field of the n-pole pair generated by the stator are not affected by the rotor current, and the rotor is not affected. A control magnetic field for supporting the levitation can be formed. As a result, stable levitation position control can be performed even in a magnetic levitation motor including an induction rotor.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1B shows a cage rotor having a width W of a normal skew angle. The cage-shaped rotor has a large number of metal conductor bars 10 arranged substantially parallel to the rotation axis on the outer periphery of a columnar rotor formed by laminating thin silicon steel plates, and both ends of which are also end rings 12 which are also metal conductors. It is fixed with. The above illustration shows aa ', bb', cc ', d-
The four conductor bars 11 of d 'are representatively shown.

In such a conventional cage-shaped rotor, a skew has been performed in which the arrangement of the conductor bars is not completely parallel to the rotation axis direction but is slightly shifted. This skew angle is as small as about one pitch of conductors arranged on the outer periphery of the rotor. However, this prevents an abrupt change in the magnetic flux linked to the conductor bar, and has the effects of improving the starting characteristics of the induction machine and suppressing harmonics.

FIG. 1A shows a cage rotor of a two-pole drive induction motor according to one embodiment of the present invention. The conductor bar 11 of the two-pole driven cage rotor has a skew of π (radian) as shown in a developed view at the bottom of the figure.
In other words, the conductor bar has a width W of the cylindrical rotor,
It is arranged diagonally from the front to the back along the outer surface. The illustrated conductor bar 11 is a representative example in which only four of the conductor bars 11 are actually arranged.

That is, as shown in FIG. 1A, the conductor bars aa ′, bb ′, cc ′, and dd ′ are respectively formed along the outer peripheral surface of the rotor by π ( Radian).

FIG. 2 shows a quadrupole control magnetic field and 2
4 shows an arrangement state of stator windings that generate a pole driving magnetic field.
The stator shown in the figure has a coil n for generating a two-phase four-pole control magnetic field.
a, nb and coils nα, n for generating a two-phase two-pole driving magnetic field
β is wound respectively. A skew angle of 180 degrees is provided on the rotor, and the radius of the conductor bar fixed on the circumference with respect to the rotation center of the rotor is R. Further, the magnetic flux and the magnetic flux density of the four-pole control magnetic field and the two-pole drive magnetic field generated in the gap between the rotor and the stator are Φ ₄ , Φ ₂ , B ₄ , and B ₂ , respectively. Now, a four-pole control magnetic field synchronized with the stator stationary, 2
Consider a state in which the pole driving magnetic field rotates at an angular velocity ω (n =
2, m = 1).

FIG. 3 shows a quadrupole control magnetic field when ωt = 0 and 2
The magnetic flux density linked to the rotor by the pole driving magnetic field and the positional relationship in the circumferential direction (θ direction) of the conductor bars aa ′, bb ′, cc ′, and dd ′ are shown. The magnetic flux density distribution of the quadrupole control magnetic field is B ₄ cos (2θ + ωt) when the amplitude is B _{4. The} magnetic flux density distribution of the quadrupole driving magnetic field is B ₂ cos (θ + ωt). Further, the induced electromotive voltage generated is a change in magnetic flux linked to the conductor, and the respective derivatives are shown in FIG.

Since the induced voltage generated in the minute portion Δl of the conductor bar is ΔE = ΔΦ / Δt, an induced voltage obtained by integrating the conductor bar over its entire length is generated.

Therefore, as shown in the figure, the conductor bars bb 'and dd' due to the two-pole driving magnetic field respectively have a voltage corresponding to the negative half cycle of Φ2 and a voltage corresponding to the positive half cycle of Φ2. A voltage is generated. Therefore, negative and positive induced voltages are generated at the conductor bars bb 'and dd', respectively. This means that, on the stator side, since a two-pole rotating drive magnetic field is formed, induced currents in opposite directions flow through bb 'and dd', respectively. On the other hand, on the stator side, since a two-pole rotating drive magnetic field is formed, this current becomes a rotor drive current and generates a rotating torque.
On the other hand, in the conductor bars aa 'and cc', a positive and negative induced voltage is generated in one conductor bar, so that the induced voltage is canceled out to zero for one conductor bar as a whole. . However, since this portion corresponds to a portion centered on a portion where the magnetic flux of the two-pole rotating magnetic field formed by the stator is zero, a driving torque is not originally generated. Accordingly, a cage rotor having a skew angle of π (radian) operates in the same manner as a normal cage rotor with respect to a bipolar driving magnetic field.

For the four-pole control magnetic flux Φ4, the conductor bar a
The induced voltages generated at -a ', bb', cc ', and dd' cancel all within one conductor bar. That is, for example, the conductor bar aa 'interlinks with the magnetic flux .PHI.4 for one period as shown in the figure, so that the induced voltage, which is the integral value of the minute distance .DELTA.l generated in one conductor bar, becomes zero. This relationship is true for all other conductor bars bb ', cc', d-
The same applies to d '. That is, by applying a skew of π (radian) to the conductor bars of the cage rotor, the total of the magnetic fluxes in which each conductor bar interlinks with the four-pole position control magnetic flux Φ4 becomes zero, and the induced voltage is applied to each conductor bar. Does not occur. As a result, no induced current is generated in each conductor bar of the cage rotor by the quadrupole position control magnetic field formed by the stator.

Further, with reference to FIG. 4, the above-mentioned relationship will be described in detail using equations. The sum of the induced electromotive forces due to the quadrupole control magnetic field generated for the conductor bar bb ′ is given by the following equation (1).
As shown in (2), the offset is zero.

(Equation 1)

(Equation 2)

On the other hand, the sum of the induced electromotive forces due to the bipolar driving magnetic field is generated with a periodicity as shown by the equation (3).

(Equation 3)

For the conductor bar dd ', the sum of the induced electromotive forces induced by the quadrupole control magnetic field is also 0, but the sum by the dipole drive magnetic field is the same in the opposite direction. Eventually, only the induced electromotive force generated by the bipolar driving magnetic field is generated in the conductor bar, the induced current flows, and a torque is generated as an induction machine. At the same time, since no induced current due to the quadrupole control magnetic field is generated in the cage rotor, the control magnetic flux is controlled as intended, and the rotor can be stably rotated and levitated. The above-mentioned matter is satisfied in the relationship of n = m ± 1 also in the relationship between the number of drive magnetic pole pairs of n = 2 or more and the number of control magnetic pole pairs.

FIG. 5 is a diagram showing a part of FIG. 4 for an n-pole pair. Similarly to the above equation, the sum of the induced electromotive forces generated in one conductor bar aa ′ or the like by the rotation of the control magnetic field having the n-pole pair is represented by equation (4).

(Equation 4)

As shown in equation (5), the value in square brackets ([]) in equation (4) is always 0 for a control magnetic field of n pole pairs.
And no induced current is generated.

(Equation 5)

On the other hand, in the case of a driving magnetic field composed of m pole pairs, the value does not become 0 as shown in the equation (6) but becomes a value synchronized with ω, indicating the generation of an induced current, and as a result, generating a rotational force. . The magnitude becomes the maximum amplitude when n = 2, m = 1 or 3.

(Equation 6)

The cage rotator of the present invention only applies a skew angle of approximately 2π / n to the conventional cage rotator. Therefore, a rotor of a stable magnetic levitation motor can be manufactured by only slightly changing the conventional manufacturing process, and a low-cost and high-rigidity rotor can be manufactured.

FIG. 6 is a diagram for explaining a second embodiment of the present invention. As described above, since the conductor bar has a large skew angle, the current flowing in an oblique direction on the outer peripheral surface of the rotor 20 causes the rotating magnetic field formed by the stator 21 to apply a rotational torque to the rotor 20 together with the rotational torque in the θ direction. (Z) Directional force is generated. That is, the force F that the induced current receives from the magnetic field
Has both a rotational torque Fθ and an axial force FZ, so that it can be balanced with the axial thrust Fm.

FIG. 7 shows a rotating shaft 22 in which rotors 20 and 22 having the same skew angle and different skew directions are connected and fixed. Axial forces Fa and Fa 'are generated in the rotor simultaneously with torque (circumferential force) T. The axial forces generated by this large skew angle are equal in magnitude but opposite in direction if the two devices are operating in a similar manner. For this reason, the axial force of the rotating shaft is canceled simultaneously with the generation of the torque, and the rotor is passively and stably supported in the axial direction by using the rotor according to the first embodiment of the present invention.

FIG. 8 shows another example of the cancellation of the axial force. This is an example of application to a rotating machine that uses one magnetic levitation motor 25 according to the first embodiment and one conventional magnetic bearing 26 to support a rotating shaft 22 having blades 23 that generate an axial fluid force. . It is assumed that the rotation of the wings 23 generates an axial fluid force FA, while the magnetic levitation motor 25 generates an axial force Fa simultaneously with the torque. Since the magnitude is proportional to the torque, the axial force Fa increases with the increase of the fluid force FA.
The load capacity of the magnetic bearing 26 for offsetting or reducing the axial force and supporting in the axial direction can be reduced. For this reason, miniaturization of the rotating machine as a whole,
The price can be reduced.

[0032]

According to the present invention, conventionally, it is difficult to manufacture,
The rotor of a magnetic levitation induction motor, which is costly and long in the axial direction and is unsuitable as a high-speed rotor, is a stable magnetic levitation motor rotor with only minor modifications to the conventional cage rotor manufacturing process. Can be manufactured as This makes it possible to manufacture a low-cost and high-rigidity rotor whose axial length is the same as that of a general cage induction rotor. In addition, the passive stabilizing force in the axial direction can be increased by the combination of the rotors according to the present invention, and it is possible to reduce the size and size of the rotating machine as a whole.

[Brief description of the drawings]

FIG. 1 is a perspective view and a development view of a cage rotor, and FIG.
FIG. 3B is an example in which a skew angle of π radian is applied according to the first embodiment of the present invention, and FIG. 3B is an example in which a conventional skew angle is applied.

FIG. 2 is a diagram illustrating a relationship between a winding of a stator that generates a magnetic field of two-pole drive and four-pole control and an arrangement of conductor bars of a rotor.

FIG. 3 is a diagram illustrating an induced electromotive voltage generated by a two-pole driving magnetic field and a four-pole control magnetic field generated in a conductor bar.

FIG. 4 is an explanatory diagram for calculating the induced electromotive force.

FIG. 5 is an explanatory diagram for calculating the induced electromotive force.

FIG. 6 is a diagram illustrating generation of an axial force by the rotating machine according to the embodiment.

FIG. 7 is a view showing a rotating machine according to a second embodiment of the present invention in which axial forces are offset.

FIG. 8 is a view showing a rotating machine according to a third embodiment of the present invention in which axial forces are offset.

[Explanation of symbols]

 11 Skewed conductor bar 12 End ring 20 Rotor 21 Stator 22 Rotation axis

Claims (3)

[Claims] 1. A control magnetic field of an n-pole pair is superimposed on a driving magnetic field in synchronization with a driving magnetic field of a rotating m-pole pair to apply a rotating force to the rotating magnetic pole and, at the same time, detected by a displacement detecting means of the rotating magnetic pole. In the induction motor-type magnetic levitation motor in which the control magnetic field is increased or decreased from the displacement of the rotating magnetic pole to magnetically levitate the rotating magnetic pole, the rotating magnetic pole comprises a plurality of conductor bars and a conductor end ring to which both ends thereof are fixed. A cage rotor, wherein the skew angle of the conductor bar is approximately 2π / n (radian:
n = 2 or more). 2. The magnetic levitation motor according to claim 1, wherein two rotors are connected and arranged so that their skew angles are equal in magnitude and opposite in direction. 3. The magnetic levitation motor according to claim 1, wherein the skew angle is provided on a conductor bar of the rotor so as to oppose the axial force in a rotating machine that generates an axial force. .