JPS6010505B2 - synchronous motor - Google Patents

Description

[Detailed description of the invention] This invention relates to a synchronous motor.

Normally, when a high torque exceeding the rated voltage is applied to a synchronous motor, the ampere turns caused by the excitation coil become large, which increases the vibration of the rotor and makes it more likely to step out. Therefore, braking was applied to the rotor from the slave using a washer or the like. However, this method has a problem in that the minimum starting voltage becomes high. Therefore, an object of the present invention is to provide a synchronous motor that can prevent step-out during voltage application without increasing the minimum starting voltage.

FIG. 1 is a sectional view of an embodiment of a synchronous motor of the present invention. In the figure, 1 is a stator yoke, 2 is an excitation coil to which an alternating voltage is applied, 3 is a non-magnetic material bearing, 4 is a stator magnetic pole tooth plate, 5 is a permanent magnet rotor, 6 is a soft magnetic material support,
7 is a soft magnetic disc, 8 is a rotating shaft, and 9 is a coil frame. The permanent magnet rotor 5 is a disc-shaped rotor in which a pair of magnetic poles are alternately magnetized adjacent to each other in an annular shape. Further, the magnetic pole tooth plate 4 faces the rotor 5 and has a large number of magnetic pole teeth extending radially from the inner and outer circumferential portions as shown in FIG. In response, a magnetic field is created, and the multipolar permanent magnet rotor 5 is automatically started and rotationally driven. Further, as shown in FIG. 2, the magnetic pole tooth plate 4 has a large number of magnetic poles 10 formed by bending the outer peripheral edge of the magnetic pole tooth group P. The number of magnetic poles 10 is 1/N of the number n of motor poles (N is 1 or 2). In this figure, N=2. FIG. 3 shows a sectional view taken along the line X--X in FIG. 1. As is clear from this figure, the magnetic pole tooth plate 4
The same number of magnetic poles 11 as the outer peripheral magnetic poles 10 of the soft magnetic disk 7
It is bent and formed. That is, magnetic poles 10 and 1
The magnetic poles 1 and 10 face each other with a certain gap in between, and as shown in FIG.
It is determined to be displaced in the rotational direction of the rotor with respect to the center of zero. To explain this point in more detail, as shown in FIG. It is clear that this occurs at a position offset in the rotational direction from the center with respect to the wide magnetic pole teeth 12, so for example, the magnetic pole 11 on the rotor side is connected to the magnetic pole N or S of the rotor
When provided at the center of the stator, the magnetic pole 10 of the stator facing the
Alternatively, the stator magnetic pole teeth 12 and 13 may be located slightly closer to the center than the position offset in the rotational direction with respect to the center of the wide magnetic pole tooth 12.

As a result, at the position of the maximum torque received when the rotor 5 rotates with one cycle of voltage, and in the vicinity of the voltage peak value, the magnetic poles 11 face the magnetic poles 10 with a slight deviation in the rotational direction, A leakage magnetic flux attraction force acts between them, a braking action occurs, and the shaded portion is removed. In addition,
For convenience of explanation, Fig. 4 shows the wide magnetic pole teeth 12 and narrow magnetic pole teeth 13 of the stator magnetic pole teeth in an expanded form. This is the resistance force, and the broken line part is the torque that is generated when the exciting current flows in the same direction every half cycle in one cycle.Actually, the direction of the current is reversed every half cycle, so it does not occur in the rotor 5. . As a result of this configuration,
When the rated voltage is applied to the excitation coil 2, the rotor 5 is automatically started and rotated due to the interaction between the magnetic pole tooth plate 4 and the permanent magnet of the rotor 5. On the other hand, when the applied voltage to the excitation coil 2 becomes high, the excitation coil 2 The magnetic flux generated increases, and the leakage magnetic flux is transferred from the inner cylindrical part la of the stator yoke 1 to the magnetic support 6 to the magnetic disk 7 to the magnetic pole 1 1 to the magnetic pole 10 to the outside of the stator yoke. It passes through a magnetic path formed by the cylindrical portion lb.

As a result, electromagnetic attraction in the counter-rotation direction is generated as a braking force between the magnetic poles 10 and 11, and this braking force reduces the torque ripple of the generated torque, suppresses vibration of the rotor, and prevents step-out. In this case, it is necessary to increase the electromagnetic attraction braking force near the peak value of the AC excitation voltage. Therefore, as shown in FIG. 4, the center of the magnetic pole 11 needs to be displaced in the rotor rotation direction with respect to the center of the magnetic pole 10 near the peak value of the AC excitation voltage V. In other words, when the rotor is near the peak value of the excitation voltage V, the stator magnetic pole 10
The electromagnetic attractive force due to the leakage magnetic flux between the rotor and the rotor magnetic poles 11 acts on the rotor in the counterrotation direction of the rotor, and thus acts as a rotational braking force. To explain this in more detail, when N = 1, the number of magnetic poles 10 is the same as the number of motor poles, so braking is applied every rotation equivalent to one pitch of the rotor, and the applied force is applied as shown in Figure 8. At each positive and negative peak value of the voltage, an electromagnetic attractive force due to leakage magnetic flux between the stator magnetic pole 10 and the rotor magnetic pole 11 near the peak value of the excitation voltage V is applied to the rotor 5. Since it acts in the counter-rotational direction, a braking action is produced for each pitch of the rotor 5.
On the other hand, N! In the case of 2, the magnetic poles 10 and 11 face each other and generate an attractive force due to leakage magnetic flux (no leakage magnetic flux is generated when they do not face each other). Braking will be applied, resulting in the state shown in Fig. 4. Note that in FIGS. 4 and 8, the shaded portion of the voltage waveform indicates the range in which leakage magnetic flux occurs. 6 and 7 in order to change the rotational characteristics of the rotor 5 so as to prevent the step-out phenomenon when high voltage is applied, which is the object of the present invention, and to ensure stable rotation without increasing the starting voltage. Like N=
1, that is, the number of magnetic poles of each of the magnetic poles 10 and 11 is the same as the number of poles of the motor, and a braking force is applied to the rotor near the peak value of the voltage applied to the coil every time the rotor 5 rotates for one pitch. It goes without saying that this is the most desirable thing, but as the number of motor poles increases compared to the size of the motor, the widths of the magnetic poles 10 and 11 become smaller, making it difficult to form them. Depending on N=
Set it to 2.

In the case of N=2, it is inevitable that the effect of improving the rotational characteristics of the rotor is weaker than in the case of N=1. However, even in the case of N=2, it can be said that it contributes to preventing step-out when high voltage is applied without increasing the starting voltage. Although the magnetic pole io is formed on the outer peripheral edge of the magnetic pole tooth plate 4 in this embodiment, it may be formed on the outer cylindrical portion lb of the stator yoke 1, as shown in FIG.

As described above, the synchronous motor of the present invention applies braking force to the rotor using leakage magnetic flux of the stator yoke that occurs when high voltage is applied, suppresses rotor vibration, and thereby prevents step-out. Therefore, it can contribute to the prevention of step-out when voltage is applied without increasing the minimum starting voltage as would be the case when using conventional washers, etc., and thereby expand the synchronous rotation voltage range. can. Also, by suppressing vibration, the life span will be extended.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a sectional view of one embodiment of the synchronous motor of the present invention, FIG. 2 is a partial plan view of the stator magnetic pole tooth plate, and FIG.
4 is an explanatory diagram showing the positional relationship of the generated torque Q corresponding to the stator magnetic pole teeth when N=2,
FIG. 5 is a sectional view of a main part of another embodiment of the present invention, and FIG. 6 shows that the number of poles of the stator magnetic pole tooth plate is equal to the number of poles of the stator magnetic pole (
FIG. 7 is a cross-sectional view corresponding to FIG. 3, and FIG. 8 shows the arrangement of each magnetic pole and the relationship of magnetic leakage to applied voltage and phase when N=1. FIG. 1... Stator yoke, la... Inner cylindrical part, lb
...Outer cylindrical part, 2...Coil, 4...
...Magnetic pole tooth plate, 5...Permanent magnet rotor, 6...
Soft magnetic support (leakage flux path), 7... Soft magnetic disc (leakage flux path), 10... Stator magnetic pole, 11... Rotor magnetic pole. Figure 1 Figure 2 Figure 3 Figure 5 Figure 4 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1. A cylindrical stator yoke, a magnetic pole tooth plate provided on an end surface of the cylindrical stator yoke, and an excitation coil arranged at the center of the stator yoke to alternately excite the magnetic pole tooth plate;
In a self-starting synchronous motor including a permanent magnet rotor facing the magnetic pole tooth plate, 1/N of the number n of the synchronous motor poles (N is 1 or 2) is attached to the outer peripheral edge of the cylindrical stator yoke. stator magnetic poles having the same number of poles as the stator magnetic poles are formed on the outer peripheral edge of the permanent magnet rotor so as to face the stator magnetic poles, The permanent magnet rotor is provided with a magnetic body that forms a leakage flux path of the excitation coil at the center of the stator yoke, and the rotor magnetic pole center is located near the peak value of the voltage applied to the excitation coil when the stator magnetic pole A synchronous motor characterized in that an electromagnetic attraction braking force due to leakage magnetic flux of a stator yoke acts between the stator magnetic poles and the rotor magnetic poles in a relationship in which they are displaced from the center in the rotational direction.