JPH0145832B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to induction motors, and in particular, to an induction motor that improves the support structure of a stator core by a housing and optimizes the combination of the number of slots in the stator and rotor to reduce noise. Regarding phase induction motors. [Prior Art] Induction motors are widely used because of their simple structure and excellent reliability, and single-phase induction motors are the mainstream for consumer use. For products used for consumer use, there is a very high demand for not only torque characteristics but also quietness. There are two causes of electromagnetic noise in induction motors.
The first cause is that the electromagnetic force applied between the stator and rotor fluctuates due to fluctuations in the main magnetic flux that fluctuates in response to the alternating current flowing through the windings, causing the stator to fluctuate, which is twice the power frequency. vibration and noise at a frequency of As a method to reduce this noise, a patent application was made in 1970.
-There is one described in Publication No. 28615. On the other hand, the second cause is caused by groove harmonics generated by the slots provided in the stator and rotor, and is greatly affected by the combination of the number of slots in the stator and rotor. In particular, in the case of two poles, no matter how many slots are selected from among the finite number of slots, either noise or torque characteristics must be sacrificed.
In addition, the second cause of noise has a relatively high frequency and is therefore unpleasant to the ears. Conventionally, selection has been made with emphasis on torque characteristics, which are the most important in terms of performance, and on the basis that vibration and noise are unavoidable. [Object of the Invention] An object of the present invention is to solve the above problems and provide a single-phase induction motor that not only has excellent torque characteristics but also has low noise and vibration. [Summary of the Invention] Focusing on the above, the present invention includes a stator in which a two-pole winding is applied to a slot 2 formed on the inner periphery of a stator core 1, and a stator that is formed on a cylinder and has the inner peripheral surface thereof In an induction motor that has a housing 8 that supports a stator and a rotor that is rotatably supported by a bearing inside the stator, and has 24 stator slots and 30 rotor slots, the stator Projections 7 are formed at four locations on the outer periphery of the stator core 1 at an angle of 45 degrees with respect to a line passing through the pole center of the winding, and the cylindrical housing 8 is supported by these four projections 7. and a predetermined distance 〓G between the housing 8 other than the protrusion 7 and the stator core.
In addition, the size of this cavity increases from the vicinity of the protrusion 7 to the distance from the protrusion 7. [Example] An example of the present invention will be described based on the drawings. FIG. 1 is a sectional view of the stator portion, and FIG. 2 is a partial sectional view of the rotor. In FIG. 1, reference numeral 1 denotes a stator core in which 24 slots 2 are provided.
A main winding 3 and an auxiliary winding 4 are provided in this slot. Further, on the outer periphery 5 of the stator, protrusions 7 are provided at four positions at approximately 45 degrees with respect to the center line 6 passing through the pole center of the main winding 3, and the housing 8 is press-fitted with these protrusions 7. I support it. A space G is provided between the stator core 1 and the housing 8 except for the protrusion 7. The space G2 that is away from the protrusion 7 is larger than the space G1 near the protrusion 7. This reduces the chance of the housing 8 hitting the stator core 1 even if the housing 8 flows for some reason, and this air G2 becomes a passage for cooling air, which is also effective in suppressing temperature rise. In Fig. 2, numeral 9 indicates a stator core, and this stator core 9 has 30 slots 10 and a secondary conductor 1.
1 is provided. When an alternating current is passed through the windings 3 and 4 of the induction motor having such a configuration, an excitation force in a vibration mode as shown at 12 is applied to the stator core 1 due to the fluctuation of the alternating current, and the power supply frequency increases. produces an elliptical motion twice that of the In the present invention, the stator core is fitted into the housing 8 only by the protrusion 7 provided at the position where the amplitude of this vibration is the smallest, so the transmission of vibration is eliminated and the generation of noise is suppressed. . By the way, in induction motors, as mentioned above, the generation of groove harmonics due to the slots is unavoidable, and it is known that abnormal phenomena occur depending on the combination of the number of stator slots and the number of rotor slots. In actual design, it is required to create a combination that does not cause abnormal phenomena, but in the case of two-pole windings, it has been said that the above-mentioned problem cannot be solved no matter how the combination is used. That is, in the case of two poles, the number of stator slots is 24 or 36, and for small machines of several hundred watts or less, it is common to have 24 slots. If the number of stator slots is 24, the number of rotor slots is 26, 28, 30,
Table 1 shows the experimental results of changes in characteristics when changing the number of parts to 32 and 34.

[Table] As is clear from this table, regardless of the number of rotor slots, the performance of torque characteristics, vibration, and noise, or both, is not improved. The number of stator slots is N _S and the number of rotor slots is
If N _R , N _R = N _S , N _R = N _S ±2P, N _R = N _S ±
It is known that a large synchronous torque is generated when starting with 4P (where P is the number of pole pairs, and P = 1 in the case of 2 poles), but when the number of rotor slots is 26
As is clear from Table 1, in the case of No. 1 and No. 28, problems occur during starting. It is also known that when the range of N _R ≦1.25N _S is exceeded, heat generation on the rotor surface increases and efficiency decreases _.
=24, the upper limit is N _R =30. In addition, if the number of rotor slots is odd, the electromagnetic force will not be balanced with respect to the rotor center, and a force will be generated that vibrates the rotor in the radial direction, resulting in extremely large vibration noise, so it must be an even number. . Due to these constraints, conventionally it has not been possible to select the number of slots that will improve all characteristics, and it has been necessary to prioritize the torque characteristics and make selections that avoid the generation of noise and vibration. I didn't get it. On the _other hand _, due to the groove harmonics caused by _{the slots , the stator} core 1 becomes ,…
), the stator core 1 vibrates in the form shown by the broken line in FIG. 3. N _S with good torque characteristics
When N = 30, a large noise was generated before applying the present invention, but in the above equation, when N = 2, the modulating force of the mode changes the vibration of M = 2, and this is because the power frequency is 50 Hz. At this time, a noise mode of 1300 Hz is generated, and the vibration mode of the stator core caused by this is an elliptic motion as shown at 12 in FIG. 1 and in FIG. 3. Therefore, in the embodiment of the present invention, as described above, protrusions are provided at four positions on the outer periphery of the stator core, each forming a central angle of about 45 degrees with respect to the center line 6 passing through the pole center of the stator winding. 7, and the stator core is supported by these four protrusions. As a result, the above-mentioned elliptical motion is not propagated to the outside, and therefore the generation of noise can be significantly reduced. The frequency f _Z of the generated noise is calculated as f _Z = {K ₂ ×N _R /P (1-s) ₊ O _- 2 × N} × f, where f is the power supply frequency and s is the slip amount of the induction motor. expressed. The noise comparison results showing the effects of the invention will be explained with reference to FIG. Figure 4A shows the case of the conventional configuration, and Figure 4B shows the case of the conventional configuration.
shows the case of the present invention. All of these are
The stator winding has 2 poles, the number of stator slots is 24, the number of rotating slots is 30, the power supply voltage is 100V, and the power supply frequency is 50Hz. As is clear from this figure, the sound pressure level of the generated noise is much lower in Figure 4B. For example, when compared at a noise frequency of 1300 Hz in vibration mode M=2, the sound pressure level in the configuration of this embodiment is reduced to 25 dB, compared to 40 dB in the conventional configuration. [Effects of the Invention] As described above, the present invention includes a stator in which a two-pole winding is applied to the slot 2 formed on the inner periphery of the stator core 1, and a stator that is formed on a cylinder and that It has a housing 8 that supports the stator, and a rotor that is rotatably supported by a bearing inside the stator, and the number of stator slots is 24 and the number of rotor slots is 24.
30, protrusions 7 are formed at four locations on the outer periphery of the stator core 1, each at an angle of 45 degrees with respect to a line passing through the pole center of the stator winding, and the protrusions 7 at these four locations are The structure is such that the cylindrical housing 8 is supported by a predetermined distance G between the housing 8 other than the protrusion 7 and the stator core, and this space is separated from the protrusion 7 from the vicinity of the protrusion 7. Accordingly, by increasing the empty space size, noise and vibration can be significantly reduced while maintaining good torque characteristics.
Furthermore, it is possible to provide a single-phase induction motor with less temperature rise.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a stator showing the configuration of an embodiment of the present invention, FIG. 2 is a sectional view of a rotor, and FIG. 3 is a sectional view of a rotor.
The figure is a vibration mode explanatory diagram, and FIG. 4 is a comparison diagram of noise characteristics. DESCRIPTION OF SYMBOLS 1...Stator core, 2...Slot, 3...Main winding, 4...Auxiliary winding, 7...Protrusion, 8...Housing, 9...Rotor core, 11...Secondary conductor , G... empty.

Claims (1)

[Scope of Claims] 1. A stator in which a two-pole winding is applied to a slot 2 formed on the inner periphery of a stator core 1, and a housing that is formed on a cylinder and supports the stator on its inner periphery. 8 and a rotor rotatably supported by a bearing inside the stator, and the number of stator slots is
24. In an induction motor with 30 rotor slots, protrusions 7 are formed at four locations on the outer periphery of the stator core 1, each at an angle of 45 degrees with respect to a line passing through the pole center of the stator winding. The cylindrical housing 8 is supported by the four protrusions 7, and a predetermined distance G is provided between the housing 8 other than the protrusions 7 and the stator core. A single-phase induction motor characterized in that the void dimension increases as the distance from the protrusion 7 increases.