JPH0521975Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Field of industrial application The present invention relates to an induction motor, and more particularly, to an induction motor that eliminates vibration and noise caused by eccentricity of a stator and rotor.

(b) Prior Art Induction motors are often used in blowers and the like, but eccentricity between the stator and rotor causes an imbalance in magnetic flux, which causes vibration and noise.
That is, as shown in Fig. 1, the induction motor is
The main winding M is inserted into the slot 2 formed in the stator 1.
...and auxiliary winding A are wound thereon. Then, the rotor 4 is stored in the rotor storage space 3 of the stator 1. At this time, there is no problem if the center O _S of the stator 1 and the center O _R of the rotor 4 coincide, but
It is difficult to make the two centers O _S and O _R completely coincide with each other, resulting in a pinch point g1 and a wide point g2 of the air gap.

Now, the connection of each winding of the stator 1 of a conventional induction motor is as shown in FIG.
1, M2, M3, M4 and auxiliary winding A1, 12, A
3 and A4 are each connected in series with the same winding. Therefore, both main and auxiliary windings M and A have I _M and
A current called _IA flows. Now, looking at the main windings M1 to M4, since each of the main windings M1 to M4 is connected in series, the magnetomotive force excited in each of the main windings M1 to M4 is the same. However, as described above, each air gap differs depending on the eccentricity of the stator 1 and rotor 4. Since the wide point g2 and the narrow point g1 of the air gap have different magnetic resistances, the amount of magnetic flux generated is different. Therefore,
The rotating magnetic field does not become a circular magnetic field, but an elliptical magnetic field,
This causes magnetic imbalance and causes vibration.

Furthermore, as the rotor 4 rotates, the points g1 and g2 of the air gap sequentially move, causing the electric motor to generate vibrations and accompanying noise. Such magnetic imbalance also occurs in the auxiliary winding.

(c) Purpose of the device The purpose of this device is to eliminate the imbalance of magnetic flux caused by the eccentricity between the stator and rotor, thereby eliminating the vibration and noise of the motor caused by the imbalance of magnetic flux.

(d) Structure of the invention This invention was made to achieve the above-mentioned purpose, and is structured as follows. In other words, 2n (n = 1, 2,...) main and auxiliary windings are wound around the stator core, and the main and auxiliary windings are mechanically spaced 180 degrees apart from each other in parallel. This is an induction motor in which the windings are connected to form a pair of windings, and these windings are connected in series.

(E) Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 3.

Four main windings M and four auxiliary windings A are wound in each slot 2 formed in a stator core 1 made of laminated steel plates. The main windings M1 to M4 and the reinforcing wires A1 to A4 each have the same number of turns. The main windings M1 to M4 and the auxiliary windings A1 to A4 are connected as shown in FIG. That is, a pair of main windings M1 and M3, M2 and M4, which are mechanically separated by 180 degrees, and a pair of auxiliary windings A1 and A3, A2 and A4 are connected in parallel, respectively, and a pair of windings M1 and M3, M2 and M4 are connected in parallel. Line group M1,
M3 and M2, M4 and A1, A3 and A2, A4
Connect in series.

In the figure, 5 is a capacitor, 6 is a switch, and 7 is a power supply.

Now, to explain the case where the rotor 4 is in the positional relationship shown in FIG. 1, the main winding M4 faces the air gap g1, and the main winding M2 faces the air gap g2.

The magnetic flux generated in each of the main windings M2 and M4 in this state will be explained.

Main windings M2 and M4 each have the same number of turns,
Assuming that the number of turns is N, the induced voltage E2 induced in the winding M2 and the induced voltage E4 induced in the winding M4 can be expressed as in the following equation.

E2=NdΦ2/dt...(1) E4=NdΦ4/dt...(2) However, Φ2 and Φ4 indicate the magnetic fluxes interlinking with the windings M2 and M4.

Next, calculate components such as leakage reactance of each winding.
Assuming that Ra, the currents flowing through each winding are _IM2 and _IM4 , and the applied voltages are V2 and V4, V=E2+ _RaIM2 ...(3) V=E4+ _RaIM4 ...(4).

However, since windings M2 and M4 are connected in parallel, V ₂ =V ₄ .

Therefore, from equations (3) and (4), E2+RaI _M 2=E4+RaI _M 4 (5).

Furthermore, since RaI _M 2 and RaI _M 4 are extremely small, E2≈E4 (6).

From equations (1), (2) and (6), NdΦ2/dt≒NdΦ4/dt...(7) Then, Φ2≒Φ4 becomes.

Therefore, regardless of the size of the air gap, the magnetic fluxes generated in the windings M2 and M4 are the same.
This also applies to the auxiliary winding.

That is, the current I _M flowing through each winding M2, M4
2 and I _M 4 are not the same, currents that generate the same induced voltage flow in each of the windings M2 and M4, and the resulting magnetic fluxes are the same.

Therefore, even if there is non-uniformity in the air gap, magnetic flux imbalance does not occur, and vibration and noise are eliminated.

(f) Effect of the invention As explained above, according to the invention, even if the stator and rotor are eccentric and the air gap between them varies, the magnetic flux generated in each winding is the same. Therefore, magnetic flux imbalance does not occur, and vibration and noise caused by magnetic flux imbalance can be eliminated.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of an induction motor, FIG. 2 is a circuit diagram showing a conventional example, and FIG. 3 is a circuit diagram showing an embodiment of the present invention. 1...Rotor, 2...Slot, 4...Rotor, M1, M2, M3, M4...Main winding, A1,
A2, A3, A4...Auxiliary winding.

Claims (1)

[Scope of utility model registration request] 2n pieces for each stator core (n=1, 2,...)
The main windings and the auxiliary windings are connected in parallel with each other mechanically separated by 180 degrees to form a pair of winding groups, and these winding groups are connected in series. An induction motor characterized by: