KR20170100964A - Induction motor for noise reduction - Google Patents

Abstract

The present invention relates to an induction motor with reduced noise, which maximizes efficiency while minimizing mechanical vibration and noise generated during a high-speed operation by an optimized rate of the number of slots of a stator and a rotor. According to the present invention, in a 50 hp class three-phase induction motor, the number of poles of a rotor system is 2 and the number of stator slots and rotor slots are 24 and 34 respectively, so a rate of the number of slots is 1.42.

Description

[0001] Induction motor for noise reduction [0002]

The present invention relates to an induction motor, and more particularly, to a noise reduction induction motor that maximizes efficiency while minimizing mechanical vibration and noise generated during high-speed operation by an optimal number of slots of a stator and a rotor .

Generally, the three-phase induction motor is made by stacking the outer stator and the inner rotor with thin steel plates, each of which is provided with a slot.

In such a three-phase induction motor, a coil is inserted in the stator slot. Since each phase of the three phases is one coil, at least several coils are used, so that the number of slots of the stator is 24, 36, 48, 64 ... And many are hundreds. The phase coils are arranged to move in the space at an electric angle of 120 degrees. When a three-phase voltage is applied to the three-phase coil of the stator, a three-phase current flows to generate a rotating magnetic field.

On the other hand, the rotor has a cage-like shape in which a casting of a copper rod or an aluminum that is not coated is inserted into a slot, and a winding type in which a three-phase winding is used. A bipolar motor can generate a multipolar rotor system by changing the number of stator slots and the stator winding method when the stator winding generates two pole stator systems. As the number of poles increases, the speed of the rotating magnetic field decreases, and the speed of the rotor also rotates at a lower speed. The speed of the rotating system is 120 f / p per minute when p is the number of poles and f is the frequency, which is called the synchronous speed. If the rotor is an electrically closed circuit, the induction electromotive force (electromotive force) is generated in the rotor conductor by the rotor system, causing the induced current to flow and rotating as an electric motor by interaction with the magnetic field generated in the stator winding. The direction of rotation is the same as the direction of the rotating magnetic field, but the speed of the rotor is always slower than the speed of the rotating magnetic field. The value obtained by dividing the difference by the synchronous speed is called a slip, and the influence of the value of the slip on the operation of the motor is large. For example, when the slip is 1, the rotor is in the stopped state and when the slip is 0, the rotor rotates at the synchronous speed. In this case, the output of the motor becomes 0. Generally, the value of slip at the rated output is several percent. This is true whether the rotor is of the farming type or the winding type.

Generally, three phase induction motors are dwarfed and have four poles. When a rated frequency of 60 Hz is applied, the synchronous speed is 1,800 rpm. The rotor has a slip of several percent and rotates near the synchronous speed. The three-phase terminal (three-phase terminal) of the wire-wound type exits through a collector ring and a brush provided on the shaft. By connecting a resistor having a proper value to the three-phase terminal, the speed can be controlled, the inflow current when starting can be reduced, and the torque can be further increased. Methods for controlling the speed of the squirrel cage motor include voltage / frequency constant control and vector control.

Such induction motors are simple to use and have a relatively low maintenance cost and robustness against external operating environments, and are thus widely applied to products requiring high-speed rotation.

However, in the case of an induction motor rotating at a high speed, it is not easy to minimize the occurrence of noise and vibration while satisfying the electric characteristics and efficiency, and accordingly, a design for reducing noise and vibration is inevitable.

Korean Published Patent Application No. 2014-0083489 (Apr.

It is an object of the present invention to minimize the mechanical vibration and noise generated during high-speed operation by the optimized number of slots of the stator and the rotor, And to provide a noise reducing induction motor for maximizing efficiency.

In order to achieve the above object, the noise reduction induction motor according to the technical idea of the present invention is a 50 hp class three-phase induction motor in which the number of poles of the rotary system is 2, the number of stator slots and the number of rotor slots are 24 And 34, and the ratio of the number of slots is 1.42.

Here, the stator has an inner diameter of 110 mm and an outer diameter of 240 mm, and the rotor has an inner diameter of 45 mm and an outer diameter of 106.8 mm.

Further, the rotor slot may include a cylindrical conductor.

The output efficiency of the noise reduction induction motor may be 96% or more.

The stack length of the stator and the rotor is 90 mm, respectively.

The noise reduction induction motor according to the present invention can minimize the mechanical vibration and noise generated during high-speed operation by the optimized number of slots of the stator and the rotor in the 50 hp class three-phase induction motor.

1 is a sectional view for explaining a configuration of a noise reduction induction motor according to an embodiment of the present invention;
2 is a graph showing a radial air magnetic flux density graph for an electric angle for measuring mechanical characteristics of a noise reducing induction motor according to an embodiment of the present invention
3 is a graph showing a frequency analysis of a radial gap magnetic flux density for measuring mechanical characteristics of a noise reduction induction motor according to an embodiment of the present invention
4 is a graph showing the radial void magnetic flux density graph for the electric angle of the prior art for comparison with the noise reduction induction motor according to the embodiment of the present invention
5 is a frequency analysis graph of a radial void magnetic flux density of the prior art for comparison with a noise reduction induction motor according to an embodiment of the present invention
6 is a graph showing the comparison of the radial excitation force with respect to the electric angle of the prior art with the noise reduction induction motor according to the embodiment of the present invention
FIG. 7 is a graph showing a frequency analysis comparative graph of a noise reducing induction motor according to an embodiment of the present invention and a prior art radial excitation force

The noise reducing induction motor according to the embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing. In the accompanying drawings, the dimensions of the structures are enlarged to illustrate the present invention, and are actually shown in a smaller scale than the actual dimensions in order to understand the schematic structure.

Also, the terms first and second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. On the other hand, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

1 is a sectional view for explaining the construction of a noise reduction induction motor according to an embodiment of the present invention.

As shown in the figure, in the conventional noise reduction induction motor according to the embodiment of the present invention, the ratio of the number of slots of the stator 110 and the rotor 120 in a conventional 50 hp class three-phase induction motor in which the number of poles of the rotor system is two The number of slots of the stator 110 and the number of slots of the stator 110 are reduced to 2/3 and the number of slots of the stator 110 and the rotor 120 is increased to 1.42 And has a unique configuration.

In this case, if the ratio of the number of slots of the rotor 120 to the number of slots of the stator 110 is 1 or more, even if the ratio of the number of slots increases, the electrical characteristics are not changed even though the performance saturation region is increased. It has been found out that there is a change that minimizes the noise and vibration generated in the induction motor.

The noise reduction induction motor according to the embodiment of the present invention has a structure in which the number of slots of the stator 110 and the rotor 120 described above is set to 24 and 34 to 1.42, The inner diameter and the outer diameter of the rotor 120 are 45 mm and 106.8 mm, respectively, and the stack length of the stator 110 and the rotor 120 is Respectively. The slot 120 of the rotor 120 is formed in a cylindrical shape different from that of the slot 110 of the stator 110. Table 1 below shows the specifications of the noise reduction induction motor with such specifications.

Output [hp] Torque [Nm] Speed [rpm] Voltage [VL _{-L_rms} ] Frequency [Hz] 50 24 15,000 190 250

The characteristics of the stator and the rotor of the noise reduction induction motor (model 2) according to the embodiment of the present invention are compared with those of a general 50 hp class induction motor, as shown in Tables 2 and 3 below.

Specification model1 model2 Outer diameter [mm] 190 240 Inner diameter [mm] 110 110 Number of slots 36 24 Stacking length [mm] 90 90

Specification model1 model2 Outer diameter [mm] 109 106.8 Inner diameter [mm] 45 45 Number of slots 33 34 Diameter of bar [mm] 5 5 Area of the bar [mm ² ] 28.27 19.64 Stacking length [mm] 90 90 Resistance (75 ° C) [Ω] 0.01223 0.019054

The performance of the noise reduction induction motor according to the embodiment of the present invention is compared with the performance of a general 50 hp class induction motor.

model1 model2 Speed [rpm] 14,785 14,656 Input current (rms) [A] 125.53 85.8 Rated output [kW] 37.62 37.75 Rated torque [Nm] 24.3 24.6 Iron loss [W] 260 428.07 Stator winding loss [W] 683 255.85 Rotor winding loss [W] 297 260.34 Stray loss [W] 376 377.55 efficiency[%] 95.9 96.62

The noise reduction induction motor model 2 according to the embodiment of the present invention shown in the above Tables 2 to 4 and the induction motor model 1 according to the prior art can be compared with each other according to the prior art induction motor, The noise reduction induction motor has a slot number ratio of 0.92 and 1.42, but the electric characteristics are similar. Generally, when the ratio of the number of slots of the rotor 120 to the number of slots of the stator 110 is 1 or more, there is a performance saturation characteristic in which the electrical characteristics such as the starting torque, the maximum torque, to be.

Generally, the noise and vibration characteristics in the induction motor are determined by the electromagnetic excitation force generated in the stator 110. The electromagnetically exciting force includes a tangential excitation force and a radial excitation force. In the case of an electromagnetic excitation force, a force that tangentially strikes the teeth of the stator 110 affects the ripple component of the torque, An excitation force having a frequency corresponding to the least common multiple of the number of slots and the number of slots of the rotor 120 is generated. Also, as the least common multiple of the number of slots increases, the frequency of the excitation force increases and the magnitude tends to decrease. Therefore, in order to reduce the tangential force (or torque ripple), it is important to select the combination of the stator 110 and the rotor 120 slot considering the least common multiple of the number of slots.

In the noise reduction induction motor according to the embodiment of the present invention, the number of slots of the stator 110 and the number of slots of the rotor 120 are 24 and 34, respectively, and the minimum common multiple is 408. However, The number of slots and the number of rotors (120) are 36 and 33, respectively, and the least common multiple is 396, which is not very high and similar.

On the other hand, the radial eccentric force is a force to radially bias the teeth of the stator 110. As the number of slots of the rotor 120 increases, the frequency of the excitation force increases and the magnitude thereof tends to decrease. In this respect, the noise reduction induction motor according to the embodiment of the present invention, in which the number of slots of the rotor 120 is 34, is smaller than that of the prior art motor with equivalent number of slots of the rotor 120, It can be expected that the excitation force will be lowered.

FIGS. 2 to 7 show the results of measurement of the mechanical characteristics of model 1 and model 2 constructed according to the above specifications.

2 and 3 show the radial void magnetic flux density (Br) for the electrical angle in the model 2 corresponding to the embodiment of the present invention and its frequency analysis, which is shown in FIGS. 4 and 5 Compared with the radial air flux density (Br) of the model1, the fundamental wave component of the radial flux density is increased due to the decrease of the number of stator slots, but the harmonic components are remarkably low. If the harmonic components of the radial air magnetic flux density are reduced, the harmonic components of the electromagnetic excitation force in the radial direction acting as the main cause of the mechanical noise and vibration in the stator teeth can be reduced.

Figures 6 and 7 show the radial excitation force and the frequency analysis of the electrical angle for model 2 and model 2, respectively. As predicted from the radial air magnetic flux density distribution, in the model 2 according to the embodiment of the present invention, the fundamental wave component of the radial force acting on the stator tooth due to the reduction of the number of stator slots is increased, but it is a major cause of vibration and noise It can be confirmed that the harmonic components that have been reduced are remarkably reduced.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It is clear that the present invention can be suitably modified and applied in the same manner. Therefore, the above description does not limit the scope of the present invention, which is defined by the limitations of the following claims.

110: stator 111: slot of the stator
120: Rotor 121: Slot of rotor

Claims (5)

In a 50 hp class three-phase induction motor,
The number of poles of the rotating system is 2, the number of stator slots and the number of rotor slots are 24 and 34, respectively, and the number of slots is 1.42. The method according to claim 1,
The stator had an inner diameter of 110 mm and an outer diameter of 240 mm,
Wherein the rotor has an inner diameter of 45 mm and an outer diameter of 106.8 mm. 3. The method of claim 2,
Wherein the rotor slot is provided with a cylindrical conductor bar. 3. The method of claim 2,
Wherein the noise reduction induction motor has an output efficiency of 96% or more. In a 50 hp class three-phase induction motor,
The number of poles of the rotating system is 2, the number of stator slots and the number of rotor slots are 24 and 34, respectively, and the number of slots is 1.42,
The stator has an inner diameter and an outer diameter of 110 mm and 240 mm, respectively, and the rotor has an inner diameter and an outer diameter of 45 mm and 106.8 mm, respectively, and a stack length of the stator and rotor is 90 mm, respectively Noise Reduction Induction Motor.

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