JP2862568B2 - Electric motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention relates to a motor which may be driven by a non-sinusoidal power supply such as an inverter.

2. Description of the Related Art When an electric motor, for example, an induction motor is operated at a variable speed, a power supply voltage and a frequency may be variably controlled by an inverter. However, when the motor is driven by the inverter, there is a problem that noise or vibration is increased as compared with the case where the motor is driven by a commercial AC power supply. In pursuit of this cause, the voltage and current waveforms output from the commercial AC power supply are sine waves, while the voltage and current waveforms output from the inverter are non-sinusoidal and It contains relatively many harmonic components in addition to the fundamental frequency components in the frequency domain (3-80 Hz). When an electric motor is driven by such an inverter, a high-frequency component generates a harmonic magnetic flux in the winding, and the harmonic magnetic flux causes magnetostriction in the stator core of the stator and the rotor core of the rotor, so that noise or noise is generated. The vibration was getting bigger.

Conventionally, in order to reduce such electromagnetic noise, an inductor is inserted between the motor and the inverter to smooth the current flowing through the winding of the motor, and to reduce the high frequency with respect to the fundamental frequency component included in the current. The ratio of components is reduced, thereby reducing electromagnetic noise.

(Problems to be Solved by the Invention) However, in the above-described conventional configuration, since an inductor is inserted between the motor and the inverter, not only the harmonic component contained in the current flowing through the winding of the motor but also the commercial frequency region The fundamental frequency component also decreases. For this reason, there has been a problem that operating characteristics such as power factor or starting torque are deteriorated. Further, since an inductor is separately required, there is a problem that an installation space is increased.

Therefore, an object of the present invention is to prevent adverse effects of harmonic components when driven by a non-sinusoidal power supply, to achieve low noise and low vibration, and to prevent deterioration of operation characteristics and increase in installation space. To provide an electric motor.

[Structure of the Invention] (Means for Solving the Problems) In the electric motor of the present invention, low magnetostrictive iron plates made of an iron plate containing approximately 6.5% of silicon are laminated on portions of the laminated iron core located at both ends in the axial direction. It is characterized in that it is constituted by a laminated iron core and the other part is constituted by a laminated iron core in which an iron plate containing 3.5% or less of silicon, a pure iron plate or a cold-rolled iron plate is laminated.

(Operation) According to experimental results, the harmonic magnetic flux generated by the harmonic current flowing through the winding of the motor has a property of being concentrated at both axial ends of the laminated core. Therefore, according to the above-described means, even if a current containing a large amount of harmonic components flows through the winding by driving the motor by the inverter, the harmonic magnetic flux caused by the current is located at both axial ends of the laminated core. Since it is generated in the low magnetostrictive material, the magnetostriction generated in the laminated core by the harmonic magnetic flux is reduced. On the other hand, since the middle part of the laminated core, which is a part other than the low magnetostrictive material, is a normal laminated core, magnetic flux caused by the current of the fundamental wave component can be generated in the normal laminated core part, and the low magnetostrictive material Even if there is, the saturation of the main magnetic flux can be avoided, so that the operating characteristics can be prevented from deteriorating. Further, since an external device for the electric motor is not required separately, it is possible to prevent the installation space from becoming large.

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

First, in FIG. 1, reference numeral 1 denotes a frame, and 2 denotes a stator disposed inside the frame 1. This stator 2
Is composed of a stator core 3 and a stator winding 4 which are laminated cores. A plurality of slots 5 are formed in the inner periphery of the stator core 3, and the stator windings 4 are wound in the slots 5, while 6 is the stator 2.
, Which is rotatably provided inside the rotor. The rotor comprises a rotor shaft 7, a rotor core 8 which is a laminated core, and a rotor conductor 9. A plurality of slots 10 are formed in the outer peripheral portion of the rotor core 8, and the rotor conductor 9 is mounted in the slots 10. Reference numeral 11 denotes an end ring, which is attached to both ends of the rotor core 8.

The stator core 3 is composed of laminated cores 12 and 13 in which portions located at both ends in the axial direction are laminated with low magnetostrictive iron plates (for example, iron plates containing 6.5% silicon) which are low magnetostrictive materials. An intermediate portion of the stator core 3 other than the portions located at the above-mentioned both ends is constituted by a normal laminated core 14. This normal laminated core 14
A low-silicon steel plate, for example, an iron plate containing 3.5% or less of silicon, a pure iron plate, or a cold-rolled steel plate is laminated alone or in combination. In addition, the rotor core 8 has a low magnetostrictive iron plate (for example, a low magnetostrictive material) in which portions located at both ends in the axial direction are low magnetostrictive materials.
Cores 15 and 16 laminated with 6.5% silicon-containing iron plate)
It consists of. An intermediate portion of the rotor core 8 other than the portions located at the both ends is formed of a normal laminated iron core 17. The ordinary laminated iron core 17 is formed by laminating low-silicon steel plates, for example, silicon-containing iron plates of 3.5% or less, pure iron plates or cold-rolled steel plates, alone or in combination.

Next, the operation of the above configuration will be described. When the above-described motor is driven by the inverter, the current flowing through the stator winding 4 includes a fundamental component (for example, a low frequency such as 50 Hz or 60 Hz) and a harmonic component (for example, a high frequency such as 1 kHz or 2 kHz). . According to experimental results, harmonic magnetic fluxes generated in the stator windings 4 by harmonic components of the current are concentrated at both axial ends of the stator core 4 and both axial ends of the rotor core 8. There is a nature to do. In this case, portions of the stator core 3 located at both ends in the axial direction are constituted by laminated cores 12 and 13 in which low magnetostrictive iron plates are laminated, and are located at both ends in the axial direction of the rotor core 8. Is formed by laminated cores 15 and 16 in which low magnetostrictive iron plates are laminated, so that the above-mentioned harmonic magnetic flux
Almost no magnetostriction occurs even after passing through 6. Therefore, electromagnetic noise can be reduced, and noise or vibration can be reduced. In addition, the electromagnetic noise of harmonic magnetic flux (not shown) generated in the rotor conductor 9 by the harmonic component of the current induced in the rotor conductor 9 can be similarly reduced. On the other hand, the fundamental wave magnetic flux generated in the stator winding 4 due to the fundamental wave component of the current flowing in the stator winding 4 has a structure in which an intermediate portion of the stator core 3 is formed of a normal laminated iron core 14, The middle part of the child core 8 is a normal laminated core
As a result, since the fundamental wave magnetic flux passes through these laminated iron cores 14 and 17, the magnetic resistance is small, and the loss is also small. The result of measuring the noise data of the present embodiment is indicated by a point d in FIG. In FIG. 2, point a shows the result of measuring noise data of a conventional configuration in which the stator core and the rotor core are all formed of ordinary laminated cores. Points b and c show the results of measuring the noise data of Comparative Examples 1 and 2. In Comparative Example 1, as shown in FIG. 3, the central portion of the stator core and the rotor core was constituted by a laminated core 18 on which low magnetostrictive iron plates were laminated, and the other portions were formed by ordinary laminating. It is composed of iron cores 19 and 20. In Comparative Example 2, as shown in FIG. 4, the stator core and the rotor core are configured by alternately stacking laminated cores 21 having low magnetostrictive iron plates laminated thereon and ordinary laminated cores 22. And, Comparative Examples 1 and 2
About 14% of the low magnetostrictive iron plate is used in total core volume ratio. As is clear from FIG. 2, the present embodiment can reduce noise. When the stator core and the rotor core are configured by laminating only low magnetostrictive iron plates, it is possible to reduce electromagnetic noise due to harmonic magnetic flux, but the saturation characteristic of magnetic flux density deteriorates. There is a disadvantage that the exciting current increases, and the manufacturing cost also increases.

According to the present embodiment having such a configuration, in order to reduce electromagnetic noise due to harmonic magnetic flux during driving of the inverter, portions of the stator core 3 located at both ends in the axial direction are laminated with low magnetostrictive iron plates. It is composed of iron cores 12 and 13, and the portions located at both axial ends of the rotor core 8 are merely composed of laminated cores 15 and 16 in which low magnetostrictive iron plates are laminated. As a result, since the fundamental frequency component of the current flowing through the stator winding 4 in the commercial frequency region does not decrease, it is possible to prevent the operating characteristics from deteriorating. Further, since an external device such as an inductor is not required separately, the installation space can be reduced.

In the above embodiment, the laminated iron cores 12, 13, 15, and 16 were used by laminating 6.5% silicon-containing iron plates as the low magnetostrictive material.
The present invention is not limited to this, and a plastic mold body mixed with iron powder may be used as the low magnetostrictive material. Further, the present invention is applied to an inversion type in which the rotor 6 is rotated inside the stator 2, but may be applied to an inversion type in which the rotor is rotated outside the stator.

Further, in the above embodiment, both ends in the axial direction of the stator core 3 and the rotor core 8 are respectively made of low magnetostrictive material. Instead, either the stator core or the rotor core may be used. One of the two ends may be made of a low magnetostrictive material at both ends in the axial direction. Also in this case, the magnetostriction of at least one end of the two cores in the axial direction is reduced, so that the overall noise can be reduced accordingly.

[Effects of the Invention] As is apparent from the above description, the present invention can prevent adverse effects of harmonic components when driven by a non-sinusoidal power supply, can achieve low noise and low vibration, and furthermore, deteriorate operating characteristics. In addition, an excellent effect that an increase in the installation space can be prevented can be achieved.

[Brief description of the drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is a partial sectional view, FIG. 2 is a graph of noise data measurement results, and FIG. 3 is a sectional view of an iron core of Comparative Example 1. FIG. 4 is a sectional view of an iron core of Comparative Example 2. In the drawing, 2 is a stator, 3 is a stator core (laminated core), 6
Is a rotor, 8 is a rotor core (laminated core), 12,13,15,16
Are laminated iron cores with low magnetostrictive iron plates (low magnetostrictive material), 14,17
Indicates a normal laminated iron core.

Continuation of the front page (58) Fields investigated (Int.Cl. ⁶ , DB name) H02K 17/00-17/44 H02K 1/00-1/16 H02K 1/18-1/26 H02K 1/28-1 / 34

Claims (1)

(57) [Claims] A portion of the laminated core located at both ends in the axial direction is constituted by a laminated core obtained by laminating low magnetostrictive iron plates made of an iron plate containing approximately 6.5% of silicon, and the remaining portion is formed of silicon. An electric motor comprising an iron core, a pure iron plate or a cold-rolled iron plate containing not more than 3.5% of a laminated core.