CN115694035A

CN115694035A - Motor and electric device provided with same

Info

Publication number: CN115694035A
Application number: CN202210898029.0A
Authority: CN
Inventors: 前谷达男; 礒村宣典; 胡峰
Original assignee: Wolong Electric Group Co Ltd
Current assignee: Wolong Electric Drive Group Co Ltd
Priority date: 2021-07-30
Filing date: 2022-07-28
Publication date: 2023-02-03
Also published as: JP2023021030A

Abstract

The present invention relates to a motor and an electric device including the motor. The motor includes: a stator including a stator core around which a stator winding is wound; a rotating body that holds the plurality of magnets in a circumferential direction or holds the plurality of magnets in a spoke shape from the center, while facing the stator; a rotor including the rotating body and a rotor penetrating the rotating bodyA shaft for fastening the rotating body to the center; a first bearing and a second bearing that support the rotating body; a first metal bracket for fixing the first bearing; and a second metal bracket for fixing the second bearing, wherein a capacitance C is provided between any one of the first metal bracket and the second metal bracket and a zero reference potential of a drive circuit for applying a voltage to the stator winding _nb1 The capacitive component of (1).

Description

Motor and electric device provided with same

Technical Field

The present disclosure relates to a motor and an electric device including the motor, and more particularly, to a motor improved to suppress occurrence of electric corrosion of a bearing and an electric device including the motor.

Background

In recent years, brushless motors are often driven by an inverter of a Pulse Width Modulation (PWM) system (hereinafter, referred to as PWM system as appropriate). In the case of such PWM inverter driving, the neutral point potential of the stator winding varies due to switching of the power element. The variation of the neutral point potential is divided into a voltage on the outer ring side of the bearing and a voltage on the inner ring side of the bearing according to the electrostatic capacitance distribution of the motor.

Since the electrostatic capacitance distribution on the stator side of the stator winding and the outer ring side of the bearing is different from the electrostatic capacitance distribution on the rotor side of the electrostatic capacitance distribution on the stator winding and the inner ring side of the bearing, a potential difference (hereinafter, referred to as a shaft voltage) is generated between the outer ring of the bearing and the inner ring of the bearing. It is known that the shaft voltage includes a high-frequency component generated by switching, and when the shaft voltage reaches an insulation breakdown voltage of an oil film of grease inside the bearing, a minute current flows inside the bearing due to insulation breakdown of the oil film of grease, and roughness is generated on a metal surface inside the bearing, thereby generating electric corrosion (see, for example, non-patent document 1 and patent documents 1 to 4).

In addition, when the electric corrosion progresses, a wave-like abrasion phenomenon occurs in an inner ring of the bearing, an outer ring of the bearing, or balls of the bearing, and causes abnormal noise, which is one of the main factors of the motor failure.

Patent document 1: japanese patent laid-open No. 2010-158152

Patent document 2: japanese patent No. 4935934

Patent document 3: japanese patent laid-open publication No. 2007-159302

Patent document 4: WO2015/001782

[ non-patent document 1 ]

Journal of the Electrical society of thesis D,2012, vol.132, no6, pp.666-672 of "Axis Voltage suppression based on ungrounded common mode equivalent Circuit for inverter-driven brushless DC Motor

Disclosure of Invention

The purpose of the present disclosure is to suppress the occurrence of electrolytic corrosion in a bearing in a motor and an electrical device provided with the motor.

An electric motor according to an aspect of the present disclosure includes:

a stator including a stator core around which a stator winding is wound;

a rotating body that holds the plurality of magnets in a circumferential direction or holds the plurality of magnets in a spoke shape from the center, while facing the stator;

a rotor including the rotating body and a shaft that penetrates the center of the rotating body and fastens the rotating body;

a first bearing and a second bearing for supporting the rotating body;

a first metal bracket for fixing the first bearing; and

a second metal bracket for fixing the second bearing,

an electrostatic capacitance C is provided between any one of the first metal bracket and the second metal bracket and a zero reference potential of a drive circuit for applying a voltage to the stator winding _nb1 The capacitive component of (a) is,

the electrostatic capacitance between the stator winding and the bracket on the stator side is defined as C _sb1 ，

Will include the electrostatic capacitance C between the stator winding and the stator core _i And an electrostatic capacitance C between the stator core and the magnet _g And an electrostatic capacitance C between the stator winding and the magnet _sm And an electrostatic capacitance C of the magnet _m The electrostatic capacitance on the inner rotor side is defined as a composite electrostatic capacitance B1,

the electrostatic capacitance between the zero reference potential of the drive circuit and the axis is defined as C _ns ，

The stator on the stator sideAn electrostatic capacitance between the winding and the other of the first metal bracket and the second metal bracket is defined as C _sb2 ，

The electrostatic capacitance between the other bracket and a zero reference potential of a drive circuit for applying a voltage to the stator winding is defined as C _nb2 When the utility model is used, the water is discharged,

the electrostatic capacitance C _sb1 And the electrostatic capacitance C _nb1 Ratio of (A to B) < R > _X1 (C _sb1 /C _nb1 ) And the synthesized electrostatic capacitance B1 and the electrostatic capacitance C _ns Ratio of R _Y1 (B1/C _ns ) The degree of similarity or consistency is similar or consistent,

the electrostatic capacitance C _sb2 And the electrostatic capacitance C _nb2 Ratio of (A to B) < R > _X2 (C _sb2 /C _nb2 ) And the electrostatic capacitor C _sb1 And the electrostatic capacitance C _nb1 Ratio of R _X1 (C _sb1 /C _nb1 ) Approximately or uniformly.

According to one embodiment of the present disclosure, it is possible to suppress occurrence of electrolytic corrosion of a bearing in a motor and an electric device including the motor.

Drawings

Fig. 1 is a schematic configuration diagram of a cross section of a motor in embodiment 1 as one embodiment of the present disclosure.

Fig. 2 is a model diagram of the electrostatic capacitance distribution of the motor according to embodiment 1.

Fig. 3 shows the electrostatic capacitance, the shaft voltage, and the voltage division ratio R of the capacitive component of the motor according to embodiment 1 _X1 To partial pressure ratio R _Y1 Ratio of (R) _X1 /R _Y1 ) And a partial pressure ratio R _X2 To partial pressure ratio R _X1 Ratio of (R) _X2 /R _X1 ) A graph of the relationship of (a).

Fig. 4 is a schematic configuration diagram showing a cross section of a motor according to a modification of embodiment 1.

Fig. 5 is a perspective view of an embodiment of an electric device using the motor according to embodiment 1.

Fig. 6 is a perspective view of an embodiment of another electric device using the motor according to embodiment 1.

Fig. 7 is a perspective view of an embodiment of another electric apparatus using the motor according to embodiment 1.

Fig. 8 is a schematic configuration diagram of a cross section of a motor in embodiment 1 as another embodiment of the present disclosure.

Fig. 9 is a schematic configuration diagram of a cross section of a conventional motor.

Fig. 10 is a model diagram of the electrostatic capacitance distribution of the motor of fig. 9.

Fig. 11 is a schematic configuration diagram of a cross section of another conventional motor.

Fig. 12 is a model diagram of the electrostatic capacitance distribution of the motor of fig. 11.

Fig. 13 is a schematic configuration diagram of a cross section of another conventional motor.

Fig. 14 is a model diagram of the electrostatic capacitance distribution of another conventional motor.

Detailed Description

(insight underlying the present disclosure)

Before the embodiments of the present disclosure are explained, the basic findings of the present disclosure will be explained.

Conventionally, in the following documents, in order to suppress the electric corrosion of the bearing, a countermeasure has been proposed in which the oil film of the grease in the bearing is made equal to or less than the dielectric breakdown voltage by lowering the shaft voltage, so that the dielectric breakdown of the oil film of the grease in the bearing does not occur. In addition, the following documents propose measures for reducing damage to the metal surface inside the bearing by reducing the discharge energy due to dielectric breakdown of the oil film of the grease inside the bearing by lowering the shaft voltage.

The above-mentioned documents are described in detail below.

Fig. 9 is a schematic configuration diagram of a cross section of an inner rotor type brushless radial motor 50 of patent document 1. Patent document 1 is the same as non-patent document 1.

As shown in fig. 9, the motor 50 includes a first metal bracket 1, a second metal bracket 2, a first bearing 5a, a second bearing 5b, a shaft 4, a rotor 10, and a stator 18.

The rotor 9 has a rotor core 8 and a magnet 11 as a permanent magnet. The rotor 10 has a rotating body 9 and a shaft 4. The stator 18 has a stator core 6 and a stator winding 3.

As shown in fig. 9, the outer ring of the first bearing 5a is connected to the first metal bracket 1, and the outer ring of the second bearing 5b is connected to the second metal bracket 2. The inner race of the first bearing 5a and the inner race of the second bearing 5b are connected by the shaft 4 and electrically conducted. The first metal bracket 1 and the second metal bracket 2 are electrically short-circuited by the conductive member 13.

Patent document 1 (fig. 9) electrically short-circuits the first metal bracket 1 and the second metal bracket 2 by the conductive member 13, and matches the capacitances of the first metal bracket 1 and the second metal bracket 2. In addition, patent document 1 (fig. 9) discloses a method of reducing the shaft voltage by providing a dielectric layer 20 on the rotating body 9 and changing the capacitance of the rotating body 9.

Fig. 10 is a model diagram of the electrostatic capacitance distribution of the motor 50 of patent document 1, which was obtained by the inventors of the present invention in consideration of fig. 9 in detail. In the motor 50 of patent document 1, when the electrostatic capacitance distribution is examined with reference to the stator core 6, the voltage distribution of the motor 50 is mainly affected by the capacitive reactance that is the reciprocal of the impedance, and therefore, as shown in fig. 5 of non-patent document 1, a model of the electrostatic capacitance distribution is described.

Electrostatic capacitance C between stator winding 3 and first metal bracket 1 _sb1 Schematically representing the accumulated charge of the first bearing 5a, the first shaft voltage V _sh1 And (4) rising. If the first axis voltage V _sh1 When the voltage rises and reaches the dielectric breakdown voltage of the grease film inside the bearing, dielectric breakdown occurs. Electrostatic capacitance C between stator winding 3 and second metal bracket 2 _sb2 And also with the electrostatic capacitance C _sb1 Similarly, the second shaft voltage V, which is a charge accumulated in the second bearing 5b, is schematically represented _sh2 And (4) rising. If the second axis voltage V _sh2 When the voltage rises, dielectric breakdown occurs.

The voltage generated between the outer ring side (the portion 1 in fig. 10) of the first bearing 5a and the zero potential reference N (12) of the drive circuit is equal to the voltage generated between the zero reference potential N of the drive circuit and the stator winding 3Voltage V generated between the potential S of the sexual point _com The voltage is divided according to the electrostatic capacitance distribution on the stator side.

Further, a voltage generated between the outer ring side (the portion 2 in fig. 10) of the second bearing 5b and the zero potential reference N (12) of the drive circuit is set to be equal to a voltage V generated between the zero reference potential N (12) of the drive circuit and the neutral point potential S of the stator winding 3 _com The voltage is divided according to the electrostatic capacitance distribution on the stator side.

The voltages generated on the inner ring side of the first bearing 5a and the inner ring side of the second bearing 5b (the portion 4 in fig. 10) and the zero potential reference N (12) of the drive circuit are relative to the voltage V generated between the zero potential reference N (12) of the drive circuit and the neutral point potential S of the stator winding 3 _com The voltage is divided according to the electrostatic capacitance distribution on the rotor side.

The inventors of the present invention have designed and examined a model diagram of the capacitance distribution shown in fig. 10, and have found the following findings. First axis voltage V _sh1 And a second axis voltage V _sh2 The difference between the voltage generated on the outer ring side of the first bearing 5a and the voltage generated on the outer ring side of the second bearing 5b and the voltage generated on the inner ring side is obtained. Therefore, it was found that in order to reduce the first axis voltage V _sh1 And a second axis voltage V _sh2 It is effective to match or approximate the electrostatic capacitance distribution on the stator side to the electrostatic capacitance distribution on the rotor side.

The voltages generated on the outer ring side of the first bearing 5a and the outer ring side of the second bearing 5b and the zero potential reference N (12) of the drive circuit become the electrostatic capacitance C between the stator winding 3 and the first metal bracket 1 _sb1 And an electrostatic capacitance C between the stator winding 3 and the second metal bracket 2 _sb2 The combined electrostatic capacitance A2, and the electrostatic capacitance C between the zero reference potential N (12) of the driving circuit and the first metal bracket 1 _nb2 Partial pressure ratio R of _A2 (synthetic electrostatic capacitance A2/C _nb2 ) Is multiplied by the voltage V _com The resulting voltage.

Further, voltages generated on the inner ring side of the first bearing 5a, the inner ring side of the second bearing 5b, and the zero potential reference N (12) of the drive circuit act to wind the statorElectrostatic capacitance C between group 3 and stator core 6 _i And electrostatic capacitance C between stator core 6 and magnet 11 _g And electrostatic capacitance C between stator winding 3 and magnet 11 _sm And the electrostatic capacitance C of the magnet 11 _m The combined electrostatic capacitance B2 and the electrostatic capacitance C between the zero reference potential N of the drive circuit and the shaft 4 _ns Partial pressure ratio R of _B2 (Combined Electrostatic capacitance B2/C _ns ) Is multiplied by the voltage V _com The resulting voltage.

As a result of intensive studies by the inventors of the present invention, it was found that the first axis voltage V was reduced _sh1 And a second shaft voltage V _sh2 The voltage division ratio R needs to be made _A2 (synthetic electrostatic capacitance A2/C _nb2 ) To partial pressure ratio R _B2 (Combined Electrostatic capacitance B2/C _ns ) Consistent or approximate. The partial pressure ratio R will be set as follows _A2 To partial pressure ratio R _B2 The case of coincidence or approximation is simply referred to as a match.

As a result, patent document 1 shows that the capacitance C is _sb1 、C _sb2 、C _ns Since the capacitance is smaller than the combined capacitance B2, the capacitance of the combined capacitance B2 is made smaller in order to match the capacitances.

In patent document 1, in fig. 9, in the capacitance distribution on the rotor 10 side, a dielectric layer 20 is provided on the rotating body 9 to form a capacitance C _d . The electrostatic capacitance C of the dielectric is known _d In fig. 10, which is a model diagram of the electrostatic capacitance distribution, the electrostatic capacitance C with the magnet 11 _m An electrostatic capacitor C is inserted in series _d The resultant electrostatic capacitance B2 is reduced to thereby obtain matching with the electrostatic capacitance distribution on the stator side, and as a result, the first axis voltage V _sh1 And a second axis voltage V _sh2 Becomes low.

Electrostatic capacitance C of dielectric layer 20 _d The distance in the thickness direction of the dielectric layer 20 (the distance in the short direction of the dielectric layer 20 in fig. 9) is inversely proportional to the length (the distance in the long direction of the dielectric layer 20 in fig. 9) and is proportional to the length. Therefore, in order to reduce the electrostatic capacitance C _d The width of the dielectric layer 20 (the distance in the thickness direction of the dielectric layer 20) needs to be increased.

However, in patent document 1, since stress is applied to the dielectric layer 20 as a rotational torque as shown in fig. 9, the dielectric layer 20 may be restricted in width in order to secure its strength. In this case, it was considered that a desired capacitance could not be obtained and the axis voltage did not decrease. In addition, in patent document 1, there is a problem as follows: in the motor 50 using the rotating body 9 holding a plurality of permanent magnets (magnets) in a radial shape from the center in the radial direction, it is necessary to shorten the length of the permanent magnet (magnet) 11 by increasing the width of the dielectric layer 20, which results in deterioration of the performance of the motor 50.

Next, patent document 2 will be explained.

Fig. 11 is a schematic configuration diagram of a cross section of the motor 50 of patent document 2. Fig. 12 is a model diagram of the capacitance distribution obtained by the inventors of the present invention in consideration of the motor 50 of fig. 11.

As shown in fig. 11, the first metal bracket 1 and the second metal bracket 2 are short-circuited by the conductive member 13. The resistance adjustment member 14 is inserted between the stator core 6 and one of the first metal bracket 1 and the second metal bracket 2. Fig. 11 shows a structure in which the resistance adjustment member 14 is inserted between the stator core 6 and the second metal bracket 2.

When a capacitor having a capacitance is used as the impedance adjusting member 14, the impedance adjusting member 14 serving as a capacitance for impedance adjustment is set to the capacitance C _i 、C _sb1 And C _sb2 The combined electrostatic capacitances of (a) are connected in parallel. And, by increasing the electrostatic capacitance C _i 、C _sb1 And C _sb2 The combined capacitance of (2) is matched with the capacitance of the rotor side. Thus, in patent document 2, it is found that the first axial voltage V is obtained as a result _sh1 And a second axis voltage V _sh2 Becomes low.

However, it is difficult to establish a method of connecting the impedance adjusting member 14 to the stator core 6. In addition, the following problems are considered: since the molding is performed after the connection, the connection portion is separated during the production process.

Next, patent document 3 will be explained.

Fig. 13 is a schematic configuration diagram of a cross section of the motor 50 of patent document 3.

In patent document 3, a short-circuiting member 25 short-circuits the stator core 6 to either one of the first metal bracket 1 and the second metal bracket 2. In fig. 13, the stator core 6 and the second metal bracket 2 are short-circuited to reduce the first shaft voltage.

The structure of patent document 3 is similar to that of fig. 10 of patent document 2. Further, it is disclosed that the structure of patent document 3 is comparative example 3 of patent document 2, and there is a problem that waveform collapse occurs in the axis voltage.

This is presumably because the capacitance between the stator core 6 and the short-circuited second metal bracket 2 is increased, but the capacitance between the stator core 6 and the first metal bracket 1 which is not short-circuited is not changed. Therefore, it is considered that the shaft voltage of the first bearing 5a does not decrease and the electrolytic corrosion suppressing effect is small.

Finally, patent document 4 will be explained.

Fig. 14 is a model diagram of the electrostatic capacitance distribution that the inventors of the present invention consider with respect to the motor 50 shown in patent document 4.

As shown in fig. 14, the following method is disclosed: electrically insulating the first metal bracket 1 and the second metal bracket 2, and forming a capacitance C between the stator core 6 and the first metal bracket 1 _sb1 And electrostatic capacitance C between stator core 6 and second metal bracket 2 _sb2 Set to approximate or coincide, thereby reducing the shaft voltage.

However, in patent document 4, the capacitance C is adjusted _sb1 And an electrostatic capacitance C _sb2 In contrast, since it is necessary to adjust the size of the components and the distance between the components, the outer dimensions and the shape of the motor may be increased.

In addition, the matching adjustment function of the electrostatic capacitance is insufficient for the electrostatic capacitance distribution on the rotor side, and the first shaft voltage and the second shaft voltage cannot be sufficiently reduced. Therefore, it is considered that the waveform of the first and second shaft voltages, which are phenomena of insulation breakdown of the grease of the first and second bearings' a and 5b, is broken, and there is a problem in the electrolytic corrosion life in long-term operation.

The present inventors have found the above-mentioned problems and have intensively studied to solve the problems, and have found the essence to achieve the object.

Fig. 1 is a schematic structural view of a cross section of a motor 50 of the present disclosure.

As shown in fig. 1, the motor 50 includes a first metal bracket 1 and a second metal bracket 2 disposed at both ends of the motor 50, a first bearing 5a and a second bearing 5b, a shaft 4, a rotor 10, and a stator 18.

A first bearing 5a fixed to the first metal bracket 1 is disposed at a central portion of the first metal bracket 1. A second bearing 5b fixed to the second metal bracket 2 is disposed at the center of the second metal bracket 2. The shaft 4 is supported and rotated by a first bearing 5a and a second bearing 5b.

An electrostatic capacitance C is provided between the first metal bracket 1 and a zero reference potential N (12) of a drive circuit for applying a voltage to the stator winding 3 _nb1 The capacitive component 15.

Here, one of the first metal bracket 1 and the second metal bracket 2 will be referred to as a first metal bracket 1, and the other will be referred to as a second metal bracket 2.

Fig. 2 is a diagram showing a model of the electrostatic capacitance distribution of the motor 50 of fig. 1.

On the left stator 18 side, a capacitance C is provided between the first metal bracket 1 and the zero reference potential N (12) _nb1 The capacitive component 15 of (a). The electrostatic capacitance between the stator winding 3 and the first metal bracket 1 is C _sb1 . On the stator 18 side of the first bearing 5a, a capacitance C _sb1 And an electrostatic capacitance C _nb1 Constituting a series circuit XX1. Voltage dividing ratio R of series circuit XX1 on stator 18 side _X1 Is an electrostatic capacitance C _sb1 Electrostatic capacitance C _nb1 . The partial pressure ratio R can also be adjusted _X1 Abbreviated as electrostatic capacitance C _sb1 And an electrostatic capacitance C _nb1 Ratio of R _X1 (C _sb1 /C _nb1 )。

The electrostatic capacitance between the stator winding 3 and the second metal bracket 2 is C _sb2 . The electrostatic capacitance between the second metal bracket 2 and the zero reference potential N (12) of the drive circuit for applying a voltage to the stator winding 3 is C _nb2 . Static capacitance C _sb2 And an electrostatic capacitance C _nb2 Constituting a series circuit XX2. Voltage division ratio R of series circuit XX2 on stator 18 side _X2 Is an electrostatic capacitance C _sb2 Electrostatic capacitance C _nb2 . The partial pressure ratio R can also be adjusted _X2 Abbreviated as electrostatic capacitance C _sb2 And an electrostatic capacitance C _nb2 Ratio of R _X2 (C _sb2 /C _nb2 )。

On the stator 18 side, the series circuit XX1 and the series circuit XX2 constitute a parallel circuit. The voltage V applied to the stator winding 3 _com Is applied to the series circuit XX1 and the series circuit XX2.

On the rotor 10 side on the right side, the electrostatic capacitance C between the stator winding 3 and the stator core 6 _i And electrostatic capacitance C between stator core 6 and magnet 11 _g And electrostatic capacitance C between stator winding 3 and magnet 11 _sm And the electrostatic capacitance C of the magnet 11 _m The circuit is formed in series and/or in parallel to form a series-parallel combination circuit. The capacitance of the series-parallel combination circuit is a series-parallel combination capacitance B1 (hereinafter, simply referred to as a combination capacitance B1).

The electrostatic capacitance between the shaft 4 and the zero reference potential N (12) of the drive circuit is C _ns 。

The electrostatic capacitance B1 and the electrostatic capacitance C are combined on the rotor 10 side of the first bearing 5a and the second bearing 5B _ns A series circuit YY1 is formed. Voltage division ratio R of series circuit YY1 on rotor 10 side _Y1 Is a composite electrostatic capacitance B1/electrostatic capacitance C _ns . The partial pressure ratio R can also be adjusted _Y1 Simply referred to as a synthesized electrostatic capacitance B1 and an electrostatic capacitance C _ns Ratio of (A to B) < R > _Y1 (B1/C _ns )。

The series circuit YY1, the series circuit XX1, and the series circuit XX2 constitute a parallel circuit. Applied to a statorVoltage V of winding 3 _com Is applied to the series circuit YY1.

As described above, the present inventors have found that: in order to reduce the first axis voltage V _sh1 And a second axis voltage V _sh2 It is effective to match or approximate the electrostatic capacitance distribution on the stator side to the electrostatic capacitance distribution on the rotor side.

In the present disclosure, a capacitance C is provided between the first metal bracket 1 and a zero reference potential N (12) of a drive circuit that applies a voltage to the stator winding 3 _nb1 The capacitive element 15 of (2), the ratio R _X1 (C _sb1 /C _nb1 ) To ratio R _Y1 (B1/C _ns ) Approximately or uniformly. In addition, by making the ratio R _X2 (C _sb2 /C _nb2 ) To ratio R _X1 (C _sb1 /C _nb1 ) The electrostatic capacitance distribution on the stator side and the electrostatic capacitance distribution on the rotor side are matched (matched or approximated) to be approximate or coincident, thereby reducing the shaft voltage.

Based on the above examination, the inventors of the present invention have conceived the mode of the present disclosure described below.

An electric motor according to an aspect of the present disclosure includes:

a stator including a stator core around which a stator winding is wound;

a first bearing and a second bearing for supporting the rotating body;

a first metal bracket for fixing the first bearing; and

a second metal bracket for fixing the second bearing,

The electrostatic capacitance between the stator winding on the stator side and the other of the first metal bracket and the second metal bracket is defined as C _sb2 ，

The electrostatic capacitance between the other bracket and a zero reference potential of a drive circuit for applying a voltage to the stator winding is defined as C _nb2 When the temperature of the water is higher than the set temperature,

the electrostatic capacitance C _sb1 And the electrostatic capacitance C _nb1 Ratio of R _X1 (C _sb1 /C _nb1 ) And the synthesized electrostatic capacitance B1 and the electrostatic capacitance C _ns Ratio of R _Y1 (B1/C _ns ) The degree of similarity or consistency is similar or consistent,

the electrostatic capacitance C _sb2 And the electrostatic capacitance C _nb2 Ratio of R _X2 (C _sb2 /C _nb2 ) And the electrostatic capacitor C _sb1 And the electrostatic capacitance C _nb1 Ratio of R _X1 (C _sb1 /C _nb1 ) Approximately or uniformly.

According to the above aspect, the capacitance C of the capacitive element is adjusted _nb1 Making the above ratio R _X1 (C _sb1 /C _nb1 ) With the above ratio R _Y1 (B1/C _ns ) Approximately or uniformly, and by making the above-mentioned ratio R _X2 (C _sb2 /C _nb2 ) With the above ratio R _X1 (C _sb1 /C _nb1 ) Approximately or uniformly distributing the electrostatic capacitance on the stator side and the static electricity on the rotor sideThe capacitance distribution is approximated or uniform, and occurrence of electrolytic corrosion of the bearing in the motor can be suppressed.

Hereinafter, more specific embodiments of the present disclosure will be described. However, unnecessary detailed description may be omitted. For example, detailed descriptions of already well-known matters and repeated descriptions of substantially the same configuration may be omitted. This is to avoid unnecessarily lengthy descriptions that follow, which will be readily understood by those skilled in the art. The drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims. In the following description, the same or similar components are denoted by the same reference numerals.

(embodiment mode 1)

Hereinafter, a motor showing one embodiment of the present disclosure will be described with reference to the drawings.

Fig. 1 is a schematic configuration diagram showing a cross section of an inner rotor type and brushless radial type motor 50 according to an embodiment of the present disclosure.

As shown in fig. 1, a first metal bracket 1 having conductivity and a second metal bracket 2 having conductivity are disposed at both ends of a motor 50. The outer diameter of the second metal bracket 2 is the same as or larger than the outer diameter of the first metal bracket 1. This enables the shaft 4 to rotate while stably supporting the bearing.

A first bearing 5a fixed to the first metal bracket 1 and a second bearing 5b fixed to the second metal bracket 2 are disposed at the center portions of the first metal bracket 1 and the second metal bracket 2. The shaft 4 is supported and rotated by a first bearing 5a and a second bearing 5b. The shaft 4 protrudes from the second metal bracket 2.

The stator 18 generates a rotating magnetic field, and the rotor 10 is rotated by the rotating magnetic field. The rotor 10 is inserted into the stator 18 with a gap therebetween inside the stator 18.

The stator 18 has a stator core 6 and a stator winding 3 as a winding. The stator core 6 is interposed with a resin 7 for insulating the stator core 6, and the stator winding 3 is wound around the stator core. The stator 18 is molded with resin together with other fixing members such as the first metal bracket 1 and the second metal bracket 2. In embodiment 1, the stator 18 having a substantially cylindrical outer shape is formed by integrally molding these members. The molded integral component functions as a housing of the motor 50. The first metal bracket 1 and the second metal bracket 2 may be insulated from the stator core 6 by a space.

The rotor 10 rotates in the motor 50, and thus has a shaft 4 and a rotating body 9. The rotor 9 has a rotor core 8 and a magnet 11 as a permanent magnet of a ferrite magnet. The rotor 10 has a shaft 4 so as to penetrate through the center of the rotor core 8 while holding a plurality of magnets 11 on the outer periphery of the rotor core 8. The rotor 10 may hold a plurality of magnets 11 arranged in a spoke-like manner from the center, facing the stator 18.

A first bearing 5a and a second bearing 5b that support the shaft 4 are attached to the shaft 4. The first bearing 5a and the second bearing 5b are cylindrical bearings having a plurality of iron balls, and the inner ring sides of the first bearing 5a and the second bearing 5b are fixed to the shaft 4.

The first bearing 5a and the second bearing 5b are fixed to the outer ring side of the first bearing 5a and the second bearing 5b by a first metal bracket 1 and a second metal bracket 2 having conductivity, respectively. In fig. 1, a first bearing 5a is fixed to a first metal bracket 1, a second bearing 5b is fixed to a second metal bracket 2, a shaft 4 is supported by the first bearing 5a and the second bearing 5b, and a rotor 10 is rotatably supported. The shaft 4, the inner race of the first bearing 5a, and the inner race of the second bearing 5b are electrically conducted.

Further, in the motor 50, a printed circuit board 12 on which a drive circuit (not shown) for generating a rotating magnetic field is mounted is disposed between the rotor 10 and the second metal bracket 2. For example, an inverter circuit or the like is mounted in the drive circuit to apply a voltage to the stator winding 3.

In the motor 50 configured as described above, a voltage is applied to the stator winding 3 by the drive circuit, and a current flows through the stator winding 3, thereby generating a magnetic field from the stator core 6. Then, an attractive force and a repulsive force are generated in accordance with the polarities of the rotating magnetic field from stator core 6 and the magnetic field from magnet 11, and rotor 10 is rotated about shaft 4 by these forces.

As shown in fig. 1, a capacitance C is provided between the first metal bracket 1 and a zero reference potential N (12) of the drive circuit _nb1 The capacitive component 15.

The conducting part 13 as a conductive line is connected to both ends of the capacitive part 15.

One end of the conductive member 13 connected to the right side of the capacitive member 15 is electrically connected to the first metal bracket 1, and the other end of the conductive member 13 is electrically connected to the capacitive member 15. One end of the conductive member 13 connected to the left side of the capacitive member 15 is electrically connected to the capacitive member 15, and the other end of the conductive member 13 is electrically connected to the zero reference potential N (12) of the drive circuit.

The capacitive component 15 is, for example, a ceramic capacitor. The capacitive component 15 is a molded article in which electrodes are provided on both sides of a resin such as PBT, for example. The form of the capacitive element 15 is not particularly limited as long as it stores electric charges. The electrostatic capacitance of the capacitive part 15 is C _nb1 。

The capacitive element 15 may be disposed anywhere as long as it is disposed inside the motor 50, for example, between the housing of the motor 50 and the stator 18 and disposed on the inner wall of the housing.

Fig. 2 is a model diagram of the electrostatic capacitance distribution of the motor 50 according to embodiment 1.

In fig. 2, the left side shows the capacitance distribution on the stator 18 side and the right side shows the capacitance distribution on the rotor 10 side, with the first bearing 5a and the second bearing 5b located at the center as a boundary.

The voltage V applied to the stator winding 3 by the drive circuit _com Is a potential difference between the neutral point potential S (3) and the zero reference potential N (12).

On the left stator 18 side, a capacitance C is provided between the first metal bracket 1 and the zero reference potential N (12) _nb1 The capacitive component 15. The electrostatic capacitance between the stator winding 3 and the first metal bracket 1 is C _sb1 . On the stator 18 side of the first bearing 5a, a capacitance C _sb1 And an electrostatic capacitance C _nb1 Constituting a series circuit XX1. Stator 18 side stringVoltage dividing ratio R of series circuit XX1 _X1 Is an electrostatic capacitance C _sb1 Electrostatic capacitance C _nb1 。

The electrostatic capacitance between the stator winding 3 and the second metal bracket 2 is C _sb2 . The electrostatic capacitance between the second metal bracket 2 and the zero reference potential N (12) of the drive circuit for applying a voltage to the stator winding 3 is C _nb2 . Static capacitance C _sb2 And an electrostatic capacitance C _nb2 Constituting a series circuit XX2. Voltage division ratio R of series circuit XX2 on stator 18 side _X2 Is an electrostatic capacitance C _sb2 Electrostatic capacitance C _nb2 。

On the stator 18 side, the series circuit XX1 and the series circuit XX2 constitute a parallel circuit. Voltage V applied to the stator winding 3 _com Is applied to the series circuit XX1 and the series circuit XX2.

On the right rotor side, the electrostatic capacitance C between the stator winding 3 and the stator core 6 _i And electrostatic capacitance C between stator core 6 and magnet 11 _g And electrostatic capacitance C between stator winding 3 and magnet 11 _sm And the electrostatic capacitance C of the magnet 11 _m The circuits are formed in series and/or in parallel to form a series-parallel combination circuit. The electrostatic capacitance of the series-parallel combination circuit is a combined electrostatic capacitance B1.

The electrostatic capacitance B1 and the electrostatic capacitance C are combined on the rotor 10 side of the first bearing 5a and the second bearing 5B _ns A series circuit YY1 is formed. Voltage division ratio R of series circuit YY1 on rotor 10 side _Y1 Is a composite electrostatic capacitance B1/electrostatic capacitance C _ns 。

The series circuit YY1, the series circuit XX1, and the series circuit XX2 constitute a parallel circuit. Voltage V applied to the stator winding 3 _com Is applied to the series circuit YY1.

In order to match (approximate or coincide) the electrostatic capacitance distribution on the stator 18 side with the electrostatic capacitance distribution on the rotor 10 side, the electrostatic capacitance C of the capacitive component 15 is set _nb1 The adjustment is performed so as to satisfy the following

conditions

1 and 2.

(Condition 1) the voltage division ratio R of the series circuit XX1 _X1 (C _sb1 /C _nb1 ) Voltage division ratio R with series circuit YY1 _Y1 (B1/C _ns ) Approximately or uniformly.

(Condition 2) the voltage division ratio R of the series circuit XX2 _X2 (C _sb2 /C _nb2 ) Voltage division ratio R with series circuit XX1 _X1 (C _sb1 /C _nb1 ) Approximately or uniformly.

FIG. 3 is a diagram showing a process of changing the electrostatic capacitance C of the capacitive part 15 _nb1 Measuring the shaft voltage V of the first bearing 5a _sh1 (hereinafter, referred to as first axis voltage V) _sh1 ) And a second shaft voltage V of the second bearing 5b _sh2 (hereinafter, referred to as second axis voltage V) _sh2 ) The experimental results of (1).

In the experiment, the electrostatic capacitance C of the magnet 11 _m The diameter of the rotor 10 was 51mm at 21pF, and the first bearing 5a and the second bearing 5b were 608 made by marburga (mineba). The electrostatic capacitance of the rotating body 9 at this time is 10pF.

Grease with a consistency of 239 was used for the first bearing 5a and the second bearing 5b. The power supply voltage of neutral point potential S (3) of stator winding 3 is 391V, and rotor 10 is rotated at a rotation speed of 1000 r/min.

In fig. 3, the horizontal axis represents the electrostatic capacitance C of the capacitive element 15 _nb1 The value of (c). The vertical axis on the left side of fig. 3 is the first axis voltage V _sh1 And a second shaft voltage V _sh2 . The vertical axis on the right side of FIG. 3 is the partial pressure ratio R _X1 (C _sb1 /C _nb1 ) To partial pressure ratio R _Y1 (B1/C _ns ) Ratio of (R) _X1 /R _Y1 ) And a partial pressure ratio R _X2 (C _sb2 /C _nb2 ) To partial pressure ratio R _X1 (C _sb1 /C _nb1 ) Ratio of (R) _X2 /R _X1 )。

For a first axis voltage V _sh1 And a second axis voltage V _sh2 In the measurement of (3), the voltage of the inner ring is measured with reference to the outer ring of the first bearing 5a and the second bearing 5b, and the voltage of the inner ring is positive when it is high relative to the outer ring and negative when it is low relative to the outer ring.

First axis voltage V _sh1 The curve of (A) is a black circle of a solid lineCurve of points, second axis voltage V _sh2 The curve of (b) is a solid black-sided curve. Ratio (R) _X1 /R _Y1 ) Is the black four-sided curve of the dotted line, ratio (R) _X2 /R _X1 ) The curve of (b) is the curve of the dotted black dot.

According to FIG. 3, the first shaft voltage V _sh1 The curve of (d) (the curve of the solid black dot) is a curve extending from the lower left to the upper right of fig. 3. Second axis voltage V _sh2 The curve of (b) (the solid black-sided curve) is a curve extending from the upper left to the lower right of fig. 3.

As can be seen from FIG. 3, in the electrostatic capacitance C _nb1 When the value of (A) is small, the first axis voltage V _sh1 Becomes a negative small voltage, the second axis voltage V _sh2 Becomes a positive large voltage. It is known that if the capacitance C is increased _nb1 Of value (V) of (1), the first axis voltage V _sh1 Gradually becomes a large value, the second axis voltage V _sh2 Gradually becoming a small value.

First axis voltage V _sh1 And a second axis voltage V _sh2 Is a potential difference between the voltage of the outer ring and the voltage of the inner ring of the first bearing 5a and the second bearing 5b.

As shown in fig. 3, by adjusting the capacitance C _nb1 Thereby the first axis voltage V _sh1 And a second axis voltage V _sh2 Can be reduced to + -5V or less (| 5V | or less) which is a standard for insulation breakdown of grease of a general bearing. At this time, it was also confirmed that the waveform collapse of the shaft voltage waveform, which is a phenomenon of dielectric breakdown of the grease film of the first bearing 5a and the second bearing 5b, did not occur.

In fig. 3, for example, when the electrostatic capacitance of the rotating body 9 is 10pF, the first axis voltage V is _sh1 And a second axis voltage V _sh2 The electrostatic capacitance C of the capacitive element 15 satisfying |5V |, or less _nb1 The range of (A) is 10.0pF to 16.3 pF.

At this time, the ratio (R) according to FIG. 3 _X1 /R _Y1 ) Curve of (d), ratio (R) _X1 /R _Y1 ) The range of (A) is 0.6 to 1.0. That is, by adjusting the capacitance C _nb1 Can make the ratio R _X1 (C _sb1 /C _nb1 ) To ratio R _Y1 (B1/C _ns ) Approximately or uniformly. Ratio (R) according to FIG. 3 _X2 /R _X1 ) Curve of (c), ratio (R) _X2 /R _X1 ) The range of (A) is 0.75 to 1.25. That is, by adjusting the capacitance C _nb1 Can make the ratio R _X2 (C _sb2 /C _nb2 ) To ratio R _X1 (C _sb1 /C _nb1 ) Approximately or uniformly.

Furthermore, the first axis voltage V _sh1 And a second axis voltage V _sh2 Capacitance C of capacitive part 15 satisfying |5V |, or less _nb1 The range of (d) varies depending on the electrostatic capacitance of the rotating body 9.

The above mechanism will be described in detail with reference to fig. 2.

As shown in fig. 2, the present disclosure provides a capacitor C between the first metal bracket 1 and the zero reference potential N (12) of the drive circuit _nb1 The capacitive component 15.

The series circuit XX1, the series circuit XX2 and the series circuit YY1 constitute a parallel circuit to which a voltage V applied to the stator winding 3 is applied _com 。

As shown in FIG. 3, if the electrostatic capacitance C is set _nb1 Increasing the ratio (R) of the curve of the black four sides as a dotted line _X1 /R _Y1 ) Varying from top left to bottom right. Then, the first axis voltage V is known _sh1 And a second axis voltage V _sh2 Falls within a range of |5V | (R) _X1 /R _Y1 ) The range of (2) is 0.6 to 1.0. Therefore, by adjusting the electrostatic capacitance C _nb1 Can make the voltage division ratio R _X1 (C _sb1 /C _nb1 ) To partial pressure ratio R _Y1 (B1/C _ns ) And (6) matching.

As shown in FIG. 3, the capacitance C is set _nb1 Increasing the ratio (R) of the curve of the black dot as a dotted line _X2 /R _X1 ) Changing from bottom left to top right. Then, the first axis voltage V is known _sh1 And a second axis voltage V _sh2 Falls within a range of |5V | (R) _X2 /R _X1 ) The region (c) is 0.75 to 1.25 inclusive. Therefore, by adjusting the electrostatic capacitance C _nb1 Can make the voltage division ratio R _X2 (C _sb2 /C _nb2 ) To partial pressure ratio R _X1 (C _sb1 /C _nb1 ) And (6) matching.

In summary, the capacitance C of the capacitive element 15 is adjusted _nb1 The following

conditions

1 and 2 are satisfied, and the capacitance distribution on the stator 18 side can be matched (approximated or matched) with the capacitance distribution on the rotor 10 side. As a result, the first axis voltage V can be reduced _sh1 And a second axis voltage V _sh2 And the effect of suppressing the electric corrosion is obtained.

(Condition 1) Voltage division ratio R of series circuit XX1 _X1 (C _sb1 /C _nb1 ) Voltage division ratio R with series circuit YY1 _Y1 (B1/C _ns ) Approximately or uniformly.

The motor 50 according to embodiment 1 is excellent in manufacturability because the capacitive component 15 can be easily attached to an empty portion inside the motor 50.

In addition, since the motor 50 according to embodiment 1 is compact in size, the motor 50 does not increase in outer diameter or shape.

(modification example)

Fig. 4 is a schematic configuration diagram showing a cross section of a motor 50 according to a modification.

A point different from fig. 1 is that, as shown in fig. 4, a printed circuit board 12 is disposed between the first metal bracket 1 and the stator winding 3. Further, a capacitance C is arranged between the second metal bracket 2 and a zero reference potential N (12) of a drive circuit for applying a voltage to the stator winding 3 _nb2 The capacitive component 15.

The model diagram of the electrostatic capacitance distribution of the motor 50 in fig. 4 is the electrostatic capacitance C in fig. 2 _nb2 Replaced by an electrostatic capacitor C _nb2 And a capacitive component 15. In addition, the electrostatic capacitance C of fig. 2 _nb1 The capacitive part 15 of (2) is only the electrostatic capacitance C _nb1 。

(embodiment mode 2)

As an example of the electric device according to the present disclosure, a configuration of an air conditioning indoor unit will be described in detail as embodiment 2. The electric device according to the present disclosure is not limited to this example.

In fig. 5, a brushless motor 101 is provided in a casing 111 of an air conditioning indoor unit 110. A cross flow fan 112 as a blowing fan is attached to a rotation shaft of the brushless motor 101. The brushless motor 101 is driven by a motor driving device 113. The brushless motor 101 is rotated by the energization from the motor driving device 113, and the cross flow fan 112 is rotated in association therewith. The rotation of the cross flow fan 112 causes air conditioned by the indoor heat exchanger (not shown) to be blown into the room. The electric motor 50 of embodiment 1 described above can be applied to the brushless motor 101.

The electric device of the present disclosure includes a brushless motor and a housing on which the brushless motor is mounted, and employs the electric motor 50 of embodiment 1 as the brushless motor.

(embodiment mode 3)

As an example of the electric device according to the present disclosure, a configuration of an air conditioning outdoor unit will be described in detail as embodiment 3.

In fig. 6, the outdoor unit 201 includes a brushless motor 208 inside a casing 211. The brushless motor 208 has a blower fan 212 attached to a rotating shaft.

The outdoor unit 201 is partitioned into a compressor room 206 and a heat exchanger room 209 by a partition plate 204 erected on a bottom plate 202 of a casing 211. The compressor room 206 is provided with a compressor 205. The heat exchanger 207 and the blower fan motor are disposed in the heat exchanger chamber 209. An electronic component box 210 is provided above the partition plate 204.

The blower fan motor rotates in accordance with the rotation of the brushless motor 208 driven by the motor driving device housed in the electronic component box 210, and the blower fan 212 rotates to blow air to the heat exchanger chamber 209 through the heat exchanger 207. The electric motor 50 of embodiment 1 described above can be applied to the brushless motor 208.

(embodiment mode 4)

As an example of the electric device according to the present disclosure, a configuration of a water heater will be described in detail as embodiment 4.

In fig. 7, a brushless motor 333 is provided in a case 331 of a water heater 330. A blower fan 332 is attached to a rotating shaft of the brushless motor 333.

The brushless motor 333 is driven by a motor driving device 334. The brushless motor 333 is rotated by the energization from the motor drive device 334, and the blower fan 332 is rotated in accordance with the rotation. The rotation of the blower fan 332 causes air necessary for combustion to be supplied to a fuel vaporization chamber (not shown). The electric motor 50 of embodiment 1 described above can be applied to the brushless motor 333.

In fig. 1 of embodiment 1, the capacitive element 15 is disposed inside the motor 50, but the capacitive element 15 may be disposed outside the motor 50 as shown in fig. 8. The capacitive component 15 may be disposed at any place as long as it is disposed outside the motor 50, for example, on the outer wall of the casing of the motor 50. The capacitive member 15 may be provided at a position separated from the motor 50, for example.

In fig. 8, the left conductive member 13 electrically connects the zero reference potential N (12) of the drive circuit provided in the printed circuit board 12 and the capacitive member 15. The left conducting member 13 passes through an opening (not shown) provided in a housing of the motor 50, and reaches the outside of the motor 50 from the inside of the motor 50. The right conductive member 13 is disposed outside the housing of the motor 50, since it electrically connects the capacitive member 15 and the first metal bracket 1.

This makes it possible to make the motor 50 more compact. The embodiment of fig. 8 is not limited to embodiment 1, and can be applied to embodiments 2 to 4.

In fig. 1 of embodiment 1, the printed circuit board 12 provided with the drive circuit is provided inside the motor 50, but the printed circuit board 12 provided with the drive circuit may be provided outside the motor 50. In this case, the motor 50 can be made compact.

In embodiments 2 to 4, the blower fan is used as the member that rotates the motor 50, but the blower fan is not particularly limited as long as the member is rotated by the motor 50.

Further, the inventions according to embodiments 1 to 4 can be replaced or combined as long as no contradiction occurs.

As described above, the present disclosure includes the motor described in the following items and an electric device including the motor.

[ item 1 ]

An electric motor is provided with:

a stator including a stator core around which a stator winding is wound;

a first bearing and a second bearing for supporting the rotating body;

a first metal bracket for fixing the first bearing; and

a second metal bracket for fixing the second bearing,

[ item 2 ]

The motor according to item 1, wherein the one bracket is the first metal bracket, and the other bracket is the second metal bracket.

[ item 3 ]

The motor according to

item

1 or 2, wherein the ratio R is _X2 (C _sb2 /C _nb2 ) With the above ratio R _X1 (C _sb1 /C _nb1 ) Ratio of (R) _X2 /R _X1 ) The value of (A) is 0.75 to 1.25.

[ item 4 ]

The motor according to any one of items 1 to 3, wherein the first metal bracket and the second metal bracket are insulated from the stator core by an insulating resin or a space.

[ item 5 ]

The motor according to any one of items 1 to 4, wherein the capacitive member is provided inside the motor.

[ item 6 ]

The motor according to any one of items 1 to 4, wherein the capacitive component is provided outside the motor.

[ item 7 ]

The motor according to any one of items 1 to 6, wherein a printed circuit board including the drive circuit is provided inside the motor.

[ item 8 ]

The motor according to any one of items 1 to 6, wherein a printed circuit board including the drive circuit is provided outside the motor.

[ item 9 ]

An electric device having mounted thereon the motor according to any one of items 1 to 8 and a blower fan driven by the motor.

Claims

1. An electric motor is provided with:

a stator including a stator core around which a stator winding is wound;

a rotating body that holds the plurality of magnets in a circumferential direction or holds the plurality of magnets in a spoke-like manner from the center, while facing the stator;

a first bearing and a second bearing that support the rotating body;

a first metal bracket that fixes the first bearing; and

a second metal bracket fixing the second bearing,

the electric motor is characterized in that it is provided with,

applying electricity to the stator winding on any one of the first metal bracket and the second metal bracketAn electrostatic capacitor C is arranged between zero reference potential of the voltage drive circuit _nb1 The capacitive component of (a) is,

defining an electrostatic capacitance between the stator winding on the stator side and the one bracket as C _sb1 ，

Will contain the electrostatic capacitance C between the stator winding and the stator core _i And an electrostatic capacitance C between the stator core and the magnet _g Electrostatic capacitance C between the stator winding and the magnet _sm And the electrostatic capacitance C of the magnet _m The electrostatic capacitance on the inner rotor side is defined as a composite electrostatic capacitance B1,

defining an electrostatic capacitance between a zero reference potential of the driving circuit and the shaft as C _ns ，

Defining an electrostatic capacitance between the stator winding on the stator side and the other of the first metal bracket and the second metal bracket as C _sb2 ，

Defining an electrostatic capacitance between the other bracket and a zero reference potential of a drive circuit that applies a voltage to the stator winding as C _nb2 When the utility model is used, the water is discharged,

the electrostatic capacitance C _sb1 And the electrostatic capacitance C _nb1 Ratio of R _X1 I.e. C _sb1 /C _nb1 And the synthesized electrostatic capacitance B1 and the electrostatic capacitance C _ns Ratio of R _Y1 I.e. B1/C _ns Are close to or identical with each other in terms of,

the electrostatic capacitance C _sb2 And the electrostatic capacitance C _nb2 Ratio of R _X2 I.e. C _sb2 /C _nb2 And the electrostatic capacitor C _sb1 And the electrostatic capacitance C _nb1 Ratio of R _X1 I.e. C _sb1 /C _nb1 Approximately or uniformly.

2. The motor according to claim 1,

the one bracket is the first metal bracket, and the other bracket is the second metal bracket.

3. The motor according to claim 1 or 2,

the ratio R _X2 I.e. C _sb2 /C _nb2 With the ratio R _X1 I.e. C _sb1 /C _nb1 Ratio of R _X2 /R _X1 The value of (b) is 0.75 to 1.25.

4. The motor according to claim 1 or 2,

the first metal bracket and the second metal bracket are insulated from the stator core by an insulating resin or a space.

5. The motor according to claim 1 or 2,

the capacitive component is disposed inside the motor.

6. The motor according to claim 1 or 2,

the capacitive component is disposed outside the motor.

7. The motor according to claim 1 or 2,

the printed circuit board provided with the drive circuit is provided inside the motor.

8. The motor according to claim 1 or 2,

the printed circuit board provided with the drive circuit is provided outside the motor.

9. An electrical apparatus, characterized in that it comprises,

the motor according to claim 1 or 2 and a blower fan driven by the motor are mounted.