KR20200104125A - Motor drive apparatus - Google Patents

Abstract

The present invention relates to a motor driving device. According to an embodiment of the present invention, the motor driving device comprises: a stator fixed to the inside of a housing and including a plurality of teeth wound with a plurality of coils; a rotor disposed in the stator and rotating by a magnetic field generated from a plurality of coils; a rotating shaft connected along the center of the rotor; a motor unit including a magnetic bearing for floating the rotating shaft to match the rotor with the center of the stator; and a control unit applying a current to the plurality of coils and controlling operation of the magnetic bearing. The stator is arranged so that one reference tooth set among a plurality of teeth is located at the center of a lower end of the housing, and the control unit applies the current to the coil wound around the reference tooth first to vertically align a magnetic pole of the rotor before the operation of the magnetic bearing, thereby preventing a collision between the rotor and the magnetic bearing when aligning an initial position of the rotor using the magnetic bearing.

Description

Motor drive device {MOTOR DRIVE APPARATUS}

The present invention relates to a motor driving apparatus capable of preventing component damage by blocking a collision between a rotating shaft of a rotor and a magnetic bearing during an initial operation of a magnetic bearing.

The chiller system is a cooling device or refrigeration device that supplies cold water to a cold water consumer such as an air conditioner or refrigerator.

The chiller system includes a compressor, a condenser, an expander and an evaporator through which refrigerant is circulated.

In order to compress a large amount of refrigerant at a high rate, the compressor uses a magnetic bearing that magnetically floats a rotating shaft rotating in a motor.

As a prior document related to the present invention, Korean Laid-Open Patent Publication No. 10-2015-0179994 discloses a chiller system.

The conventional chiller system disclosed herein includes a compressor for compressing a refrigerant, a condenser for condensing the compressed refrigerant, an expansion valve for expanding the condensed refrigerant, and an evaporator for evaporating the expanded refrigerant.

However, as shown in FIG. 1, the conventional compressor includes a motor unit 10 having a stator 11 and a rotor 12.

Coils C1, C2, and C3 are wound around the teeth of the stator 11. Current is applied to each of the coils C1, C2, and C3 to generate a magnetic field.

The rotor 12 is composed of a magnetic material and rotates by the magnetic field of the coils C1, C2, C3.

If the motor unit 10 is in a stationary state, the rotor 12 has a first force F1 due to its own weight and a second force F2 that is an attractive force between the rotor 12 and the stator 11, which is a magnetic substance. ) Occurs. As a result, the rotor 12 is positioned below the center line H2 of the stator 11 by the first and second forces F1 and F2.

However, in order to drive the motor unit 10 in a stopped state, the center of the rotor 12 and the center of the stator 11 must match. In other words, the magnetic bearing 13 must provide the levitation force F4 corresponding to the sum of the first and second forces F1 and F2 to the rotor 12, and the rotor 12 is the motor unit 10 In order to drive the stator 11 and the center line can maintain the initial alignment state that matches.

However, when the levitation force F4 suddenly acts on the rotor 12 during the operation of the magnetic bearing 13, the rotor 12 (or the rotating shaft connected to the rotor 12) as in the state B in the state A of FIG. 1 The problem of colliding with the magnetic bearing 13 could occur.

And even after the rotor 12 is injured, severe vibration is generated until the rotor 12 is stably positioned on the center line of the stator 11 as shown in the state C of FIG. 1, and thus there is difficulty in stable control.

Further, in the conventional case, since a large levitation force F4 must be provided to the rotor 12 using the magnetic bearing 13, there is a problem that the cost of the magnetic bearing 13 increases.

Therefore, when the magnetic bearing 13 is operated, the rotor 12 and the rotating shaft connected to the rotor 12 do not directly collide with the magnetic bearing 13, and a technical solution that can be matched with the center line of the stator 11 is It is a necessary situation.

An object of the present invention is to provide a motor driving device capable of preventing a collision between a rotor (or a rotating shaft of a rotor) and a magnetic bearing in using a magnetic bearing to initially match the center between the rotor and the stator for driving the motor. will be.

It is an object of the present invention to provide a motor driving apparatus capable of smoothly floating a rotor (or a rotating shaft of a rotor) to a center line of a stator, and reducing the amount of required floating force to be provided through a magnetic bearing.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention that are not mentioned can be understood by the following description, and will be more clearly understood by examples of the present invention. In addition, it will be easily understood that the objects and advantages of the present invention can be realized by the means shown in the claims and combinations thereof.

The motor driving apparatus according to the present invention for solving one of the above problems prevents the impulse between the rotor (or rotational shaft) and the magnetic bearing when using a magnetic bearing to match the center of the rotor with the center of the stator prior to driving the motor unit. It is characterized by a technical feature to prevent.

Specifically, the motor driving apparatus according to an aspect of the present invention includes a stator and a rotor disposed in the stator and rotating, a rotating shaft connected to the center of the rotor, a motor unit including a magnetic bearing, and driving the motor unit and the magnetic bearing. It includes a control unit that controls the operation.

The stator is fixed inside the housing and includes a plurality of teeth on which a plurality of coils are wound.

The rotor is disposed in the stator and can rotate by magnetic fields generated from a plurality of coils.

The rotation shaft may be connected along the center of the rotor, and the rotation shaft may be arranged in a form surrounded by the magnetic bearing inside the magnetic bearing.

Magnetic bearings can float the rotating shaft to align the rotor with the center of the stator.

The control unit may control the application of current to the plurality of coils to control driving of the motor unit, that is, the rotation of the rotor.

In addition, the control unit may control the operation of the magnetic bearing to raise the position of the rotor so that the center of the rotor coincides with the center of the stator.

More specifically, in the motor driving apparatus of the present invention, the stator may be disposed such that one reference tooth set among the plurality of teeth is located at the center of the lower end of the housing. In addition, before applying current to the plurality of coils, the controller may first apply current to the coil wound around the reference tooth to align the magnetic poles of the rotor up and down before the magnetic bearing is operated. Accordingly, it is possible to reduce the levitation force required by the magnetic bearing, and prevent a collision with the magnetic bearing when the rotor is levated.

More specifically, the stator is disposed so that one reference tooth set among the plurality of teeth is located at the center of the lower end of the housing, and the control unit applies a current to the reference teeth first before applying current to the plurality of coils. The stimulus can be aligned up and down.

In addition, the controller rotates the current vector in the direction of 90 degrees while the current is applied, so that the magnetic poles of the rotor are aligned left and right in a direction crossing the direction of gravity.

Subsequently, after the magnetic poles of the rotor are aligned to cross the direction of gravity, the magnetic bearing can be operated to match the rotor to the center of the stator using the levitation force provided by the magnetic bearing.

Subsequently, the controller may control the operation of the magnetic bearing to align the rotor with the center of the stator, and then apply current to the plurality of coils to rotate the rotor.

According to this configuration, it is possible to reduce the levitation force required by the magnetic bearing, thereby reducing cost, and prevent a collision between the rotor (or rotating shaft) and the magnetic bearing due to the sudden injury of the rotor. In addition, the rotor can be moved in a smooth motion and the position of the rotor can be stably controlled precisely.

On the other hand, in the motor driving apparatus according to the embodiment of the present invention, the plurality of teeth included in the stator includes three teeth that protrude to have a predetermined length inward toward the center of the stator. The three teeth can be formed radially with a central angle of 120 degrees between them. And the plurality of coils includes at least three coils wound around three teeth.

At this time, the reference tooth is located at the center of the lower end of the housing, and the center of the reference tooth may be located in a straight line up and down with the center of the stator. And, of the three teeth, the remaining two teeth excluding the reference teeth may be located at the top so as to have the same height from the reference teeth. Based on the virtual center line passing through the center of the reference teeth and the stator, the remaining two teeth excluding the reference teeth Teeth can be arranged symmetrically left and right.

In addition, the motor driving apparatus according to an embodiment of the present invention further includes at least one backup bearing that is disposed surrounding a rotation shaft to reduce friction of the rotation shaft when the rotor rotates.

In addition, the motor driving apparatus according to the embodiment of the present invention further includes at least one guide bearing disposed in the housing on the opposite side of the magnetic bearing with respect to the backup bearing, and disposed to face a plate provided at one end of the rotation shaft. do.

According to the present invention, when the center between the rotor and the stator is initially aligned by using the magnetic bearing for driving the motor, collision between the rotor (or the rotating shaft of the rotor) and the magnetic bearing can be prevented. Accordingly, collisions between parts generated during the process of floating the rotor at the initial stage of motor driving, as well as vibration and friction, are reduced, thereby increasing the durability life of the parts, preventing breakage, and improving product reliability.

In addition, according to the present invention, it is possible to arrange the stator so that one set tooth or image is located at the lower end. As a result, current is applied only to the coil wound on the teeth disposed at the bottom, and the current vector is rotated 90 degrees in the current applied state, and then the rotor (or rotating shaft) is operated through the process of operating the magnetic bearing. You can rotate along. As a result, the motion of moving the rotor (or the rotor rotation shaft) to match the center line of the stator is implemented smoothly, and the rotor can be moved to a stable and accurate position using a relatively small levitation force. Accordingly, cost can be reduced by reducing the load of the magnetic bearing, and reliability of motor control can be improved.

In addition to the above-described effects, specific effects of the present invention will be described together while describing specific details for carrying out the present invention.

1 is a conceptual diagram illustrating a general motor operation sequence.
2 is a block diagram showing a motor driving apparatus according to an embodiment of the present invention.
3 is a schematic cross-sectional view of a motor part of a motor driving apparatus according to an embodiment of the present invention.
Figure 4 is a cross-sectional view of the section "AA" of Figure 3;
5 is a flowchart illustrating a method of controlling a motor driving apparatus according to an embodiment of the present invention.
6 is an operation state diagram for each step for explaining the control operation of the motor driving apparatus according to an embodiment of the present invention.
7 is a view showing a stop state of the motor unit in the motor driving apparatus according to an embodiment of the present invention.
8 is a view showing three operation sequences before and after 90 degree rotation of a current vector and application of a current to a motor in the motor driving apparatus according to an embodiment of the present invention.
9 is a view showing a state in which the magnetic bearing is operated in the motor driving apparatus according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings so that those skilled in the art can easily implement the present invention. The present invention may be implemented in various different forms, and is not limited to the embodiments described herein.

In order to clearly describe the present invention, parts irrelevant to the description have been omitted, and the same reference numerals are assigned to the same or similar components throughout the specification. Further, some embodiments of the present invention will be described in detail with reference to exemplary drawings. In adding reference numerals to elements of each drawing, the same elements may have the same numerals as possible even if they are indicated on different drawings. In addition, in describing the present invention, when it is determined that a detailed description of a related known configuration or function may obscure the subject matter of the present invention, a detailed description thereof may be omitted.

In describing the constituent elements of the present invention, when a constituent element is described as being “connected”, “coupled” or “connected” to another constituent element, the constituent element is directly connected to or to be connected to the other element. However, it should be understood that other components may be "interposed" between each component, or that each component may be "connected", "coupled" or "connected" through other components.

2 is a block diagram showing a motor driving apparatus according to an embodiment of the present invention.

Referring to FIG. 2, a motor driving apparatus according to an embodiment of the present invention includes a motor unit 100 and a control unit 200.

The motor unit 100 may include various types of motors, but is not limited to a specific type, and various types of motors conventionally known may correspond to this.

The control unit 200 controls the operation of the motor unit 100. Specifically, the control unit 200 may control the operation of various components constituting the motor unit 100.

For example, the controller 200 may control the application of current to a plurality of coils C1, C2, C3, see FIG. 4 included in the motor unit 100.

In addition, the controller 200 may control movement of the rotor 120 (see FIG. 3) to coincide with the center of the stator 110 (see FIG. 3) before the motor unit 100 operates.

In other words, the control unit 200 may control the provision of the levitation force through the magnetic bearing 130 so as to float the rotor 120 (see FIG. 3) to a predetermined height.

3 is a schematic cross-sectional view of a motor part of a motor driving apparatus according to an embodiment of the present invention, and FIG. 4 is a cross-sectional view of a section "A-A" of FIG. 3.

As shown, the motor unit 100 according to an embodiment of the present invention includes a housing 105, a stator 110, a rotor 120, a rotating shaft 125, and a magnetic bearing 130.

The housing 105 is formed to form the exterior of the motor unit 100.

A predetermined space is provided inside the housing 105. A rotor 120 connected to the rotating shaft 125 through an inner space of the housing 105, a stator 110 surrounding the rotor 120, and a magnetic bearing 130 are provided.

In addition, a backup bearing 140 and a guide bearing 150 are further provided inside the housing 105.

The backup bearing 140 is disposed surrounding the rotation shaft 125.

The backup bearing 140 is provided with at least one or more, preferably at least one at each of both ends of the rotation shaft 125, and serves to reduce rotational friction of the rotation shaft 125 when the rotor 120 rotates.

The guide bearing 150 is located in the housing 105 at the opposite end of the magnetic bearing with respect to the backup bearing.

For example, the guide bearing 150 may be disposed to face a pair with a circular plate 127 provided at one end of the rotation shaft 125 therebetween. The plate 127 may maintain a set distance from each other by an attractive force or a repulsive force between the pair of guide bearings 150. The guide bearing 150 can be controlled by the control unit 200.

The housing 105 may be formed in a cylindrical shape, but is not necessarily limited to the illustrated shape, and may be changed into various shapes according to the stator 110 and the rotor 120.

The stator 110 is fixed inside the housing 105.

The stator 110 includes a plurality of teeth 111, 113, 115 (see FIG. 4) on which a plurality of coils C1, C2, C3, see FIG. 4 are wound.

The stator 110 may be formed of a metal material that guides the magnetic force line.

In addition, a plurality of teeth 111, 113, 115 (refer to FIG. 4) may be disposed at equal intervals with a certain central angle therebetween through the inner diameter of the stator 110.

In addition, a plurality of teeth 111, 113, 115 (see FIG. 4) may be disposed to surround the outer diameter of the rotor 120 with a predetermined gap from the rotor 120.

A coil (C1, C2, C3, see FIG. 4) is wound on each of the plurality of teeth (111, 113, 115, see FIG. 4), and each coil (C1, C2, C3, see FIG. 4) has a different phase current Is applied, and as a result, a magnetic field required for rotation of the rotor 120 is generated.

The rotor 120 is located inside the stator 110 and is disposed with the stator 110 with a constant gap.

The rotor 120 rotates by a magnetic field generated from a plurality of coils C1, C2, C3, see FIG. 4.

Specifically, the rotor 120 is made of a magnetic material. That is, the rotor 120 has an N-pole in a half portion and an S-pole in the other half of the circular cross section.

The rotation shaft 125 refers to a shaft member connected along the center of the rotor 120. Accordingly, the center of the rotation shaft 125 may coincide with the center of the rotor 120.

The rotation shaft 125 is formed to extend along the center of the rotor 120 to have a predetermined length in the longitudinal direction of the rotor 120 as shown in FIG. 3, and is disposed at the center of the inner space of the housing 105. .

For example, the rotation shaft 125 may be integrally formed with the rotor 120. In this case, the rotation shaft 125 may be formed smaller than the diameter of the rotor 120 and may extend a predetermined length in the front and rear directions along the center of the rotor 120.

The magnetic bearing 130 serves to match the center of the rotor 120 with the center of the stator 110 before operating the motor unit 100.

To this end, the magnetic bearing 130 provides a levitation force to the rotor 120 by generating a magnetic force of a required size. As a result, the rotation shaft 125 may be floated to be located at the center of the magnetic bearing 130.

In this way, the magnetic bearing 130 generates a magnetic force to float the rotor 120, more specifically, the rotation shaft 125 to the height of the center of the stator 110.

For example, the magnetic bearing 130 may be configured to include an electromagnet or the like.

Accordingly, the magnetic bearing 130 may generate a magnetic force of an electrically required size according to a control signal from the controller 200 (see FIG. 2 ).

Further, the magnetic bearing 130 may be disposed to surround both ends of the rotation shaft 125 extending before and after the rotor 120 based on the position of the rotor 120.

In this case, the same current is applied to the plurality of magnetic bearings 130 to generate magnetic force of the same magnitude.

On the other hand, when the motor unit 100 is operated, the rotor 120 made of a magnetic material is a stator due to a change in the magnetic field generated by a plurality of coils (C1, C2, C, 3, see Fig. 4) wound around the stator 110. It rotates inside of (110).

Accordingly, during the operation of the motor unit 100, the center of the rotor 120 coincides with the center of the stator 110.

By the way, when the motor unit 100 is stopped, the rotor 120 is moved to the lower side of the stator 110 by its own weight. The backup bearing 140 limits the lower moving range of the rotor 120 so that the rotor 120 does not contact the inner surface of the stator 110.

However, in this case, the center of the rotor 120 does not coincide with the center of the stator 110.

Therefore, in order to operate the motor unit 100 in a stopped state, the initial alignment process of first aligning the center of the rotor 120 and the center of the stator 110 by floating the rotor 120 (or the rotation shaft 125) is need.

5 is a flowchart illustrating a control method of a motor driving apparatus according to an embodiment of the present invention, and FIG. 6 is a state diagram of operation of each step for explaining a control operation of the motor driving apparatus according to an embodiment of the present invention. to be.

7 to 9 are views showing three operation sequences according to a motor unit's stop state, application of current, and 90 degree rotation of a current vector, and a magnetic bearing operation state.

Hereinafter, a method for controlling a motor driving apparatus according to an embodiment of the present invention will be described in detail with reference to FIGS. 5 to 9.

Referring to FIG. 5, the motor driving apparatus includes a lower coil current application step (S110), a current vector 90 degree rotation step (S120), a magnetic bearing operation step (S130), and a motor unit operation initialization step (S140).

Referring to FIG. 6, the stator 110 includes a plurality of teeth. The plurality of teeth includes three teeth 111, 113 and 115 protruding inwardly toward the center of the stator 110 to have a predetermined length.

The three teeth 111, 113, 115 are formed to protrude radially toward the center of the stator 110 with a central angle of 120 degrees between them.

In addition, three coils C1, C2, C3 are wound one by one on each of the three teeth 111, 113, and 115.

First, according to the control method of the motor driving apparatus according to an embodiment of the present invention, the lower coil current application step (S110) is first performed.

Here, in the lower coil current application step (S110), a reference tooth 111 is selected, the reference tooth 111 is disposed under the stator 110, and the core C1 wound around the reference tooth 111 is It means the step of applying current.

The stator 110 is provided with three teeth 111, 113, 115. Among them, one is set as the reference tooth 111. The set reference tooth 111 may be located at the lower center of the housing 105 (more specifically, it means the inner lower center of the stator 110 ).

Subsequently, the control unit 200 (see FIG. 7) first applies a required current to the coil C1 wound around the reference tooth 111 among the three coils C1, C2, and C2.

Accordingly, the rotor 120 is positioned under the stator 110 in proximity to the reference teeth 111, and the magnetic poles of the rotor 120 (eg, N pole, S pole) are aligned vertically. For example, the magnetic poles of the rotor 120 may be vertically aligned so that the S pole of the rotor 120 faces upward and the N pole faces downward.

According to this configuration, before the motor unit 100 in a stopped state is initially operated, the magnetic poles (eg, N-pole, S-pole) of the rotor 120 are vertically aligned.

Specifically, the reference tooth 111 is located at the center of the lower end of the housing 105 as shown in FIG. 6. That is, the center of the width of the reference tooth 111 is positioned vertically and vertically with the center of the stator 110, and may be disposed in a straight line in a direction perpendicular to each other.

Meanwhile, of the three teeth 111, 113 and 115, the remaining two teeth 113 and 115 excluding the reference tooth 111 may be positioned above the reference teeth 111 so as to have the same height.

And the reference tooth 111 is located at the bottom of the inner hollow of the stator 110, the remaining two teeth (113, 115) of the stator 110 with the reference tooth 111 and a predetermined central angle (θ) between It can project radially toward the center. In this case, the central angle θ between the three teeth 111, 113 and 115 may be formed to be constant at 120 degrees.

Next, following the lower coil current application step (S110), a current vector 90 degrees rotation step (S120) is performed.

In this step (S120), the control unit 200 rotates the current vector in the direction of 90 degrees. As a result, the rotor 120 whose polarity is aligned vertically rotates by 90 degrees in the counterclockwise direction and moves.

At this time, the magnetic poles (eg, N pole, S pole) of the rotor 120 are aligned left and right to cross the direction of gravity. For example, the S pole of the rotor 120 is directed to the left of FIG. 6, the N pole is directed to the right of FIG. 6, and the magnetic poles of the rotor 120 are formed to cross the gravitational direction formed up and down.

Next, following the rotation of the current vector by 90 degrees (S120), the magnetic bearing operation step (S130) and the motor unit operation initialization step (S140) are sequentially performed.

In the magnetic bearing operation step (S130), the magnetic bearing 130 is operated so that the magnetic poles (eg, N-pole, S-pole) cross the gravitational direction by the rotation of the current vector in the direction of 90 degrees. Provides the required amount of levitation force. Accordingly, the rotor 120 floats to a height h2 corresponding to the center line of the stator 110 and the centers of each other may be controlled to coincide.

Then, the motor unit operation initialization step (S140) is performed. The controller 200 controls the magnetic bearing 130 to match the rotor 120 to the center of the stator 110. In addition, the control unit 200 operates the motor unit 100 by applying current to the plurality of coils C1, C2, and C3.

7 is a view showing a stop state of the motor unit in the motor driving apparatus according to an embodiment of the present invention.

Referring to FIG. 7, as the motor unit 100 is in a stopped state, a current is not applied to the coil C1 of the reference tooth 111 by the control unit 200.

Accordingly, the rotor 120 is only positioned under the stator 110 by its own weight, and the magnetic poles of the rotor 120 are not aligned vertically.

8 is a diagram illustrating three operation sequences before and after 90 degree rotation of a current vector and application of a current to a motor in the motor driving apparatus according to an embodiment of the present invention.

Referring to FIG. 8, the controller 200 applies a current to the coil C1 of the reference tooth 111 (S110), and as a result, the rotor 120 is positioned under the stator 110 and the rotor 120 )'S stimuli are aligned up and down. For example, the S pole of the rotor 120 may be aligned at the top, and the N pole may be aligned at the bottom.

Subsequently, when the current vector is rotated in the direction of 90 degrees (S120), the rotor 120 moves in the R direction, and the polarity of the rotor 120 is aligned so as to cross the direction of gravity. For example, the S pole of the rotor 120 may be aligned to the left, and the N pole may be aligned to the right.

9 is a view showing a state in which the magnetic bearing is operated in the motor driving apparatus according to an embodiment of the present invention.

Referring to FIG. 9, the control unit 200 operates the magnetic bearing 130. As a result, the magnetic bearing 130 floats the rotor 120 so that the center of the rotor 120 coincides with the center position of the stator 110. Thereafter, the controller 200 rotates the rotor 120 by applying current to the plurality of coils C1, C2, and C3, whereby the operation of the motor unit 100 may be implemented.

As described above, according to the configuration and operation of the embodiment of the present invention, when the center between the rotor and the stator is initially matched by using the magnetic bearing for driving the motor, collision between the rotor (or the rotating shaft of the rotor) and the magnetic bearing is prevented. Can be prevented.

Accordingly, collisions between parts generated during the process of floating the rotor at the initial stage of motor driving, as well as vibration and friction, are reduced, thereby increasing the durability life of the parts, preventing breakage, and improving product reliability.

Further, according to the configuration and operation of the embodiment of the present invention, it is possible to arrange the stator so that one set tooth or phase is located at the lower end. In addition, current is applied only to the coil wound on the teeth disposed at the bottom, and the current vector is rotated 90 degrees in the current applied state, and then the rotor (or rotating shaft) is adjusted to the inner diameter of the magnetic bearing through the process of operating the magnetic bearing. Can be rotated accordingly.

As a result, the motion of moving the rotor (or rotating shaft) to match the center line of the stator is implemented smoothly, and the rotor can be moved to a stable and accurate position using a relatively small levitation force.

And it is possible to reduce the cost by reducing the load of the magnetic bearing and improve the reliability of motor control.

As described above with reference to the drawings illustrated for the present invention, the present invention is not limited by the embodiments and drawings disclosed in the present specification, and various by a person skilled in the art within the scope of the technical idea of the present invention. It is obvious that transformation can be made. In addition, even if not explicitly described and described the effects of the configuration of the present invention while describing the embodiments of the present invention, it is natural that the predictable effects of the configuration should also be recognized.

C1, C2, C3: coil
100: motor unit
105: housing
110: stator
111, 112, 113: Teeth
120: rotor
125: rotary shaft
127: plate
130: magnetic bearing
140: backup bearing
150: guide bearing
200: control unit

Claims (10)

A stator fixed to the inside of the housing and including a plurality of teeth on which a plurality of coils are wound,
A rotor disposed in the stator and rotating by a magnetic field generated from the plurality of coils,
A rotating shaft connected along the center of the rotor,
A motor unit including a magnetic bearing that floats the rotation shaft so that the rotor is aligned with the center of the stator;
Includes; a control unit for applying current to the plurality of coils and controlling the operation of the magnetic bearing,
The stator is disposed such that one reference tooth set among the plurality of teeth is located at the center of the lower end of the housing,
The control unit applies a current to the coil wound on the reference tooth first to align the magnetic poles of the rotor up and down before the magnetic bearing is operated.
Motor-drive unit.
The method of claim 1,
The control unit,
After applying a current to the reference tooth, the current vector is rotated in the direction of 90 degrees while the current is applied, so that the magnetic poles of the rotor are aligned left and right to cross the direction of gravity.
Motor-drive unit.
The method of claim 2,
The control unit,
After the magnetic poles of the rotor are aligned to cross the direction of gravity, the magnetic bearing is operated to match the rotor to the center of the stator using the levitation force provided by the magnetic bearing.
Motor-drive unit.
The method of claim 3,
The control unit,
After controlling the operation of the magnetic bearing to match the rotor to the center of the stator, applying current to the plurality of coils to rotate the rotor
Motor-drive unit.
The method of claim 1,
The plurality of teeth,
It includes three teeth protruding to have a predetermined length inward toward the center of the stator,
The three teeth are formed radially with a central angle of 120 degrees between each other
Motor-drive unit.
The method of claim 5,
The plurality of coils,
Including at least three coils wound around the three teeth
Motor-drive unit.
The method of claim 5,
The reference tooth is located in the center of the lower end of the housing,
The center of the reference tooth is located in a straight line up and down with the center of the stator
Motor-drive unit.
The method of claim 7,
Of the three teeth, the remaining two teeth excluding the reference teeth are positioned at the top so as to have the same height from the reference teeth.
Motor-drive unit.
The method of claim 1,
At least one backup bearing disposed around the rotation shaft to reduce friction of the rotation shaft when the rotor rotates;
Motor drive device further comprising a.
The method of claim 9,
At least one guide bearing disposed in the housing on the opposite side of the magnetic bearing with respect to the backup bearing and disposed to face a plate provided at one end of the rotation shaft;
Motor drive device further comprising a.

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