KR20200099773A - Motor - Google Patents

Abstract

According to an embodiment of the present invention, provided is a motor which minimizes heating. The motor comprises: a stator including main windings to which a mixed current, in which a first current having a first frequency to generate a stator field, but having a different phase, and a second current having a second frequency consisting of a predetermined multiple than the first frequency to generate a third harmonic are mixed, is applied; and a rotor including a harmonic winding generating a harmonic current from the third harmonic generated by the second current and a field winding generating a rotor field based on the harmonic current.

Description

Electric motor {Motor}

The present invention relates to a motor, and more particularly, to a motor that supplies a mixed current including a first current for generating a stator field and a second current for inducing a rotor field to a main winding of a stator.

An electric motor is a device that converts electrical energy into mechanical energy by using the force received by a conductor through which an electric current flows in a magnetic field. Among them, a synchronous motor (SM) refers to a motor in which a rotor can rotate at a constant speed in synchronization with a rotation field of a stator. The rotor of a synchronous motor has the advantage of being able to maintain a constant rotational speed even in a variable voltage environment.

Such synchronous motors include a permanent magnet synchronous motor (PMSM) and a wound rotor synchronous motor (WRSM).

A permanent magnet synchronous motor may use a permanent magnet to generate a rotor magnetic field (flux). Permanent magnet synchronous motors can provide a fixed speed in synchronization with the frequency of the power source despite fluctuations in load or voltage, and are widely used in various industrial and household applications due to their high efficiency and excellent performance of high torque density. have. In particular, a permanent magnet synchronous motor can be useful in that it can provide a fixed speed in synchronization with the main frequency within the range allowed by the design specifications of the motor. However, there are limitations in application because the unit cost of rare earth magnets used in permanent magnet synchronous motors is expensive.

On the other hand, the field-winding type synchronous motor has an advantage in terms of cost because it does not use a permanent magnet unlike a permanent magnet motor. A field winding type synchronous motor uses a field winding instead of a permanent magnet in the rotor, and the field winding receives DC current to generate the rotor magnetic field.

In general, when the field winding of the rotor receives electric current, it requires the use of a brush or a slip-ring. Mechanical loss occurs, magnetic field loss, and difficulty in maintenance management.

Furthermore, although a recent WFSM (wound-field synchronous machine) has been developed, there is a difficulty as a separate configuration is required for supplying current to induce a rotor field.

One technical problem to be solved by the present invention is to provide an electric motor driven with a minimum inverter.

Another technical problem to be solved by the present invention is to provide an electric motor that does not use brushes and slip rings.

Another technical problem to be solved by the present invention is to provide an electric motor that minimizes heat generation at a star point to which the main windings are connected.

The technical problem to be solved by the present invention is not limited to the above.

An electric motor according to an embodiment of the present invention has a first frequency to generate a stator field, but a first current having a different phase and a second frequency that is a predetermined multiple than the first frequency to generate a third harmonic. A stator including main windings to which a mixed current in which a second current is mixed is applied; And a rotor including a harmonic winding generating a harmonic current from the third harmonic generated by the second current, and a field winding generating a rotor field based on the harmonic current.

According to an embodiment, a mixing unit for mixing the first signal having the first frequency and the second signal having the second frequency; And an inverter having a mixed current generator configured to generate the mixed current based on the first signal and the second signal mixed by the mixing unit.

According to an embodiment, the number of inverters may be one.

According to an embodiment, the mixed current may include a second current of the same phase even when the phases of the first current are different.

According to an embodiment, the main windings are grouped according to the phase, one end of each main winding is electrically connected to a terminal providing the mixed current, and the other end of each main winding is electrically connected to each other. I can.

According to an embodiment, in a connection node in which the other ends of each of the main windings are electrically connected to each other, the second currents included in each of the mixed currents may have the same potential sign.

According to an embodiment, the connection node may be connected to an electric line other than the main winding.

According to an embodiment, one end of the electric line may be electrically connected between one diode and the other diode.

According to an embodiment, the number of poles of the main winding may be the same as the number of poles of the field winding.

According to an embodiment, when the second frequency is n times greater than the first frequency, the number of poles of the harmonic winding may be n times greater than that of the main winding.

According to an embodiment, a rotor tooth is provided along the circumferential direction of the rotor, a slot is provided in the rotor tooth, the harmonic winding is formed on the rotor tooth, and the field winding is the rotor tooth. And may be formed in the slot.

The mixed current supplied to the electric motor according to an embodiment of the present invention may be generated by a single inverter.

In an electric motor according to an embodiment of the present invention, a rotor may generate a rotor field based on a third harmonic generated in a stator.

The electric motor according to an embodiment of the present invention can minimize heat generation at a star point to which the main windings are connected.

1 is a view for explaining an electric motor according to an embodiment of the present invention.
2 is a diagram for describing an electric motor according to an embodiment of the present invention from a circuit perspective.
3 is a view for explaining in detail a rotor according to an embodiment of the present invention.
4 and 5 are views for explaining an inverter according to an embodiment of the present invention.
6 and 7 are simulation results for explaining a mixed current according to an embodiment of the present invention.
8 and 9 are diagrams for explaining a means for solving heat generation and heat generation at a connection node according to an embodiment of the present invention.
10 is a diagram for describing a winding factor order according to an embodiment of the present invention.
11 is a diagram for explaining an electric motor in consideration of a winding factor order according to an embodiment of the present invention.
12 to 15 show simulation results of an electric motor according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the technical idea of the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content may be thorough and complete, and the spirit of the present invention may be sufficiently conveyed to those skilled in the art.

In the present specification, when a component is referred to as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. In addition, in the drawings, the shape and size are exaggerated for effective description of technical content.

In addition, in various embodiments of the present specification, terms such as first, second, and third are used to describe various components, but these components should not be limited by these terms. These terms are only used to distinguish one component from another component. Accordingly, what is referred to as a first component in one embodiment may be referred to as a second component in another embodiment. Each embodiment described and illustrated herein also includes its complementary embodiment. In addition, in the present specification,'and/or' is used to mean including at least one of the elements listed before and after.

In the specification, expressions in the singular include plural expressions unless the context clearly indicates otherwise. In addition, terms such as "include" or "have" are intended to designate the presence of features, numbers, steps, elements, or a combination of the features described in the specification, and one or more other features, numbers, steps, and configuration It is not to be understood as excluding the possibility of the presence or addition of elements or combinations thereof. In addition, in the present specification, "connection" is used to include both indirectly connecting a plurality of constituent elements and direct connecting.

Further, in the following description of the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

1 is a view for explaining an electric motor according to an embodiment of the present invention, Figure 2 is a view for explaining the electric motor according to an embodiment of the present invention from a circuit perspective, and Figure 3 is an embodiment of the present invention 4 and 5 are views for explaining an inverter according to an embodiment of the present invention, and FIGS. 6 and 7 are views for explaining a rotor according to an embodiment of the present invention. This is a simulation result to explain the current.

Referring to FIG. 1, an electric motor 1000 according to an embodiment of the present invention may include a stator 100 and a rotor 200. Each configuration is described in detail below.

Stator(100)

The stator 100 may be provided on one side of the rotor 200, for example, outside in the radial direction, and may provide rotational force to the rotor 200. To this end, the stator 100 may be created in a cylindrical shape including a hollow inside, and the rotor 200 may rotate while being inserted into the hollow of the stator 100.

According to an embodiment, the stator 100 may include a plurality of teeth 110 on which the main winding is seated. For example, the plurality of teeth 111 may be arranged in a circumferential direction inside the cylinder of the stator 100.

The stator 100 may include a main winding 120 that generates a magnetic field so that the rotor 200 can rotate. The main winding 120 may be grouped according to a phase of an applied current. For example, the main winding 120 to which a three-phase current consisting of Iu, Iv, and Iw is applied is a first main winding 120u to which Iu current is applied, a second main winding 120v to which Iv current is applied, Iw It may include a third main winding (120w) to which current is applied. Referring to FIG. 1, each of the main windings 120u, 120v, and 120w is formed on the tooth 110, and may be formed as a double layer. In this case, the same group of main windings may be formed in a specific tooth, and a different group of main windings may be formed in a specific tooth.

Rotor(200)

The rotor 200 may rotate with respect to the stator 100 by a rotor field generated by the rotor 200 and a stator field generated by the stator 100.

To this end, the rotor 200 may include a harmonic winding 220, a rectifier 230, and a field winding 240. The harmonic winding 220 and the field winding 240 may be arranged along the circumferential direction of the rotor 200.

More specifically, a plurality of teeth 211 are provided along the circumferential direction of the rotor 200, and the harmonic winding 220 and the field winding 240 may be formed on the plurality of teeth 211, respectively.

1 and 3, the harmonic winding 220 may be formed in a tooth 211 and a slot 213 formed on one side of the tooth. In this case, the harmonic winding 220 provided in the slot 213 may be formed of a double layer.

The field winding 240 may be provided on the tooth 211.

According to an example, the number of poles of the main winding 120 may be the same as the number of poles of the field winding 240. This is to generate torque due to the interaction between the stator field generated in the main winding 120 and the rotor field generated in the field winding 240.

The number of poles of the harmonic winding 220 may be n times greater than the number of poles of the main winding 120. For example, when the frequency of the current for generating the third harmonic supplied to the main winding 120 is n times greater than the frequency of the current for generating the stator field supplied to the main winding 120, the harmonic The number of poles of the winding 220 may be n times greater than the number of poles of the main winding 120. This is to induce a harmonic MMF in the harmonic winding 220 by the third harmonic generated in the main winding 120.

Mixed current

A mixed current may be applied to the main winding 120.

The mixed current may have a component in which a first current having a first frequency to generate a stator field and a second current having a second frequency that is a predetermined multiple of the first frequency to generate a third harmonic are mixed. In this case, the magnitude of the first current may be greater than that of the second current.

The mixed current can be generated in a single inverter. Hereinafter, generation of a mixed current of an inverter according to an embodiment of the present invention will be described with reference to FIGS. 4 and 5.

4 and 5, the inverter may include at least one of a mixer 10, a comparator 20, and a mixed current generator 30.

The mixer 10 may mix a first signal S1 having a first frequency and a second signal S2 having a second frequency. As described above, the second frequency may be greater than the first frequency. For example, the second frequency may be three times greater than the first frequency. Hereinafter, for convenience of description, it is assumed that the first frequency is 60 Hz and the second frequency is 180 Hz.

The mixer 10 may generate a mixed signal S3 by mixing the first signal S1 and the second signal S2. The mixed signal S3 may be expressed by the following equation.

In this case, Vmodref_singnal is a representation of the mixed signal S3 based on a voltage. The first part of Vmodref_singnal is a component by the first signal S1, and the second part is a component by the second signal S2.

The comparator 20 may generate an inverter gating pulse GP by comparing the mixed signal S3 and the carrier signal CS.

The inverter gating pulse GP may be generated to correspond to each phase. That is, in the case of a three-phase current, a first inverter gating perk (GP1) for generating Iu, a second inverter gating perk (GP2) for generating Iv, and a third inverter gating perk (GP3) for generating Iw are generated. I can.

The inverter gating pulse GP may be supplied to a switching gate of the mixed current generator 30. More specifically, the first inverter gating pulse GP1 is supplied to the switching gate for generating Iu current, the second inverter gating pulse GP2 is supplied to the switching gate for generating Iv current, and the third inverter gating pulse ( GP3) can be supplied as a switching gate for generating Iw current.

Accordingly, the mixed current generation unit 30 may generate a mixed current by controlling the flow of the current by the voltage source 36 with the inverter gating pulse GP supplied to the switching gate. That is, the mixed current generation unit 30 may generate Iu, Iv, and Iw.

The generated Iu, Iv, and Iw can be expressed mathematically as follows.

I1 means the current peak of the first current, k is the peak ratio of the second current to the first current, w means the electric angular frequency, and t means the time.

Referring to FIG. 6, it can be confirmed that Iu, Iv, and Iw are properly generated corresponding to each phase. When Iu is Fourier transformed among the simulation results of FIG. 6, it can be confirmed that the first current having a first frequency of 60 Hz and a second current having a second frequency of 180 Hz are independently mixed as shown in FIG. have.

The generated currents Iu, Iv, and Iw may be supplied to the first main winding 120u, the second main winding 120v, and the third main winding 120w, respectively.

Accordingly, the main winding 120 may generate a stator field, that is, MMF. The MMF generated by the main winding 120 by receiving currents Iu, Iv, and Iw may be expressed as an equation as follows.

NΦ means the number of turns per phase, and is the electric angle. In this case, the second part of the MMF equation is a mathematical expression of the third harmonic.

The mixed current according to an exemplary embodiment of the present invention has been described above with reference to FIGS. 4 to 7.

Hereinafter, a driving method of an electric motor according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

A mixed current may be applied to the main winding 120 of the motor 1000. That is, the mixed current Iu may be applied to the main winding 120u, the mixed current Iv may be applied to the main winding 120v, and the mixed current Iw may be applied to the main winding 120w.

A first current having a first frequency among the mixed currents may generate a stator field. In contrast, a second current having a second frequency among the mixed currents may generate a third harmonic.

The third harmonic may induce the harmonic winding 220 of the rotor 200. As described above, since the number of poles of the harmonic winding 220 is designed to correspond to the third harmonic, the harmonic winding 220 may be induced by the third harmonic.

The harmonic current generated by the induction of the harmonic winding 220 may be rectified by the rectifier 230. The harmonic current rectified by the rectifier 230 may be provided to the field winding 240. The field winding 240 may generate a rotor field through a rectified harmonic current. As described above, since the number of poles of the main winding 120 and the number of poles of the field winding 240 are the same, the interaction between the stator field generated by the main winding 120 and the rotor field generated by the field winding 240 As a result, the rotor 200 can rotate.

8 and 9 are diagrams for explaining a means for solving heat generation and heat generation at a connection node according to an embodiment of the present invention.

1 and 2, one end of the first main winding 120u, the second main winding 120u, and the third main winding 120u according to an embodiment of the present invention is supplied with a mixed current. It may be electrically connected to the mixed current generation unit 30.

In addition, the other ends of the first main winding 120u, the second main winding 120u, and the third main winding 120u may be electrically connected to each other at a connection node N (refer to FIG. 2).

A first current and a second current constituting a mixed current flow through the connection node N. In this case, the first current does not significantly affect heat generation of the connection node, but since each phase of the second current has a potential of the same sign, heat may be generated in the connection node.

For a detailed description, reference will be made to FIG. 8. 8 shows only the first current (Iu_Fun, Iv_Fun, Iw_Fun) components of the mixed current. That is, Iu_Fun, which is the first current of the mixed current, flows through the first main winding 120u, Iv_Fun, which is the first current of the mixed current, flows through the second main winding 120v, and the mixed current flows through the third main winding 120w. The first current, Iu_Fun, flows.

Current flowing through each main winding is joined at the connection node (N). At this time, the current flowing through each main winding has a potential of a different sign at the connection node (N). Referring to time T1 of FIG. 8, it can be seen that Iv_Fun of a positive voltage and Iu_Fun and Iw_Fun of a negative voltage join the connection node N at the time T1. In this case, in the second main winding 120v, an electric line may be naturally formed in the directions of the first and third main windings 120u and 120w. It can be seen that the positive voltage Iv_Fun and Iw_Fun and the negative voltage Iu_Fun join the connection node N at the time point T2. In this case, an electric line may be naturally formed from the second and third main windings 120v and 120w to the first main winding 120u. That is, since the electric line is naturally formed, the first currents Iu_Fun, Iv_Fun, and Iw_Fun of each phase may flow through the connection node N.

In contrast, the second current among the mixed currents may cause heat generation at the connection node N. For a detailed description, referring to FIG. 9, the second current among the mixed currents has the same frequency and phase regardless of each phase. In other words, the first second current in a mixed current supplied to the main windings (120u) (Iu_3 ^rd) component and the second main winding (120v) a second current (Iv_3 ^rd) component and the third main windings of the mixed current supplied to the The second current (Iw_3 ^rd ) component of the mixed current supplied to (120w) has the same frequency and phase. This is because the second current has a frequency of n times compared to the first current, eg, 3 times as previously assumed.

That is, the connection node (N) at the time point T3, the Iu_3 ^rd consisting of only a positive voltage, Iv_3 ^rd, the Iw_3 ^rd joined. Also connected to the node (N) at the point in time T4 has thereby joined the Iu_3 ^rd, Iv_3 ^rd, Iw_3 ^rd only consists of a negative voltage. That is, when the second currents of each phase merge, since there is no difference in potential sign, a current flow disturbance occurs, and a current flow disturbance may mean that unintended heat generation occurs in the connection node N.

Accordingly, the electric motor 1000 according to an embodiment of the present invention is configured to further include an electric line 40 electrically connected to the connection node N. The electric line 40 (refer to FIGS. 2 and 5) is for removing the second current joined at the connection node N through a path other than the main windings 120. To this end, one end of the electric line 40 is connected to the connection node N, and the other end of the electric line 40 is between the first diode 32 and the second diode 34 provided in series. Can be provided. That is, since the electric line 40 is connected between the back-to-back diodes, the problem of unintended heat generation of the connection node N can be solved at low cost.

10 is a diagram for explaining a winding factor order according to an embodiment of the present invention, and FIG. 11 is a diagram for explaining an electric motor in consideration of a winding factor order according to an embodiment of the present invention.

Referring to FIG. 10, as a motor structure capable of utilizing both KW1 by the first current and KW3 by the second current, it was confirmed that 18 slots of 4 poles and 42 slots of 9 poles are appropriate. That is, the 4-pole 18-slot and 9-pole 42-slot motors can be selected with a structure that can utilize both KW1 and KW3. In the case of the four-pole 18 slots, an electric motor may be provided as shown in FIG. 1, and in the case of the nine-pole 42 slot, the electric motor may be provided as shown in FIG. Hereinafter, the four-pole 18 slots will be referred to as the first experimental example, and the nine-pole 42 slot will be referred to as the second experimental example. Hereinafter, a simulation result of an electric motor according to these embodiments will be described.

12 to 15 show simulation results of an electric motor according to an embodiment of the present invention.

Referring to FIG. 12, it can be seen that the No-load EMF forms a sine wave and comes out well in both the first and second experimental examples.

Referring to FIG. 13, a harmonic current generated by a harmonic winding can be checked, and referring to FIG. 14, a field current in which the harmonic current is rectified by the rectifier can be checked.

Referring to FIG. 15, in the case of the first experimental example, it can be confirmed that the torque ripple is 41.96% and the average torque is 5.28727Nm, and in the case of the second experimental example, it can be confirmed that the torque ripple is 34.05% and the average torque is 5.2724Nm.

That is, according to the simulation results described with reference to FIGS. 12 to 15, it can be confirmed that both the first and second experimental examples operate properly based on the mixed current.

As described above, the present invention has been described in detail using preferred embodiments, but the scope of the present invention is not limited to specific embodiments, and should be interpreted by the appended claims. In addition, those who have acquired ordinary knowledge in this technical field should understand that many modifications and variations can be made without departing from the scope of the present invention.

Claims (11)

A mixed current in which a first current having a first frequency to generate a stator field but having a different phase and a second current having a second frequency that is a predetermined multiple than the first frequency to generate a third harmonic are mixed A stator including main windings to which are applied; And
An electric motor comprising a rotor comprising a harmonic winding generating a harmonic current from the third harmonic generated by the second current and a field winding generating a rotor field based on the harmonic current. The method of claim 1,
A mixing unit for mixing the first signal having the first frequency and the second signal having the second frequency; And
An electric motor including an inverter having a mixed current generating unit generating the mixed current based on the first signal and the second signal mixed by the mixing unit. The method of claim 2,
The number of inverters is one, motor. The method of claim 1,
The mixed current includes a second current of the same phase even when the phases of the first current are different. The method of claim 1,
The main windings are grouped according to the phase,
One end of each main winding is electrically connected to a terminal providing the mixed current, and the other end of each main winding is electrically connected to each other. The method of claim 5,
In a connection node in which the other ends of each of the main windings are electrically connected to each other, the second currents included in each of the mixed currents have the same potential sign. The method of claim 6,
The connection node is connected to an electric line other than the main winding, an electric motor. The method of claim 7,
One end of the electric line is electrically connected between one diode and the other diode. The method of claim 1,
The number of poles of the main winding is the same as the number of poles of the field winding. The method of claim 1,
When the second frequency is n times greater than the first frequency, the number of poles of the harmonic winding is n times greater than that of the main winding. The method of claim 1,
A rotor tooth is provided along the circumferential direction of the rotor,
A slot is provided in the rotor tooth,
The harmonic winding is formed on the rotor teeth,
The field winding is formed in the rotor tooth and the slot, the electric motor.

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