KR101306009B1 - 4/5 Two Phase SRM - Google Patents

Abstract

As a new approach in selecting the number of rotor poles and stator poles, it relates to a 4/5 pole two-phase switched reluctance motor that keeps the flux flowing through the shortest distance. The stator has four stator poles, the rotor has five rotor poles, and the motor has a two phase configuration.
By using the switched reluctance motor as described above, the efficiency and torque generation can be increased by using a short magnetic flux instead of the long diameter magnetic flux used in the conventional SRM.

Description

4/5 pole two phase switched reluctance motor {4/5 Two Phase SRM}

FIELD OF THE INVENTION The present invention relates to a 4/5 pole two phase switched reluctance motor (SRM), particularly as a new approach in the selection of rotor poles and number of stator poles, whereby the magnetic flux flows through the shortest distance. / 5-pole two-phase SRM.

Switched reluctance motor (SRM) rotates the rotor by using the reluctance torque according to the change of magnetic reluctance. The manufacturing life is low, maintenance-free, high reliability, and almost permanent life. There is this.

In addition, SRM has excellent features such as high reliability and low hysteresis losses. For this reason, SRMs have received a lot of attention recently and have been discussed as a good alternative in drive applications.

SRM as described above is an electrical machine in which torque is developed by a path that minimizes the reluctance magnetic path of the stator phase winding in which the rotor is excited. The structure of the SRM is simple and is formed by steel lamination at the stator and rotor. In the conventional SRM, there is no permanent magnet (PM) in its structure, while the H-SRM (hybrid-switched reluctance motor) has a PM.

That is, SRM has many advantages over other DC or AC machines because of its simple structure and robust configuration. The advantages of SRM include low maintenance costs, fault tolerance, and a wide speed range in the constant power range. Due to these advantages and the inherent simple structure, SRM guarantees reliable low cost variable speed drive and will certainly replace many electric drive devices in the future.

However, SRMs also have disadvantages, such as high torque ripple and acoustic noise. Since the SRM has a double salient structure, the phase change causes torque ripple. This torque ripple is a result of the nonlinear torque current-angle characteristics and the individual properties of the mechanism torque generation.

The most common two-phase SR motor is a 4/2 construction. The 4/2 SRM has four stator and two rotor poles. This structure represents a different number of stator-rotor poles in the SRM. SRMs generally have unequal numbers of stator-rotor poles. The same number of stator-rotor poles is applied to avoid the possibility of dead zone torque generation. Deadzone is a condition that occurs when all rotor poles are aligned with the stator poles and cannot produce output torque. In this state, the motor cannot generate a selfstarting rotation. In general, self-starting problems arise in one or two phase SRMs.

In addition, much research is being done on high speed 4/2 SRMs as described, for example, in the literature.

 Jin-Woo Ahn; Huynh Khac Minh Khoi; Dong-Hee Lee; , "Design and analysis of high speed 4/2 SRMs for an air-blower," Industrial Electronics (ISIE), 2010 IEEE International Symposium on, vol., No., Pp. 1242-1246, 4-7 July 2010.

An object of the present invention is to provide a 4/5 pole two-phase switched reluctance motor excellent in output and efficiency as compared with the conventional motor, which is made to solve the above problems.

In order to achieve the above object, the switched reluctance motor according to the present invention is a switch reluctance motor having a rotor and a stator, wherein the stator has four stator poles, and the rotor has five rotor poles. And the motor is characterized in that the two-phase.

In the switched reluctance motor according to the present invention, a nonuniform void is formed on the surface of the rotor.

In the switched reluctance motor according to the present invention, the air gap is formed by connecting two different radii.

In the switched reluctance motor according to the present invention, the voids are gradually connected at intervals of 7 °, and are formed by using a lower surface of 35 degrees on the left side of the rotor structure and an upper surface of 10 degrees on the right side. It is characterized by.

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As described above, according to the 4 / 5-pole two-phase switched reluctance motor according to the present invention, the effect that the efficiency and torque generation can be increased by using short magnetic flux instead of the long diameter magnetic flux used in the conventional SRM is obtained. Lose.

1 is a view showing the structure of a motor according to the present invention,
2 shows a non-uniform void of a motor according to the invention,
3 shows a magnetic flux path according to the invention for each phase,
4 is a view showing the state of FIG. 2 in 3D,
5 is a diagram showing a magnetic flux distribution of a motor according to the present invention;
6 is a view showing a torque generation of a motor according to the present invention having a variety of phase currents;
7 is a view showing an average torque and a continuous torque of the motor according to the present invention,
8 is a view showing an inductance characteristic of a motor according to the present invention,
9 is a view showing a flux-linking profile of a motor according to the present invention;
10 is a view showing a matlab simulation model of a motor according to the present invention;
11 shows an ideal inductance and inductance profile according to the invention according to the phase current,
12 shows a phase resistance of a motor according to the present invention;
13 is a view showing a simulation result of a motor according to the present invention;
14 shows a 4/5 motor according to the invention with uniform voids;
15 is a view showing a result showing a comparison between a motor and a conventional motor according to the present invention,
16 shows the efficiency curve of the motor according to the invention.

These and other objects and novel features of the present invention will become more apparent from the description of the present specification and the accompanying drawings.

First, the concept of the present invention will be described.

In the present invention, a new 4/5 pole two-phase switched reluctance motor is designed and analyzed.

The motor according to the invention uses four stator and five rotor poles. The stator pole configuration is to keep the magnetic flux of the motor flowing through the shortest distance. The motor according to the invention has no dead zone and can operate in any rotor position. The present invention uses two types of voids on the rotor pole surface. The motor according to the present invention is compared with the conventional SRM, and the performance of the proposed motor according to the present invention is predicted and simulated using finite element analysis (FEA) and matlab software. As a result, the structure according to the present invention had better performance in terms of torque generation.

Hereinafter, the structure of this invention is demonstrated according to FIGS.

1 is a view showing the structure of a motor according to the present invention, Figure 2 is a view showing a non-uniform void of the motor according to the invention, Figure 3 shows a magnetic flux path according to the invention for each phase 4 is a view showing the state of FIG. 2 in 3D.

As shown in Figure 1, the 4/5 SRM according to the present invention consists of a rotor (Stator) and a rotor (Rotor) provided on the outer periphery of the shaft (Shaft), the stator has four stator poles, The rotor is a two-phase motor with five rotor poles.

The motor according to the invention uses a short magnetic flux instead of the long diameter magnetic flux applied in a 4/2 motor. The advantage of a short flux is that it can increase efficiency and torque generation while reducing core losses.

Motors using short fluxes require lower MMFs to produce the same output torque. In addition, the amount of current in the motor or the number of turns of the winding can be reduced. Short magnetic flux requires the two closest poles that cooperate to flow the flux from one pole to the other. This pole configuration requires specific winding connections.

The five rotor poles in the motor according to the invention ensure that zero torque generation does not occur and that there is a self starting capability at any rotor position.

Non-uniform voids are used for the rotor surface of the motor according to the invention, as shown in FIG. This void reduces the likelihood that the motor generates zero torque at any rotor position. As a result, this type of void is only good for one direction rotation.

Non-uniform voids are obtained by connecting two different radii of the rotor pole surface to each other. In the motor according to the present invention, as shown in FIG. 2, the concept of gradually connecting at intervals of 7 ° is used. On the left side of the rotor structure, the lower surface of 35 degrees is used, while on the right side, the upper surface of 10 degrees is used.

The motor according to the invention is designed in only one direction, the direction of which is counterclockwise. The rotor tip side uses an asymmetric edge. This configuration makes the top edge of the rotor faster than the other parts.

Therefore, the optimum distribution of the saturation magnetic flux can be obtained. The use of a gradual transformer rotor surface makes the torque generation in the motor according to the invention more smooth in transition.

The magnetic flux in the motor according to the invention flows through the shortest path distance. Two stator poles connected are responsible for circulating the magnetic flux in one phase.

Fig. 3 (a) shows the magnetic flux path for phase A, and Fig. 3 (b) shows the magnetic flux path for phase B.

In addition, the stator pole of the motor according to the present invention is arranged in a manner to avoid the dead zone state. This stator pole is symmetrically separated in one phase and mirrored for the other phase. The two stator phases are connected between the phases. This stator phase connection is very important for the flow of magnetic flux. Magnetic flux can flow to the interphase connections.

The connecting part is shown on the left and right inside of the stator of FIG. 3, and is also shown in the 3D figure as shown in FIG. 4.

Next, an analysis and simulation of a 4 / 5-pole two-phase switched reluctance motor applied to the present invention will be described.

First, the FEA interpretation is described.

In order to verify and analyze the characteristics of the motor according to the invention, 2D FEA analysis is used. By magnetic analysis through FEA software, the predicted magnetic flux distribution of the motor can be analyzed. The magnetic flux distribution of the motor affects the performance and characteristics of the motor. The amount of flux generated should be delivered as quickly and as possible in the circulation path.

Such a fast flux path may only be possible when the flux flows through the shortest path as applied to the motor according to the invention. Figure 5 shows the magnetic flux distribution of the motor according to the present invention. Fig. 5 (a) shows the magnetic flux distribution of the A phase and Fig. 5 (b) shows the magnetic flux distribution of the B phase.

That is, the magnetic flux of one phase not only flows through the short path but also shows that the amount of magnetic flux flowing through the diameter path is small. This condition reduces the efficiency and also creates an unbalanced radial force. By appropriate choice of bearing or structural deformation, this unbalanced radial force can be avoided.

In the present invention, as shown in Figure 3, the reduction in the stator phase connection as possible as possible to make the motor robust.

Torque generation in the present invention is an important parameter in motor design. Torque generation amount indicates motor performance. Higher torque generation with smaller motor sizes has always been the goal of motor designers. The torque generation of the motor is a function of the rotor position and the phase current. For different rotor positions and excitation phase currents, different torque amounts are generated. The torque generation of each individual phase can be estimated using equation (1).

....(1)

....(One)

Where k is the number of phases, i _k is the phase current, and W _c is magnetic co-energy.

The torque produced by the SR motor is not linear with the excitation current. Material and structure play an important role here. Using different materials produces different properties.

The motor structure plays a significant role in generating the torque shape. The structure of the motor according to the invention utilizes asymmetric voids, which delivers torque shape generation asymmetrically with respect to the elevated and sink states. 6 shows torque generation of a motor according to the invention with varying phase currents.

The maximum current of the motor according to the invention is limited to 10 A, exceeding this value saturates the output torque and produces higher magnetic flux densities in excess of 1.8T in the core material, which affects core loss and overheating. .

The number of rotor poles for five rotors is sufficient to produce one phase torque at a rotor position of 72 °. The neutral commutation angle at which the torque passes from the positive to the negative is 36 degrees mechanical.

At this 36 ° neutral current angle, the motor can generate 37% of the maximum torque. This means that the SRM according to the invention does not have a dead zone even in the minimum torque region as in the neutral current angle. This current angle is used to switch phases in the continuous torque generation. Continuous torque is produced by non-overlapping switching of phases with a neutral current angle. Through this continuous torque, the average torque can be analyzed.

The average torque produced by the motor according to the invention is 0.28 Nm, which is still acceptable for the target requirement. 7 shows the average torque and the continuous torque of the motor according to the invention.

The torque generation is proportional to the square of the phase current of the motor and the inductance variation with respect to the rotor position. The inductance slop of the motor according to the invention is usually nonlinear to the current angle, which is due to nonuniform voids on the rotor surface (see FIG. 2). The rise-up inductance slop (0-36 °) is less than the sink-down slop (36-72 °). This characteristic causes the maximum inductance to shift slightly from the initial value to a higher angle of rotor position. This shifted inductance is related to the asymmetric torque generation of the motor according to the invention. 8 is a view showing the inductance characteristics of the motor according to the present invention.

In addition, the positive torque region in the motor according to the invention is wider than the negative region. To produce continuous torque, the positive torque region of the motor naturally produces continuous torque without an overlap angle between them. This wide torque range is an advantage because non-uniform voids in the motor are applied. On the other hand, a large amount of torque area reduces the maximum torque generation.

The amount of flux-linkage is also a parameter of motor performance. As the flux-chain number increases, the performance of the motor also improves. 9 is a view showing a flux-linking profile of a motor according to the present invention.

Next, the matlab simulation will be described.

To verify the motor according to the invention, a simple matlab simulink model is used. The model is built on the FEA analysis. The torque, flux-linkage and phase inductance of the motor according to the invention are transferred to three different lookup tables. Therefore, the characteristics of the motor according to the present invention are shown. 10 is a view showing a matlab simulation model of a motor according to the present invention.

Rotation of the motor is maintained by switching the phase current of the stator phase winding in synchronization with the rotor position. This rotor position is determined to excite the phase. Based on the FEA analysis, it is known that the inductance produced by the motor according to the invention increases from 0 ° rotor position and gradually decreases from 40 ° mechanical rotor position. Figure 11 shows the ideal inductance according to the phase current and the inductance profile according to the invention.

This model excites phase A at 0 ° and turns off at 36 °, while phase B is turned on at 36 ° and turned off at 72 °, with no overlap between them. The phase resistance R is essential in view of the relationship between the input voltage V and the magnetic flux winding λ. The relationship between them is represented by equation (2).

....(2)

....(2)

The motor according to the invention is a novel motor with a short magnetic flux. In the short magnetic flux of the motor, the stator yoke must flow the magnetic flux in only one direction. This configuration allows only one side of the stator yoke to flow magnetic flux, whereas in a conventional motor, the magnetic flux flows through both sides of the stator poles.

Although the number of resistors in the motor according to the invention is large, the total resistance is smaller than the total resistance of the conventional motor. 12 shows the phase resistance of a motor according to the invention. The total resistance of the motor according to the invention is represented by equation (3).

...(3)

... (3)

The simulation was performed at 1000 rpm without applying the optimal control method. From this simulation, output performances such as torque, excitation current and efficiency can be predicted. According to the simulation results, the motor according to the present invention can generate 0.35 Nm output torque with a minimum torque of 0.28. This result is slightly different from the FEA interpretation. The difference from this simulation is due to the overlap angle between the phases. For the overlap angle, the two excitation phases can generate torque at the same time, so that the torque generation in the overlap region (minimum torque region) is higher than the switching phase at the neutral current angle. Figure 13 shows a simulation result of the motor according to the present invention, Figure 13 (a) is a torque generation, Figure 13 (b) is a phase current. Fig. 13C shows the magnetic flux windings, respectively.

The motor according to the invention uses non-uniform voids at the rotor pole surface. By this condition, the torque is widened in the positive area while being small for the maximum torque generation. This nonuniform rotor pole surface type can be used for fan or blower applications.

In order to compare the performance of the motors according to the invention, several types of motors are used. In this comparison, the model according to the invention used uniform pores on the rotor pole surface. This uniform void creates a uniform torque profile for the positive and negative regions. Figure 14 shows a 4/5 motor according to the invention with uniform voids.

The motor according to the present invention and the conventional SR motors (4/2, 6/4, 8/6, 12/8) were compared. The comparison model uses the same input parameters and dimensions. In order to keep the current density as close as possible to the others, the number of turns is different. Different winding times are used to have the same magnetic drive force.

Since the phases of the motors are not identical at the time of comparison, the comparison is made based only on the single excitation phase of each motor. This comparison is done with standard motors that do not optimize the structure.

Figure 15 shows the result showing the comparison between the motor according to the present invention and the conventional motor, Figure 16 shows the efficiency curve of the motor according to the present invention.

From this comparison, as shown in FIG. 15, the motor according to the invention develops a 15% higher torque than the 4/2 SR motor. However, this is 14% lower than 6/4 motors. The number of rotor poles is related to the switching frequency of the SR drive. Increasing the number of rotor poles, such as 12/8, results in a higher switching frequency but a smaller torque interval. It can be seen from FIG. 16 that 12/8 requires four times the switching time compared to achieving one switching time by a 4/2 motor. The switching frequency is related to the efficiency of the motor. The higher the switching frequency, the higher the switching loss.

By calculating the conversion and core loss of the motor according to the invention, the efficiency curve can be predicted. The efficiency curve shows the relationship between output power, torque, speed, and motor losses.

The efficiency curve of FIG. 16 shows that the motor according to the invention can produce 78% of the efficiency at base speed 1000 rpm. Below the base speed, the motor can achieve efficiencies above 80%.

As described above, in the motor to which the present invention is applied, two voids are used, that is, uniform voids and non-uniform voids. Uniform voids are used to compare the model according to the invention with conventional structures. On the other hand, nonuniform voids were used to increase the positive torque range.

Although the present invention has been described in detail with reference to the above embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention.

The 4/5 pole two phase switched reluctance motor according to the invention is applied in the field of electric motors.

Claims (5)

A switched reluctance motor having a rotor and a stator,
The stator has four stator poles,
The rotor has five rotor poles,
The motor is two-phase,
Non-uniform voids are formed on the surface of the rotor,
The air gap is switched reluctance motor, characterized in that formed by connecting two different radii. delete delete The method of claim 1,
The voids are gradually connected at intervals of 7 degrees, and are formed using a lower surface of 35 degrees on the left side of the rotor structure and an upper surface of 10 degrees on the right side. delete

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