KR20020081862A - Hybrid Excitation Method for Reduction of Vibration and Acoustics Noise of SRM - Google Patents

Abstract

PURPOSE: A hybrid excitation method is provided to reduce the vibration and the noise by using the hybrid excitation method as combination of a 1 phase excitation method and a 2 phase excitation method. CONSTITUTION: A hybrid excitation method is used as an SRM driving method. The hybrid excitation method is to overlap 1 phase excitation method and 2 phase excitation method to each other. In the hybrid excitation method, a phase conductive angle is increased to use the 2 phase synchronous exciting sections. A C-dump circuit including a booster circuit is used as a driving inverter. The phase conductive angle is increased to overlap exciting sections of the 1 phase excitation and the 2 phase excitation. An influence of sub torque is reduced in a phase commutation process by using the C-dump circuit including the booster circuit.

Description

Hybrid Excitation Method for Reduction of Vibration and Acoustics Noise of SRM

The present invention relates to reduction of torque pulsation and noise and vibration using a hybrid excitation method in driving a switched reluctance motor.

Switched Reluctance Motor (hereinafter referred to as SRM) drive system is a relatively reliable power electronic drive device that is simple to manufacture, inexpensive, and withstands accidents and is a relatively reliable power electronic drive device for industrial equipment, aircraft, automobiles, home appliances, etc. In terms of high torque / volume and output, high efficiency variable speed operation, and economical inverter power, it has characteristics that can be compared with conventional induction motor and permanent magnet motor.

Despite these advantages, however, SRMs exhibit higher levels of noise and vibration than conventional drives.

SRM has already been applied to noise-sensitive applications such as mines, but it is difficult to apply to home appliances and offices. In other words, torque ripple and noise are the limiting factors in the application of the SRM's torque generation mechanism. These noises are generated by vibrating the stator frame in the radial direction when each phase is turned on and off as well as the tangential force acting as the main rotational force during the generation of the reluctance stoke.

The direction of development research until recently was focused on proper magnetic circuit design and control method aimed at improving torque, efficiency, reliability, and cost. However, in recent years, researches on the suppression of torque pulsation and the reduction of noise and vibration have been actively conducted to broaden the scope of precision control and home appliances.

The force in the rotational direction acts as a rotational torque on the rotor, which increases or decreases in magnitude depending on the rotor position angle, that is, torque pulsation, thereby lowering the stability of the torque-speed characteristic of the motor. Torque pulsation is caused by the pulsation in the torque generating section and the commutation action between phases. Among them, a relatively large torque pulsation caused by a relatively inconsistent commutation action has been shown, and a method of properly superimposing them has been proposed.

In addition, vibration and noise generation causes largely mechanical and electromagnetic causes. Mechanical causes include noise due to mechanical problems such as concentricity of concentricity, straightness, contact friction, unbalanced weight manufacturing, and mechanical vibrations and friction with air in applications such as bearings. Electromagnetic causes include contraction and expansion by sudden changes in magnetomotive force occurring at the moment of phase switch on and off. According to several studies, the vibration and noise of SRM are mainly caused by the fluctuation of the radial direction of the stator.

Accordingly, the present invention proposes a hybrid excitation method in which a one-phase excitation method and a two-phase excitation method are combined in order to improve the sudden change of the magnetomotive force, which is the above problem, to reduce vibration and noise.

1 is a magnetic flux distribution diagram of three-phase 6 / 4SRM phase and hybrid excitation.

2 is an inductance profile and a phase current waveform diagram of a hybrid excitation method.

Figure 3 is a torque waveform diagram according to the rotor position of the SRM.

4 is a circuit diagram of a C-dump inverter for hybrid excitation.

5 is an operation of the C-dump inverter for hybrid excitation.

6 is a phase current in a hybrid excitation method.

7 is a characteristic of the driving characteristics and the recovery circuit of the motor according to the ratio of ratio.

8 is a test motor specification

9 is a configuration diagram of a vibration noise measuring system.

10 is vibration characteristics by the conduction angle adjustment of the C-dump inverter.

11 shows the vibration, noise and efficiency characteristics of the single-phase excitation method and hybrid excitation method.

Comparison diagram.

Research to reduce vibration and noise of SRM is being conducted in various ways. Until now, studies on vibration and noise reduction have been carried out by adjusting the mechanical structure, adjusting the winding method, and adjusting the excitation method.

In the present invention, as a method of alleviating a sudden change in magnetomotive force, which is a main cause of vibration and noise, a hybrid excitation method of overlapping the other phases before one switch off is adopted. In other words, the torque pulsation was remarkably reduced due to the proper overlap between the female phases. However, this method has a disadvantage of lowering efficiency, which is compensated by using a C-dump inverter. The validity of this method was verified through experiments implemented by simulation and control system. In order to maximize the variable reluctance torque, the mechanical structure of SRM has a double-pole type pole structure and a single excitation method. Noise is generated. Such vibration and noise are generated by vibrating the stator frame in the radial direction when each phase is turned on and off, as well as the tangential force acting as the main rotational force during the generation of the reluctance torque.

According to a recent study, the vibrations and noises of SRM switching are shown at the time of switching on and off, respectively. In particular, most of the control is focused on reducing vibration and noise at the time of switching off. In addition, if the longer the potato period after the switch off, vibration, noise is alleviated, but the efficiency is worse.

In order to achieve the above object, in the hybrid excitation method of the present invention, the conduction angle is increased to use the two-phase simultaneous excitation section. Due to the increased conduction period, the off point of the phase switch is selected in a section in which the inductance is quite large, and the extinguishing time of the phase current (commutation) becomes long during phase commutation. As a result, the SRM operation efficiency is reduced, and in order to improve the present invention, the C-dump circuit using the boost circuit is configured as a drive inverter, and vibration, noise, and efficiency characteristics are examined.

The winding configuration of SRM for hybrid excitation of a 6/4 pole SRM drive system is the same as that of the existing single winding excitation phase. In order to effectively use the combination of the variable mutual inductance component of the two-phase excitation method, the direction of the magnetic flux path is generated in one direction by changing the phase excitation direction on the b phase among the excitation directions of the winding in FIG.

1 shows a magnetic flux path for each excitation section in a hybrid excitation method. When the phase b is excited in the magnetic flux path of FIG. 1 (a) with respect to the phase excitation of a phase, the magnetic flux path of FIG. When the two phase excitation-off phase in a flux region is formed a magnetic flux path in Fig. 1 (b), the magnetic flux path to some degree while maintaining constant the last one degree of the magnetic flux path of the one phase excitation (c) of. Therefore, it is possible to reduce the sudden change in the magnetomotive force at the time of phase switch-off by the two-phase excitation technique.

Figure 2 shows the inductance and each phase current waveform according to the hybrid excitation method. By turning on the c phase before the b phase is turned off, the two phases are operated between the sections 2-3 in FIG. 2 to reduce excessive vibration and noise generated when the b phase is turned off. The generated torque pulsation can be reduced.

3 shows simulated torque according to the phase excitation method (Opera of Vector Fields). Hybrid excitation is driven by a suitable combination of one-phase excitation and two-phase excitation. Fig. 3 (a) shows the torque generated by the single phase excitation method, and Fig. 3 (b) shows the torque generated when the two phases are excited at the same time. Here, the phase difference between the generated torques when the first phase is excited and the second phase is simultaneously excited can be seen. When properly combined, it can be seen that torque pulsation can be reduced and vibration and noise can be reduced by appropriate control combined with one phase before switching off.

3 (c) shows that the flat torque is obtained by appropriately selecting the excitation sections of the 1 phase and the 2 phases. In the torque graph of FIG. 3 (c), a constant torque can be obtained by taking a section in which the torque of the initial phase 1 woman is the maximum and taking a torque of the phase 2 phase woman at a time when the torque section of the phase 1 woman decreases. In this way, the torque pulsation caused by the failure of the current commutation between phases among the causes of the torque pulsation can be significantly reduced. In addition, by exciting two phases instantaneously, a sudden change in magnetomotive force can be avoided and vibration and noise are reduced.

In the hybrid excitation method, a smooth torque as shown in FIG. 3 (c) can be obtained. However, in the hybrid excitation method, the conduction angle of the phase is increased to take a two-phase excitation section, and the off-conversion point of the phase switch is selected in a section where the inductance is considerably large due to the increased conduction angle. The extinguishing time of the phase current becomes long. As a result, in this study, a C-dump inverter having a power regenerative unit composed of a boost circuit is applied to reduce the influence of the negative torque during phase current (commutation). This circuit separates the control of the phase switch from the control of the power regenerative chopping switch, requiring a significant number of switches and having complete independence between the phases to allow phase currents to overlap. At the same time, the magnitude of the energy recovery capacitor voltage is equal to the magnitude of the reverse voltage, and the burden on the capacitor operating voltage is greatly reduced.

5 shows an operating state of the inverter when a current is commutated from a to b. Assuming that the voltage of the energy recovery capacitor is constant, a power supply voltage by switching on is applied across the upper winding line, and a reverse voltage is applied by switching off.

Fig. 5 (b) shows a section in which a and b phases are simultaneously conducted, and Figs. 5 (c), (d) and (e) show the b phases operating and converting a phase into a mechanical output using a recovery circuit. The process of recovering the magnetic energy into the power supply voltage in accordance with the operation of the chopper switch in the magnetic circuit is not performed.

FIG. 6 shows phase current waveforms of an asymmetric inverter and a utilized C-dump inverter during hybrid excitation. In the hybrid excitation method of the asymmetric inverter, it is shown in Fig. 6 (a) that the current arc extinguishing time becomes considerably longer by increasing the torque angle for two-phase superposition. On the other hand, in the hybrid excitation method using the C-dump inverter, since the accumulated energy of the phase winding is recovered to the capacitor for a very short time, the current can be quickly extinguished during the commutation of the phase current as compared to the asymmetric inverter. 7 shows the operation characteristics and the recovery circuit characteristics of the motor according to the application ratio. It can be seen that the optimum value of the noise and the recovery capacitor voltage for efficiency is most appropriate in that the application ratio is about 0.7. The motor used in this experiment is a 600 [W] class 12/8 pole SRM with 16 and 17 degrees of arc angle of the rotor and stator, respectively, as shown in Fig. 8, and the dynamometer and vibration for the load test and the vibration and noise test. It was configured as shown in Figure 9 using an acceleration sensor and a noise measuring instrument. Here, the vibration acceleration sensor was attached to the frame surface of the stator pole, and the noise detector was installed radially at 1 foot from the frame.

The comparison between the one-phase excitation method and the hybrid excitation method according to the speed is shown in FIG. 11. Fig. 11 (a) shows the vibration and Fig. 11 (b) compares the noise. As both methods increase speed, the vibration and noise increase, but the hybrid excitation method is smaller than the one-phase excitation method in all speed sections. In particular, there is no phenomena that increase in size at a constant speed, as in the one-phase excitation method. Overall, the efficiency characteristics are almost similar to the one-phase excitation method and the hybrid excitation method. As a result, noise excitation can be reduced by adopting a hybrid excitation method, and a decrease in efficiency can be improved by using a C-dump inverter.

As described above, in the present invention, a hybrid excitation method is applied as a method of reducing a sudden change in the electromagnetic force in the radial direction, and vibration and noise can be reduced by using the hybrid excitation method. In addition, it can be seen from the simulation that the torque pulsation caused by the inability of current action between phases can be significantly reduced. However, in the hybrid excitation method, the efficiency is reduced by the generation of the negative torque due to the longer conduction section. This reduction in efficiency can be improved by using a C-dump inverter, and vibration and noise can be improved through efficient hybrid excitation. Therefore, the present invention will contribute to the practical application by applying SRM to precision devices and household electronics.

Claims (1)

In order to maximize the variable reluctance torque, the SRM has a double pole type of stator and rotor structure, and it is driven by a single excitation method, which provides relatively high vibration and noise compared to conventional rotor type motors due to the torque generation mechanism. Occurs. These vibrations and noises are generated by vibrating the stator frame in the radial direction when each phase is turned on and off as well as the tangential force acting as the main rotational force during the generation of the reluctance torque. In particular, the vibration and noise are severe when switching off, so care must be taken to reduce the vibration and noise when switching off. In addition, if the longer the potato period after the switch off, vibration, noise is alleviated but the efficiency is worse. In order to achieve the above object, the present invention adopts a hybrid excitation method of superimposing a one-phase excitation method and a two-phase excitation method, which are SRM driving methods, when driving an SRM. In the hybrid excitation method, the conduction angle is increased to use the two-phase simultaneous excitation section. Due to the increased conduction period, the off time of the phase switch is selected in a section where the inductance is quite large, so that the phase current extinguishing time becomes long during phase commutation. As a result, the SRM operation efficiency is significantly reduced, and in order to improve this, the present invention configures a C-dump circuit using a boost circuit as a drive inverter. In other words, the phase conduction angle is increased in order to superimpose the female section of one-phase and two-phase females for one-phase female for low noise and low vibration driving in SRM driving, resulting in the reduction of secondary torque during commutation. In order to reduce the influence, the hybrid excitation method using the C-dump inverter composed of Boost circuit and the efficiency, noise, vibration and recovery capacitor according to the control mode and duty ratio of the C-dump inverter composed of Boost circuit in SRM operation Matter about recovery voltage.