KR100586991B1 - method for determining early position angle of 3 phase motor - Google Patents

Abstract

The present invention relates to a method for determining the initial position angle of a three-phase motor, the method comprising the steps of selectively exciting the three-phase to detect the excitation phase current; Calculating a current difference between the detected excitation phase currents; Calculating a rotor position of the three-phase motor based on the magnitude of the current difference; If necessary, conducting additional excitation to detect current. As a result, the initial driving time of the motor can be shortened and erroneous measurement of the rotor position due to the error of the measurement current can be prevented.

Rotor, initial position detection, 3-phase motor

Description

Method for determining early position angle of three phase motor}

1 is a graph of the current difference and the difference value of the excitation current with respect to the mechanical angle of the rotor of the interior Permanent Magnet (IPM),

2 is a schematic configuration diagram of a motor driving apparatus according to an embodiment of the present invention;

3 is a flowchart illustrating a method for calculating an initial position of a motor rotor according to an embodiment of the present invention;

4 shows classification results of the basic test current, current difference, and current difference corresponding to the machine angle.

* Explanation of symbols for main parts of the drawings

1: 3 phase motor 3: Inverter

5: current detection unit 7: inverter control unit

11: stator 12: rotor

R1 ~ R3: Resistor L1 ~ L3: Inductor

Q1 ~ Q6: Transistor

The present invention relates to a method for determining the initial position angle of a three-phase motor.

The phase to be excited to obtain the maximum torque is determined by the position of the rotor of the motor. When the rotor is rotating, the position of the rotor can be measured according to the counter electromotive force, and based on this, the motor is driven by selectively exciting an appropriate phase to obtain the maximum torque.

In the initial operation of the motor, the position sensor is used because the position of the rotor cannot be measured according to the counter electromotive force. Failure to excite the proper phase according to the position of the rotor may cause initial drive to fail, drive time may be long, and unnecessary power consumption may occur.

 In a structure in which a driving environment is difficult to mount a sensor such as a compressor, various sensing methods are used. For example, by energizing the stator, the rotor is forced to align and start driving from the aligned position.

Korean Patent Laid-Open Publication No. 10-2000-0024078 discloses another method of measuring the initial position of a rotor without using a sensor.

That is, the excitation phase current is measured a total of six times according to the two-phase excitation method, and the current difference between the excitation phase currents measured when the same phase is excited. At this time, the position of the rotor can be detected based on the calculated current difference, but the decomposition angle is only an electric angle of about 60 degrees.

Then, the difference value between the calculated current differences is calculated again, and based on this, it is calculated whether the rotor is located at a point that cannot be calculated as the current difference of the excitation phase current, that is, at a point where the magnetoresistance becomes minimum.

By the way, the initial position measurement method of the rotor, it was confirmed that it is difficult to determine the initial position of the rotor in the motor of the IPM (Interior Permanent Magnet) type, which is mainly used in home appliances motors such as compressors.

Figure 1 is a graph of the current difference and the difference value of the excitation current with respect to the mechanical angle of the rotor in an IPM (Interior Permanent Magnet) type 4-pole motor.

As shown in FIG. 1, it can be seen that since the amplitudes of the graphs are not large, the differences between them are also small. Therefore, this small current magnitude is likely to cause an error in the initial position calculation of the rotor.

In addition, as described above, the conventional initial driving method requires a switching time of six times because of the two-phase excitation method. In six cycles of switching, the initial position of the rotor is increased in proportion to the number of cycles per cycle since the initial position of the rotor is determined based on the data measured by switching for several cycles. . If the number of switching can be reduced, it will be effective to reduce the initial run time.

Accordingly, an object of the present invention is to provide a method for determining an initial position angle of a three-phase motor which can be applied to various types of motors and can accurately measure the initial position of the rotor.

According to the present invention, there is provided a method for determining an initial position angle of a three-phase motor, the method comprising: selectively exciting three phases to detect an excitation phase current; Calculating a current difference between the detected excitation phase currents; Comprising the step of calculating the position of the rotor of the three-phase motor based on the magnitude of the current difference can be achieved by the initial position angle determination method of the three-phase motor.

Wherein the driving method further comprises classifying the current difference according to a magnitude; The step of calculating the rotor position may be based on the classification result of the current difference.

In the detecting phase of the excitation phase current, the three-phase excitation may be configured to excite the excitation phase current into any one of the phase terminals of the three-phase motor and the remaining phase terminals flow out of the introduced excitation phase current.

The driving method may include selecting any two of the phase terminals of the three-phase motor according to the calculated position of the rotor to inject the excitation current and inject the excitation current introduced from the other one of the phase terminals. Exciting the phase motor; Detecting the leaked excitation phase current; The method may further include calculating a position of the rotor based on the detected magnitude of the excitation current.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

2 is a schematic configuration diagram of a motor driving apparatus according to an embodiment of the present invention. As shown in Fig. 2, the motor drive device has a three-phase motor 1, an inverter 3, a current detector 5, and an inverter controller 7.

The three-phase motor 1 has a stator 11 and an internal rotor 12 including resistors R1 to R3 and inductors L1 to L3. Each phase terminal of the three-phase motor 1 is connected to the inverter 3, and when an excitation phase current flows and a current flows through the inductors L1 to L3, a magnetic field is formed to rotate the internal rotor 12.

The inverter 3 has six switching transistors Q1 to Q6. The two are connected in series and connected to the phase terminals of the three-phase motor 1, and one of them (hereinafter referred to as "top transistors Q1 to Q3") is connected to the plus terminal of the external Vdc. One (hereinafter referred to as "lower transistors Q4 to Q6") is connected to the negative terminal.

The excitation phase current supplied from the inverter 3 to the three-phase motor 1 is detected by the current detector 5, and the base terminals of the transistors Q1 to Q6 are biased by a bias signal input from the inverter controller 7. Switching is controlled.

The inverter control unit 7 drives the inverter 3 in accordance with the three-phase excitation method. For example, one of the three upper transistors Q1 to Q3 of the inverter 3 is turned on, and two lower transistors Q4 to Q6 having a phase different from the turned on phase are turned on. According to the three-phase excitation method, six current flows can be symbolized as shown in Table 1 below.

Here, the arrow indicates the direction of the current between the phase terminals U, V, and W. FIG. For example, "U-> V, W" means that the excitation phase current flowing into the U phase terminal of the three-phase motor 1 flows out to the V, W phase terminal.

The inverter controller 7 switches the inverter 3, and selectively switches transistors Q1 to Q6 of the inverter 3 based on the current detected from the current detector 5.

3 is a flowchart illustrating a method for calculating an initial position of the motor rotor 12 according to the embodiment of the present invention.

Hereinafter, a method of calculating the initial position of the rotor 12 by the inverter controller 7 based on the detection current will be described in detail with reference to FIG. 3.

First, the inverter controller 7 selectively switches transistors Q1 to Q6 such that the basic test currents U1, V1, and W1, which are classified in Table 1, flow.

The current measuring unit 5 measures the current magnitudes of the basic test currents U1, V1, and W1 generated by the switching of the inverter control unit 7 (30).

The current difference is calculated between the measured basic test currents (31). The position of the rotor 12 can be accurately predicted according to the calculated current difference of the excitation phase currents. If this is represented digitally, the decomposition angle of the rotor 12 relative to the position angle varies depending on the number of bits used for quantization (32).

In the present embodiment, the current difference is classified into '1', '0', and '-1' according to the magnitude thereof. The classification criteria classify '0' when the current difference is within a predetermined reference range and '1' or '-1' when the current difference is above or below the reference range.

Fig. 4 shows the classification results of the basic test current, current difference and current difference corresponding to the machine angle in the two-pole motor.

As the machine angle changes in units of 30 degrees, it can be seen that the classification result of the current difference with respect to the basic test current changes. In other words, if the classification result is expressed as (U1-V1, V1-W1, W1-U1), it becomes (1, -1, -1 (0)) at 0 degrees and (-1 (0), -1, 1).

At this time, '-1 (0)' means that the classification result can be -1 or 0, and the oblique line on the graph is only a line connecting discrete points '-1', '0' and '1'. will be. Therefore, the classification result in a certain range of 0 to 30 degrees of the machine angle appears as either the classification result for 0 degrees or 30 degrees.

According to the three-phase excitation method, the magnitude of the basic test current shown in FIG. 4 is larger than that of the two-phase excitation method measured under the same conditions. This is because the magnitude of the load on the three-phase excitation method is smaller than that of the two-phase excitation method. That is, since the current flowing from one of the upper transistors Q1 to Q3 is branched out to the two lower transistors Q4 to Q6, the equivalent impedance of the load viewed from the branch point is the parallel connection relationship of the loads connected to each phase terminal. Becomes smaller compared to the two-phase excitation method.

As described above, since the magnitude of the current measured according to the three-phase excitation method is larger than that of the two-phase excitation method, the present invention according to the three-phase excitation method is incorrect for the initial position of the rotor 12 due to the error of the measurement current. Measurement can be prevented.

Referring again to Figure 4, it can be seen that the classification result of the current difference is repeated in units of 180 degrees in accordance with the change in the machine angle. For example, the classification results for 0 degrees, 180 degrees, 30 degrees and 210 degrees coincide.

To distinguish these overlapping mechanical angles, one of the additional test currents classified in Table 1 may be measured and taken as reference. That is, as shown in FIG. 4, it can be seen that at 0 degrees, the additional test current 'V2' has a larger value than the basic test current 'V1', whereas at 180 degrees, 'V1' has a larger value than 'V2'. .

Therefore, the position of the rotor 12 is calculated with two mechanical angles through the classification result of the current difference with respect to the basic test current (33), and one additional test current is selectively measured according to the calculated mechanical angle (34). Finally, the position of the rotor 12 may be calculated 35.

As a result, the present embodiment can calculate the position of the rotor 12 through a total of four switching operations including three basic test currents and one additional test current, thereby reducing the initial driving time of the motor. In addition, the present embodiment can obtain a finer decomposition angle of 30 degrees than the prior art, but of course, when the current difference is classified into several levels, a more accurate decomposition angle can be obtained.

Although some embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that the embodiments may be modified without departing from the spirit or spirit of the invention. . It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

As described above, according to the present invention, it is possible to shorten the initial driving time of the motor and to prevent erroneous measurement of the rotor position due to the error of the measurement current.

Claims (4)

In the initial positioning angle determination method of the three-phase motor, Selectively exciting three phases to detect an excitation phase current; Calculating a current difference between the detected excitation phase currents; Calculating a rotor position of the three-phase motor based on the magnitude of the current difference. The method of claim 1, Classifying the current difference according to magnitude; The calculating of the rotor position, the initial position angle determination method of the three-phase motor, characterized in that based on the result of the classification of the current difference. The method according to claim 1 or 2, In the step of detecting the excitation phase current, the three-phase excitation of the three-phase motor is characterized in that the excitation phase current flows into any one of the phase terminals of the three-phase motor and the remaining phase terminals are excited to flow out the introduced excitation phase current. Initial position angle determination method. The method of claim 3, According to the calculated position of the rotor, selecting any two of the phase terminal of the three-phase motor to excite the three-phase motor so that the excitation current flows in and the excitation current flowing from the other phase terminal flows out Wow; Detecting the leaked excitation phase current; And recalculating the position of the rotor based on the detected magnitude of the excitation phase current.

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