JP2016123264A - Rotational direction detection device and air conditioning system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a rotational direction of a motor by a simple configuration while suppressing erroneous determination due to influence of noise.SOLUTION: In a rotational direction detection device (4), a detection unit (41) detects whether or not inter-line induced voltages (Yun, Vvn) coincide with each other. A filter unit (42) passes only a component belonging to a predetermined frequency band at least in one of the inter-line induced voltages (Vun, Vvn) in the vicinity of mutual coincidence of the inter-line induced voltages (Vun, Vvn). A determination unit (44) determines a rotational direction of a motor (2) on the basis of a filter value outputted from the filter unit (42).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for detecting a rotation direction of an electric motor in an electric motor control device.

  Patent Document 1 discloses a configuration including a rotational position detection device in an electric motor control device that controls an electric motor having a permanent magnet. And in the 3rd-5th embodiment, the structure provided with the rotation direction specific | specification part which specifies the rotation direction of an electric motor in addition to the rotation position detection apparatus is disclosed.

JP 2014-45648 A

  In the third embodiment of Patent Document 1, the rotational direction specifying unit receives from the detection unit that the two-phase line-to-line induced voltages based on the minimum phase or the maximum phase coincide with each other. And the rotation direction of an electric motor is pinpointed using the voltage value of the line induced voltage when the line induced voltage of two phases corresponds mutually. However, in this configuration, there is a possibility of erroneous determination if the induced voltage fluctuates due to noise, for example.

  Moreover, in 1st Embodiment of patent document 1, a filter is provided and the noise of a line induced voltage is suppressed. However, in this configuration, if the filter cutoff frequency is lowered, the upper limit of the rotational speed of the motor that can detect the rotational direction is lowered. Therefore, the lower limit of the filter cutoff frequency is determined by the upper limit of the rotational speed that needs to be detected (for example, 5000 rpm). Is limited. For this reason, when the frequency component of the noise is small or close to the frequency component of the fundamental wave of the line induced voltage when rotating at the upper limit of the rotation speed, the noise cannot be sufficiently suppressed. The amplitude of the line induced voltage is proportional to the absolute value of the rotation speed of the motor, whereas the amplitude of noise is not proportional to the absolute value of the rotation speed of the motor. For this reason, for example, when the rotational speed of the electric motor is slow, the influence of noise tends to be relatively large because the amplitude of the induced voltage is small, and the rotational direction of the electric motor may be erroneously determined due to the noise. On the other hand, for example, if the cut-off frequency of the filter is lowered, the frequency component of the line induced voltage is removed when the rotation speed of the motor is high, so that the upper limit of the detectable rotation speed is lowered.

  Moreover, in 5th Embodiment of patent document 1, a rotation direction specific | specification part specifies whether a rotation direction is a normal rotation direction or a reverse rotation direction using the voltage waveform of a line induced voltage. However, in this configuration, when the rotational speed of the electric motor is not known, the normal rotation estimated waveform or the reverse rotation estimated waveform cannot be calculated, and thus the normal rotation similarity or the reverse rotation similarity cannot be calculated while detecting the line induced voltage. When the forward rotation similarity or reverse rotation similarity is calculated while detecting the line induced voltage after detecting the rotation speed of the motor in advance, the rotation direction is specified only for the time required to detect the rotation speed of the motor. Is delayed. In addition, when the rotation speed is changing, the change in the rotation speed cannot be detected correctly, so that the forward rotation similarity or the reverse rotation similarity cannot be calculated correctly even if the rotation speed of the electric motor is detected in advance. For example, when the rotational speed is changing, in order to determine the rotational direction, it is necessary to store the value of the line induced voltage, for example, for one cycle. For this reason, a large-capacity storage device is required, and the amount of calculation required also increases.

  An object of the present invention is to make it possible to detect the rotation direction of an electric motor with a simple configuration regardless of the magnitude of the rotation speed of the electric motor while suppressing erroneous determination due to the influence of noise.

In the first invention,
A field magnet (22) including a permanent magnet, and an armature (21) including windings (21u, 21v, 21w) of three or more phases, the field (22) and the armature (21), Is a device (4) for detecting the direction of rotation of the electric motor (2) that rotates relatively,
Among the phase potentials (Vu, Vv, Vw) output from the armature (21) by the induced electromotive force, one of the minimum phase and the maximum phase is set as a reference potential, and the first phase potential (Vu) A first line induced voltage (Vun) that is a potential difference with respect to the reference potential and a second line that is a potential difference between the second phase potential (Vv) other than the first phase potential (Vu) with respect to the reference potential. A detection unit (41) for detecting whether or not the induced voltage (Vvn) between the two coincides;
In response to the detection result of the detection unit (41), the first line induced voltage is in the vicinity when the first line induced voltage (Vun) and the second line induced voltage (Vvn) coincide with each other. (Vun) and the second line induced voltage (Vvn), at least one of the filtering unit (42) that allows only a component belonging to a predetermined frequency band to pass through,
A determination unit (44) for determining a rotation direction of the electric motor (2) based on a filtered value that is an output of the filtering unit (42);
The filtering unit (42) outputs the filtered value in each of a plurality of types of frequency bands,
The determination unit (44) selects a filtered value whose upper limit of the frequency band is relatively low as the rotational speed of the electric motor (2) is relatively slow, and the selected filtered value is selected as the rotational value of the electric motor (2). Used for direction determination.

  According to this configuration, in the rotation direction detection device (4), the detection unit (41) detects whether the first line induced voltage (Vun) and the second line induced voltage (Vvn) coincide with each other. Is done. The filtering unit (42) receives the detection result of the detecting unit (41), and in the vicinity where the first line induced voltage (Vun) and the second line induced voltage (Vvn) coincide with each other, the first line For at least one of the line induced voltage (Vun) and the second line induced voltage (Vvn), only components belonging to a predetermined frequency band are passed. The determination unit (44) determines the rotation direction of the electric motor (2) based on the filtered value output by the filtering unit (42). As a result, the rotation direction of the electric motor (2) is determined by the filtered value in which the noise of the line induced voltage is reduced in the vicinity when the line induced voltages coincide with each other. It is possible to avoid the erroneous determination caused. Moreover, in order to determine the direction of rotation, it is only necessary to filter the line induced voltage and store a filtered value with a smaller amount of data than the value of the line induced voltage for one period. No device is required and the amount of computation is small. Furthermore, when the filtered values in each of the plurality of types of frequency bands are output and the rotational speed of the electric motor (2) is relatively slow, the filtering value with the lower upper limit of the frequency band is selected, and conversely the electric motor (2 ) Is relatively fast, a filtered value with a relatively high upper frequency band is selected. In other words, the noise component is sufficiently extracted when the rotational speed of the motor (2) is relatively slow and the effect of noise is relatively large while sufficiently extracting the component of the line induced voltage regardless of the rotational speed of the motor (2). Is sufficiently removed, and the component of the line induced voltage can be prevented from being removed when the rotation speed of the electric motor (2) is relatively high and the influence of noise is relatively small. Since the filtered value selected in this way is used for the determination of the rotation direction, the rotation direction can be reliably determined regardless of the rotation speed of the electric motor (2). In addition, since it is not necessary to detect the rotational speed of the electric motor (2) in advance, there is no time delay for detecting the rotational speed, and at the same time, the rotational direction of the electric motor (2) can be changed even if the rotational speed changes. It can be judged correctly.

In the second invention, in the first invention,
The filtering unit (42) outputs an integrated value integrated over an integrated time determined corresponding to each frequency band as the filtered value,
The integration time is relatively shorter as the upper limit of the frequency band is relatively higher.

  According to this configuration, the filtering unit (42) integrates at least one of the first inter-line induced voltage (Vun) and the second inter-line induced voltage (Vvn) over an integration time corresponding to the frequency band, and provides a filtered value. The integrated value is output. The determination unit (44) determines the rotation direction of the electric motor (2) based on the integrated value output by the filtering unit (42). As a result, the rotational direction of the electric motor (2) is determined by the integrated value output by integrating the line induced voltages in the vicinity when the line induced voltages coincide with each other. A misjudgment due to fluctuations can be avoided. Moreover, since it is only necessary to perform integration calculation and temporarily store the integration value for determination of the rotation direction, a large-capacity storage device is not required and the calculation amount is small. Further, when the upper limit of the frequency band is relatively high, the integrated value is output over a relatively short integration time, and when the upper limit of the frequency band is relatively low, the integrated value is output over a relatively long integration time. . Since the output integrated value is used for the determination of the rotation direction, erroneous determination of the rotation direction can be avoided reliably.

In the third invention, the air conditioner includes the rotation direction detecting device (4) according to the first or second invention, the electric motor (2), and a fan driven by the electric motor (2).

  According to the present invention, the direction of rotation of the electric motor (2) is determined by the filtered value in which the noise of the line induced voltage is reduced in the vicinity when the line induced voltages coincide with each other. A misjudgment due to fluctuations can be avoided. In addition, the filtered values in each of a plurality of types of frequency bands are output, and the filtered value selected corresponding to the rotational speed of the electric motor (2) is used for determining the rotational direction. 2) The direction of rotation can be determined correctly. In addition, since it is not necessary to detect the rotational speed of the electric motor (2) in advance, there is no time delay for detecting the rotational speed, and at the same time, the rotational direction of the electric motor (2) can be changed even if the rotational speed changes. It can be judged correctly.

Schematic configuration of electric motor control device provided with rotation direction detection device according to embodiment Graph showing examples of changes in induced voltage in forward direction Graph showing examples of changes in line-to-line induced voltage in the forward direction Graph showing examples of changes in line-to-line induced voltage in the reverse direction The graph which shows the example of change of the difference of the integrated value of the line induced voltage in the normal rotation direction A graph showing an example of a change in the difference between integrated values of the line induced voltage in the reverse direction Graph showing an example of changes in the difference between integrated values of line induced voltage during forward rotation and reverse rotation Specific configuration example of the filtering unit in the rotation direction detection device of the first embodiment Timing chart showing an operation example of the filtering unit of the first embodiment The flowchart which shows the operation example of the filter part of Embodiment 1. 6 is a flowchart illustrating an operation example of a determination unit in the rotation direction detection device according to the first embodiment. Other specific configuration examples of the filtering unit in the rotation direction detection device Specific configuration example of the filtering unit in the rotation direction detection device of the second embodiment 9 is a flowchart illustrating an operation example of a determination unit in the rotation direction detection device according to the second embodiment.

Embodiment 1
The first embodiment will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a schematic configuration of an electric motor control device including a rotation direction detection device according to an embodiment. The motor control device shown in FIG. 1 includes a power conversion unit (1), a motor (2), a voltage detection unit (3) for detecting a line induced voltage, and a motor (2) from the detected line induced voltage. And a rotation direction detection device (4) for detecting the rotation direction of.

  The power conversion unit (1) has an input side connected to DC lines (L1, L2) and an output side connected to AC lines (Pu, Pv, Pw). A DC voltage is applied between the DC lines (L1, L2) by, for example, a converter (not shown). The converter converts, for example, an AC voltage from a commercial AC power source into a DC voltage, and applies this between DC lines (L1, L2). As such a converter, for example, a diode rectifier circuit formed by a diode bridge can be employed. A capacitor (C) provided between the DC lines (L1, L2) smoothes the DC voltage. The power converter (1) converts the DC voltage applied to the DC lines (L1, L2) into a three-phase AC voltage and applies it to the AC lines (Pu, Pv, Pw).

  In the illustration of FIG. 1, the power conversion unit (1) is a voltage source inverter. More specifically, the power converter (1) includes switching elements (Sup, Svp, Swp, Sun, Svn, Swn) and diodes (Dup, Dvp, Dwp, Dun, Dvn, Dwn). The switching elements (Sxp, Sxn (x represents u, v, w, the same applies hereinafter)) are, for example, insulated gate bipolar transistors and the like, and are connected in series between the DC lines (L1, L2). The diodes (Dxp, Dxn) are connected in antiparallel with the switching elements (Sxp, Sxn), respectively, and have an anode on the DC line (L2) side. The AC line (Px) is connected to the midpoint between the switching elements (Sxp, Sxn).

  These switching elements (Sxp, Sxn) are controlled so as to conduct exclusively. When both switching elements (Sxp, Sxn) are conducting, the DC lines (L1, L2) are short-circuited via the switching elements (Sxp, Sxn), which causes a large current to flow through the switching elements (Sxp, Sxn). It is. And by appropriately controlling these switching elements (Sxp, Sxn), the power conversion unit (1) can convert a DC voltage into an AC voltage.

  Note that the diodes (Dxp, Dxn) are not essential if the switching elements (Sxp, Sxn) are capable of reverse conduction (conduction from the DC line (L2) to the DC line (L1)). For example, when a MOS field effect transistor having a parasitic diode is employed as the switching element (Sxp, Sxn), the diode (Dxp, Dxn) is unnecessary.

  The electric motor (2) includes an armature (21) and a field (22). The armature (21) has three-phase armature windings (21u, 21v, 21w), and the armature windings (21u, 21v, 21w) are connected to AC lines (Pu, Pv, Pw), respectively. . A three-phase AC voltage from the power converter (1) is applied to the armature windings (21u, 21v, 21w). As a result, an alternating current flows through the armature winding (21u, 21v, 21w), and a rotating magnetic field is applied to the field magnet (22). The field magnet (22) has a permanent magnet and supplies a field magnetic flux to the armature (21). The field (22) receives a rotating magnetic field from the armature (21) and rotates relative to the armature (21).

  In the illustration of FIG. 1, since the electric motor (2) having three-phase armature windings (21u, 21v, 21w) is assumed, the power conversion unit (1) outputs a three-phase AC voltage. However, this is not necessarily the case. An N-phase motor larger than three phases may be employed, and an N-phase power converter may be employed as well. In the illustration of FIG. 1, the armature windings (21u, 21v, 21w) are connected to each other by so-called star connection, but may be connected to each other by so-called triangular connection.

  The electric motor (2) is used for a blower such as a fan or a blower, for example. For example, the electric motor (2) may drive a fan or a compressor mounted on a heat pump (such as an air conditioner or a hot water supply device). For example, when driving a fan mounted on an outdoor unit placed outdoors, the flow of outdoor air (1) even when the power converter (1) does not output AC voltage to the motor (2) ( The motor (2) is rotated by the wind. Therefore, when starting such an electric motor (2), it is necessary to detect the relative rotation direction of the armature (21) and the field (22) (the rotation direction of the electric motor (2)). Of course, even if the compressor or the fan is not rotated by an external force, the compressor or the fan rotates due to inertia. Therefore, even when the compressor or the fan is rotated again, it is necessary to detect the rotation direction.

  When the electric motor (2) rotates, the magnetic flux passing through the armature winding (21u, 21v, 21w) changes based on the rotation. Along with this, an induced electromotive force based on the rotation is generated in each of the armature windings (21u, 21v, 21w), and the electric motor (2) has a phase potential (hereinafter, referred to as “phase potential”) on the AC line (Pu, Pv, Pw). (Also called induced voltage) (Vu, Vv, Vw).

  FIG. 2 shows an example of changes in the induced voltage (Vu, Vv, Vw). As illustrated in FIG. 2, the induced voltage (Vu, Vv, Vw) takes a substantially sinusoidal shape that varies depending on the rotational position (electrical angle) of the electric motor (2). In addition, in FIG. 2, the induced voltage (Vu, Vv, Vw) when an electric motor (2) rotates to a normal rotation direction is illustrated. In the forward rotation direction, the induced voltage (Vv, Vw) advances 120 degrees with respect to the induced voltage (Vu, Vv). In other words, such a rotation direction is defined as a normal rotation direction.

  The voltage detector (3) detects the line induced voltage (Vun, Vvn). The line-to-line induced voltage (Vun, Vvn) refers to a potential difference between the induced voltage (Vu, Vv) and the reference potential. Here, the induced voltage of the minimum phase among the induced voltages (Vu, Vv, Vw) is adopted as the reference potential of the line induced voltage (Vun, Vvn).

  For example, in the forward rotation direction shown in FIG. 2, the induced voltage (Vu) takes the minimum value in the range where the rotational position is 30 to 150 degrees. Therefore, in this range, the line induced voltage (Vun) is zero. In addition, since the induced voltage (Vv) is the minimum phase induced voltage in the range of the rotational position of 150 to 270 degrees, the line induced voltage (Vun) is the induced voltage (Vu) and the minimum phase induced voltage (Vu) in this range. Vv).

  FIG. 3 shows a change in the line induced voltage when the rotation direction is the forward rotation direction. As shown in FIG. 3, the line-to-line induced voltage (Vun) becomes zero when the rotational position is in the range of 30 to 150 degrees and becomes a potential difference (Vu−Vv) when the rotational position is in the range of 150 to 270 degrees. The potential difference (Vu−Vw) is in the range of 270 to 360 degrees and 0 to 30 degrees. On the other hand, the line-to-line induced voltage (Vvn) becomes zero when the rotational position is in the range of 150 to 270 degrees, and the potential difference (Vv−Vw) becomes rotational when the rotational position is in the range of 270 to 360 degrees and 0 to 30 degrees. The potential difference (Vv-Vu) is in the range of 30 to 150 degrees.

  FIG. 4 shows a change in the induced voltage between the lines when the rotation direction is the reverse direction. In the reverse direction, the induced voltages (Vv, Vw) are delayed by 120 degrees with respect to the induced voltages (Vu, Vv), respectively. Therefore, the line induced voltage (Vun, Vvn) at this time has a waveform as shown in FIG.

  The voltage detector (3) has a path (31, 32) for connecting each of the AC lines (Pu, Pv) to which the induced voltage (Vu, Vv) is applied and the DC line (L2), In the path (31, 32), the voltage between each of the AC lines (Pu, Pv) and the DC line (L2) is detected as a line induced voltage (Vun, Vvn).

  In addition, when the power converter (1) is controlled to output an AC voltage to the AC line (Pu, Pv, Pw), the voltage detector (3) appropriately generates the line-to-line induced voltage (Vun, Vvn). Since it cannot detect, a voltage detection part (3) detects a line induced voltage in the state in which a power converter (1) does not output an alternating voltage. That is, the line induced voltage is detected in a state where all the switching elements (Sxp, Sxn) are controlled to be non-conductive.

  In the example of FIG. 1, the voltage detection unit (3) includes voltage dividing resistors (R11, R12, R21, R22). The voltage dividing resistors (R11, R12) are connected in series in the path (31). The voltage dividing resistors (R21, R22) are connected in series in the path (32).

  In such a voltage detector (3), during the period in which the induced voltage (Vw) is the minimum phase induced voltage, the line induced voltage (Vun) is the path (31), the DC line (L2), and the diode (Dwn ) Between the AC lines (Pu, Pw) via At this time, since a voltage is applied to the diode (Dwn) in the forward direction, the voltage is almost zero. Therefore, the voltage across the voltage dividing resistors (R11, R12) is almost equal to the potential difference between the induced voltage (Vu) and the induced voltage (Vw) of the minimum phase, that is, the line induced voltage (Vun). Similarly, the voltage across the voltage dividing resistors (R21, R22) substantially matches the potential difference between the induced voltage (Vv) and the induced voltage (Vw) of the minimum phase, that is, the line induced voltage (Vvn).

  Also, during the period when the induced voltage (Vv) is the minimum phase induced voltage, the line induced voltage (Vun) is the AC line (Pu, Pv) via the path (31), DC line (L2) and diode (Dvn). Applied between At this time, since a voltage is applied to the diode (Dvn) in the forward direction, the voltage is almost zero. Therefore, at this time, the voltage across the entire voltage dividing resistor (R11, R12) substantially coincides with the line induced voltage (Vun). On the other hand, since the potentials of the DC line (L2) and the AC line (Pv) are substantially equal to each other, the voltage across the voltage dividing resistors (R21, R22) is almost zero. Since the line induced voltage (Vvn) is zero during this period, the voltage across the voltage dividing resistors (R21, R22) substantially matches the line induced voltage (Vvn).

  During the period when the induced voltage (Vu) is the minimum phase induced voltage, the line induced voltage (Vvn) is the path (32), the DC line (L2) and the AC line (Pu, Pv) via the diode (Dun). Applied between. At this time, since a voltage is applied to the diode (Dun) in the forward direction, the voltage is almost zero. Therefore, at this time, the voltage across the voltage dividing resistor (R21, R22) is almost equal to the line induced voltage (Vvn), and the voltage across the voltage dividing resistor (R11, R12) is the line induced voltage (Vun). Almost matches. Therefore, the voltage applied to the voltage dividing resistors (R11, R12) corresponds to the line induced voltage (Vun), and the voltage applied to the voltage dividing resistors (R21, R22) corresponds to the line induced voltage (Vvn). . Therefore, the line induced voltage (Vun, Vvn) can be detected by detecting these voltages.

  In the example of FIG. 1, the voltage detection unit (3) detects the voltage of the voltage dividing resistor (for example, the voltage dividing resistor (R12) on the DC line (L2) side) in the path (31) as the line induced voltage (Vun). The voltage of the voltage dividing resistor (for example, the voltage dividing resistor (R22) on the DC line (L2) side) in the path (32) is detected as the line induced voltage (Vvn). As a result, the line induced voltage (Vun, Vvn) can be detected with a smaller voltage value. The difference between the voltage dividing ratio of the voltage dividing resistors (R11, R12) and the voltage dividing ratio of the voltage dividing resistors (R21, R22) is desirably small. This is because when these differences occur, a difference occurs between the time when the magnitude relationship of the divided resistance voltage changes and the time when the magnitude relationship between the line induced voltages (Vun, Vvn) changes.

  As described above, the voltage detection unit (3) has the paths (31, 32) for connecting the DC line (L2) and each of the AC lines (Pu, Pv). , 32) can be detected as line induced voltage (Vun, Vvn).

  According to such a voltage detector (3), for example, the line induced voltage (Vun, Vvn) can be easily obtained as compared with the following case. That is, the induced voltage (Vu, Vv, Vw) is detected, the induced voltage of the minimum phase is extracted from the detected induced voltage (Vu, Vv, Vw), and the minimum phase is detected from the detected induced voltage (Vu, Vv). Compared with the case where the induced voltage (Vun, Vvn) is calculated by subtracting the induced voltage, the induced voltage (Vun, Vvn) can be easily obtained.

  In addition, when the line induced voltage (Vup, Vvp) based on the maximum phase is adopted, the voltage detector (3) is connected between each of the AC lines (Pu, Pv) and the DC line (L1). What is necessary is just to detect a voltage.

<Rotation direction detector (4)>
The rotation direction detection unit (4) detects the rotation direction (D) of the electric motor (2) using the line induced voltage (Vun, Vvn) detected by the voltage detection unit (3). The rotation direction detection unit (4) includes an analog / digital conversion unit (40a, 40b), a detection unit (41), a filtering unit (42), a rotation speed calculation unit (43), and a determination unit (44). It has. Here, the rotation direction detection unit (4) includes a microcomputer and a storage device. The microcomputer executes each processing step described in the program. The storage device can be composed of one or more of various memories such as RAM (Random-Access-Memory) and various storage devices such as a hard disk device. The storage device stores various information, data, and the like, stores a program executed by the microcomputer, and provides a work area for executing the program. It can be understood that the microcomputer functions as various means corresponding to each processing step described in the program, or can realize that various functions corresponding to each processing step are realized. In addition, various procedures executed by the rotation direction detection unit (4), or various means or various functions to be realized may be realized by hardware.

  The analog / digital converters (40a, 40b) convert the line induced voltage (Vun, Vvn) into a digital signal, respectively.

  The detection unit (41) receives the line induced voltage (Vun, Vvn) converted into a digital signal and detects whether the line induced voltages (Vun, Vvn) coincide with each other. The detection here can be realized, for example, by using a known comparison unit that compares the magnitudes of the line induced voltages (Vun, Vvn). More specifically, when the magnitude relation between the line induced voltages (Vun, Vvn) is switched, it can be determined that the line induced voltages (Vun, Vvn) match each other. For example, in the example of FIGS. 3 and 4, when the rotational position is 150 degrees, the line induced voltage (Vun) exceeds the line induced voltage (Vvn), and the state A (Vun <Vvn) is changed to the state A (Vun). > Vvn). At this time, it is determined that the line induced voltages (Vun, Vvn) coincide with each other. When the rotational position is 330 degrees, the line induced voltage (Vvn) exceeds the line induced voltage (Vun), and the state A (Vun> Vvn) is changed to the state B (Vun <Vvn). . At this time, it is determined that the line induced voltages (Vun, Vvn) coincide with each other.

  The filtering unit (42) integrates the line induced voltage (Vun, Vvn) converted into a digital signal from a predetermined timing for a predetermined integration time, and outputs an integrated value as a filtered value. . Here, when it is notified from the detection unit (41) that the line induced voltages (Vun, Vvn) match each other, the filtering unit (42) starts integration. Also, in the filtering unit (42), a plurality of types of integration times are set, and the integration values for each integration time are output. Here, the plurality of types of integration times have a predetermined relationship with a plurality of types of frequency bands. That is, a relatively long integration time corresponds to a relatively low upper limit of the frequency band, and a relatively short integration time corresponds to a relatively high upper limit of the frequency band. doing.

  The rotation speed calculation unit (43) detects the rotation speed of the electric motor (2) using the output from the detection unit (41). The rotation speed calculation unit (43) detects the absolute value of the rotation speed. That is, the time from when the line induced voltages (Vun, Vvn) coincide with each other until the line induced voltages (Vun, Vvn) coincide with each other corresponds to the electrical angle half cycle of the electric motor (2). . Therefore, the rotation speed calculation unit (43) is notified from the detection unit (41) that the line induced voltages (Vun, Vvn) match each other, and then the detection unit (41) detects the line induced voltage. The time until it is notified that (Vun, Vvn) match each other is measured, and this time is acquired as the electrical angle half cycle of the electric motor (2). Of course, using the output from the detection section (41), the time of one cycle of the electrical angle of the electric motor (2) or the time of two or more cycles may be measured. And the rotational speed calculated | required from the measured time is output to a determination part (44). Alternatively, as data that indirectly represents the rotational speed, the electrical angle half cycle time of the electric motor (2) may be output to the determination unit (44).

  The determination unit (44) obtains the rotation direction of the electric motor (2) using the integrated value of the line induced voltage (Vun, Vvn) output by the filtering unit (42). The determination unit (44) acquires the rotation speed of the electric motor (2) or data representing the rotation speed from the rotation speed calculation unit (43). Then, one of a plurality of integrated values output by the filtering unit (42) is selected from the rotation speed, and the rotation direction of the electric motor (2) is obtained using the selected integrated value.

  Here, the rotation direction determination method in the present embodiment will be described.

  As shown in FIG. 3, in the forward rotation direction, the line induced voltage (Vun, Vvn) at a rotational position of 150 degrees (when the line induced voltage Vun exceeds the line induced voltage Vvn) is a relatively small value (for example, zero). Take. On the other hand, the line induced voltage (Vun, Vvn) at the rotational position 330 degrees (when the line induced voltage Vun is lower than the line induced voltage Vvn) takes a relatively large value (ΔV in FIG. 3). On the other hand, as shown in FIG. 4, in the reverse rotation direction, the line induced voltage (Vun, Vvn) takes a relatively large value (ΔV in FIG. 4) at the rotational position of 150 degrees. On the other hand, at the rotation position of 330 degrees, the line induced voltage (Vun, Vvn) takes a relatively small value (for example, zero).

  Due to such characteristics, the rotational direction of the electric motor (2) can be detected by comparing the line induced voltages (Vun, Vvn) at the rotational positions of 150 degrees and 330 degrees. That is, when the line induced voltage (Vun, Vvn) at the rotational position 150 degrees is smaller than the line induced voltage (Vun, Vvn) at the rotational position 330 degrees, it can be determined as the forward rotation direction. When the line induced voltage (Vun, Vvn) at a degree is greater than the line induced voltage (Vun, Vvn) at the rotational position 330 degrees, it can be determined that the direction is the reverse direction.

  However, in the above determination method, there is a possibility of erroneous determination due to the influence of noise. That is, since the magnitude comparison is performed using the detected value of the line induced voltage at the time when the two-phase line induced voltages at the rotation positions of 150 degrees and 330 degrees coincide with each other, If the detected voltage value fluctuates, an error may occur in the size comparison. As a cause of noise, for example, noise caused by the switching operation of another power conversion unit disposed on or near the same substrate can be cited. For example, when the electric motor (2) is rotating in the forward rotation direction, noise is added to the line induced voltage (Vun, Vvn) at the rotation position 150 degrees, and the line induced voltage (Vun at the rotation position 330 degrees). , Vvn), the reverse direction is erroneously determined. Note that the frequency component of noise caused by the switching operation is generally higher than the frequency component of the line induced voltage (Vun, Vvn).

  Therefore, in the present embodiment, the line induced voltage (Vun, Vvn) is integrated for a predetermined integration time from the time when the line induction voltages (Vun, Vvn) coincide with each other, and the obtained integrated value is used. Then, the rotation direction of the electric motor (2) is determined. The determination unit (44) compares the integrated value after the rotational position of 150 degrees and the integrated value after the rotational position of 330 degrees, and if the integrated value after the rotational position of 150 degrees is smaller, the forward rotation direction is determined. If it is larger, it is determined as the reverse direction. By using the integrated value of the line induced voltage (Vun, Vvn), the influence of noise can be reduced and erroneous determination can be suppressed. In addition, since the integrated value is only calculated and stored, a large-capacity storage device is not required and the calculation amount is small.

  In this determination, it is not necessary to perform integration for both of the line induced voltages (Vun, Vvn), and only one of them may be integrated. Further, integration is performed for both line induced voltages (Vun, Vvn), and the absolute value of the difference between the integrated value after the rotational position of 150 degrees and the integrated value after the rotational position of 330 degrees is larger. The voltage (Vun, Vvn) may be used for determining the rotation direction. That is, as shown in FIGS. 5 and 6, the larger absolute value (in FIG. 5, the integrated value at the rotation position of 150 degrees or more from the integrated value at the rotation position of 330 degrees or more of the line induced voltage (Vvn) is calculated. FIG. 6 shows a value obtained by subtracting the integrated value after the rotational position of 150 degrees from the integrated value of the inter-line induced voltage (Vun) after the rotational position of 330 degrees (in FIG. 6). If the line induced voltage (Vun, Vvn) of the difference (hereinafter also referred to as Vun_diff) is used for the determination of the rotation direction, the accumulated time is 1 of the electrical angle half cycle at both forward rotation and reverse rotation. Even if / 3 is exceeded, the magnitude relationship between the integrated value after 330 degrees in the rotational direction and the integrated value after 150 degrees in the rotational direction does not change, so that erroneous determination of the rotational direction can be avoided more reliably. In addition, as described below, even when the line-induced voltage (Vun, Vvn) with the smaller absolute value is used for the determination of the rotation direction, an erroneous determination of the rotation direction by appropriately setting the integration time Can be avoided.

  When integrating only one of the line induced voltages (Vun, Vvn), it is desirable that the integration time be less than 1/3 of the electrical angle half cycle. In the forward rotation direction shown in FIG. 3, the integrated value of the line induced voltage (Vun) from the rotational position 150 degrees to 210 degrees advanced by 1/3 of the electrical angle half cycle, and the electrical angle half period from the rotational position 330 degrees. The integrated value of the line induced voltage (Vun) up to 30 degrees advanced by 1/3 becomes the same value. For this reason, if the integrated value of the line induced voltage (Vun) whose integration time is 1/3 or more of the electrical angle half cycle is used, the rotational direction is erroneously determined. In the reverse rotation direction shown in FIG. 4, the integrated value of the line induced voltage (Vvn) from the rotational position 150 degrees to 90 degrees delayed by 1/3 of the electrical angle half cycle, and the electrical angle half period from the rotational position 330 degrees. The integrated value of the line induced voltage (Vvn) up to 270 degrees delayed by 1/3 is the same value. For this reason, if the integrated value of the line induced voltage (Vvn) whose integration time is 1/3 or more of the electrical angle half cycle is used, the rotational direction is erroneously determined. By setting the integration time to be less than 1/3 of the electrical angle half cycle, it is possible to detect the rotational direction without erroneous determination using any of the line induced voltages (Vun, Vvn). Here, it is more desirable that the integration time is set to about 1/6 of an electrical angle half cycle. As shown in FIG. 7, the difference (Vun_diff) in the line induced voltage (Vun) during forward rotation takes a maximum value in 1/6 of the electrical angle half cycle, and accordingly, the integration time is set in the vicinity thereof. An erroneous determination of the rotation direction can be prevented more reliably. As shown in the figure, the same applies to the difference (Vvn_diff) in the line induced voltage (Vvn) during the reverse rotation.

  Furthermore, in this embodiment, a plurality of types of integration times are used for the integration calculation of the line induced voltages (Vun, Vvn). Then, according to the rotation speed of the electric motor (2), one of the integrated values at each integrated time is selected, and the selected integrated value is used for the determination of the rotation direction. Thereby, it is possible to select an appropriate integration time in the rotation direction determination according to the rotation speed. In particular, by selecting a relatively long integration time (that is, by selecting an integration value whose frequency band upper limit is relatively low) in low-speed rotation where the influence of noise is large, erroneous determination due to the influence of noise is made. Can be suppressed. In addition, in high speed rotation where the electrical angle half cycle is shortened, by selecting a relatively short integration time (that is, by selecting an integration value having a relatively high frequency band upper limit), the integration time is converted into an electrical angle. The rotation direction can be less than 1/3 of a half cycle, and the rotation direction can be detected without erroneous determination using any of the line induced voltages (Vun, Vvn). For example, 1/3 of the electrical angle half cycle is obtained from the rotation speed of the electric motor (2), and the longest integrated time that is 1/3 or less of the electrical angle half cycle is selected from a plurality of types of integrated time.

<Filter section (42)>
FIG. 8 shows a specific configuration example of the filtering unit (42). The filtering unit (42) in FIG. 8 is configured as an integration unit, and includes a Vun integration counter (51a), a Vvn integration counter (51b), an integration time setting unit (52), and an integration value storage unit (53). And. The Vun integration counter (51a) detects the line induced voltage (Vun) (digital signal) received from the analog / digital converter (40a) and the line induced voltage (Vun, Vvn) from the detector (41). Starting from the notified timing, a plurality of types of integration times set in the integration time setting unit (52) are integrated. The Vvn integration counter (51b) detects the line induced voltage (Vvn) (digital signal) received from the analog / digital converter (40b) and the line induced voltage (Vun, Vvn) from the detector (41). Starting from the notified timing, a plurality of types of integration times set in the integration time setting unit (52) are integrated. The integrated values output by the Vun integration counter (51a) and the Vvn integration counter (51b) are stored in the integration value storage unit (53). In addition, when integrating only one of the line induced voltages (Vun, Vvn), either the Vun integration counter (51a) or the Vvn integration counter (51b) can be omitted.

  FIG. 9 is a timing chart showing an operation example of the filtering unit (42), and FIG. 10 is a flowchart showing an operation example of the filtering unit (42). Here, it is assumed that three types of high-speed integration time (TS), medium-speed calculation time (TM), and low-speed integration time (TL) are set as a plurality of types of integration time.

When the detection unit (41) detects the coincidence of the line induced voltages (Vun, Vvn) (yes in S11), the Vun integration counter (51a) and the Vvn integration counter (51b) perform integration calculation in the filtering unit (42). Start (S12). When the high-speed integration time (TS) has elapsed, the Vun integration counter (51a) and the Vvn integration counter (51b) use the integration values at that time (A _S and B _{S in} FIG. 9) as the integration values for high speed. Stored in the integrated value storage unit (53) (S13). Next, when the intermediate speed integration time (TM) has elapsed, the Vun integration counter (51a) and the Vvn integration counter (51b) use the integration values at that time (A _M and B _{M in} FIG. 9) for the medium speed. The integrated value is stored in the integrated value storage unit (53) (S14). Further, when the low-speed integration time (TL) has elapsed, the Vun integration counter (51a) and the Vvn integration counter (51b) use the integration values at that time (A _L and B _{L in} FIG. 9) as the integration values for low speed. Stored in the integrated value storage unit (53) (S15). Thereafter, the Vun integration counter (51a) and the Vvn integration counter (51b) stop the integration calculation and reset the integration value. Such an operation is performed each time the detection unit (41) detects the coincidence of the line induced voltages (Vun, Vvn).

  FIG. 11 is a flowchart showing an operation example of the determination unit (44). When determining the rotation direction of the electric motor (2), the determination unit (44) first acquires the rotation speed (or data that indirectly represents the rotation speed) from the rotation speed calculation unit (43) (S21). Then, the rotational speed is compared with the high / medium speed threshold (S22). When the rotational speed is higher than the high / medium speed threshold (Yes in S22), the accumulated value storage unit (53) of the filtering unit (42) is stored. The high-speed integrated value is selected from the stored integrated values and read (S23). On the other hand, when the rotation speed is equal to or lower than the high / medium speed threshold (No in S22), the rotation speed is compared with the medium / low speed threshold (S24). When the rotation speed is higher than the medium / low speed threshold (Yes in S24), the medium speed integrated value is selected and read out from the integrated values stored in the integrated value storage section (53) of the filtering section (42) ( S25). On the other hand, when the rotational speed is equal to or lower than the medium / low speed threshold (No in S24), the low speed integrated value is selected and read out from the integrated values stored in the integrated value storage section (53) of the filtering section (42). (S26).

  Thereafter, the rotation direction of the electric motor (2) is determined by the above-described method using the read integrated value (S27). That is, the integrated value after the rotational position of 150 degrees and the integrated value after the rotational position of 330 degrees are compared in magnitude, and if the integrated value after the rotational position of 150 degrees is smaller, it is determined as the forward rotation direction, and is larger. Is determined to be in the reverse direction. Note that the determination method of the rotation direction is not limited to this. For example, the integrated value after the rotational position 150 degrees or the integrated value after the rotational position 330 degrees may be compared with a predetermined threshold, and the rotational direction may be determined based on the comparison result.

  FIG. 12 shows another specific configuration example of the filtering unit (42). The filtering unit (42) in FIG. 12 includes a Vun storage unit (55a), a Vvn storage unit (55b), an integration calculation unit (56), an integration time setting unit (57), and an integration value storage unit (58). And. The Vun storage unit (55a) stores the line induced voltage (Vun) (digital signal) received from the analog / digital converter (40a) within a predetermined time range, and the line induced voltage (Vun) (Vun) (delayed by a predetermined time) ( Digital signal). The Vvn storage unit (55b) stores the line induced voltage (Vvn) (digital signal) received from the analog / digital converter (40b) within a predetermined time range, and the line induced voltage (Vvn) (Vvn) ( Digital signal). The integration calculation unit (56) has a plurality of types of integration time set in the integration time setting unit (57), starting from the timing when the coincidence of the line induced voltages (Vun, Vvn) is notified from the detection unit (41). The line induced voltage (Vun) stored in the Vun storage unit (55a) and the line induced voltage (Vvn) stored in the Vvn storage unit (55b) are integrated. The integrated value output by the integrated calculation unit (56) is stored in the integrated value storage unit (58). In addition, when performing integration of only one of the line induced voltages (Vun, Vvn), either the Vun storage unit (55a) or the Vvn storage unit (55b) can be omitted. The operation as shown in FIG. 9 can also be executed by the filtering section (42) of FIG.

  As described above, according to the present embodiment, in the rotation direction detection device (4), the detection unit (41) detects whether or not the line induced voltages (Vun, Vvn) coincide with each other. The filtering unit (42) receives the detection result of the detection unit (41), and at least one of the line induced voltages (Vun, Vvn) in the vicinity when the line induced voltages (Vun, Vvn) coincide with each other. Accumulate. The determination unit (44) determines the rotation direction of the electric motor (2) based on the integrated value output by the filtering unit (42). As a result, the rotational direction of the electric motor (2) is determined by the integrated value of the line induced voltage in the vicinity when the line induced voltages coincide with each other. Can be avoided. Moreover, since it is only necessary to perform integration calculation and temporarily store the integration value for determination of the rotation direction, a large-capacity storage device is not required and the calculation amount is small.

  Further, in the present embodiment, integrated values for each of a plurality of types of integrated times (TS, TM, TL) are output, and the integrated values selected from these are used for determining the rotational direction. Can be reliably avoided.

  Furthermore, since the integrated value selected according to the rotation speed of the electric motor (2) is used for determination of the rotation direction, erroneous determination of the rotation direction can be avoided more reliably. Furthermore, when the rotational speed of the electric motor (2) is relatively slow, the determination unit (44) selects an integrated value for a relatively long cumulative time, and when the rotational speed of the electric motor (2) is relatively high Selects an integrated value in a relatively short integration time, so that erroneous determination caused by fluctuations in induced voltage due to noise can be reliably avoided even when the motor (2) is operating at low speed. At the same time, it is possible to reliably determine the direction of rotation of the electric motor (2) regardless of the rotation speed.

  In addition, since it is not necessary to detect the rotational speed of the electric motor (2) in advance, there is no time delay for detecting the rotational speed, and at the same time, the rotational direction of the electric motor (2) can be changed even if the rotational speed changes. It can be judged correctly.

  In the above-described embodiment, the timing at which the line induced voltages (Vun, Vvn) coincide with each other is set as the start point of the integrated time of the line induced voltages (Vun, Vvn). However, the present invention is not limited to this. For example, the integration may be started after a minute time has elapsed from the timing when the line induced voltages (Vun, Vvn) coincide with each other. Alternatively, the integration may be started slightly before the timing at which the line induced voltages (Vun, Vvn) coincide with each other. For example, in the configuration example of FIG. 8, the timing at which the Vun integration counter (51a) and the Vvn integration counter (51b) are notified of the start of integration and the coincidence of the induced voltage (Vun, Vvn) between the lines is detected from the detection unit (41). Can be delayed for a predetermined time. In the configuration of FIG. 12, since the line induced voltage (Vun, Vvn) is stored in the Vun storage unit (55a) and the Vvn storage unit (55b), the start of integration can be set at an arbitrary timing. . Further, the start of integration may be set at an arbitrary timing according to the integration time. For example, half the integration time from the timing when the line induced voltages (Vun, Vvn) match each other so that the integration time is almost the same before and after the timing when the line induced voltages (Vun, Vvn) match each other. Integration may be started from before.

  That is, in the present invention, the integration time of the line induced voltages (Vun, Vvn) may be set in the vicinity of the point in time where the line induced voltages (Vun, Vvn) coincide with each other. The neighborhood here means, for example, in the present embodiment, in the result of comparing the integrated value in the vicinity of the rotation angle of 150 degrees and the integrated value in the vicinity of the rotation angle of 330 degrees, according to the rotation direction of the electric motor (2), It is sufficient that the difference is within a range.

  In the above-described embodiment, three types of integration time are set. However, the number of types of integration time is not limited to three, and may be two or four or more. Good.

  In the above-described embodiment, the integration time is selected according to the rotation speed of the electric motor (2). However, the present invention is not limited to this. For example, it is good also as a structure which selects integration time from the exterior of a rotation direction detection apparatus (4).

  In the above-described embodiment, the integrated value is used for determining the rotational direction. However, the average value may be calculated by dividing the integrated value by the integrated time, and this average value may be used for determining the rotational direction. Good.

  In the above-described embodiment, the line induced voltage (Vun, Vvn) is used as the two line induced voltages, but the line induced voltage (Vun, Vwn) may be used, An induced voltage (Vvn, Vwn) may be used.

  Moreover, the rotation direction detection device (4) disclosed in the present embodiment can be applied to an air conditioner including an electric motor (2) and a fan driven by the electric motor (2).

Embodiment 2
Next, Embodiment 2 will be described. In the present embodiment, the configuration of the filtering section (42) is different from that in the first embodiment. Below, a different part from Embodiment 1 is mainly demonstrated.

  FIG. 13 shows a specific configuration example of the filtering unit (42). The filtering unit (42) is configured to pass only components belonging to a predetermined frequency band. Here, “only” does not mean that only components that belong to a predetermined frequency band are strictly passed, and includes cases where components in frequency bands other than the predetermined frequency band are also allowed to pass slightly. In addition, it also includes a case where components belonging to a predetermined frequency band are slightly attenuated.

  The filtering unit (42) includes a high-speed Vun low-pass filter (61a), a medium-speed Vun low-pass filter (61b), a low-speed Vun low-pass filter (61c), and a high-speed Vvn low-pass filter. A filter (61d), a medium-speed Vvn low-pass filter (61e), a low-speed Vvn low-pass filter (61f), and a low-pass filter value storage unit (62) are provided.

  The high-frequency, medium-speed, and low-speed Vun low-pass filters (61a to 61c) are set with cut-off frequencies so as to decrease in this order. The high-frequency, medium-speed, and low-speed Vvn low-pass filters (61d to 61f) are set with cutoff frequencies so as to decrease in this order. These cutoff frequencies respectively correspond to the upper limit of the frequency band in the present invention. Further, the predetermined frequency band in this case is a frequency band including components from a direct current component to the cutoff frequency. Each cutoff frequency is preferably set so as to remove a noise component superimposed on the line induced voltage (Vun, Vvn) and sufficiently pass the frequency component of the line induced voltage (Vun, Vvn). . Each cut-off frequency is preferably set so as to sufficiently pass at least the fundamental frequency component of the line induced voltage (Vun, Vvn). High-speed, medium-speed, and low-speed Vun low-pass filters (61a to 61c) are set for each of the line-to-line induced voltages (Vun) (digital signals) received from the analog / digital converter (40a). A component having a frequency component lower than the cut-off frequency is output as a filtered value. High-speed, medium-speed, and low-speed Vvn low-pass filters (61d to 61f) are set for each of the line-to-line induced voltages (Vun) (digital signals) received from the analog / digital converter (40a). A component having a frequency component lower than the cut-off frequency is output as a filtered value. Note that each low-pass filter (61a to 61f) can remove any noise component superimposed on the line induced voltage (Vun, Vvn) and pass the frequency component of the line induced voltage (Vun, Vvn). Instead of this, a band pass filter may be used as a filter for high speed, medium speed, and low speed. In this case, the higher one of the two cutoff frequencies of each bandpass filter corresponds to the upper limit of the frequency band in the present invention.

  The low-pass filter value storage unit (62) is output from each low-pass filter (61a to 61f) at the timing when the detection unit (41) is notified of the coincidence of the line induced voltage (Vun, Vvn). Stores the filtered value. The low-pass filter value storage unit (62) receives each low-pass filter (61a) after a predetermined delay time from the timing when the detection unit (41) is notified of the coincidence of the line induced voltages (Vun, Vvn). ~ 61f) may be stored as the filtered value. In this case, it is preferable to shorten the delay time as the cutoff frequency is higher. For example, the delay time corresponding to the high-speed Vun low-pass filter (61a) is set shorter than the delay time corresponding to the medium-speed Vun low-pass filter (61b), and the medium-speed Vun low-pass filter (61b) ) Is preferably set shorter than the delay time corresponding to the low-speed Vun low-pass filter (61c). For example, the delay time may be set so that the frequency component of the line induced voltage (Vun, Vvn) substantially matches the delay due to the low-pass filter. In the case of outputting a filtered value using only one of the line induced voltages (Vun, Vvn), each Vun low-pass filter (61a to 61c) or each Vvn low-pass filter (61c to 61e). ) Can be omitted.

  FIG. 14 is a flowchart showing an operation example of the determination unit (44). The same reference numerals are given to the same blocks as those in the first embodiment, and the description thereof is omitted. When the rotational speed of the electric motor (2) is higher than the high / medium speed threshold (Yes in S22), the determination unit (44) is stored in the low-pass filter value storage unit (62) of the filtering unit (42). The output values of the high-speed Vun low-pass filter (61a) and the high-speed Vvn low-pass filter (61d) are selected from the filtered values and read (S33). On the other hand, when the rotation speed is equal to or lower than the high / medium speed threshold (No in S22) and the rotation speed is higher than the medium / low speed threshold (Yes in S24), the low-pass filter value storage unit of the filtering unit (42) The output values of the medium-speed Vun low-pass filter (61b) and the medium-speed Vvn low-pass filter (61e) are selected from the filtered values stored in (62) and read (S35). On the other hand, when the rotational speed is lower than the medium / low speed threshold (No in S24), the low speed Vun low pass is selected from the filtered values stored in the low pass filter value storage unit (62) of the filter unit (42). The output values of the filter (61c) and the low-speed Vvn low-pass filter (61f) are selected and read (S36).

  Thereafter, the rotation direction of the electric motor (2) is determined using the read low-pass filter output value (filtered value) (S37). That is, the filtered value at the rotational position 150 degrees and the filtered value at the rotational position 330 degrees are compared in magnitude. If the filtered value after the rotational position 150 degrees is smaller, it is determined as the normal rotation direction, and if it is larger, the reverse rotation is performed. Determine the direction. According to this determination method, for example, even when an offset is superimposed on the line induced voltage (Vun, Vvn), the magnitude relationship between the filtered value at the rotational position 150 degrees and the filtered value at the rotational position 330 degrees is changed. Therefore, it is possible to correctly determine the rotation direction of the electric motor (2).

  As described above, according to the present embodiment, in the rotation direction detection device (4), the detection unit (41) detects whether or not the line induced voltages (Vun, Vvn) coincide with each other. The filtering unit (42) receives the detection result of the detection unit (41), and at least one of the line induced voltages (Vun, Vvn) in the vicinity when the line induced voltages (Vun, Vvn) coincide with each other. The components belonging to a predetermined frequency band are passed. The determination unit (44) determines the rotation direction of the electric motor (2) based on the filtered value output by the filtering unit (42). As a result, the rotation direction of the electric motor (2) is determined by the filtered value in which the noise of the line induced voltage is reduced in the vicinity when the line induced voltages coincide with each other. It is possible to avoid the erroneous determination caused. Moreover, in order to determine the direction of rotation, it is only necessary to filter the line induced voltage and store a filtered value with a smaller amount of data than the value of the line induced voltage for one period. No device is required and the amount of computation is small.

  Furthermore, when the rotational speed of the motor (2) is relatively slow, the determination unit (44) selects a filtered value having a relatively low upper frequency band, and the rotational speed of the motor (2) is relatively low. When it is fast, a filtered value having a relatively high upper frequency band is selected.

  For example, when the rotational speed of the electric motor (2) is relatively slow, the amplitude of the line induced voltage (Vun, Vvn) is relatively small, so the effect of superimposed noise is relatively large, and therefore the high frequency This is because it is necessary to sufficiently remove the noise component. Therefore, when the rotation speed of the motor (2) is relatively slow, pay attention to the fact that the frequency of the line induced voltage (Vun, Vvn) is relatively low, and select a filtered value with a relatively low upper frequency band. Then, the component of the line induced voltage (Vun, Vvn) is extracted. Thereby, when the rotational speed of the electric motor (2) is relatively slow, the component of the line induced voltage (Vun, Vvn) can be reliably extracted. For example, the fundamental frequency of the line induced voltage (Vun, Vvn) is obtained from the rotation speed of the electric motor (2), and the cut-off frequency is the line-to-line from multiple types of cut-off frequencies (the upper limit of the frequency band in the present invention) A filtered value having the lowest cutoff frequency above the fundamental frequency of the induced voltage (Vun, Vvn) may be selected.

  On the other hand, when the rotational speed of the motor (2) is relatively high, the frequency of the line induced voltage (Vun, Vvn) is relatively high, so that the component of the line induced voltage (Vun, Vvn) can be extracted reliably. Therefore, it is necessary to select a filtered value having a relatively high frequency band upper limit. Here, if a filtered value with a relatively high frequency band upper limit is selected, the cutoff frequency will be higher than when a filtered value with a relatively low frequency band upper limit is selected, so it is close to the cutoff frequency. There may be more frequency noise components included in the filtered value. However, when the rotational speed of the electric motor (2) is relatively high, the amplitude of the line induced voltage (Vun, Vvn) is relatively large, so that the influence of noise components included in the filtered value can be ignored. Therefore, when the rotational speed of the electric motor (2) is relatively high, the component of the line induced voltage (Vun, Vvn) can be reliably extracted.

  As described above, the direction of rotation of the electric motor (2) can be reliably determined regardless of the rotational speed of the electric motor (2). At the same time, even when the electric motor (2) is operating at a low speed, it is possible to reliably avoid erroneous determination due to fluctuations in the induced voltage due to noise.

  In addition, since it is not necessary to detect the rotational speed of the electric motor (2) in advance, there is no time delay for detecting the rotational speed, and at the same time, the rotational direction of the electric motor (2) can be changed even if the rotational speed changes. It can be judged correctly.

  In the present invention, the timing for outputting the filtered value of the line induced voltage (Vun, Vvn) may be set in the vicinity of the point in time where the line induced voltages (Vun, Vvn) coincide with each other. For example, in the present embodiment, the vicinity here refers to the result of comparing the filtered value near the rotation angle of 150 degrees and the filtered value near the rotation angle of 330 degrees, depending on the rotation direction of the electric motor (2), It is sufficient that the difference is within a range.

  In the above-described embodiment, three types of frequency bands are set. However, the number of types of frequency bands is not limited to three, and may be two or four or more. Good.

  In the above-described embodiment, the frequency band is selected according to the rotation speed of the electric motor (2). However, the present invention is not limited to this. For example, the frequency band may be selected from the outside of the rotation direction detection device (4).

  In the above-described embodiment, the line induced voltage (Vun, Vvn) is used as the two line induced voltages, but the line induced voltage (Vun, Vwn) may be used, An induced voltage (Vvn, Vwn) may be used.

  Moreover, the rotation direction detection device (4) disclosed in the present embodiment can be applied to an air conditioner including an electric motor (2) and a fan driven by the electric motor (2).

  INDUSTRIAL APPLICABILITY The present invention is useful for detecting the rotation direction of an electric motor regardless of the magnitude of the rotation speed of the electric motor with a simple configuration without being affected by noise.

2 Motor 4 Rotation direction detection device 21 Armature 22 Field 41 Detection unit 42 Filter unit 43 Rotational speed calculation unit 44 Determination unit

Claims (3)

A field magnet (22) including a permanent magnet, and an armature (21) including windings (21u, 21v, 21w) of three or more phases, the field (22) and the armature (21), Is a device (4) for detecting the direction of rotation of the electric motor (2) that rotates relatively,
Among the phase potentials (Vu, Vv, Vw) output from the armature (21) by the induced electromotive force, one of the minimum phase and the maximum phase is set as a reference potential, and the first phase potential (Vu) A first line induced voltage (Vun) that is a potential difference with respect to the reference potential and a second line that is a potential difference between the second phase potential (Vv) other than the first phase potential (Vu) with respect to the reference potential. A detection unit (41) for detecting whether or not the induced voltage (Vvn) between the two coincides;
In response to the detection result of the detection unit (41), the first line induced voltage is in the vicinity when the first line induced voltage (Vun) and the second line induced voltage (Vvn) coincide with each other. (Vun) and the second line induced voltage (Vvn), at least one of the filtering unit (42) that allows only a component belonging to a predetermined frequency band to pass through,
A determination unit (44) for determining a rotation direction of the electric motor based on a filtered value that is an output of the filtering unit (42);
The filtering unit (42) outputs the filtered value in each of a plurality of types of frequency bands,
The determination unit (44) selects a filtered value whose upper limit of the frequency band is relatively low as the rotational speed of the electric motor (2) is relatively slow, and the selected filtered value is selected as the rotational value of the electric motor (2). A rotation direction detecting device used for determining a direction. In claim 1,
The filtering unit (42) outputs an integrated value integrated over an integrated time determined corresponding to each frequency band as the filtered value,
The rotation direction detection device according to claim 1, wherein the integration time is relatively shorter as the upper limit of the frequency band is relatively higher. The rotation direction detection device (4) according to claim 1 or 2,
The electric motor (2);
An air conditioner comprising a fan driven by the electric motor (2).

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