JP6288121B2 - Rotation direction identification device - Google Patents

Description

  The present invention relates to a rotation direction specifying device.

  Patent Document 1 describes a technique for specifying the rotation direction of an electric motor. In this patent document 1, the rotation direction is specified using the induced voltage generated in the electric motor along with the rotation. Specifically, the induced voltage of the minimum phase or the maximum phase is set as a reference potential, and a line induced voltage that is a potential difference between the reference potential and the induced voltage is used. The magnitude relationship between the first-phase line-induced voltage and the second-phase line-induced voltage is periodically switched. In Patent Document 1, for example, the sign of the deviation between the value of the first-phase line-induced voltage when the magnitude relationship is switched and the value of the first-phase line-induced voltage when the magnitude relationship is switched next is positive or negative. The rotation direction is specified according to the above.

JP 2014-045648 A

  Actually, it is not always possible to acquire the line induced voltage at the timing when the magnitude relationship is switched. That is, the line induced voltage can be acquired at a second timing different from the first timing at which the magnitude relationship is switched. The electrical angle corresponding to the period (deviation) between the first timing and the second timing is larger as the rotational speed is higher. Therefore, the higher the rotational speed, the more error occurs in the acquired line induced voltage. If the sign of the deviation is reversed by this error, the direction of rotation is specified incorrectly.

  Therefore, the present invention proposes to provide a rotation direction specifying device capable of specifying a rotation direction with improved tolerance.

  A first aspect of the rotational direction specifying device according to the present invention is a device for specifying the rotational direction of a synchronous motor (2) having a field (22), wherein the synchronous motor is driven by an induced electromotive force of the synchronous motor. Among the phase potentials (Vu, Vv, Vw) to be output, when any one of the minimum phase and the maximum phase is set as a reference potential, the first line is a potential difference between the first phase potential and the reference potential. An induced voltage (Vun) and a second line induced voltage (Vvn) that is a potential difference between the second phase potential other than the first phase potential and the reference potential are detected as a set for each detection period. A line-to-line induced voltage detector (3) and a first deviation (ΔVun) obtained by subtracting the second value (Vun2) of the first line-induced voltage from the first value (Vun1) of the first line-induced voltage. ) And a second deviation (ΔVvn) obtained by subtracting the second value (Vvn2) of the second line induced voltage from the first value (Vvn1) of the second line induced voltage. A rotation direction specifying unit (4) for specifying a rotation direction based on the sign of the deviation having a larger absolute value, wherein the rotation direction specifying unit includes the first line induced voltage and the second line induced voltage. The magnitude relationship with the voltage is determined, and the first value (Vun1) of the first line induced voltage and the first value (Vvn1) of the second line induced voltage are the determination results of the magnitude relationship. Are detected as the set in a first predetermined period including a first time point at which the first and second lines are switched, and the second value (Vun2) of the first inter-line induced voltage and the second value (Vvn2) of the second inter-line induced voltage. Is detected as the set in a second predetermined period including a second time point where the determination result of the magnitude relationship is switched unlike the first time point, and in a period between the first time point and the second time point, The determination result of the magnitude relationship is maintained.

  A second aspect of the rotational direction identification device according to the present invention is the rotational direction identification device according to the first aspect, wherein the rotational direction identification unit (4) includes the absolute value of the first deviation and the second value. When the absolute values of the deviations are equal to each other and the polarity of the first deviation is different from the polarity of the second deviation, the rotation direction is not specified.

  A third aspect of the rotational direction specifying device according to the present invention is the rotational direction specifying device according to the first or second aspect, wherein the first inter-line induced voltage (Vun) and the second inter-line induced voltage. A filter (6) for filtering (Vvn) is further provided, and the deviation is obtained based on the first line induced voltage and the second line induced voltage after being filtered.

  According to the first aspect of the rotation direction specifying device according to the present invention, the tolerance can be improved and the rotation direction can be specified appropriately.

  According to the second aspect of the rotation direction specifying device according to the present invention, erroneous detection can be avoided.

  According to the 3rd aspect of the rotation direction specific apparatus concerning this invention, the specific precision of a rotation direction can be improved.

It is a figure which shows an example of a notional structure of an electric motor control apparatus. It is a figure which shows a typical example of the induced voltage in a normal rotation direction. It is a figure which shows a typical example of the line induced voltage in a normal rotation direction. It is a figure which shows a typical example of the line induced voltage in a reverse rotation direction. It is a figure which shows an example of a notional structure of an electric motor control apparatus. It is a figure which shows a typical example of the deviation in a normal rotation direction. It is a figure which shows a typical example of the deviation in a reverse rotation direction. It is a flowchart which shows an example of operation | movement of a rotation direction specific apparatus. It is a figure which shows an example of a notional structure of an electric motor control apparatus. It is a figure which shows an example of an induced voltage between lines schematically. It is a figure which shows a typical example of the deviation in a normal rotation direction. It is a figure which shows a typical example of the deviation in a reverse rotation direction.

First embodiment.
As shown in FIG. 1, the electric motor drive device includes a power conversion unit 1 and a rotation direction specifying device 5.

  Power conversion unit 1 is connected to DC lines L1 and L2 on its input side, and connected to AC lines Pu, Pv and Pw on its output side. A DC voltage is applied between the DC lines L1 and L2. In the illustration of FIG. 1, a capacitor C1 is provided between the DC lines L1 and L2 to smooth the DC voltage. The power conversion unit 1 is an inverter, for example, which converts the DC voltage into an AC voltage and applies it to the AC lines Pu, Pv, and Pw.

  An electric motor 2 is connected to the AC lines Pu, Pv, Pw. The electric motor 2 is a synchronous motor including an armature 21 and a field 22. The armature 21 has three-phase armature windings 21u, 21v, and 21w, and the armature windings 21u, 21v, and 21w are connected to AC lines Pu, Pv, and Pw. The three-phase AC voltage from the power converter 1 is applied to the armature windings 21u, 21v, and 21w. As a result, an alternating current flows through the armature windings 21 u, 21 v, 21 w, and a rotating magnetic field is applied to the field magnet 22. The field magnet 22 has a permanent magnet, for example, 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, and 21w is assumed, the power conversion unit 1 outputs a three-phase AC voltage. However, the present embodiment is not necessarily limited to this. An N-phase motor 2 larger than the three-phase may be employed, and the N-phase power conversion unit 1 may be similarly employed. In the example of FIG. 1, the armature windings 21u, 21v, and 21w are connected to each other by so-called star connection, but may be connected to each other by so-called triangular connection.

  In such an electric motor drive device, when the electric motor 2 rotates in a state in which the power converter 1 does not output an AC voltage to the electric motor 2, the magnetic flux passing through the armature windings 21u, 21v, 21w is in the rotation. Change based on. Accordingly, an induced electromotive force based on the rotation is generated in each of the armature windings 21u, 21v, and 21w, and the electric motor 2 has a phase potential (hereinafter also referred to as an induced voltage) Vu in each of the AC lines Pu, Pv, and Pw. , Vv, Vw are output (see also FIG. 2).

  Such an electric motor 2 may be used for a blower such as a fan or a blower. Further, for example, the electric motor 2 may drive a fan or a compressor mounted on a heat pump (air conditioner, hot water supply device, etc.). For example, when the fan is mounted on an outdoor unit arranged outdoors and the fan is driven, even if the power conversion unit 1 does not output an AC voltage to the electric motor 2, the fan has an outdoor air flow (wind). Rotate by. Even if the compressor or the fan is not rotated by an external force such as an air flow (wind), the compressor or the fan rotates by inertia.

  The rotation direction identification device 5 includes a line induced voltage detection unit 3 and a rotation direction identification unit 4. The line induced voltage detector 3 detects a plurality of line induced voltages described below as a set for each detection period. In describing the line-to-line induced voltage, first, the induced voltages Vu, Vv, and Vw will be described. The induced voltages Vu, Vv, Vw take a substantially sine wave shape that varies depending on the rotational position (electrical angle) of the electric motor 2 as illustrated in FIG.

  FIG. 2 illustrates the induced voltages Vu, Vv, Vw when the electric motor 2 rotates in the forward direction. In the forward rotation direction, the induced voltages Vv and Vw advance 120 degrees with respect to the induced voltages Vu and Vv, respectively. In other words, such a rotation direction is defined as a normal rotation direction.

  The largest voltage among the induced voltages Vu, Vv, and Vw is called the maximum phase induced voltage, and the smallest voltage is called the minimum phase induced voltage. As shown in FIG. 2, the induced voltage of the maximum phase and the induced voltage of the minimum phase are switched over time. For example, in the forward rotation direction (FIG. 2), the induced voltage Vu takes the minimum value when the rotational position is in the range from 30 degrees to 150 degrees. Therefore, in this range, the induced voltage of the minimum phase is the induced voltage Vu.

  The line-to-line induced voltage is a potential difference of the induced voltage with respect to the reference potential when the induced voltage of the minimum phase is set as the reference potential. For example, the U-phase line-to-line induced voltage Vun is a potential difference between the U-phase induced voltage Vu and the minimum-phase induced voltage Vu. In the range from 30 degrees to 150 degrees, the induced voltage of the minimum phase is the induced voltage Vu, so that the line induced voltage Vun is zero in this range as illustrated in FIG. When the rotational position is in the range from 150 degrees to 270 degrees, the induced voltage Vv is the minimum phase induced voltage. In this range, the line induced voltage Vun is the difference between the induced voltage Vu and the minimum phase induced voltage Vv. The potential difference between them is a waveform as illustrated in FIG. The same applies to other ranges. The line-to-line induced voltage Vvn is a potential difference between the induced voltage Vv and the induced voltage of the minimum phase, and takes the waveform illustrated in FIG.

  When the rotation direction is the reverse direction, the induced voltages Vv and Vw are delayed by 120 degrees with respect to the induced voltages Vu and Vv, respectively. Therefore, the line induced voltages Vun and Vvn at this time take the waveforms illustrated in FIG.

  The line induced voltage detector 3 may include a line induced voltage calculator 31 as shown in FIG. For example, induced voltages Vu, Vv, and Vw are input to the line induced voltage calculator 31. For example, the line induced voltage calculator 31 may convert the input induced voltages Vu, Vv, and Vw from analog data to digital data. Thereafter, the line-to-line induced voltage calculation unit 31 handles induced voltages Vu, Vv, and Vw of digital data. The line-to-line induced voltage calculation unit 31 extracts the induced voltage of the minimum phase from the induced voltages Vu, Vv, and Vw. This can be executed by determining the magnitude of the induced voltages Vu, Vv, Vw. This determination can be made using, for example, a comparator. Then, the inter-line induced voltage calculation unit 31 calculates, for example, the inter-line induced voltages Vun and Vvn and outputs them to the rotation direction specifying unit 4.

  The line induced voltage calculation unit 31 may be realized by software or hardware. FIG. 5 schematically shows an example of the line induced voltage detection unit 3 realized by hardware. FIG. 5 also shows an example of the internal configuration of the power conversion unit 1. For example, the power conversion unit 1 includes switching elements Sup, Svp, Swp, Sun, Svn, Swn and diodes Dup, Dvp, Dwp, Dun, Dvn, Dwn. Switching elements Sxp, Sxn (x represents u, v, w, and so on) are connected in series between the DC lines LH, LL.

  The diodes Dxp and Dxn are connected in parallel to the switching elements Sxp and Sxn, respectively. The forward directions of the diodes Dxp and Dxn are directions from the DC line LL to the DC line LH. An AC line Px is drawn from a connection point connecting the switching elements Sxp and Sxn. These AC lines Pu, Pu, Pw are connected to the electric motor 2.

  The line induced voltage detector 3 detects a voltage applied between the AC line Pu and the DC line LL as a line induced voltage Vun, and detects a voltage applied between the AC line Pv and the DC line LL. Detected as a line-to-line induced voltage Vvn. For example, the line induced voltage detector 3 includes voltage dividing resistors R1 to R4. The voltage dividing resistors R1 and R2 are connected in series between the AC line Pu and the DC line LL, and the voltage dividing resistors R3 and R4 are connected in series between the AC line Pv and the DC line LL. Yes. The voltage at the connection point connecting the voltage dividing resistors R1 and R2 (the voltage across the voltage dividing resistor R2 in FIG. 5) is output as the voltage Vun0 reflecting the line induced voltage Vun, and the voltage dividing resistors R3 and R4 are connected. The voltage at the connection point (the voltage across the voltage dividing resistor R4 in FIG. 5) is output as the voltage Vvn0 reflecting the line induced voltage Vvn.

  In the example of FIG. 5, for example, the voltages Vun0 and Vvn0 are input to the AD conversion units 32 and 33, respectively. The AD conversion units 32 and 33 convert the voltages Vun0 and Vvn0 from analog data to digital data, respectively, and output line induced voltages Vun and Vvn as digital data.

  The rotation direction identification unit 4 identifies the rotation direction of the electric motor 2 based on the line induced voltages Vun and Vvn as digital data obtained from the AD conversion units 32 and 33. First, the basic concept of the identification method will be explained. Referring to FIGS. 3 and 4, the rotational position when the magnitude relationship between line induced voltages Vun and Vvn is switched takes 150 degrees or 330 degrees regardless of the rotational direction. Moreover, the rotational position when the line-induced voltage Vun exceeds the line-induced voltage Vvn takes 150 degrees regardless of the rotation direction, and the rotational position when the line-induced voltage Vun falls below the line-induced voltage Vvn is Take 330 degrees regardless of the direction of rotation.

  On the other hand, the line-to-line induced voltages Vun and Vvn when the rotation position is 150 degrees have different values depending on the rotation direction. As shown in FIG. 3, the line induced voltages Vun and Vvn are zero in the forward rotation direction, and as shown in FIG. 4, the line induced voltages Vun and Vvn take positive values in the reverse direction. Similarly, the line-to-line induced voltages Vun and Vvn when the rotation position is 330 degrees also take different values depending on the rotation direction. In the forward direction, the line induced voltages Vun and Vvn take positive values, and in the reverse direction, the line induced voltages Vun and Vvn are zero.

  Therefore, the rotation direction can be specified based on this difference. For example, the deviation between the line induced voltage Vun when the rotational position is 150 degrees and the line induced voltage Vun when the rotational position is 330 degrees is calculated, and the rotational direction is determined according to the sign of the deviation. Can be specified. Specifically, when the first deviation obtained by subtracting the line induced voltage Vun when the rotational position is 150 degrees from the line induced voltage Vun when the rotational position is 330 degrees is positive, the rotation is performed. The direction can be specified as the forward direction. When the first deviation is negative, the rotation direction can be specified as the reverse rotation direction.

  Similarly, a line induced voltage Vvn may be used. For example, when the second deviation obtained by subtracting the line induced voltage Vvn when the rotational position is 150 degrees from the line induced voltage Vvn when the rotational position is 330 degrees is positive, the rotational direction is rotated forward. It can be identified as a direction. When the second deviation is negative, the rotation direction can be specified as the reverse rotation direction.

<Error>
Actually, however, an error occurs with respect to the timing of acquiring the line induced voltages Vun and Vvn. For example, this error occurs due to the time required for AD conversion. As the error, for example, the line induced voltage Vun is detected at a timing delayed from the timing at which the rotational position becomes 330 degrees. In the illustration of FIG. 3, this line induced voltage Vun is indicated by the symbol Vun1. Similarly, the line induced voltage Vun is detected at a timing delayed from the timing at which the rotational position becomes 150 degrees, for example. In the illustration of FIG. 3, this line induced voltage Vun is indicated by the symbol Vun2. And the error which arises in the line induced voltage Vun becomes large, so that the deviation | shift amount of this timing is large. The same applies to the line-to-line induced voltage Vvn.

  Also, the higher the rotational speed, the faster the rotational position changes. Therefore, the rotational position when detecting the line induced voltage Vun is further away from the desired value (150 degrees, 330 degrees) as the rotational speed is higher. Therefore, the higher the rotational speed, the greater the error that occurs in the line induced voltage Vun. The same applies to the line-to-line induced voltage Vvn.

  Next, it is examined how much the rotational direction is erroneously specified when an error in the rotational position occurs. As described above, since the switching of the magnitude relationship between the line induced voltages Vun and Vvn occurs every 180 degrees, this phase difference is desirably 180 degrees. Therefore, an error is introduced while assuming that the phase difference is 180 degrees. Here, the phase difference Δθ between the rotational position when the line induced voltage Vun is detected and a desired value (150 degrees, 330 degrees) is introduced as an error for the rotational position. The deviation ΔVun between the value Vun1 and the value Vun2 and the deviation ΔVvn between the value Vvn1 and the value Vvn2 are expressed by the following equations.

ΔVun = Vun (330 degrees + Δθ) −Vun (150 degrees + Δθ) (1)
ΔVvn = Vvn (330 degrees + Δθ) −Vvn (150 degrees + Δθ) (2)
Vun (α) represents the line induced voltage Vun when the rotational position is α, and Vvn (α) represents the line induced voltage Vvn when the rotational position is α. Therefore, Vun (330 degrees + Δθ) and Vun (150 degrees + Δθ) indicate the values Vun1 and Vun2, respectively, and Vvn (330 degrees + Δθ) and Vvn (150 degrees + Δθ) indicate the values Vvn1 and Vvn2, respectively.

  Referring to FIG. 3, for example, when phase difference Δθ is in the range of zero to 60 degrees, value Vun2 increases while value Vun1 decreases as phase difference Δθ increases. Therefore, in this range, the deviation ΔVun decreases as the phase difference Δθ increases. 6 and 7 schematically show an example of changes in the deviations ΔVun and Vvn with respect to the phase difference Δθ. In FIG. 6, the rotation direction is the forward rotation direction, and in FIG. 7, the rotation direction is the reverse rotation direction. Hereinafter, first, the deviation ΔVun will be described.

  As shown in FIG. 6, when the phase difference Δθ is in a range from −150 degrees to 30 degrees, the deviation ΔVun is positive. On the other hand, as shown in FIG. 7, when the phase difference Δθ is in the range from −30 degrees to 150 degrees, the deviation ΔVun is negative. Therefore, when the phase difference Δθ is in the range from −30 degrees to 30 degrees, the deviation ΔVun is positive during forward rotation and negative during reverse rotation. That is, if the line induced voltage Vun is detected with a phase difference Δθ (error) within a range from −30 degrees to 30 degrees, even if the deviation ΔVun is calculated based on the line induced voltage Vun, the deviation ΔVun is calculated based on the deviation ΔVun. To correctly identify the direction of rotation.

  On the other hand, for example, when the phase difference Δθ is within a range from 30 degrees to 150 degrees, the deviation ΔVun becomes positive both during forward rotation and during reverse rotation. That is, the deviation ΔVun is always positive regardless of the rotation direction. Therefore, if the line induced voltage Vun is detected with a phase difference Δθ (error) within a range from 30 degrees to 150 degrees, the rotation direction cannot be detected correctly. Similarly, if the polarity of the deviation ΔVun in the other range and the rotation direction are considered, it can be seen that the rotation direction cannot be detected correctly in the other range. The same applies to the deviation ΔVvn.

  As described above, in the basic concept, it can be seen that the allowable phase difference Δθ (error) is in the range from −30 degrees to 30 degrees.

<Specification of rotation method>
Therefore, in the present embodiment, the rotation direction specifying unit 4 determines the magnitude relationship between the line induced voltages Vun and Vvn. Then, from the value Vun1 of the line induced voltage Vun in the first state (for example, 330 degrees) in which the magnitude relation between the line induced voltages Vun and Vvn is switched, the magnitude relation judgment result is first after the first state. A deviation ΔVun obtained by subtracting the value Vun2 of the line induced voltage Vun2 in the second state (for example, 150 degrees) to be switched, and a deviation ΔVvn obtained by subtracting the value Vvn2 in the first state from the value Vvn1 in the first state of the line induced voltage Vvn. The direction of rotation is specified based on the sign of the deviation having the larger absolute value. That is, when the absolute value of the deviation ΔVun is larger than the absolute value of the deviation ΔVvn, the rotational direction is specified according to the sign of the deviation ΔVun, and when the absolute value of the deviation ΔVun is smaller than the absolute value of the deviation ΔVvn, The direction of rotation is specified according to positive and negative.

  Referring to FIG. 6, for example, when the phase difference Δθ is in a range from zero degrees to 60 degrees during forward rotation, the absolute value of deviation ΔVvn is larger than the absolute value of deviation ΔVun. Therefore, at this time, the rotation direction is specified based on the deviation ΔVvn. At this time, since the deviation ΔVvn becomes positive during normal rotation, the rotation direction can be correctly specified. Referring to FIG. 7, at the time of reverse rotation, when the phase difference Δθ is in the range from zero degrees to 60 degrees, the absolute value of the deviation ΔVun is larger than the absolute value of the deviation ΔVvn. Therefore, at this time, the rotation direction is specified based on the deviation ΔVun. At this time, since the deviation ΔVun is negative, the rotation direction can be correctly specified.

  Referring to FIG. 6, for example, when the phase difference Δθ is in a range from −60 degrees to zero degrees during forward rotation, the absolute value of the deviation ΔVun is larger than the absolute value of the deviation ΔVvn. Therefore, at this time, the rotation direction is specified using the deviation ΔVun. At this time, since the deviation ΔVun is positive, the rotation direction can be correctly specified. Referring to FIG. 7, for example, when the phase difference Δθ is within a range from −60 degrees to zero degrees during reverse rotation, the absolute value of deviation ΔVvn is larger than the absolute value of deviation ΔVun. Therefore, at this time, the rotational direction is specified using the deviation ΔVvn. At this time, since the deviation ΔVvn is negative, the rotation direction can be correctly specified.

  As described above, according to this identification method, the rotational direction can be correctly identified even if the line induced voltages Vun and Vvn are detected with the phase difference Δθ (error) in the range from −60 degrees to 60 degrees. Can do. That is, according to the present embodiment, the allowable phase difference Δθ (error) can be expanded to a range from −60 degrees to 60 degrees. In other words, it is possible to improve the upper limit value of the rotation speed that can appropriately specify the rotation direction. Or a detection cycle can be lengthened, for example, a voltage detector with a slow detection speed can be used.

<Example of specific operation>
FIG. 8 is a diagram illustrating an example of the operation of the rotation direction specifying device 5. First, in step ST1, the line induced voltage detector 3 detects values Vun1 and Vvn1 (hereinafter also referred to as line induced voltages Vun1 and Vvn1) of the line induced voltages Vun and Vvn. For example, when it is determined that the rotational position has become 330 degrees, the line induced voltages Vun and Vvn are detected as the line induced voltages Vun1 and Vvn1. A specific example will be described. When it is determined that the line induced voltage Vun is lower than the line induced voltage Vvn, that is, when it is determined that the line induced voltage Vun is smaller than the line induced voltage Vvn from a state where the line induced voltage Vun is greater than the line induced voltage Vvn. The line induced voltages Vun and Vvn are detected as line induced voltages Vun1 and Vvn1, respectively.

  Next, in step ST2, the line induced voltage detector 3 detects values Vun2 and Vvn2 of the line induced voltages Vun and Vvn (hereinafter also referred to as line induced voltages Vun2 and Vvn2). For example, when it is determined that the rotational position has reached 150 degrees, the line induced voltages Vun and Vvn are detected as the line induced voltages Vun2 and Vvn2. A specific example will be described. The line induced voltage detector 3 detects the line induced voltages Vun and Vvn at every predetermined detection cycle. When it is determined that the line induced voltage Vun exceeds the line induced voltage Vvn, that is, when it is determined that the line induced voltage Vun is larger than the line induced voltage Vvn from a state where the line induced voltage Vun is smaller than the line induced voltage Vvn. In addition, the line induced voltages Vun and Vvn are detected as the line induced voltages Vun2 and Vvn2, respectively.

  Next, in step ST3, the rotation direction specifying unit 4 subtracts the line induced voltage Vun2 from the line induced voltage Vun1 to calculate the deviation ΔVun, and subtracts the line induced voltage Vvn2 from the line induced voltage Vvn1. Then, the deviation ΔVvn is calculated.

  Next, in step ST4, the rotation direction specifying unit 4 calculates absolute values of the deviations ΔVun and ΔVvn, and determines which of the absolute values of the deviations ΔVun and ΔVvn is larger. When it is determined that the absolute value of the deviation ΔVun is larger than the absolute value of the deviation ΔVvn, in step ST5, the rotation direction specifying unit 4 specifies the rotation direction according to the sign of the deviation ΔVun. On the other hand, when it is determined in step ST4 that the absolute value of the deviation ΔVun is smaller than the absolute value of the deviation ΔVvn, in step ST6, the rotation direction specifying unit 4 specifies the rotation direction according to the sign of the deviation ΔVvn.

  In short, the rotation direction specifying unit 4 may specify the rotation direction as follows. That is, a first deviation ΔVun obtained by subtracting the value Vun2 of the line induced voltage Vun from the value Vun1 of the line induced voltage Vun, and a value Vvn2 of the line induced voltage Vvn subtracted from the value Vun1 of the line induced voltage Vun. Of the two deviations (ΔVvn), the rotational direction is specified based on the sign of the deviation with the larger absolute value. The value Vun1 of the line induced voltage Vun and the value Vvn1 of the line induced voltage Vvn are detected as a set. The detection as a set here means that the line induced voltages Vun and Vvn are detected with a timing difference that can be considered to be substantially the same timing. The value Vun2 of the line induced voltage Vun and the value Vvn2 of the line induced voltage Vvn are detected as a set. The line induced voltage Vun value Vun1 is one of a pair of values that differ in magnitude relationship with the line induced voltage Vvn among the line induced voltages Vun detected adjacently. The adjacent detection here refers to two detections consecutive in the detection cycle. A pair of values refers to two values before and after the magnitude relationship between the line induced voltages Vun and Vvn is switched. The value Vun2 of the line induced voltage Vun is the first difference between the line induced voltage Vvn after the line induced voltage Vvn takes the value Vvn1 among the line induced voltages Vun detected adjacently. One of a pair of values.

  In the above example, the line induced voltages Vun and Vvn are used, but at least two of the line induced voltages Vun, Vvn and Vwn may be adopted.

<When deviations ΔVun and ΔVvn are equal>
Referring to FIGS. 6 and 7, when phase difference Δθ is zero, deviations ΔVun and ΔVvn are equal to each other and become positive during forward rotation and negative during reverse rotation. Therefore, when the deviations ΔVun and ΔVvn are equal to each other, the rotation direction may be specified using either one.

  On the other hand, referring to FIG. 6, when the phase difference Δθ is in the range of −120 degrees to −60 degrees or in the range of 60 degrees to 120 degrees, the absolute values of the deviations ΔVun and ΔVvn are equal to each other, and the deviation ΔVun , ΔVvn are opposite in polarity. Therefore, according to the above-described specifying method, the rotation direction cannot be properly detected in these ranges.

  Therefore, when the rotational direction specifying unit 4 determines that the absolute values of the deviations ΔVun and ΔVvn are substantially equal to each other and the polarities of the deviations ΔVun and ΔVvn are opposite to each other, the rotational direction need not be specified. According to this, it can avoid specifying a rotation direction accidentally.

<Filter>
FIG. 9 is a diagram schematically showing a configuration of another example of the rotation direction specifying device. Compared with FIG. 1, a filter 6 is further provided. The filter 6 receives the line induced voltage and filters the line induced voltage. Specifically, the harmonic component is removed from the line induced voltage, and the line induced voltage after the removal is output to the rotation direction specifying unit 4. The filter 6 may be a low-pass filter, for example, or may calculate an average value or an integral value. As a result, harmonic noise can be removed to improve accuracy.

<Noise>
Although a part of the noise generated in the line induced voltage is removed by the filter 6, not all the noise can be removed. If the filter 6 is not provided, the noise remains as it is. FIG. 10 is a diagram schematically showing an example of the line induced voltages Vun and Vvn. FIG. 10 shows an example when the line induced voltages Vun and Vvn have values close to each other. That is, an example of the vicinity where the line induced voltages Vun and Vvn intersect is shown. In the example of FIG. 10, the same level of noise is generated in the line induced voltages Vun and Vvn.

  Thus, when the same level of noise is generated in both line induced voltages Vun and Vvn, the noise value when the rotational position is 150 degrees and the noise value when the rotational position is 330 degrees are different. For example, the same level of noise is generated in the deviations ΔVun and ΔVvn.

  11 and 12 schematically show an example of the deviations ΔVun and ΔVvn when such noise occurs. In FIG. 11, the deviations ΔVun and ΔVvn are translated upward by the same amount (the larger value), and in FIG. 12, the deviations ΔVun and ΔVvn are translated downward by the same amount (the smaller value). Yes. In FIG. 11, a range in which a deviation having a larger absolute value is positive is indicated by a range A1. That is, according to this specifying method, the rotation direction can be correctly specified in the range A1. In FIG. 11, the width of the range A1 exceeds 240 degrees. On the other hand, in FIG. 12, although the width of the range A1 is smaller than 120 degrees, it is wider than 60 degrees (range from −30 degrees to 30 degrees) by the specific method based on the basic concept. That is, it can be seen that the present identifying method is effective even in a state where noise occurs.

  In the above example, the phase potential of the minimum phase is adopted as the reference potential, but the phase potential of the maximum phase may be adopted.

  Further, in the above-described example, the value Vun1 is one of a pair of values that differ in magnitude relationship with the line induced voltage Vvn among the line induced voltages Vun detected adjacently. However, this is not necessarily the case. For example, a line induced voltage Vun before or after several (for example, 9 or less) detection cycles may be adopted as the value Vun1. More generally, the line induced voltage Vun in a predetermined period including the time when the determination result of the magnitude relationship between the line induced voltages Vun and Vvn is switched may be used as the value Vun1. The same applies to the values Vun2, Vvn1, and Vvn2.

  As described with reference to FIGS. 6 and 7, when the phase between the detection time point of the values Vun1 and Vvn1 and the detection time point of the values Vun2 and Vvn2 is 180 degrees, the phase difference Δθ is from −60 degrees. When it is up to 60 degrees, the rotation direction can be specified. Further, when the phase difference Δθ is −120 to −60 degrees and 60 degrees to 120 degrees, it can be determined that the rotation direction cannot be correctly specified. Therefore, as the predetermined period, for example, a period of ± 120 degrees including a time point when the determination result of the magnitude relation between the line induced voltages Vun and Vvn is switched can be adopted. Further, from the viewpoint of specifying the rotation direction, as the predetermined period, for example, a period of ± 60 degrees including a time point when the determination result of the magnitude relation between the line induced voltages Vun and Vvn is switched may be adopted.

  However, in order to specify the rotation direction, the values Vun1 and Vvn1 are preferably values detected at a time close to the time when the determination result is switched, for example, the value at the time when the determination result is switched, or one of the detections. It may be a value detected at a time point before the cycle or a time point after one detection cycle.

  Further, in order to reduce the influence of noise, the rotational direction specifying unit 4 tentatively determines the magnitude relationship of the line induced voltage, and when the tentative determination result is maintained a plurality of times (over a predetermined period), The magnitude relationship may be determined. For example, a case is considered in which it is temporarily determined that the line induced voltage Vun is greater than the line induced voltage Vvn at a certain time. Even if it is temporarily determined that the line induced voltage Vun is smaller than the line induced voltage Vvn at the next time point, the magnitude relationship is not yet determined at this time point. When it is temporarily determined that the line induced voltage Vun is smaller than the line induced voltage Vvn at the next time point, it is determined that the line induced voltage Vun is smaller than the line induced voltage Vvn. In this case, the magnitude relation is determined when the provisional determination result of the magnitude relation is maintained twice. In this way, by determining the magnitude relationship over a plurality of temporary judgment results, even if the magnitude relation between the line induced voltages Vun and Vvn is switched by instantaneous noise, the switching can be ignored. That is, noise can be ignored.

  In this case, as the predetermined period, a period from when the provisional determination result of the magnitude relationship between the first line induced voltage and the second line induced voltage is switched to when it is finally determined that the magnitude relationship is switched is set as the predetermined period. Also good. For example, when the magnitude determination is maintained three times and the magnitude relation is determined, three detection cycles can be adopted as the predetermined period. In this case, if the predetermined period is shortened, the required delay devices can be reduced.

2 Motor 3 Line-to-line induced voltage detection unit 4 Rotation direction identification unit 5 Rotation direction identification device 6 Filter 22 Field

Claims (3)

A device for specifying the rotation direction of a synchronous motor (2) having a field (22),
The first phase potential when any one of the minimum phase and the maximum phase among the phase potentials (Vu, Vv, Vw) output by the synchronous motor by the induced electromotive force of the synchronous motor is a reference potential. First line induced voltage (Vun), which is a potential difference with respect to the reference potential, and a second line induced voltage (Vvn), which is a potential difference between the second phase potential other than the first phase potential and the reference potential. ), And a line induced voltage detector (3) that detects a set for each detection cycle,
A first deviation (ΔVun) obtained by subtracting a second value (Vun2) of the first line induced voltage from a first value (Vun1) of the first line induced voltage, and the second line induced voltage Of the second deviation (ΔVvn) obtained by subtracting the second value (Vvn2) of the second line induced voltage from the first value (Vvn1), the rotation direction is determined based on the sign of the deviation with the larger absolute value. A rotation direction specifying part (4) for specifying,
The rotation direction specifying unit determines a magnitude relationship between the first line induced voltage and the second line induced voltage,
The first value (Vun1) of the first inter-line induced voltage and the first value (Vvn1) of the second inter-line induced voltage include a first time point at which the determination result of the magnitude relationship is switched. Detected as the set in a predetermined period,
The second value (Vun2) of the first inter-line induced voltage and the second value (Vvn2) of the second inter-line induced voltage are different from each other in the determination result of the magnitude relationship, unlike the first time point. Detected as the set in a second predetermined period including a second time point,
The rotation direction specifying device (5), wherein the determination result of the magnitude relationship is maintained in a period between the first time point and the second time point.   The rotation direction specifying unit (4) has an absolute value of the first deviation (ΔVun) and an absolute value of the second deviation (ΔVvn) substantially equal to each other, and the polarity of the first deviation is the same as the polarity of the second deviation. The rotation direction specifying device (5) according to claim 1, wherein when it is different, the rotation direction is not specified. A filter (6) for filtering the first line induced voltage (Vun) and the second line induced voltage (Vvn);
The rotational direction specifying device (5) according to claim 1 or 2, wherein the deviation is obtained based on the first line induced voltage and the second line induced voltage after being filtered.

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