JP4720565B2 - Rotation speed detector - Google Patents

Description

  The present invention relates to a rotation speed detection device that detects a rotation speed of a rotor of an induction motor using a rotor groove frequency.

  For example, Patent Document 1 discloses an apparatus that detects the rotational speed of an induction motor using rotor groove harmonics. This apparatus includes slip frequency detecting means for detecting a slip frequency corresponding to the rotation speed of the electric motor using the rotor groove frequency of the induction motor.

  The slip frequency detecting means includes a phase voltage detector that detects an input voltage of each phase of the induction motor and an adder that adds the detected phase input voltages. By adding each phase input voltage by the adder, the fundamental frequency component and the third harmonic component of each phase input voltage are reduced.

  Here, in each phase input voltage detected by the phase voltage detector, in addition to the slip frequency included in the required rotor groove harmonic, the fundamental frequency component and the third harmonic component described above, and further the inverter circuit A carrier frequency component related to the switching operation is included. In particular, when the inverter circuit is PWM-controlled, many harmonic components corresponding to the carrier frequency component of the PWM signal appear in the phase voltage signal of the induction motor. As a result, the S / N ratio at the time of detecting the slip frequency is deteriorated by the carrier frequency component and the harmonic component.

For this reason, in the apparatus described in Patent Document 1, the carrier frequency of the PWM signal is set to a value higher than the frequency of the rotor groove harmonics of the induction motor. As a result, the frequency band corresponding to the carrier frequency component of the PWM signal is different from the frequency band of the rotor groove harmonic. Then, by providing a filter circuit (a low-pass filter or a band-pass filter) that attenuates the signal in the carrier frequency band and passes the slip frequency component of the rotor groove harmonic, the S / N of the detection signal of the slip frequency component is provided. The ratio is improved.
JP 7-236294 A

  The filter circuit of Patent Document 1 is used as an attenuation unit that attenuates only a signal in a carrier frequency band. The fundamental frequency component, the third harmonic component, etc. are reduced by adding the input voltage of each phase in the adder, but the influence is completely removed for reasons such as imbalance of winding impedance. It is not possible. For this reason, when the fundamental frequency component or the third harmonic component is dominant with respect to the slip frequency component of the rotor groove harmonic, the filter circuit of Patent Document 1 is used to cope with the rotation speed of the induction motor. There is a problem that it is difficult to accurately detect the slip frequency.

  In view of such a problem, a method of extracting only the groove harmonic component using a bandpass filter having a function of changing the frequency band according to the operation state of the induction motor has been proposed. On the other hand, depending on the application of the induction motor (for example, in the case of an electric supercharger), it may be necessary to detect the rotational speed at other times. Conventionally, a method of detecting the rotational speed by applying a rotating magnetic field exceeding the maximum rotational speed of the induction motor for a short time so as not to enter the regenerative mode has been adopted, but when the rotational speed range of the induction motor is wide In particular, there is a problem in that the groove harmonics deviate from the band of the filter at the time of low-speed rotation, and the rotation speed cannot be calculated.

  The present invention has been made in view of the above-described problems, and an object to be solved is to provide a rotation speed detection device capable of detecting the rotation speed of an induction motor in a wide speed range.

  Hereinafter, each means suitable for solving the above-described problems will be described with additional effects and the like as necessary.

1. In an induction motor in which a rotor is driven to rotate by exciting a stator by an AC signal generated by an inverter circuit, a rotation speed detection device that detects the rotation speed of the rotor,
Anti-phase excitation control means for controlling the inverter circuit to apply a rotating magnetic field in a direction opposite to the rotating direction to the stator;
Rotation for calculating the rotation speed of the rotor using a rotor groove harmonic from a voltage signal applied to the stator in a state where a reverse rotating magnetic field is applied to the stator by the antiphase excitation control means. A rotational speed detecting device comprising: a speed calculating means.

According to the means 1, the reverse phase excitation control means controls the inverter circuit to apply a rotating magnetic field in the direction opposite to the rotation direction to the stator, and the rotation speed calculation means applies to the stator by the reverse phase excitation control means. With the reverse rotating magnetic field applied, the rotational speed of the rotor is calculated from the voltage signal applied to the stator using the rotor groove harmonics . Then, by applying a reverse rotating magnetic field to the stator, the detectable frequency range is expanded to the low frequency side, and for example, it is possible to detect the rotational speed in the low speed rotation during other control. Furthermore, the rotational speed can be accurately calculated from the voltage signal using the rotor groove harmonics resulting from the rotor structure.

2. The reverse phase excitation control means applies a reverse rotation magnetic field to the stator within a period in which the rotation torque of the rotor does not occur, and the rotation speed calculation means determines a rotor from a voltage signal applied to the stator. The rotational speed detection device according to claim 1, wherein the rotational speed of the rotor is calculated using a groove harmonic .

According to the means 2, the reverse phase excitation control means applies the reverse rotating magnetic field to the stator and the rotational speed calculating means rotates from the voltage signal applied to the stator within the period in which the rotational torque of the rotor does not occur. Since the rotational speed of the rotor is calculated using the co- groove harmonics, the rotational speed of the rotor in the other control operation can be reliably detected.

  3. After a predetermined time has elapsed since the induction motor was started, the reverse phase excitation control means is configured to perform control switching from a reverse rotating magnetic field for detecting rotational speed to a positive rotating magnetic field for generating rotational torque. The rotational speed detecting device according to means 1 or 2, characterized in that.

  According to the means 3, the control switching from the reverse rotating magnetic field for detecting the rotational speed to the positive rotating magnetic field for generating the rotating torque is performed by the reverse phase excitation control means after a predetermined time has elapsed since the induction motor was started. The rotation speed calculation means can accurately calculate the rotation speed of the rotor according to the direction of the rotating magnetic field.

  4). 4. The rotational speed detecting device according to claim 3, wherein the control switching of the rotating magnetic field is executed after at least one cycle of the reverse rotating magnetic field has elapsed.

  According to the means 4, since the control switching of the rotating magnetic field is executed after at least one cycle of the reverse rotating magnetic field has elapsed, the rotating speed calculating means can accurately calculate the rotating speed of the rotor.

  5. The rotational speed detection device according to claim 3 or 4, wherein the current supply to the induction motor is turned off for a predetermined time before the control switching of the rotating magnetic field is executed.

  According to the means 5, since the energization to the induction motor is turned off for a predetermined time before executing the control switching of the rotating magnetic field, the current pulsation and the overvoltage are prevented, and the rotation speed calculating means The rotational speed can be calculated accurately.

6 . Means 1 or 2 configured to change the frequency band of the bandpass filter means used for extracting the rotor groove harmonics according to the direction of the rotating magnetic field applied to the stator. The rotational speed detection apparatus described in 1.

According to the means 6 , since the frequency band of the bandpass filter is changed according to the direction of the rotating magnetic field applied to the stator, the range of rotor groove harmonics that can be extracted is expanded, and a wide range of rotational speeds are obtained. Can be detected.

7 . AC signal generating means, bandpass filter means for extracting only signals of frequency components belonging to a desired frequency band, detection means for detecting rotor groove harmonics from signals extracted by the bandpass filter means, A rotational speed detection device comprising rotational speed calculation means for calculating the rotational speed of the induction motor based on a groove frequency that is a frequency of a rotor groove harmonic,
The rotational speed is calculated by the rotational speed calculating means in a state where a rotating magnetic field opposite to the rotor rotating direction of the induction motor is applied to the stator by the AC signal generating means. Rotation speed detection device.

According to the means 7 , a rotating magnetic field in a direction opposite to the rotor rotating direction of the induction motor is applied to the stator by the AC signal generating means, and in this state, the detecting means rotates from the signal extracted by the bandpass filter means. The child groove harmonic is detected, and the rotation speed calculation means calculates the rotation speed of the induction motor based on the groove frequency which is the frequency of the rotor groove harmonic. Then, by applying a reverse rotating magnetic field to the stator, the detectable frequency range is expanded to the low frequency side, and for example, it is possible to detect the rotational speed in the low speed rotation during other control.

8 . The reverse rotation magnetic field is applied to the stator by the AC signal generation means within the period in which the rotation torque of the rotor is not generated, and the rotation speed calculation means is configured to calculate the rotation speed. The rotational speed detecting device according to claim 7 .

According to the means 8 , the reverse rotation magnetic field is applied to the stator by the AC signal generating means and the rotational speed calculating means calculates the rotational speed within the period in which the rotational torque of the rotor is not generated. The rotational speed of the rotor can be reliably detected.

9 . After a predetermined time has elapsed since the induction motor was started, the AC signal generating means is configured to perform control switching from a reverse rotating magnetic field for detecting rotational speed to a positive rotating magnetic field for generating rotating torque. The rotational speed detection device according to claim 7 or 8 , characterized in that:

According to the means 9 , the control switching from the reverse direction rotating magnetic field for detecting the rotational speed by the AC signal generating means to the positive direction rotating magnetic field for generating the rotating torque is performed after a predetermined time has elapsed since the induction motor was started. The rotation speed calculation means can accurately calculate the rotation speed according to the direction of the rotating magnetic field.

10 . 10. The rotational speed detecting device according to claim 9 , wherein the control switching of the rotating magnetic field is executed after at least one cycle of the reverse rotating magnetic field has elapsed.

According to the means 10 , since the control switching of the rotating magnetic field is executed after at least one period of the reverse rotating magnetic field has elapsed, the rotating speed calculating means can accurately calculate the rotating speed.

11 . The rotational speed detection device according to claim 9 or 10 , characterized in that energization of the induction motor is turned off for a predetermined time before executing the control switching of the rotating magnetic field.

According to the means 11 , the energization to the induction motor is turned off for a certain period of time before executing the control switching of the rotating magnetic field, so that current pulsation and overvoltage are prevented, and the rotation speed calculating means It can be calculated accurately.

12 . The rotational speed detection device according to any one of means 7 to 11 , wherein a frequency band of the bandpass filter means used for extracting rotor groove harmonics is changed according to the direction of the rotating magnetic field.

According to the means 12 , since the frequency band of the bandpass filter is changed according to the direction of the rotating magnetic field applied to the stator, the range of extractable rotor groove harmonics is expanded, and a wide range of rotational speeds Can be detected.

  Hereinafter, an embodiment of a rotational speed detection device embodying the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an overall configuration of a motor control device including a rotation speed detection device according to the present embodiment.

  In FIG. 1, a motor 30 is a cage rotor in which an aluminum alloy is cast in a groove of a laminated iron core, and a stator composed of a stator core and three-phase (U phase, V phase, W phase) stator windings. And is equivalent to the induction motor of the present invention.

  The inverter circuit 20 has a switching circuit made up of a plurality of switching elements (power transistors, GTO thyristors, IGBTs, thyristors, etc.) as is well known, and the 120 ° U-phase, V-phase, and W-phase currents that are shifted AC signals are generated and supplied to the stator windings of each phase of the motor 30. As a result, a rotating magnetic field is formed by the stator windings of each phase of the motor 30, and the cage rotor of the motor 30 is rotated by the rotating magnetic field.

  The controller 10 includes, for example, a microcomputer including a CPU, a ROM, a RAM, and the like as is well known, and outputs a switching control signal to the switching circuit of the inverter circuit 20. In this case, the controller 10 can perform variable control of the rotation speed of the motor 30 by changing the excitation frequency of the U-phase, V-phase, and W-phase currents output from the inverter circuit 20 according to the switching control signal. The controller 10 constitutes the reverse phase excitation control means of the present invention. Converter circuit 50 converts an alternating current into a direct current and outputs the direct current to controller 10.

  The inverter circuit 20 may be either a voltage type inverter or a current type inverter, and the inverter control method may be either a voltage control method or a current control method.

  The motor control device according to the present embodiment includes a rotation speed detection device 40 that detects the actual rotation speed of the motor 30 and outputs it to the controller 10 for the above-described variable rotation speed control of the motor 30. As a result, the controller 10 can perform feedback control so that the actual rotational speed of the motor 30 matches the target rotational speed.

  Hereinafter, the rotation speed detection device 40 will be described in detail. The rotational speed detection device 40 in the present embodiment detects the rotational speed of the motor 30 using the rotor groove frequency. First, the rotor groove frequency and the principle of detecting the rotation speed using the rotor groove frequency will be briefly described with reference to FIGS. 2 is a schematic diagram schematically showing a cross section of the motor 30, and FIG. 3 is a graph showing the magnetic flux density B around the rotor.

  As described above, since the motor 30 includes the cage rotor 31 in which the aluminum alloy 32 is cast in the groove of the laminated iron core 33, the permeability of the rotor 31 is different between the iron core portion and the aluminum alloy portion. Different. For this reason, when a rotating magnetic field is formed by the stator winding 34, the magnetic flux in the gap is modulated according to the number of grooves in which the aluminum alloy is cast. This is shown in the graph of FIG. As shown in FIG. 3, a rotor groove harmonic component is generated due to the above-described modulation, and this rotor groove harmonic component is superimposed on the fundamental wave component of the magnetic flux density B in the gap. In the present embodiment, since the number of poles of the stator of the motor 30 is two, the frequency of the fundamental wave component of the magnetic flux density during one rotation of the rotating magnetic field is input to the stator winding 34 of each phase. Equal to the frequency of the AC signal being played.

  Then, the influence of the modulation of the magnetic flux due to the above-described rotor groove harmonic component appears in each phase voltage of the stator winding 34. More specifically, each phase voltage of the motor 30 includes the frequency (excitation frequency) component of the AC signal generated by the inverter circuit 20, the harmonic component resulting from the energization method, and the harmonic (particularly the third harmonic) resulting from magnetic flux saturation. Wave) component, and further includes a rotor groove harmonic component.

Here, when the number of grooves of the rotor 31 is N _r (= 3N + 1, where N is a natural number), the rotation frequency of the rotor 31 is f _r , the excitation frequency is f, and the slip frequency is f _sl , the excitation frequency component The rotor groove frequency f _sh1 is expressed by Equation 1 below.
( _Expression 1) f _sh1 = N _r × f _r −f = 3 × N × f−N _r × f _sl
Further, the rotor groove frequency f _shn due to the nth-order harmonic component is _expressed by the following Equation 2.
( _Expression 2) f _shn = N _r × f _r −nf = 3 × N × f−6 mf−N _r × f _sl
(However, n = 6m + 1, m is a natural number)
Here, when the signs of N _r = 3N + 1 and n = 6m + 1 are reversed, the signs of Equations 1 and 2 may be reversed and considered in the same way, and thus the description thereof is omitted.

In Equations 1 and 2, parameters other than the slip frequency f _sl are known, and the slip frequency f is detected by detecting the rotor groove frequency f _sh1 based on the excitation frequency component or the rotor groove frequency f _shn based on the nth-order harmonic component. _sl is obtained. Then, by subtracting the slip frequency f _sl from the excitation frequency f, the rotation frequency f _r of the rotor 31 is calculated, whereby it is possible to determine the rotational speed of the rotor 31. In the following example, an example in which the rotor groove frequency f _sh1 based on the excitation frequency component is detected as the rotor groove frequency will be described.

  First, the rotational speed detection device 40 includes a voltage adder 41. This voltage adder 41 detects the input voltage of each phase of U phase, V phase, and W phase, and adds the detected phase voltages. By adding the phase voltages in this way, the excitation frequency component and the third harmonic component described above are canceled out and the frequency components are reduced. FIG. 4 shows an example of the signal waveform of the addition voltage signal output from the voltage adder 41. As shown in FIG. 4, the excitation frequency component and the third harmonic component are considerably reduced by the addition of each phase voltage, but it can be completely removed due to problems such as imbalance of winding impedance. Not.

  The added voltage signal output from the voltage adder 41 is an analog signal. The A / D converter 42 samples the added voltage signal at every predetermined sampling period, and converts it from an analog value to a digital value. The digital data of the addition voltage signal is input from the A / D converter 42 to the digital signal processing unit 43.

  The digital signal processing unit 43 includes a Fourier transform unit (FFT) 44 as a bandpass filter, a rotor groove frequency detection unit 45, and a rotation speed calculation unit 46. The rotation speed calculation unit 46 constitutes a rotation speed calculation means.

  The Fourier transform unit 44 stores the digital data of the addition voltage signal output from the A / D converter 42, and performs a Fourier transform process when the number of data reaches a predetermined number. Thereby, frequency spectrum data indicating the intensity of each frequency component is obtained with a predetermined frequency resolution.

  In Fourier transform, since the number of data and the resolution have a correlation, in order to obtain a predetermined frequency resolution, it is necessary to collect digital data corresponding to the frequency resolution. In this case, since the rotation speed is calculated at intervals greater than the time required to collect a predetermined number of digital data, information on the actual rotation speed of the motor 30 is insufficient and high-precision rotation speed control cannot be performed. Is also possible.

  For this reason, in the present embodiment, some digital data is redundantly used in the Fourier transform process that the Fourier transform unit 44 continuously performs. As a result, the execution interval of the Fourier transform process can be shortened without lowering the frequency resolution, so that the time until the extraction of the rotor groove frequency and the calculation of the rotation speed can be shortened.

FIG. 5 shows an example of frequency spectrum data calculated by the Fourier transform unit 44. As shown in FIG. 5, the addition voltage signal includes excitation frequency component f ₁ , third harmonic component f ₃ , higher harmonic components f ₅ , f ₇ , f ₉ , and excitation frequency component. The rotor groove frequency f _sh1 and the rotor groove frequencies f _sh5 and f _sh7 due to higher harmonic components are included.

The Fourier transform unit 44 as a band-pass filter sets a frequency band that is considered to include the rotor groove frequency f _sh1 due to the excitation frequency among these frequency components, and sets each frequency component included in this frequency band. The intensity data is output to the rotor groove frequency detector 45.

Here, a frequency band setting method in the Fourier transform unit 44 will be described. The Fourier transform unit 45 assumes that the rotor 31 is rotating in synchronization with the excitation frequency f of the AC signal applied to each stator winding 34, and the rotor groove frequency f generated by the excitation frequency f. _{Using sh0} as a reference, a frequency band for extracting the actual stator groove frequency f _sh1 by the excitation frequency f is set. Therefore, the Fourier transform unit 44 inputs information on the excitation frequency f from the controller 10 and sets a frequency band based on the excitation frequency f.

Therefore, when the excitation frequency f is changed so that the controller 10 variably controls the rotation speed of the motor 30, the Fourier transform unit 44 extracts the actual stator groove frequency f _sh1 based on the excitation frequency component. The frequency band will also change.

In the example shown in FIG. 5, a frequency band having a band corresponding to 1.3 times (1.3f) to 16 times (16f) of the excitation frequency f is set based on the specifications of the motor 30 and the like. A frequency 15 times (15f) f is _fsh0 .

In this way, by setting a relatively wide frequency band on the frequency decreasing side with _respect to f _sh0 , even if the slip size of the motor 30 changes, excitation is performed regardless of the slip size. A frequency band that can substantially cover the rotor groove frequency f _sh1 by the frequency component can be set. Therefore, the Fourier transform unit 44 can accurately extract the rotor groove frequency f _sh1 based on the excitation frequency component. However, it is desirable that this frequency band be limited to a range that does not include high-order harmonics (especially third-order harmonics) of the excitation frequency as much as possible in order to improve the S / N ratio.

When the motor 30 functions as an electric motor, a rotor groove frequency f _sh1 higher than f _sh0 is not generated, but in consideration of various errors and the like, the frequency is _higher than f _sh0. The frequency band is also expanded.

However, when the motor 30 also functions as a power generator that regenerates electric power, contrary to the example shown in FIG. 5, on the basis of f _sh0 , the frequency increases widely and the frequency decreases. A narrow frequency band may be set.

The rotor groove frequency detection unit 45 detects the rotor groove frequency f _sh1 based on the excitation frequency component based on the intensity data of each frequency component included in the frequency band output from the Fourier transform unit 44. Specifically, the frequency component having the strongest peak intensity is detected as the rotor groove frequency f _sh1 based on the excitation frequency component.

The rotor groove frequency f _sh1 based on the excitation frequency component detected by the rotor groove frequency detection unit 45 is given to the rotation speed calculation unit 46, and the rotation speed of the rotor is calculated based on the rotor groove frequency f _sh1. And output to the controller 10.

  Next, detection of the rotation speed of the rotor 31 in the process in which the motor 30 shifts from the other control operation to the self-control operation will be described with reference to FIGS. FIG. 6 is a graph showing a change in rotational frequency when shifting from other control operation to self-control operation. FIG. 7 is a flowchart showing a flow of rotation speed detection after the motor control device is activated.

  As shown in FIG. 6, the motor 30 is operated in other modes in the initial state. When the controller 10 is activated, the inverter circuit 20 is controlled to perform a reverse phase excitation for a short time (a rotating magnetic field in a direction opposite to the rotating direction of the rotor 31 is applied to the stator). The rotational speed is calculated (step 1. Hereinafter, abbreviated as S1. The same applies to the other steps). More specifically, by controlling the inverter circuit 20 to generate an AC signal having a predetermined excitation frequency, the rotation direction of the rotor 31 can be determined for a short time of about several tens of ms that does not affect the rotation speed. Applies a rotating magnetic field in the opposite direction to the stator, and in this state, the rotor groove frequency detection unit 45 detects the rotor groove frequency, and the rotation speed calculation unit 46 determines the excitation frequency and the rotor groove frequency. Calculate the rotation speed.

  Next, the power supply to the motor 30 is turned off for a certain time (S2). Then, after a lapse of a predetermined time from the start of the motor 30, normal phase excitation is performed (a rotating magnetic field in the rotation direction of the rotor 31 is applied to the stator) to generate normal torque, and the rotor The rotational speed of 31 is calculated (S3). More specifically, by controlling the inverter circuit 20 to generate an AC signal having a predetermined excitation frequency, a rotating magnetic field in the rotating direction of the rotor 31 is applied to the stator, and in this state, the rotor groove frequency is detected. The rotor groove frequency is detected by the unit 45, and the rotation speed is calculated based on the excitation frequency and the rotor groove frequency by the rotation speed calculation unit 46.

  Here, the range of the detectable rotational speed in each case of the positive phase excitation and the negative phase excitation will be described.

First, the following equation 3 is used to calculate the rotor groove frequency f _sh in the positive phase excitation. However, the number of grooves of the rotor 31 is N _r , the rotation frequency of the rotor 31 is f _r , the excitation frequency is f, and the slip is s.
( _Expression 3) f _sh = N _r × f _r −f = N _r × (1−s) × f−f = (N _r −1−N _r × s) × f
When formula 3 is converted into the formula of slip s, s = 1 / N _r × (N _r −1−f _sh / f).

Then, Fourier transform unit 44 of the band-pass filter, because it sets the frequency band more than 1.3 times the excitation frequency f (f _sh ≧ 1.3f), the slip s ≦ 0.85625. Therefore, for example, as shown in FIG. 8, when the rotation speed of the rotating magnetic field applied to the motor 30 (rotation speed per fixed time = rotation speed) is 200,000 rpm, f _r = f × (1−s) Therefore, the detectable turbo rotation speed is 200,000 × (1−0.85625) = 28,750 rpm or more.

Next, a formula for calculating the rotor groove frequency f _sh in the reverse phase excitation is shown in Formula 4 below.
( _Expression 4) f _sh = N _r × f _r + f = N _r × (1−s) × f + f = (N _r + 1−N _r × s) × f
When converted into the slip s equation, s = 1 / N _r × (N _r + 1−f _sh / f).

As described above, since f _sh ≧ 1.3f, the slip s ≦ 0.98125. Therefore, in FIG. 8, when the rotational speed of the rotating magnetic field applied to the electric supercharger is 200,000 rpm, the turbo rotational speed that can be detected during reverse phase excitation is 200,000 × (1−0.98125) = 3, 750 rpm or more, and the rotation speed detection range is expanded to the low speed side as compared with the case of positive phase excitation. In the turbo rotation region from 5,000 rpm to 170,000 rpm, the rotation speed cannot be detected in the region from 5,000 pm to 28,750 rpm during the normal phase excitation, but the rotation is performed in the entire turbo rotation region during the reverse phase excitation. It can be seen that the speed can be detected.

As is clear from the above detailed description, according to the present embodiment, the controller 10 controls the inverter circuit 20 to apply a rotating magnetic field in a direction opposite to the rotating direction to the stator, and as a band-pass filter. The Fourier transform unit 44 extracts only a signal of a frequency component belonging to a desired frequency band (1.3f to 16f) in the voltage signal applied to the stator, and the rotor groove frequency detection unit 45 is operated by the Fourier transform unit 44. The rotor groove frequency f _sh of the rotor groove harmonic attributed to the structure of the rotor 31 is detected from the signal extracted by the above, and the rotation speed calculation unit 46 determines an accurate rotation speed based on the rotor groove frequency f _sh. Can be calculated. Then, by applying the reverse rotating magnetic field to the stator, the range of the rotor groove harmonics that can be extracted by the Fourier transform unit 44 is expanded to the low frequency side, and the other control time during which no rotational torque is generated. It is possible to detect the rotation speed at low speed rotation.

  In addition, after a predetermined time has elapsed since the motor 30 was started, the controller 10 switches control from the reverse direction rotating magnetic field for detecting the rotating speed to the positive rotating magnetic field for generating the rotating torque. The rotational speed of the rotor 31 can be accurately calculated according to the rotating magnetic field direction. The predetermined time is set to be equal to or longer than the time when one cycle of the reverse direction rotating magnetic field elapses.

  In addition, since the energization of the motor 30 is turned off for a certain period of time before executing the control switching of the rotating magnetic field, the occurrence of current pulsation and overvoltage is prevented, and the rotation speed calculation unit 46 allows the rotation speed of the rotor 31 to Can be calculated accurately.

  In addition, this invention is not limited to embodiment mentioned above, A various change is possible in the range which does not deviate from the main point of this invention.

  For example, the frequency band of the Fourier transform unit 44 may be changed according to the direction of the rotating magnetic field applied to the stator. As a result, the range of rotor groove harmonics that can be extracted is expanded, and a wider range of rotation speeds can be detected.

  The present invention is applicable to, for example, detection of the rotation speed of an induction motor used for an electric supercharger of an automobile or the like.

1 is a block diagram illustrating an overall configuration of a motor control device including a rotation speed detection device according to an embodiment of the present invention. 3 is a schematic diagram schematically showing a cross section of a motor 30. FIG. It is a graph which shows distribution of the magnetic flux density B around the rotor 31 when a rotating magnetic field is formed by the stator winding. 6 is a waveform diagram showing an example of a signal waveform of an addition voltage signal output from a voltage adder 41. FIG. It is a graph which shows an example of the frequency spectrum data which the Fourier-transform part 44 calculates. It is a graph showing the change of the rotation frequency in the case of shifting from other control operation to self-control operation. It is a flowchart which shows the flow of rotation speed detection after a motor control apparatus starting. It is a figure which shows the detectable range of turbo rotation speed.

Explanation of symbols

10 Controller (Reverse phase excitation control means)
20 Inverter circuit (AC signal generating means)
30 motor (induction motor)
40 Rotational Speed Detection Device 41 Voltage Adder 42 A / D Converter 43 Digital Signal Processing Unit 44 Fourier Transform Unit (Bandpass Filter Unit)
45 Rotor groove frequency detector 46 Rotational speed calculator (Rotational speed calculator)

Claims (12)

In an induction motor in which a rotor is driven to rotate by exciting a stator by an AC signal generated by an inverter circuit, a rotation speed detection device that detects the rotation speed of the rotor,
Anti-phase excitation control means for controlling the inverter circuit to apply a rotating magnetic field in a direction opposite to the rotating direction to the stator;
Rotation for calculating the rotation speed of the rotor using a rotor groove harmonic from a voltage signal applied to the stator in a state where a reverse rotating magnetic field is applied to the stator by the antiphase excitation control means. A rotational speed detecting device comprising: a speed calculating means. The reverse phase excitation control means applies a reverse rotation magnetic field to the stator within a period in which the rotation torque of the rotor does not occur, and the rotation speed calculation means determines a rotor from a voltage signal applied to the stator. The rotational speed detection apparatus according to claim 1, wherein the rotational speed of the rotor is calculated using a groove harmonic .   After a predetermined time has elapsed since the induction motor was started, the reverse phase excitation control means is configured to perform control switching from a reverse rotating magnetic field for detecting rotational speed to a positive rotating magnetic field for generating rotational torque. The rotational speed detection device according to claim 1 or 2, wherein   4. The rotational speed detection device according to claim 3, wherein the control switching of the rotating magnetic field is executed after at least one cycle of the reverse rotating magnetic field has elapsed.   5. The rotational speed detection device according to claim 3, wherein energization of the induction motor is turned off for a predetermined time before executing the control switching of the rotating magnetic field. Depending on the direction of the rotating magnetic field applied to the stator, or claim 1, characterized in that it is configured to change the frequency band of the band-pass filter means used in order to extract the rotor groove harmonic rotational speed detection device according to 2. AC signal generating means, bandpass filter means for extracting only signals of frequency components belonging to a desired frequency band, detection means for detecting rotor groove harmonics from signals extracted by the bandpass filter means, A rotational speed detection device comprising rotational speed calculation means for calculating the rotational speed of the induction motor based on a groove frequency that is a frequency of a rotor groove harmonic,
The rotational speed is calculated by the rotational speed calculating means in a state where a rotating magnetic field opposite to the rotor rotating direction of the induction motor is applied to the stator by the AC signal generating means. Rotation speed detection device. The reverse rotation magnetic field is applied to the stator by the AC signal generation means within the period in which the rotation torque of the rotor is not generated, and the rotation speed calculation means is configured to calculate the rotation speed. The rotation speed detection device according to claim 7 . After a predetermined time has elapsed since the induction motor was started, the AC signal generating means is configured to perform control switching from a reverse rotating magnetic field for detecting rotational speed to a positive rotating magnetic field for generating rotating torque. The rotation speed detection device according to claim 7 or 8 , characterized in that. The rotational speed detection apparatus according to claim 9 , wherein the control switching of the rotating magnetic field is executed after at least one cycle of the reverse rotating magnetic field has elapsed. Wherein before executing the control switching of the rotating magnetic field, the rotation speed detecting apparatus according to claim 9 or 10, characterized in that off certain time the power supply to the induction motor. The rotational speed detection device according to any one of claims 7 to 11 , wherein a frequency band of the bandpass filter means used for extracting rotor groove harmonics is changed according to the direction of the rotating magnetic field. .

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