JP3422356B2 - Method and apparatus for detecting inertial rotation information of AC motor and motor driving method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving a polyphase AC motor by a polyphase inverter (DC-AC power converter), and a method of detecting rotation information when the AC motor is not driven, that is, when the AC motor is free running. The present invention relates to a device and a method for driving an AC electric motor.

[0002]

2. Description of the Related Art Detecting the rotation speed and the rotation direction of a motor in a free running state has a meaning in setting conditions for restarting the motor. Although the rotation speed and direction in the free running state can be detected by the rotation detector, the provision of the rotation detector not only increases the size of the device but also increases the cost.

The applicant of the present application has proposed a method for detecting the inertial rotation speed of an induction motor driven by an inverter without using a rotation detector (Japanese Patent Application No. 7-155218).
No. 31894). However, no method for detecting the rotation direction is proposed here. When the induction motor is rotated only in the forward direction, detection of the rotation direction is not required, but when rotating the induction motor in both the forward and reverse directions, information on the rotation direction during free running (inertial rotation) is required. To be done. Then, the 1st objective of this application is to provide the method and apparatus which can detect the rotation direction during inertial rotation easily.

When driving an induction motor with an inverter,
If the forward rotation drive state is simply switched to the reverse rotation drive state, not only can the rotation speed and direction be smoothly switched in a short time, but also the overcurrent protection circuit may operate and enter a stop state. is there. Therefore, a second object of the present application is to provide a method capable of smoothly switching the rotation direction.

[0005]

According to the present invention for solving the above problems and achieving the above first object, a plurality of series circuits of first and second switches are connected between a pair of DC power supply terminals. A method for detecting inertial rotation information of the AC motor during a period in which the driving of the polyphase AC motor by the polyphase inverter having the above-mentioned configuration is stopped, the first of the plurality of series circuits of the polyphase inverter being included. And at least one of the second switch is turned on at the same time, and at this time, the input currents of at least the first and second phases of the AC motor are detected to detect the input currents of the first and second phases. From the positive peak
The period until the negative peak is the first voltage level, and the negative peak
Value with the second voltage level from the period to the positive peak
Forming a signal, respectively, and inputting the first and second phases.
The input current of the first phase based on the comparison of the binary signals of the current
The input current of the second phase is
It is determined whether the position is in
Outputs information, opposite to the first rotation direction when the phase is delayed
Of the second rotation direction is output to obtain information indicating the direction of inertial rotation of the AC motor, the inertial rotation information detection method for the AC motor. Na
In order to execute the method of claim 1, it is desirable to configure the inertial rotation information detection device of the AC motor as described in claim 3 . The invention for achieving the second object is to drive a multi-phase AC motor by a multi-phase inverter having a configuration in which a plurality of series circuits of first and second switches are connected between a pair of DC power supply terminals. the method, when a drive command of the first second direction of rotation of the rotating direction opposite occurs with the AC <br/> motor in the first drive stop period after driving in the direction of rotation of the Said plurality of series circuits of polyphase inverter
Either one of the first and second switches of
Was controlled to be on, it detects an input current of the AC motor in order to detect the rotational speed of the inertial rotation of the AC motor
Then, measure the cycle or frequency of the detected input current,
The period or frequency of the rotation speed of the inertial rotation of the AC motor
Detected as degrees, and detects an input current of at least first and second phases of the AC motor to detect the rotation direction of the inertial rotation of the AC motor, the first and
Period from the positive peak to the negative peak of the input current of the second phase
From the negative peak to the positive peak
Forming binary signals with the period as the second voltage level
And comparing the binary signals of the input currents of the first and second phases
Based on the input current of the first phase to the second
Determine whether the phase input current is in the lead position or the lag position,
When the phase is advanced, the information of the first rotation direction is output and
In the phase of the second rotation direction opposite to the first rotation direction
A first step of outputting information, after the first step, corresponding to the output frequency of said first of said inverter which can be obtained by a rotational speed substantially the same rotational speed detected in step First frequency command value (f1)
And driving the inverter so that an output frequency corresponding to the first frequency command value (f1) is obtained,
Further, the output frequency and the output voltage for driving the electric motor are controlled by controlling the output frequency and the output voltage of the inverter so that the ratio V / f of the output frequency f of the inverter and the output voltage V becomes constant. In order to obtain the first output voltage value (V1) corresponding to the first frequency command value (f1) in the characteristic diagram showing the relationship, the output voltage of the inverter is changed from zero to the first output voltage value. A second step of gradually increasing toward (V1); the output frequency of the inverter is a value corresponding to the first frequency command value (f1), and the output voltage of the inverter is the first output voltage. After reaching the value (V1), the output frequency command value of the inverter is changed to the first frequency command value (f1).
From 0 to zero, and the output voltage command value of the inverter is also adjusted to the first value according to the constant V / f control.
Output voltage command value is gradually reduced toward zero, and after the third step, the output frequency of the inverter has a directivity for rotating the AC motor in the second rotation direction. And a fourth step of gradually changing the command value toward the target output frequency command value and changing the output voltage command value of the inverter according to the constant V / f control. It relates to a method of driving an electric motor.

[0006]

According to the first and third aspects of the present invention, the direction of inertial rotation is detected based on the control of the switch of the inverter and the input current of the AC motor, so this detection can be performed easily and at low cost. You can Further, it is possible to obtain information indicating the rotation direction accurately and easily. In addition, claim 2
According to the invention, the V / f constant state is created during the period of the first rotation direction, and the rotation speed is set to zero by the V / f constant control.
After that, the driving in the second rotation direction is performed under the constant V / f control, so that the switching of the rotation direction can be performed smoothly and in a short time.

[0007]

Embodiments and Examples Next, with reference to FIGS. 1 to 9, a description will be given of a method for detecting inertial rotation of an induction motor, a driving method and an apparatus according to embodiments and examples of the present invention. As shown in FIG. 1, an induction motor control and drive system includes a three-phase rectifying / smoothing circuit 2 connected to a three-phase AC power supply terminal 1 and a three-phase inverter connected between the pair of DC output terminals 2a and 2b. Circuit 3, three-phase induction motor 4 as an AC motor connected to inverter circuit 3, and inverter control circuit 5
And a first and second current detectors 6 and 7, a frequency detection circuit 8 and an inverter operation commander 9.

The inverter circuit 3 is a well-known three-phase bridge type inverter circuit, in which six IGBTs, that is, first to sixth switches Q1 to Q6 composed of insulated gate bipolar transistors are connected in a three-phase bridge, and Switch Q
Feedback diodes D1 to D6 are connected in antiparallel to 1 to Q6. That is, the first and second switches Q1,
First phase arm consisting of Q2 series circuit, and third and fourth
The output terminal 2a of the rectifying / smoothing circuit 2 using the second phase arm composed of the series circuit of the switches Q3 and Q4 and the third phase arm composed of the series circuit of the fifth and sixth switches Q5 and Q6 as DC power supply terminals, 2b, and output lines 3a, 3b, 3c are derived from the midpoint of each phase arm.

The induction motor 4 has primary windings 4a, 4b, 4
In addition to the stator composed of c, a rotor (not shown) is provided, and a load such as a fan is coupled to the rotor. In this embodiment, the primary windings 4a, 4b, 4c are Y-connected and the output lines 3a, 3 of the inverter circuit 3 are connected.
b, 3c.

The control circuit 5 controls the switches Q1 to Q6 of the inverter circuit 3 in three-phase PWM mode, and, in the steady state, sets the electric motor 4 to V / f = predetermined (where V is the inverter output voltage and f is the inverter output frequency). According to the conditions, the rotation speed is controlled to a predetermined value, and during the free running (coasting rotation) period, the three switches Q2 below the inverter circuit 3,
Q4 and Q6 are controlled to be turned on at the same time, rotation information in the free-running period is detected, and start control according to this is executed.

The first and second current detectors 6, 7 are coupled to the output lines 3a, 3c of the inverter circuit 3 and detect the inverter output current, that is, the motor input current. The output lines 6a and 7a of the current detectors 6 and 7 are connected to the inverter control circuit 5 and the frequency detection circuit 8 and used for detecting the rotation direction and the rotation speed during free running.
The outputs of the current detectors 6 and 7 are also used in an overcurrent protection circuit (not shown) for turning off all the switches Q1 to Q6 of the inverter circuit 3 at the time of overcurrent.

The frequency detection circuit 8 detects the frequency of the current obtained from the current detectors 6 and 7 during free running to obtain the rotation speed information of the electric motor 4, and can also be called a rotation speed detection circuit. Is. That is, the frequency detection circuit 8 shapes the first and second current detection waveforms into a square wave pulse, and inputs this into each counter,
The frequency is detected by counting output per unit time. The frequency measured here indicates the rotation speed of the electric motor 4. That is, the rotation speed of the electric motor 4 is Nx, the number of poles is P, and the frequency of the current detected by the current detectors 6 and 7 is f.
If m, then the relational expression Nx = 120 fm / P holds. Therefore, when the detection frequency fm is multiplied by a constant, the rotation speed, that is, the rotation speed Nx is obtained. In addition, it is possible to adopt a configuration in which the period T seconds of the current detection waveform is detected and the frequency is obtained by 1 / T. The frequency detection circuit 8 detects the frequencies based on the input currents of the two phases, and sends the average value of these frequencies to the inverter control circuit 5 through the output line 8a. Of course 1
The frequency may be detected only by the phase input current.

The operation command device 9 gives a desired rotation speed (target rotation speed) of the electric motor 4, that is, a desired frequency command, a forward rotation command and a reverse rotation command of the inverter to the control circuit 5 through lines 9a, 9b and 9c.

FIG. 2 shows the inverter control circuit 5 of FIG. 1 in detail. The inverter control circuit 5 includes a well-known PWM control circuit 11 for controlling the control electrodes of the switches Q1, Q2, Q3, Q4, Q5 and Q6, a frequency command value generation and start-up controller 12, a free running detection circuit. 13, a free running control circuit 14 and a rotation direction detection circuit 15. The rotation direction detection circuit 15 includes first and second peak detectors 16 and 17 and a phase comparator 18. It should be noted that most of the control circuit 5 is configured by a microcomputer, but in FIG. 2 it is shown in blocks by function for easy understanding.

FIG. 3 shows details of the PWM control circuit 11 shown in FIG. This inverter control circuit 11 performs PWM control as well as V / f = constant control, which is well known in Japanese Patent Laid-Open No. 57-40369, and includes an output voltage command value generator 21 and a voltage changeover switch 22. A three-phase sine wave generator 23, a triangular wave carrier generator 24,
It comprises three comparators 25, 26, 27 and a gate drive circuit 28. Output frequency command line 12a derived from the frequency command value generation and start-up controller 12 of FIG.
Indicates the frequency command value Fn of the inverter and the voltage command value generator 2
1 and three-phase sine wave generator 23. The voltage command value generator 21 responds to the frequency command value Fn on the line 12a to generate an output voltage command value Vn according to Vn / Fn = constant condition as indicated by a characteristic line 29. Three-phase sine wave generator 23
Generates the three-phase sine wave voltages Vsu, Vsv, Vsw of the frequency designated by the frequency command value Fn of the line 12a as shown in FIG. 5 (A). The amplitudes of the voltages Vsu, Vsv, Vsw are controlled so as to be proportional to the voltage Vn of the voltage command value generator 21 or the voltage Vs of the line 12c. As shown in FIG. 5A, the triangular wave carrier generator 24 generates sinusoidal wave voltages Vsu and Vs.
The triangular wave voltage Vt having a frequency (for example, 20 kHz) sufficiently higher than the frequencies of v and Vsw (for example, 0 to 60 Hz) is generated. The comparators 25, 26 and 27 have sine wave voltages Vsu, Vsv,
Comparison of Vsw and triangular wave voltage Vt is shown in FIGS.
The PWM pulse (pulse width modulation pulse) of (D) is output. The gate drive circuit 28 includes comparators 25, 26 and 27.
The PWM signals of FIGS. 5B, 5C, and 5D obtained from FIG. 5B are given to the gates (control electrodes) of the first, third, and fifth switches Q1, Q3, and Q5, and C) (D)
The PWM signal of the opposite phase to the second, fourth and sixth switches Q
Give to 2, Q4 and Q6.

The voltage changeover switch 22 has contacts a and b and is controlled by the signal on the output line 12b of the frequency command value generation and start-up controller 12 shown in FIG. 2, and the line 12c shows t2 to t3 of FIG. 9D. Voltage obtained during the period, Fig. 1
The gradient voltage obtained during the period t2 to t3 of 0 (D) is t2 to
Sending to the sine wave generator 23 through the contact b only during the t3 period,
During the other period, the output of the voltage command value generator 21 is set to the contact a.
Is sent to the sine wave generator 23 via. In this embodiment, the three-phase sine wave generator 23 is composed of a memory and a D / A converter. This memory stores a large number of sine wave data of voltage levels, and the sine wave data corresponding to the voltage command value Vn of the voltage command value generator 21 at the time of normal operation and the slope voltage command value Vs at the time of start-up 9b
Is read at the clock corresponding to the frequency command value Fn of
This is D / A converted, and the voltages Vsu, Vsv of FIG.
It becomes Vsw. A forward rotation command signal line 9b, a reverse rotation command signal line 9c, and a rotation direction information line 12e are connected to the sine wave generator 23, and Vsu and Vs are supplied during normal rotation.
A sine wave is generated at intervals of 120 degrees in the order of v and Vsw, and a sine wave is generated at intervals of 120 degrees in the order of Vsw, Vsv, and Vsu during reverse rotation. In this embodiment, as shown in FIG. 5, the gate drive circuit 28 is constructed so as to always apply the PWM pulse to the switches Q1 to Q6 of the respective phases. Based on the phase voltage Vsu, the first switch Q1 is PW in the 0 to 180 degree section.
Controlled by M pulse, kept off in 180-360 degree section, kept second switch Q2 in 0-180 degree section, PWM controlled in 180-360 degree section, and made third switch Q3 in 0-section. It keeps off in the 120-degree section and the 300-360 degree section, and performs PWM control in the 120-300 degree section,
Set the fourth switch Q4 to the 0 to 120 degree section and 300 to 3
PWM control in the 60 degree section, keep it off in the 120 to 300 degree section, and set the fifth switch Q5 to the 0 to 60 degree section and 2
PWM control is performed in the section of 40 to 360 degrees, it is kept off in the section of 60 to 240 degrees, and the sixth switch Q6 is kept off in the section of 0 to 60 degrees and the section of 240 to 360 degrees.
It is possible to perform PWM control in a frequency interval. Further, the time width of the PWM control of the first to sixth switches Q1 to Q6 can be set to 120 degrees. Further, the three-phase sine wave generator 23 is not limited to the above-mentioned embodiment, and can be composed of, for example, a fixed amplitude sine wave generator and a multiplier at this output stage. In this case, a fixed amplitude sine wave according to the frequency command is multiplied by the voltage command value to create an amplitude controlled sine wave.

Frequency command value generation and start-up controller 1 of FIG.
2 outputs the command value indicating the target frequency f0 given by the line 9a to the line 12a in the steady state, and at the time of starting (transition time) in the period t2 to t4 of FIG. 9C.
Frequency command values fs, fa and t2 to t in FIG.
The frequency command values f1, f2, f3 for 5 periods are set on the line 12a.
3, the control signal of the switch 22 of FIG. 3 is output to the line 12b, the ramp voltage Vs is output to the line 12c, and the free running control signal is output to the line 12c.
In addition, the rotation direction switching signal is output to the line 12e. That is, the frequency command value generation and activation controller 12 is based on the detection frequency fm of the output line 8a of the frequency detection circuit 8 when the normal rotation is restarted from the normal rotation inertia rotation state as shown in FIG. T2 in FIG.
The output frequency fs of the inverter at the time of restarting for the period up to t3 is determined, and this is sent to the output line 12a.
In the period from t3 to t4 in (C), the inclination frequency command value fa for acceleration is sent to the line 12a, and after t4 in FIG. 9 (C), the target frequency command value f0 in the line 9a is sent to the line 12a.
10A, and when the reverse rotation restarts from the normal inertial rotation shown in FIG. 10, the frequency command value f1 corresponding to the detection frequency fm of the line 8a is supplied during the period from t2 to t3 in FIG. 10C.
Is sent to the line 12a, and from t3 of FIG.
In the t4 period, the slope frequency command value f2 for deceleration is set in the line 1
2a, the inclination frequency command value f3 for acceleration is sent to the line 12a during the period from t4 to t5 in FIG. 10C, and the rotation direction switching signal is output to the line 12e at the time t4 in FIG. is there.

FIG. 4 is a detailed analog analog analogy of the frequency command value generation and activation controller 12 of FIG. The frequency command value generation and start-up controller 12 executes the control of FIGS. 9 and 10 in order to execute the first, second, third, fourth and fifth signal extraction switches 31, 32, 33, 34, 35, start-up frequency generator 36, OR gate 37, timer 38, trigger circuit 39, RS flip-flop 40, ramp voltage generator 41, latch circuit 42, f / V (frequency / voltage) Converter 43, forward rotation acceleration frequency generator 44a, reverse rotation acceleration frequency generator 44b, deceleration frequency generator 45
And first, second and third comparators 46, 47 and 48. The operation of each unit in FIG. 4 will be described in detail later.

In order to smoothly restart the electric motor 4 in this embodiment, information on the rotational speed (rotational speed) and the rotational direction of the inertial rotation, that is, the free running of the electric motor 4 during the non-driving period of the electric motor 4 is required. Become. In this embodiment, the switches Q1 to Q6 of the inverter circuit 3 are controlled to the zero vector state during inertial rotation, and the output current of the inverter in this state, that is, the input current of the electric motor 4 is detected by the current detectors 6 and 7, and this detection is performed. The rotation speed and the rotation direction are detected based on the currents Iu and Iw.

First, a method of detecting the rotation speed of the electric motor 4 during the inertia rotation period will be described. The free-running detection circuit 13 of FIG. 2 detects that the currents of the current detectors 6 and 7 have stopped flowing based on the signal of the line 6a, and outputs a signal indicating that the free-running period has come to the free-running control circuit 14. Give to.

The free running control circuit 14 is based on the output of the free running detection circuit 13 and the signal of the output line 12d of the timer 38 shown in FIG.
Three switches Q2 on the lower side of the inverter circuit 3 during the period t2
, Q4 and Q6 are simultaneously generated to generate a switch control signal. The free running control circuit 14
Alternatively, the PWM control circuit 11 may be used to turn on the switches Q2, Q4 and Q6 at the same time.

When the free-running control circuit 14 simultaneously turns on all the switches Q2, Q4, Q6 on one side of the inverter circuit 3 during the period from t1 to t2 in FIGS. 9 and 10, a closed circuit as shown in FIG. 6 is formed. It That is, regarding the line to which the first current detector 6 is coupled, the first phase winding 4
a-second switch Q2-fourth diode D4-second
Positive direction closed circuit of phase winding 4b, second phase winding 4b-fourth switch Q4-second diode D2-reverse direction closed circuit of first phase winding 4a, first phase winding 4a-second Switch Q2-
Forward closed circuit consisting of sixth diode D6-third phase winding 4c, third phase winding 4c-sixth switch Q6-second diode D2-reverse closed circuit consisting of first phase winding 4a Is formed. A similar closed circuit is formed in the line to which the second current detector 7 is connected. Here, the output of the first current detector 6 will be described. Since the voltage is generated in the stator windings 4a to 4c when the electric motor 4 is rotating, the current detector 6 has a periodicity as illustrated in the period from t1 to t2 in FIG. 9 (E). To detect the changing current. The cycle of this current corresponds to the rotation speed of the electric motor 4. Further, this current flows at a relatively large level because it flows in the state where the windings 4a, 4b and 4c are short-circuited by the switches Q2, Q4 and Q6. The frequency detection circuit 8 of FIG.
The frequency of the current in the period t1 to t2 in (E) and the period t1 to t2 in FIG. 10 is measured. Since the frequency detected by the frequency detection circuit 8 corresponds to the inertial rotation speed of the electric motor 4, the frequency detection circuit 8 can also be called a rotation speed detection circuit. The frequency detection circuit 8 can also detect the inverter output frequency in the normal driving state of the electric motor 4 to estimate the rotation speed. The detected frequency fm is sent to the starting frequency generator 36 and the latch circuit 42 in the frequency command value generating and starting controller 12 of FIG. 4 by the line 8a and used for restart control. This rotation speed detection method has an advantage that the structure of the detection device is simplified because a rotation type speed sensor is not used. Since the current detectors 6 and 7 are also used as the overcurrent prevention circuits of the inverter circuit 3 and the electric motor 4, the cost does not increase. Further, in this rotational speed detection method, the switches Q2, Q4, Q6 on one side of each phase arm of the inverter circuit 3 are turned on at the same time, and a current based on the free running voltage of the electric motor 4 is supplied while keeping this state. Since the frequency of the current is measured, it is possible to detect the rotation speed without the influence of noise due to the ON / OFF of the switches Q1 to Q6. Also, switches Q2 and Q4
, Q6 short-circuit the windings 4a, 4b, 4c to allow a current to flow, so that a relatively large current can be flowed during free running, and rotation speed can be detected with little influence of disturbance elements such as AC power lines.

The first and second peak detectors 16 and 17 of the rotation direction detection circuit 15 for detecting the rotation direction of the electric motor 4 in the free running period are provided to the first and second current detectors 6 and 7. It is connected to the output lines 6a and 7a.
When the electric motor 4 is coasting in the normal rotation (first direction), the detection current Iu of the first and second current detectors 6 and 7,
Iw flows in the phase relationship shown in FIG. 7 (A), and when inertially rotating in the reverse direction (second direction), the detected currents Iu and Iw of the first and second current detectors 6 and 7 are shown in FIG. Flows in the phase relationship shown in FIG. The first and second peak detectors 16 and 17 in FIG. 2 are the maximum values of the detection currents Iu and Iw (positive peak).
It has a detection means and a minimum value (negative peak) detection means, and FIG.
(A) and the sinusoidal detection current Iu shown in FIG.
Iw is shown in FIGS. 7 (B) (C) and 8 (B) (C).
The value is converted into first and second peak detection signals I1 and I2. That is, the period from the positive peak of the detection currents Iu and Iw to the next negative peak (for example, t1 to t3) is at the low level (first
Value indicating the voltage level of the second peak, and during the period from the negative peak to the next positive peak (eg, t3 to t5), the high level (second
Signals I1 and I2 having a value indicating the voltage level of 1). In short, signals I1 and I2 corresponding to those obtained by shaping the detection currents Iu and Iw of FIGS. 7 and 8 into square waves are obtained. Therefore, the signals I1 and I2 may be obtained by shaping the detection currents Iu and Iw into a square wave by the zero cross comparator. The phase comparator 18 of FIG. 2 is the binary first and second of FIG. 7 (B) (C) or FIG. 8 (B) (C) obtained from the first and second peak detectors 16 and 17. The phases of the peak detection signals I1 and I2 are compared logically. Phase comparator 1
Since 8 is for detecting the rotation direction of the electric motor 4, information on the amount of phase difference between the first and second peak detection signals I1 and I2 is unnecessary, and as shown in FIG. (Rotational direction of the
Whether the detection current Iw of the phase is advancing or the detection current Iw of the W phase is delayed with respect to the detection current Iu of the U phase due to the reverse rotation (second rotation direction) state as shown in FIG. All you have to do is determine. In this embodiment, FIG. 9 and FIG.
During the period from t1 to t2, the switch Q2 of the inverter circuit 3
When Q4 and Q6 are turned on at the same time to make them into a zero vector state, at the time of forward rotation, as shown in FIG.
When w advances 120 degrees and reverses, Iu as shown in FIG.
With respect to Iw, Iw is delayed by 120 degrees. Therefore, in the present embodiment, detection of forward rotation and reverse rotation based on the first and second peak detection signals I1 and I2 of FIGS. 7B and 8C and 8B and 8C is performed by the following first Alternatively, the second method is used. (1) In the first method, as shown in FIG. 7, when the first peak detection signal I1 changes from H (high level) to L (low level) (t1, t5, etc.), the second peak is detected. If the signal I2 is L (low level), a signal indicating normal rotation is output from the phase comparator 18, and as shown in FIG. 8, the first peak detection signal I1 changes from H to L (t1, t5
And the like), when the second peak detection signal I2 is H, a signal indicating reverse rotation is output from the comparator 18. (2) In the second method, as shown in FIG. 7, when the first peak detection signal I1 changes from L to H (t3, etc.), when the second peak detection signal I2 is H, normal rotation is shown. A signal is output from the phase comparator 18, and when the first peak detection signal I1 changes from L to H as shown in FIG.
And the like), when the second peak detection signal I2 is L, the phase comparator 18 outputs a signal indicating inversion. In order to prevent erroneous detection, the first and second peak detection signals I1,
Phase comparison is performed a plurality of times in a plurality of cycles of I2, and when the same comparison result is obtained all of a plurality of times or a predetermined number of times or more, this is output from the phase comparator 18 as rotation direction information. Of course, once the phase comparison can be performed with high reliability, the phase comparison may be performed once. First above
And as a modification of the second method, the second peak detection signal I
It is possible to detect the direction of rotation of the electric motor 4 by judging the advance or delay of the first peak detection signal I1 based on 2. Further, a well-known phase comparator used in a PLL circuit or the like for generating an output corresponding to the phase difference between the U-phase detection current Iu and the W-phase detection current Iw is used to determine the phase relationship between the two.
The state of FIG. 7 may be forward rotation, and the state of FIG. 8 may be reverse rotation. The rotation direction detection signal obtained from the phase comparator 18 of FIG. 2 is sent to the deceleration frequency generator 45 in the frequency command value generation and start controller 12 shown in FIG. 4 by the line 18a.

[0024]

[Normal rotation restart method] When the normal rotation drive is stopped at time t0 in FIG. 9 and the electric motor 4 enters the free running state, the rotation speed N gradually decreases as shown in FIG. 9 (A). When the forward rotation command line 9b is converted to a high level indicating the forward rotation command as shown in FIG. 9 (B) at time t1 during the free running period, the normal rotation command is passed through the OR gate 37 of FIG. , And the timer 38 sets t1 to t2 in FIG.
A pulse indicating a period (Ta) is generated. When the timer 38 generates a pulse indicating a period of t to t2, it is sent to the free running control circuit 14 of FIG. 2 via the line 12d. The free-running control circuit 14 is shown in FIG. 6 in response to the output of the free-running detection circuit 13 being in the free-running period and the line 12d being in the period from t1 to t2 in FIG. As shown, the switches Q2, Q4 and Q6 are controlled to be turned on at the same time. As a result, as described above, a current flows through the inverter output lines 3a, 3b, 3c, and the frequency detection circuit 8 of FIG. 1 detects the frequency fm indicating the inertial rotation speed.
Further, the rotation direction is detected by the rotation direction detection circuit 15 shown in FIG. The rotation direction detection signal is held by a hold circuit (not shown) until the restart is completed.

When the output pulse of the timer 38 falls from the high level at time t2 in FIG. 9, the ON control of the switches Q2, Q4 and Q6 by the free running control circuit 14 is finished, and at the same time, the trigger circuit 39 of FIG. A signal is generated and the flip-flop 40 is triggered. The flip-flop 40 is in the set state during the period t2 to t3 in FIG. 9 and turns on the switches 31 and 32 during the period t2 to t3. The output of the flip-flop 40 is the line 12b.
Is sent to the control terminal of the switch 22 of FIG. 3, and the switch 22 causes the ramp voltage Vs of the line 12c via the contact b.
To the sine wave generator 23. Gradient voltage generator 41 of FIG.
Generates a ramp voltage Vs in the period from t2 to t3 in FIG. 9D in response to the output of the flip-flop 40. The output of the ramp voltage generator 41 is sent to the line 12 via the switch 31.
sent to c. The starting frequency generator 36 is connected to the line 9b.
In response to the normal rotation command of the above and the output of the flip-flop 40, t2 of FIG.
The optimum starting frequency fs shown in the period up to t3 is determined and output. The optimum starting frequency fs is set to the latch circuit 42.
Similarly to, the detection frequency fm can be used. This optimum starting frequency fs is sent to the line 12a via the switch 32 and becomes the frequency command value Fn. T2 to t3 in FIG.
In the period Tb, the inverter is driven so as to generate the output voltage corresponding to the starting voltage Vs shown in FIG. The inverter output frequency in the period from t2 to t3 is kept at a constant starting frequency fs as shown in FIG. 9 (C),
The rotation speed is also kept substantially constant as shown in FIG.

The time t3 in FIG. 9 is determined by the comparator 46. One input terminal of this comparator 46 is connected to the ramp voltage generator 41, and the other input terminal is f / V (frequency
Voltage) converter 43. f / V converter 43
Converts the output frequency fs of the starting frequency generator 36 into a voltage proportional to this at the time of normal rotation restart, and converts the output frequency f1 of the latch circuit 42 into a voltage proportional to this at the time of reverse rotation restart. When the output voltage of the f / V converter 43 and the ramp voltage Vs become equal at the time t3 in FIG. 9, the output of the comparator 46 changes, and in response to this, the flip-flop 40 is reset. When the flip-flop 40 is reset, the switches 31 and 32 are turned off, and the ramp voltage Vs
And the supply of the starting frequency fs are stopped. Also,
At time t3, the control of the switch 22 of FIG. 3 by the line 12b is released, and the voltage command generator 21 is connected to the sine wave generator 23 via the contact a of the switch 22.

The forward acceleration frequency generator 44a is connected to the line 9
The forward rotation command of b, the output of the flip-flop 40, and the starting frequency fs of the starting frequency generator 36 are used as inputs.
(C) Starting acceleration frequency fa shown in the period Tc from t3 to t4
Is generated and sent to the line 12a via the switch 33. That is, in the normal rotation acceleration frequency generator 44a, the gradient voltage Vs is a value corresponding to the starting frequency fs in the state where the normal rotation command is generated, that is, fs in the constant V / f control.
In response to the voltage value corresponding to
A forward rotation acceleration frequency fa is generated which gradually increases at a predetermined gradient with s as an initial value. This forward rotation acceleration frequency fa is sent to the voltage command generator 21 and the sine wave generator 23 of FIG. 3 as a frequency command via the line 12a. This allows
The rotation speed N of the electric motor 4 smoothly increases toward the target frequency f0 as shown in FIG. 9 (A). Forward rotation acceleration frequency f
The end time t4 of the transmission of a is determined by the comparator 47. The comparator 47 compares the forward rotation acceleration frequency fa with the target frequency f0 of the line 9a, and when the two coincide, the switch 33 is turned off and the switch 35 is turned on instead. As a result, from the time t4 in FIG. 9, the target frequency f0 of the line 9a is output to the line 12a as the frequency command value Fn, and the electric motor 4 rotates at the target rotation speed as shown in FIG. 9 (A).

[0028]

[Reverse rotation restart method] Next, the reverse rotation restart of FIG. 10 will be described. When the normal rotation drive of the electric motor 4 is stopped at time t0 in FIG. 10, the free running state is entered as in the case of FIG. As shown in FIG. 10B, the line 9c is obtained at the time t1.
When a reverse rotation command is generated at, the period Ta from t1 to t2 in FIG.
In the same manner as in the period from t1 to t2 in FIG. 9, the OR in FIG.
The gate 37, the timer 38, and the free-running control circuit 14 of FIG. 2 operate to detect the frequency fm indicating the rotation speed of the electric motor 4 and the rotation direction detection circuit 15 to detect the rotation direction.

During the period from t2 to t3 in FIG. 10, t2 to t3 in FIG.
Similar to the t3 period, the trigger circuit 39, the flip-flop 40, the switches 31 and 32, the ramp voltage generation circuit 41, and the switch 22 of FIG. 3 operate. T2 to t3 in FIG.
The period is different from the period from t2 to t3 in FIG. 9 in that the starting frequency generator 36 is inoperative and the latch circuit 42 is in the operating state. The latch circuit 42 receives the set signal of the flip-flop 40 in the period t2 to t3 of FIG.
Based on the reverse rotation command of c and the detection frequency fm of the line 8a, the detection frequency fm at time t2 is held and the same control frequency f1 as fm is output. This control frequency f1 is output to the line 12a via the switch 32 as a frequency command for the period of t2 to t3. As a result, the reduction of the rotation speed N of the electric motor 4 shown in FIG. 10 (A) is stopped, and the rotation speed is kept substantially constant for the period of t2 to t3. T2 in FIG. 10 (D)
The ramp voltage Vs of the ramp voltage generator 41 gradually rises from zero volt toward the voltage V1 as in the period from t2 to t3 in FIG. In this embodiment, the gradient voltage Vs has the same gradient at the time of normal rotation restart of FIG. 9 and at the time of reverse rotation restart of FIG. 10, but the gradient voltage Vs having different gradients in FIG. 9 and FIG. Can also be generated. The determination at time t3 in FIG. 10 is the same as the determination at time t3 in FIG. However, in the case of FIG. 10, the f / V converter 43
The output frequency f1 of the latch circuit 42 is input to.

When the signal indicating the time point t3 is generated from the comparator 46 in FIG. 10, the flip-flop 40 is reset, the switches 31 and 32 are turned off, and the ramp voltage generator 41 and the latch circuit 42 are turned off. Further, switching from the contact b to the contact a of the switch 22 of FIG. 3 is executed.
At time t3 in FIG. 10, the deceleration frequency generator 45 operates in synchronization with the reset of the flip-flop 40. The deceleration frequency generator 45 uses the reverse command of line 9c and line 1c.
8a, the output frequency f1 = fm of the latch circuit 42 is initialized in response to the generation of the signal indicating t3 from the flip-flop 40 while the signal indicating the normal rotation in the period of t1 to t2 in FIG. As a value, a deceleration frequency f2 that gradually decreases with a predetermined inclination is generated as shown in FIG. The deceleration frequency f2 generated by the deceleration frequency generator 45 in the period Tc1 from t3 to t4 is transmitted through the switch 34 to the line 1
The frequency command value Fn is output to 2a. As a result,
The motor 4 is smoothly decelerated by the constant f / V control, and t4
At that time, the rotation speed becomes zero. The time t4 is determined by the comparator 48. This comparator 48 generates an output indicating that the deceleration frequency f2 has become zero at time t4, controls the switch 34 to be off, and controls the reverse rotation acceleration frequency generator 44b to be on.

The reverse acceleration frequency generator 44b is shown in FIG.
(C) The acceleration frequency f3 of the period Tc2 from t4 to t5 is generated, and the comparator 48 outputs t4 of FIG. 10 from the comparator 48 while the reverse rotation command shown in FIG. 10 (B) is generated in the line 9c.
When the output indicating the time point is generated, the acceleration frequency f3 shown in FIG. 10 (C) is generated and sent to the line 12a via the switch 33. The output voltage command V0 of the inverter changes in response to the acceleration frequency f3 according to the constant f / V control as shown in FIG. In FIGS. 10C and 10D, the frequency and voltage at the time of reverse rotation after t4 are shown on the side opposite to that at the time of forward rotation. T of the comparator 48
4 The signal indicating the time point, that is, the rotation direction switching control signal is line 1
It is supplied to the sine wave generator 23 of FIG. 3 via 2e. The sine wave generator 23 applies a three-phase sine wave voltage so as to reverse the electric motor 4 in response to the output of the comparator 48 at the time t4 in FIG. 10 while the reverse rotation command is being generated on the line 12c. Occur. As a result, the electric motor 4 is moved to the position shown in FIG.
As shown in (A), it rotates in the opposite direction from time t4, and
At the time point, the target frequency f0 is reached. The detection at the time point t5 in FIG. 10 is performed by the comparator 47 by the coincidence judgment between the reverse rotation acceleration frequency f3 and the target frequency f0, similarly to the detection at the time point t4 in FIG. The switch 33 is turned off and the switch 35 is turned on by the output of the comparator 47 at time t5 in FIG. 10, the target frequency f0 of the line 9a is sent to the line 12a via the switch 35, and the electric motor 4 is targeted.
Driven by. 9 and 10, the target frequency f
After the target rotation speed is obtained by 0, the output frequency of the inverter can be maintained at the target frequency and the output voltage of the inverter can be lowered to perform high efficiency operation.

Although FIG. 10 describes the switching from the forward rotation to the reverse rotation, the switching from the reverse rotation to the forward rotation is performed by the same method as the switching from the forward rotation to the reverse rotation.

As is apparent from the above, according to this embodiment, the following effects can be obtained. (1) The rotation direction can be easily detected. (2) The rotation speed can be easily detected. (3) The forward rotation restart and the reverse rotation restart can be performed easily and smoothly.

[0034]

MODIFICATION The present invention is not limited to the above-mentioned embodiments, and the following modifications are possible. (1) The inverter control circuit 5 can be composed entirely of analog circuits. (2) The frequency detection circuit 8 is replaced by the peak detection circuit 1 of FIG.
It can be configured to count one or both output pulses of 6,17. (3) A current detector is provided in all of the three-phase output lines 3a, 3b, and 3c, and the rotation direction can be detected by two combinations within the three-phase current. (4) The free running detection circuit 13 can be replaced by a power-off detection circuit or a motor stop command circuit. (5) Switches Q1 and Q3 on the upper side of the inverter circuit 3
, Q5 can be turned on simultaneously to detect the rotation speed and direction during free running. (6) The reverse rotation control can be performed by switching the generation order of the control signals given from the gate drive circuit 28 to the switches Q1 to Q6. (7) The rotation speed can be detected by another means such as a rotation detector.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a control and drive device for an induction motor according to an embodiment of the present invention.

FIG. 2 is a block diagram showing in principle the inverter control circuit of FIG. 1 in detail.

3 is a block diagram showing the PWM control circuit of FIG. 2 in detail.

FIG. 4 is a block diagram equivalently showing in detail the frequency command value generation and activation controller of FIG.

5 is a waveform chart showing a state of each part of FIG.

FIG. 6 is a circuit diagram showing a circuit for detecting a rotation speed and a direction during free running.

7 is a waveform diagram showing a state of each part of the rotation direction detection circuit of FIG. 2 in a normal rotation state.

8 is a waveform diagram showing a state of each part of the rotation direction detection circuit of FIG. 2 in a reverse rotation state.

FIG. 9 is a waveform diagram showing a state of each part of FIG. 1 at the time of restarting the normal rotation.

FIG. 10 is a waveform diagram showing a state of each part of FIG. 1 at the time of reverse rotation restart.

[Explanation of symbols]

3 inverter circuit 4 induction motor 15 Rotation direction detection circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02P 5/408-5/412 H02P 7/628-7/632 H02P 21/00 H02P 6/00-6 / 24 H02P 5/00 H02P 7/00-7/01 H02P 1/00-1/58

Claims (3)

(57) [Claims] 1. The AC motor during a period in which driving of the polyphase AC motor by a multiphase inverter having a configuration in which a plurality of series circuits of first and second switches are connected between a pair of DC power supply terminals is stopped. Is a method for detecting inertial rotation information of the multi-phase inverter, at least one of the first and second switches of the plurality of series circuits of the multi-phase inverter is controlled to be turned on at the same time, and at least the AC motor at this time is controlled. First and second
Of the input current of the first phase and the input of the first and second phases
The period from the positive peak of the current to the negative peak is the first voltage level.
Bell and the period from the negative peak to the positive peak is the second voltage.
A binary signal having a pressure level is formed, and the first and second signals are formed.
And a binary signal of the input current of the second phase
The input current of the second phase with respect to the input current of the first phase
But proceeds position or whether delayed position to determine the constant, the flow proceeds to output the information of the first rotational direction when the phase, when the delay phase outputs information of the second rotary direction opposite the first rotational direction A method for detecting inertial rotation information of an AC motor, characterized by obtaining information indicating a direction of inertial rotation of the AC motor. 2. A method for driving a multi-phase AC motor by a multi-phase inverter having a configuration in which a plurality of series circuits of first and second switches are connected between a pair of DC power supply terminals, the AC motor comprising: When a drive command in a second rotation direction opposite to the first rotation direction is generated during a drive stop period after driving in the first rotation direction, the plurality of the multi-phase inverters
One of the first and second switches of the series circuit
Controlled simultaneously turn on, input power of the AC motor in order to detect the rotational speed of the inertial rotation of the AC motor
Current and detects the period or frequency of the detected input current.
Measure this cycle or frequency to inertial rotation of the AC motor
Of detected as rotational speed, and detecting at least a first and an input current of the second phase of the AC motor to detect the rotation direction of the inertial rotation of the AC motor, wherein
From the positive peak to the negative peak of the input current of the first and second phases.
Is the first voltage level and the negative peak to positive peak
The binary signal whose second voltage level is the period until
Each of which is formed and is a binary signal of the input currents of the first and second phases.
The input current of the first phase based on
Note Whether the input current of the second phase is in the lead position or the lag position
Judges and outputs the information of the first rotation direction when the phase is advanced
However, in the case of the delay phase, the second rotation opposite to the first rotation direction is performed.
A first step of outputting information of a turning direction, and an output frequency of the inverter capable of obtaining a rotation speed substantially the same as the rotation speed detected in the first step after the first step. A first frequency command value (f1) corresponding to the first frequency command value (f1) is prepared, the inverter is driven so that an output frequency corresponding to the first frequency command value (f1) is obtained, and the output frequency f of the inverter is
Relationship between the output frequency and output voltage for the ratio V / f drives the AC power <br/> motivation by controlling the output voltage and the output frequency of the inverter to be constant and the output voltage V In order to obtain the first output voltage value (V1) corresponding to the first frequency command value (f1) in the characteristic diagram, the output voltage of the inverter is changed from zero to the first output voltage value (V1). A second step of gradually increasing toward V1), the output frequency of the inverter is a value corresponding to the first frequency command value (f1), and the output voltage of the inverter is the first output voltage value. After becoming (V1),
The output frequency command value of the inverter is gradually decreased from the first frequency command value (f1) toward zero, and the output voltage command value of the inverter is also controlled by the constant V / f. A third step of gradually decreasing from the command value toward zero; and having an orientation to rotate the AC motor in the second rotation direction after the third step, the output frequency command value of the inverter being set. The output voltage command value of the inverter is gradually changed to V
/ F, a fourth step of changing according to a constant control. 3. The AC motor during a period in which driving of the polyphase AC motor by a multiphase inverter having a configuration in which a plurality of series circuits of first and second switches are connected between a pair of DC power supply terminals is stopped. A first and second current detector for detecting the input currents of at least first and second phases of the AC motor, and the driving of the AC motor is stopped. Control means for controlling one of the first and second switches of the plurality of series circuits of the multi-phase inverter to be turned on at the same time, and a period during which the driving of the AC electric motor is stopped. From the positive peak to the negative peak of the input current of the first and second phases of the AC motor obtained from the first and second current detectors in
To the first voltage level for the period from negative peak to positive
The binary signal whose second voltage level is the period until
Binary values of the input currents of the first and second phases formed respectively
The input current of the first phase based on signal comparison
Whether the input current of the second phase is the advance position or the delay position
If the lead phase is detected, information on the first rotation direction is output.
Force, and when in the delay phase, the second rotation opposite to the first rotation direction
An inertial rotation information detection device for an AC motor, comprising: a phase comparison unit that outputs information on a rotation direction .