WO2012124157A1

WO2012124157A1 - Motor speed measurement device and motor speed monitoring device

Info

Publication number: WO2012124157A1
Application number: PCT/JP2011/056964
Authority: WO
Inventors: 純一植野; 明彦森川; 孝雄牛山; 哲也赤木; 康二井口
Original assignee: オムロン株式会社
Priority date: 2011-03-15
Filing date: 2011-03-23
Publication date: 2012-09-20
Also published as: JP5370397B2; JP2012196002A

Abstract

The present invention generates, by shaping the waveform of a pseudo AC voltage that is made by pulse modulation and that is to be supplied to an AC motor, a shaped signal that has the ON/OFF thereof switched with the same cycle as the switching of the pseudo AC voltage between plus and minus, and derives the rotational speed of the AC motor on the basis of the shaped signal. Abnormality is evaluated on the basis of the derived rotational speed, and when abnormality is evaluated as having occurred, a control signal for stopping or decelerating the AC motor is outputted.

Description

Motor speed measuring device and motor speed monitoring device

The present invention relates to a motor rotational speed measuring device and a motor rotational speed monitoring device in an AC motor.

An AC motor used in an industrial machine is designed with the expectation of three-phase AC power, and is characterized in that it can obtain a rotational speed proportional to the input frequency. Therefore, in order to accelerate or decelerate the AC motor or perform speed control, many apparatuses adopt a method of smoothly controlling an arbitrary motor speed by a frequency changer such as an inverter.

On the other hand, in an industrial machine, an apparatus or function capable of rapidly stopping the motor by monitoring an abnormal operation in which the motor rotates at an unexpected speed due to a failure or the like is considered important.

As for the motor, a speed detector such as an encoder or sensor is provided on the motor shaft as a device to prevent the motor from being operated at an unexpected speed due to human error or failure of the control device. The method of physically acquiring the difference between the rotational speed and the actual rotational speed is generally used. Patent Document 1 below discloses a technique of outputting the rotational state of the motor including the stop state to the abnormality detection means from a rotational speed sensor provided in the motor.

JP, 2010-288390, A

As described above, in the case of a motor provided with a speed detector, by feeding back the detection result to the motor control unit, even when an abnormal rotation occurs due to a failure, this can be detected, but the speed detection If this is to be added to a motor that is not equipped with a motor, it has conventionally to be physically attached by modification. However, depending on the environment, there may be cases where the speed detector can not be installed depending on the environment, etc., and even if it can be installed, there is a disadvantage that the apparatus becomes larger.

On the other hand, the technology to estimate the rotational speed of the motor from the waveform of the power supplied to the motor is adopted in the technology such as sensorless vector control of the inverter, but the method by the current detector is not suitable for the purpose of miniaturization It is not suitable for speed detection because noise is erroneously detected as a high-speed signal by voltage control using PWM modulation, which is used to simplify the system.

An object of the present invention is to provide a motor speed measuring device and a motor speed monitoring device capable of measuring and monitoring the rotation speed of an AC motor without physically adding a sensor or the like to the motor rotation shaft.

In order to achieve the above object, in the motor speed measuring device and the motor speed monitoring device according to the present invention, the motor rotation number is derived and the motor is stopped or decelerated by the following means or processes.

The motor speed measuring device according to the present invention is a motor speed measuring device connected in parallel to a power supply line of an AC motor and used, wherein an AC voltage supplied to the AC motor through the power supply line is used for the AC motor. It has a speed deriving means for deriving a rotational speed, and the speed deriving means derives a rotational speed of the AC motor by measuring a required time between zero cross positions from the waveform of the AC voltage. .

By adopting such a configuration, it is possible to obtain the rotation speed of the motor only by acquiring the AC voltage supplied to the AC motor, without installing the speed detector on the rotation shaft of the motor.

According to the present invention, it is possible to provide a motor speed measuring device and a motor speed monitoring device capable of monitoring the rotation speed of an AC motor without physically adding a sensor or the like to the motor rotation shaft.

It is a figure which shows the waveform which removed the modulation component of the time-axis direction from the input waveform by which PWM modulation was carried out, and the said waveform. FIG. 7 is a diagram showing a configuration of a speed detection unit according to the first to third embodiments. FIG. 2 is a circuit diagram showing a pulse width detection unit 201. FIG. 6 is a diagram showing the waveform of a signal processed by a pulse width detection unit 201. It is a figure which shows the whole structure of the motor speed monitoring apparatus based on 1st Embodiment. It is a figure which shows the modification of the motor speed monitoring apparatus based on 1st Embodiment. It is a figure which shows the whole structure of the motor speed monitoring apparatus based on 2nd Embodiment. It is a figure which shows the whole structure of the motor speed monitoring apparatus based on 3rd Embodiment. 7 is an operation flowchart of the abnormality detection unit 502 according to the first embodiment. It is a logic table based on 4th Embodiment. It is a circuit diagram added to pulse width detection part 201 concerning a 5th embodiment. It is a figure showing the diagnostic pulse concerning a 5th embodiment. It is a figure which shows the structure of the speed detection part 601,701 based on 4th, 5th embodiment. It is a figure which shows the structure of the signal consistency check part 204 based on 4th Embodiment.

In the present invention, an AC frequency is measured from the voltage waveform input to the motor to derive the motor speed. However, the power used by industrial motors is a circuit with a voltage such as 200 V or 400 V, which is an extremely high voltage compared to the operation of the electronic control circuit, and waveform distortion in the pseudo sine wave generated from the PWM circuit by the inverter. Because of the high rate, advanced denoising techniques are required to completely restore the pre-modulation sine wave without malfunctioning the electronics. In the following, embodiments of the invention will be described which meet the above requirements and obtain an accurate frequency.

First Embodiment
First, the outline of the speed deriving means in the present embodiment will be described with reference to FIG. 5a. The speed detection unit 501, which is a speed deriving unit, is installed in parallel with the motor 505, and acquires a three-phase power source input to the motor. Although the power supply has three phases, only the phase is different and the frequency is the same, so that at least one arbitrary phase may be acquired.

The waveform of the AC voltage input to the motor 505 (simultaneously to the speed detection unit 501) is modulated by changing the duty ratio of the pulse wave as shown in FIG. 1A, and is a signal that reproduces a sine wave by PWM. is there. Thus, the signal which represented the waveform of AC voltage in a pseudo | simulated manner by pulse modulation (PWM or PAM) is called "pseudo-AC voltage." Hereinafter, a configuration for acquiring (restoring) the input frequency from the waveform of such a pseudo AC voltage will be described.

FIG. 2 is a diagram showing the configuration of the speed detection unit 501 in the configuration shown in FIG. 5a. The speed detection unit 501 includes a pulse width detection unit 201, a pulse width measurement unit 202, and a rotation speed determination unit 203. The pulse width detection unit 201 is a waveform shaping unit according to the present invention, and generates a shaped signal that is switched on / off in the same cycle as the plus / minus switching of the pseudo AC voltage by shaping the waveform of the pseudo AC voltage. I have a role. The waveform shown in FIG. 1A passes through the pulse width detection unit 201, whereby a shaped signal having the waveform shown in FIG. 1B is obtained. The pulse width measurement unit 202 measures the width of one period of the waveform shown in FIG. 1B, and converts the reciprocal thereof as the input frequency to the motor. The rotational speed determination unit 203 determines the rotational speed of the motor from the acquired input frequency to the motor.

FIG. 3 is a diagram showing a circuit configuration of the pulse width detection unit 201. As shown in FIG. The pulse width detection unit 201 includes a comparator 101 as a first extraction unit, a comparator 102 as a second extraction unit, and an RS flip-flop 103 as a shaping signal generation unit. The power supply 104 input to the motor is stepped down and then input to the comparator 101 and the comparator 102. A reference voltage (threshold voltage) Vref1 greater than 0 V and lower than the maximum voltage of the pulse wave is smaller than 0 V and higher than the maximum voltage of the pulse wave. ) Vref2 is applied. The operation of this circuit will be described with reference to FIGS. 4 (a) to 4 (d).

The power supply 104 input to the pulse width detection unit 201 has the waveform shown in FIG. The output logic of the comparator 101 is positive when the input 104 is higher than the reference voltage Vref1. Here, when the pulse swings to the positive side (FIG. 4 (a) phase 1), the input 104 becomes higher than the reference voltage Vref1, so the output waveform when the waveform of FIG. 4 (a) is input to the comparator 101 Is as shown in FIG. 4 (b).

On the other hand, the comparator 102 is reversely connected in polarity to the comparator 101, and when the reference voltage Vref2 is higher than the input 104, the output logic is true. That is, when the pulse swings to the positive side (phase 1 in FIG. 4A), the reference voltage Vref2 is always lower than the input 104, so the output logic becomes false.

When the pulse swings to the negative side (phase 2 in FIG. 4A), the output logic of the comparator 101 is false because the input 104 is always lower than the reference voltage Vref1. On the other hand, for the comparator 102, since the reference voltage Vref2 is higher than the input 104 and the output logic is true, the output waveform when the waveform of FIG. 4A is input to the comparator 102 is as shown in FIG. become. As a result, only the positive and negative components of the input waveform can be reliably extracted by the

comparators

101 and 102.

The RS flip-flop 103 has an S input, an R input, and a Q output. The RS-type flip-flop holds the logic of the S input at the Q output, and resets the held logic when the R input becomes true. When the output (FIG. 4 (b)) of the comparator 101 described above is given to the S input of the flip flop 103 and the output (FIG. 4 (c)) of the comparator 102 is given to the R input, the waveform of the Q output 106 is obtained. Is as shown in FIG. 4 (d). This is a shaped signal obtained by removing the pulse width modulation component from the input waveform to the motor, which is the purpose of the pulse width detection unit 201.

Next, the pulse width measurement unit 202 measures the width of one period of the acquired shaped signal waveform (FIG. 4 (d)), and determines the reciprocal thereof as the input frequency to the motor. For the measurement of the pulse width, for example, using a zero crossing circuit, the cycle of timing when the applied voltage becomes zero is measured. As a result of measurement, for example, when one waveform cycle is 5 milliseconds, the input frequency to the motor becomes 200 Hz which is the reciprocal thereof.

After determining the input frequency, the rotational speed determination unit 203 derives the synchronous speed of the motor and the rotational speed based on the measured frequency. In the case of a synchronous motor, since the rotational speed of the motor matches the synchronous speed calculated from the input frequency, the formula is as shown in Formula 1.

For example, when the input frequency to the 8-pole synchronous motor is 200 Hz, the rotational speed can be determined as (2 × 200 × 8) × 60 = 3000 revolutions per minute according to the above equation. In the case of an induction motor, since the input frequency and the synchronous speed do not match, the rotational speed of the motor is obtained by subtracting the part corresponding to slip from the synchronous speed calculated above. For example, in the above example, if the slip is 0.1, then the number of revolutions can be 3000- (3000 × 0.1) = 2700 revolutions per minute. By performing the above processing, the speed detection unit 501 can derive the number of rotations of the motor.

Next, the operation of the abnormality detection unit 502 shown in FIG. 5a will be described with reference to FIG. The flowchart in FIG. 8 shows the operation of the abnormality detection unit 502. First, when the operation is started, step S801 of deriving the rotational speed of the motor from the speed detection unit 501 is executed.

Subsequently, based on the derived speed, step S802 is executed to confirm whether the rotational speed is within the allowable range. Here, if the rotational speed deviates from the allowable range, the process transitions to step S805 of outputting a control signal to the motor control unit 503, which is the motor control unit of the present invention. If the rotational speed is within the allowable range, the process proceeds to step S 803 of calculating the rotational speed increment with reference to the rotational speed stored in the previous process (when the process is the first process, it is stored in the previous process) The rotational speed is 0). Subsequently, the process proceeds to step S804 in which it is confirmed whether the rotational speed increment (motor acceleration) is within the allowable range. Here, if the acceleration deviates from the allowable range, the process transitions to step S805 for outputting a control signal to the motor control unit 503. If the acceleration is within the allowable range, the process returns to step S <b> 801 after transitioning to step S <b> 806 of temporarily storing the derived rotational speed.

Therefore, by repeatedly executing this process, the current motor speed and acceleration can be monitored, and when either the speed or the acceleration deviates from the allowable range, the control signal is output to the motor control unit 503. You can

When step S805 is executed, the abnormality detection unit 502 issues a control signal to the motor control unit 503. In the first embodiment, the motor control unit 503 is connected to an electromagnetic contactor 504 (circuit breaker) installed on a circuit of an inverter device 506, which is a motor controller, and a motor 505. Then, upon receiving the control signal, the motor control unit 503 opens the electromagnetic contactor 504. As a result, the power of the motor 505 is shut off, and the rotation of the motor 505 is stopped.

According to the present embodiment, it is possible to obtain the rotational speed of the motor without using the speed detector by acquiring the voltage waveform input to the AC motor, shaping the waveform, and deriving the rotational speed of the motor. it can. In addition, the semiconductor device is used for deriving the speed, which solves the drawback of the conventional problem that the apparatus is enlarged.

Moreover, there is an advantage that the motor can be stopped surely by shutting off the power supply using the magnetic contactor 504, and by monitoring the rotational speed or acceleration, not only the failure of the inverter device but also the tolerance is permitted. It is also possible to detect a user's operation error such as issuing an instruction exceeding the speed or performing a rapid acceleration operation exceeding the allowable range. Instead of using the magnetic contactor 504, as shown in FIG. 5b, a blocking circuit 507 may be installed in the inverter device to block the control signal.

Second Embodiment
The configuration in the second embodiment will be described with reference to FIG. The speed detection unit 601, the abnormality detection unit 602, and the motor control unit 603 are installed in parallel with the motor 605, as in the first embodiment, and the operation is the same as that of the first embodiment.

In the second embodiment, the motor control unit 603 is connected to an electromagnetic contactor 604 installed on a circuit connecting the power supply 600 and the inverter device 606. Upon receiving the control signal, the motor control unit 603 opens the electromagnetic contactor 604. As a result, the power supply of the inverter device 606 is shut off, so that the rotation of the motor 605 is stopped as in the first embodiment.

Also in the second embodiment, as in the first embodiment, the rotational speed or acceleration of the motor can be monitored without using a speed detector, but input to the inverter device 606 using the electromagnetic contactor 504 Not only the motor but also the inverter device can be simultaneously stopped by shutting off the power supply. This method is effective because when one motor drives a plurality of motors, failure of the motor drive may affect other motors.

Third Embodiment
The configuration in the third embodiment will be described with reference to FIG. The speed detection unit 701, the abnormality detection unit 702, and the motor control unit 703 are disposed in parallel with the motor 705 as in the first embodiment, but may be disposed outside the inverter device 706 or internally It may be arranged in The operation is similar to that of the first embodiment.

In the third embodiment, the motor control unit 703 is connected to a control circuit 704 which the inverter device 706 has. When receiving the control signal, motor control unit 603 outputs a signal indicating that an abnormality has occurred to control circuit 704. Thereby, the inverter device 706 reduces the number of rotations until the motor 705 is stopped urgently or no abnormal signal is detected. The response to temporarily reduce the rotational speed is effective when it is assumed that the user's abnormal operation is not a failure of the inverter device. In this case, a warning may be issued to the user.

Also in the third embodiment, as in the first embodiment, although it is possible to monitor the rotational speed or acceleration of the motor without using a speed detector, it is possible to monitor the inverter 706 instead of cutting off the power. By outputting the control signal, it is possible to adjust the speed of the motor rather than the forced stop by shutting off the power. For example, when an overspeed occurs due to a user's operation error, an alarm is issued and then the vehicle is decelerated to a predetermined speed or less, or while the speed is over, the acceleration operation is not accepted. The effect can be expected.

Fourth Embodiment
The fourth embodiment will be described with reference to FIG. In the fourth embodiment, a self-diagnosis function is realized by adding a signal integrity check unit 204 (fault diagnosis means) to the pulse width detection unit 201. Specifically, in the flip flop 103 in FIG. 3, there are an S input to which the output signal from the first extraction means is input, an R input to which the output signal from the second extraction means is input, and a shaping signal. When the Q output state is acquired and a logically impossible combination is acquired, the

speed detection units

501, 601, 701 determine that an abnormality has occurred in itself.

FIG. 9 is a diagram showing the logical states of S input, R input, and Q output, and the result of abnormality determination. The following describes each case that is determined to be normal or abnormal.

If the S input is false and the R input is false, the Q output is determined to be normal regardless of the contents of the Q output (cases 901 and 902) because the characteristics of the flip-flop are undefined because the characteristics of the flip flop are undefined.

If the S input is false and the R input is true, the Q output is always false. If the Q output is false, it is normal (case 903), and if it is true, it is determined that the flip flop is broken. Yes (case 904).

If the S input is true and the R input is false, the Q output is always true. If the Q output is true, it is normal (case 905). If it is false, it is determined that the flip flop is faulty. Yes (case 906).

The outputs from the

comparators

101 and 102 do not become true at the same time, so if the S input is true and the R input is true, it is determined that the comparator has failed (cases 907 and 908).

FIG. 13 is a circuit configuration example of the signal integrity check unit 204 using the logic circuit corresponding to FIG. In the diagnosis result 305, true is output when it is determined to be abnormal, and false is output when it is normal. If it is determined that the operation is abnormal, the pulse width detection unit 201 does not input the measurement result to the pulse width measurement unit 202, and stops the monitoring operation by locking out the device. At the same time, the user may be notified that an abnormality has occurred in the monitoring device.

The logic check according to the present embodiment may be performed continuously or at regular intervals. In order to obtain the state of each input / output, it is desirable to use a photocoupler or the like to perform insulation.

In the fourth embodiment, the logic check can prevent unintended operation of the

comparators

101 and 102 and the flip flop 103. As a result, when one of the elements degrades and breaks down, this can be detected quickly, and the user can be notified. If a failure of the pulse width detection unit 201 is detected, for example, the monitoring function may be stopped or the motor itself may be stopped or decelerated. This has the advantage that it is possible to prevent the motor from operating with speed monitoring not functioning properly.

Fifth Embodiment
The fifth embodiment will be described with reference to FIG. In the fifth embodiment, the dynamic test function is realized by adding the test signal input unit 205a to the input of the pulse width detection unit 201 and the test signal detection unit 205b to the output. In the present embodiment, the test

signal input units

205a and 205b correspond to the second failure diagnosis means of the present invention. FIG. 10 is a circuit diagram in which a test signal input unit 205a is added to the input portion of the pulse width detection unit 201 shown in FIG.

The test signal input unit 205 a includes a test input signal line 1 (107 a), a test input signal line 2 (107 b), and

photocouplers

108 and 109. Hereinafter, the operation in the case where the dynamic test is performed during motor drive monitoring will be described with reference to FIGS. 10 and 11.

When a signal is input to the test input signal line 1 (107a), the input to the pulse width detection unit 201 is clamped to Vcc by the effect of the photocoupler regardless of the input waveform supplied to the motor. When a signal is input to the test input signal line 2 (107b), the input to the pulse width detection unit 201 is similarly clamped to Vss regardless of the input waveform supplied to the motor.

Therefore, as shown in the timing chart of FIGS. 11A and 11B, when pulse signals are applied to two test input lines, the waveforms input to the

comparators

101 and 102 are as shown in FIG. It will be. The hatched portion is a portion depending on the input waveform actually supplied to the motor.

The output of the flip flop 103 is as shown in FIG. For this reason, when the waveform as illustrated is input from the test signal input unit 205a, the output result of the flip flop 103 is acquired by the test signal detection unit 205b, and the apparatus as illustrated in FIG. It can be judged.

In addition, the test signal detection unit 205 b may be arranged to be connected to the pulse width measurement unit 202 or the rotational speed determination unit 203. When connected to the pulse width measurement unit 202, it can be understood that the apparatus is normal if the frequency that matches the input test signal can be measured. Similarly, when connected to the rotational speed determination unit 203, it can be known that the apparatus is normal if the expected rotational speed is derived for the input test signal.

In the fifth embodiment, by clamping the input waveform by the test signal, dynamic failure diagnosis of the

comparators

101 and 102 and the flip flop 103 which the motor speed monitoring device has can be performed. While the fourth embodiment checks only the logic of input / output signals, this embodiment actually checks the operation of the apparatus by inputting a test signal, so both

comparators

101 and 102, for example, In the case of failure and stopping while maintaining the logic of the case 901, although this can not be detected in the fourth embodiment, detection is possible in the present embodiment. As described above, the fifth embodiment has an advantage of being able to cope with a case where the apparatus for detecting an abnormality itself has failed in addition to the fourth embodiment.

As described above, in the present invention, it has been noted that among the complex signal changes in PWM modulation, the waveform change leading to the motor rotation is only the portion that crosses zero. The period during which only the positive side of the PWM waveform is output is the waveform for the same motor magnetic pole, and it is necessary to get over the magnetic pole to get to the next magnetic pole, so the voltage is applied in the reverse direction .

In addition, since the motor is a coil, the zero cross position can be ordered relatively easily by combining it with a low pass filter that eliminates high-speed changes that the motor can not respond to, such as fundamental frequency for PWM modulation and spike noise. It is possible to sample

After detecting the zero-crossing position, it is possible to measure the main frequency that the output energy gives to the motor rotation by measuring the required time between the zero-crossing positions using a common technique. Enables accurate speed detection by an independent circuit.

The above description of the series of embodiments is merely an example for describing the present invention, and the present invention should not be interpreted as being limited to the above embodiments. For example, in the third embodiment, although the motor control unit 703 outputs a signal indicating abnormality to the inverter device 706, when the motor rotational speed does not decrease, the electromagnetic contactor disposed on the power supply line is opened. Alternatively, multiple embodiments may be combined, such as stopping the motor 705.

In the

abnormality detection units

502, 602, and 702, only the velocity may be monitored, or both of the velocity and the acceleration may be monitored. The failure determination according to the fourth embodiment may be performed by a microcomputer other than the illustrated logic circuit.

In the fourth and fifth embodiments, when it is determined that the device is malfunctioning, the monitoring operation is stopped, and a control signal is output to the

motor control units

503, 603, and 703 to drive the motor. You may stop it. As a result, it is possible to prevent the motor operation in a state where the monitoring is not operating.

The present invention may be realized by the following configuration.

The alternating current voltage may be a pseudo alternating current voltage by pulse modulation.

In many cases, a pseudo AC voltage by pulse modulation is used for control of an AC motor, and the present invention can be applied even to a motor that performs voltage control using the pulse modulation.

The motor speed monitoring device according to the present invention is a motor speed monitoring device that is used by being connected in parallel to a power supply line of an AC motor, wherein the AC speed is supplied from the AC voltage supplied to the AC motor through the power supply line. It is determined whether or not the rotational speed derived by the speed deriving means is a speed deriving means for deriving the rotational speed, and the control for stopping or decelerating the rotation of the AC motor when it is determined that the rotational speed is abnormal. Motor control means for outputting a signal, the AC voltage is a pseudo AC voltage by pulse modulation, and the speed deriving means shapes plus / minus the pseudo AC voltage by shaping the waveform of the pseudo AC voltage. And a waveform shaping means for generating a shaping signal that switches on / off in the same cycle as the switching of It is characterized by deriving the rotational speed of the AC motor Zui.

By adopting such a configuration, even if the speed detector is not installed on the rotation shaft of the motor, the rotational speed of the motor can be detected and abnormality in the speed is detected only by acquiring the AC voltage supplied to the AC motor. In this case, an instruction for stopping or decelerating can be output to the outside.

The waveform shaping means in the present invention comprises: a first extracting means for extracting only a signal of a positive component from the waveform of the pseudo alternating voltage; and a second extracting means for extracting only a signal of a negative component from the waveform of the pseudo alternating voltage And shaping signal generation means for generating and outputting the shaping signal from the output signal of the first extraction means and the output signal of the second extraction means.

Further, the first extraction means is constituted by a first comparator for comparing the pseudo AC voltage with a positive threshold voltage, and the second extraction means comprises the pseudo AC voltage and the negative threshold voltage. The shaping signal generation means may be constituted by a flip flop to which an output signal of the first comparator and an output signal of the second comparator are inputted.

As described above, since the waveform shaping means in the present invention can perform the shaping of the AC voltage waveform for deriving the rotational speed of the motor with only at least three semiconductor elements, the entire apparatus can be miniaturized. There is no need to select a sensor for each capacity of the motor's current consumption because it has the advantages of not requiring a current detector, and it is possible to change the electric circuit only when detecting the speed without changing the existing machine. It has the advantage of being able to In addition, comparing the waveform of the pseudo AC voltage with the threshold voltage has the advantage of being able to reliably shape the waveform without being affected by power supply noise.

Further, in the motor speed monitoring device according to the present invention, the combination of the logics of the three signals of the output signal of the first extraction means, the output signal of the second extraction means and the shaping signal is a possible combination. It is also preferable to have fault diagnosis means for judging whether the combination is not a possible combination and judging that the waveform shaping means is broken.

As a result, the three signals of the signal output from the first extraction means, the signal output from the second extraction means, and the shaping signal are not logically matched, that is, when a failure occurs in the device, this is detected It is possible to If a failure is detected, the user may be notified or the motor may be stopped on the basis of the non-monitoring state.

Similarly, in the motor speed monitoring apparatus according to the present invention, a test signal of a predetermined waveform is input to the first extraction unit and the second extraction unit, and the logic of the shaping signal output from the shaping signal generation unit Determining whether or not the signal corresponds to the waveform of the test signal, and determining that the waveform shaping means is broken if the signal does not correspond to the waveform of the test signal It is also preferable to have

By inputting the test signal and comparing it with the output result, it can be confirmed whether the predetermined operation is performed correctly. In the fault detection by the logic matching check, if the circuit stops in the correct logic state, the fault can not be detected, but there is an advantage that the fault detection can be surely performed as compared with this.

The control signal output from the motor control means in the present invention is a signal output to the circuit breaker for interrupting the supply of the AC voltage to the AC motor or a controller for supplying the AC voltage to the AC motor. May be

If the motor is to be stopped immediately, for example, the circuit breaker may receive a control signal to shut off the power supply to the motor. When decelerating the motor, the motor controller, for example the control circuit of the inverter device, may receive the control signal and decelerate the motor until the speed reaches an acceptable range.

By outputting a control signal to the controller of the circuit breaker or motor, it is also possible to stop the motor reliably by opening the circuit breaker, and also gives an alarm to the user and then decelerates to continue the operation. It is possible. This has the advantage of not only monitoring controller failures, but also monitoring abnormal operation of the user. Of course, if the rotational speed does not decrease even if the control signal for decelerating is output to the controller, it is determined that there is a failure, and the control signal for stopping is output to the circuit breaker, etc. You may use together.

101, 102 Comparator 103 RS flip-flop 104 Input power supply line 106 Output power supply line 107a Test signal line 1
107b test signal line 2
108, 109, 301 Photocoupler 201 Pulse Width Detection Unit 202 Pulse Width Measurement Unit 203 Rotational Speed Determination Unit 302 NOT Gate 303 AND Gate 304

OR Gate

500, 600, 700

Power Supply Device

501, 601, 701

Speed Detection Unit

502, 602, 702

abnormality detection unit

503, 603, 703 motor control unit 504

electromagnetic contactor

505, 605, 705

AC motor

506, 606, 706 inverter device 507 cut-off circuit 704 inverter control circuit

Claims

A motor speed measuring device used in parallel connection to a power supply line of an AC motor,
Speed deriving means for deriving the rotational speed of the AC motor from the AC voltage supplied to the AC motor through the power supply line;
Have
The motor speed measuring device, wherein the speed deriving means derives a rotational speed of the AC motor by measuring a required time between zero cross positions from a waveform of the AC voltage.
The motor speed measuring device according to claim 1, wherein the alternating voltage is a pseudo alternating voltage based on pulse modulation.
A motor speed monitoring device connected in parallel to a power supply line of an AC motor and used,
Speed deriving means for deriving the rotational speed of the AC motor from the AC voltage supplied to the AC motor through the power supply line;
Motor control means for determining whether or not the rotational speed derived by the speed deriving means is abnormal, and outputting a control signal for stopping or decelerating the rotation of the AC motor when it is determined that the rotational speed is abnormal. Have
The AC voltage is a pseudo AC voltage by pulse modulation,
The speed deriving means has a waveform shaping means for generating a shaping signal which is switched on / off at the same cycle as switching of the pseudo AC voltage by shaping the waveform of the pseudo AC voltage, and the waveform A motor speed monitoring device characterized in that the rotational speed of the AC motor is derived based on a shaping signal output from a shaping means.
The waveform shaping means
First extracting means for extracting only a signal of a positive component from the waveform of the pseudo AC voltage;
A second extraction unit that extracts only a negative component signal from the waveform of the pseudo AC voltage;
Shaping signal generation means for generating and outputting the shaping signal from the output signal of the first extraction means and the output signal of the second extraction means;
The motor speed monitoring device according to claim 3, comprising:
The first extraction means comprises a first comparator that compares the pseudo AC voltage with a positive threshold voltage;
The second extraction means comprises a second comparator that compares the pseudo AC voltage with a negative threshold voltage;
The motor speed monitor according to claim 4, wherein the shaping signal generation means is configured of a flip flop to which an output signal of the first comparator and an output signal of the second comparator are input. apparatus.
It is determined whether or not the combination of the logic of the three signals of the output signal of the first extraction means, the output signal of the second extraction means and the shaping signal is a possible combination, and the combination is not possible. The motor speed monitoring device according to claim 4 or 5, further comprising failure diagnosis means for judging that the waveform shaping means is broken.
A test signal of a predetermined waveform is input to the first extraction unit and the second extraction unit, and the logic of the shaping signal output from the shaping signal generation unit corresponds to the waveform of the test signal. It further comprises a second failure diagnostic means for judging whether or not the waveform shaping means is defective if it does not correspond to the waveform of the test signal. The motor speed monitoring device according to any one of claims 6 to 10.
The control signal output from the motor control means is output to a circuit breaker that shuts off the supply of AC voltage to the AC motor, or a controller that supplies AC voltage to the AC motor. The motor speed monitoring device according to any one of claims 3 to 7.