JP2000014199A - Device for judging anomaly in rotational speed sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for judging any anomaly in a rotational speed sensor which is capable of detecting any anomaly in the rotational speed sensor with accuracy and favorable responsiveness regardless of the condition of the operation of a motor and allows high reliability to be maintained. SOLUTION: A product Pnt of a speed detection value Ndet detected by a rotational speed sensor and a torque command Tref output from a speed controller is obtained using a multiplier 21, and a product Pdc of the direct- current supply voltage Vdc of an inverter and a direct-current supply current Idc is obtained using a multiplier 22. These values are input to a subtractor 23, and the subtractor is caused to output the difference between the absolute values of the product Pnt and the product Pdc as deviation ΔP. The deviation ΔP is supplied to one input of a comparator 24, and an error limit value EL generated by an error limit value generator 25 is supplied to the other input of the comparator 24. If the magnitude of a deviation ΔP exceeds the error limit value EL, an anomaly signal E indicating an anomaly in the rotational speed sensor is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for judging abnormality of a rotational speed sensor in a drive device of an AC rotary electric machine using a power converter, and more particularly to a rotational speed suitable for a motor drive control device of a vector control system. The present invention relates to a sensor abnormality determination device.

[0002]

2. Description of the Related Art In recent years, a motor driving device which uses a power conversion device such as an inverter device to supply AC power of a variable frequency to an AC rotating electric machine such as a synchronous motor or an induction motor and operates them at a variable speed. Is widely used, but in such a device, the rotation speed sensor is important because the rotation speed of the motor to be driven is detected and controlled so that it matches the given rotation speed command value. Become a component.

[0003] In particular, in an AC motor drive control device of the vector control type, the position of the magnetic pole of the field is calculated based on the detected value of the rotational speed in the case of the synchronous machine, and the position of the secondary magnetic flux is calculated in the case of the induction machine. The rotation speed sensor is a very important component because it calculates and controls the rotating magnetic field required to generate a desired torque.

Therefore, in such a motor drive control device, if an abnormality occurs in the main body of the rotation speed sensor provided therein or in the signal transmission system of the sensor, the control of the motor becomes impossible. However, these abnormalities must be detected as quickly and reliably as possible and appropriate measures must be taken.

[0005] For this reason, various detection devices for detecting an abnormality of a rotation speed sensor have been conventionally proposed. Typical examples thereof include a rotation speed command value given to an electric motor, There is known a method in which a difference between a rotation speed detected by a sensor and a speed deviation value is set as a speed deviation value, and when the difference exceeds a preset speed deviation limit value, it is determined that an abnormality has occurred in the rotation speed sensor.

Another example is that an output torque command value for an electric motor is constantly monitored, and when the value becomes abnormally large, and when the state continues for a certain period of time, an abnormality occurs in a rotation speed sensor. Is also known. This is because, in an AC motor control device using a rotation speed sensor, the output torque command value for the motor generally increases as the rotation speed detection value decreases, and this is used.

[0007]

However, the prior art described above does not say that the maintenance of the abnormality detection accuracy and the reduction of the abnormality detection time are sufficiently considered, and there is a problem in the reliability of the abnormality determination. . That is, in each of the above-described prior arts, the state quantity used for determining the abnormality of the rotation speed sensor depends on the load of the motor, such as the rotation speed command value and the output torque command value given to the motor. Is in quantity.

For this reason, it is difficult to set a reference value as a threshold value for abnormality determination, and a large reference value with a considerable margin for a normal state quantity in anticipation of a fluctuation range of an operating state such as a motor load. It is necessary to take a long time from the detection of the abnormality to the determination, and it is necessary to determine whether or not a correct abnormality has occurred by observing the situation. As a result, an accurate abnormality can be detected in a short time. Cannot do so, causing a problem in reliability.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rotational speed sensor capable of always accurately detecting abnormalities of the rotational speed sensor with good responsiveness without being affected by the operation state of the electric motor, and maintaining high reliability. An object of the present invention is to provide an abnormality determination device.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a power converter for generating AC power having a variable frequency, an AC motor supplied from the power converter, and sensor means for detecting the rotational speed of the AC motor. By controlling the power converter in accordance with the rotational speed of the AC motor detected by the sensor means, the motor drive control device of a system that operates the AC motor at a variable speed is detected by the sensor means. Means for calculating the power generated by the AC motor based on the rotation speed of the AC motor, and means for calculating the power input to the power conversion device are provided, and the power and the power are compared. This is achieved by determining whether the sensor is abnormal based on whether or not these differences exceed a preset threshold value.

When the power generated by the motor is calculated based on the rotation speed detected by the sensor, while the detected rotation speed is correct, the power is substantially proportional to the power actually generated by the motor. It also maintains a substantially proportional relationship with the electric power supplied to the electric motor.

However, when an abnormality occurs in the sensor, the power calculated based on the rotation speed detected by the sensor is not proportional to the power actually generated by the electric motor. It is possible to determine the abnormality of the sensor.

At this time, the above-mentioned proportional relationship is not affected by the load of the motor, so that an abnormality can always be determined accurately.

Therefore, in this case, the type of abnormality that can be detected is wide, such as an abnormality in the sensor output signal, an abnormality in the sensor itself, or an abnormality in the coupling between the sensor and the motor shaft. Will be possible.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an apparatus for judging abnormality of a rotational speed sensor according to the present invention will be described in detail with reference to the illustrated embodiment. FIG. 1 shows an AC motor drive control device that uses a VVVF (variable voltage variable frequency) inverter main circuit 1 that operates with DC power supplied from a DC power supply and that drives a motor 2 composed of a synchronous motor at a variable speed. This is an embodiment in which the invention is applied, and reference numeral 3 denotes a rotation speed sensor to be subjected to abnormality determination.

The inverter main circuit 1 includes a smoothing capacitor 4
And a switching circuit 5 in which, for example, six IGBTs (insulated gate bipolar transistors) are connected in a three-phase bridge, and a DC power supplied from a DC power supply (+, −) (not shown) is smoothed by the capacitor 4. After the conversion, the switching circuit 5 converts the power into three-phase AC power at a desired voltage and a desired frequency, and supplies it to the motor 2 to drive the motor 2 at a desired rotation speed. .

In practice, power is generally supplied from a commercial AC power supply. Therefore, a DC power supply is often configured to obtain DC power using a forward conversion circuit (rectifier). In this case, a so-called inverter device including a forward conversion unit and an inverse conversion unit is provided.

The rotation speed sensor 3 is connected to the rotation shaft of the motor 2 and functions to detect the rotation speed n of the motor 2 in real time and output the rotation speed N. The switching circuit 5 of the inverter circuit 1 is controlled by the rotation speed N detected by the rotation speed sensor 3, and three-phase AC power of a desired frequency and a desired frequency is supplied to the motor 2 as described above. Therefore, the rotational speed sensor 3 is an important component.

Next, the configuration and operation of the AC motor drive control device according to the embodiment of FIG. 1 will be described. A signal representing the rotation speed N detected by the rotation speed sensor 3 is input to the speed detector 6 and the magnetic pole position calculator 10.
Then, first, the signal representing the rotational speed N input to the speed detector 6 is converted into a detected speed value (speed feedback value) Ndet. Next, the speed detection value Ndet
Is supplied to a subtractor 7 where the speed is subtracted from an externally applied speed command Nref to obtain a speed deviation ΔN.

Next, the speed deviation ΔN is input to a speed controller 8, where the speed deviation ΔN is converted into a torque command Tref necessary for converging the speed deviation ΔN to 0, and the torque command Tref is transmitted to a current value / phase controller 9. Is entered. On the other hand, the rotation speed signal N input to the magnetic pole position calculator 10 is used here to calculate a signal representing the magnetic pole position M of the motor 2, and the magnetic pole position M calculated by the magnetic pole position calculator 10 is also a current value. -Input to the phase controller 9.

The current value / phase controller 9 functions to calculate a command value Iref of a current to be supplied to the motor 2. Therefore, the current value / phase controller 9 calculates a current command value Iref from the torque command Tref and the magnetic pole position M. , And input it to the current controller 11.

Therefore, the current controller 11 generates a switching pulse S to be supplied to each switching element of the switching circuit 5 according to the current command value Iref, thereby controlling the switching element of the switching circuit 5 to turn on and off. Thus, three-phase AC power is supplied to the motor 2.

And, along with this, the current controller 11
Output current value I detected from current detectors 12 and 13
out, and the frequency and pulse width of the switching pulse S are changed accordingly, so that feedback control in the direction in which the output current value Iout matches the current command value Iref is performed.

As a result, the rotational speed n of the motor 2 is controlled to the same rotational speed as the externally applied speed command Nref. At this time, even if the magnitude of the load of the motor 2 changes, the motor 2 is controlled so as to always maintain the speed command Nref. Therefore, as a whole, the motor 2 is controlled in accordance with the speed command Nref given from the outside. Can be obtained as an AC motor drive control device in which the rotational speed n of the motor is controlled.

By the way, the above is the same as that of the motor drive control device generally known as the vector control system. However, in the embodiment of the present invention, a sensor abnormality detector 14 is further provided, thereby It is configured to obtain the abnormality determination of No. 3. Therefore, the configuration and operation of the sensor abnormality detector 14 will be described below.

As shown in FIG. 1, the sensor abnormality detector 14
Inputs the speed detection value Ndet, the torque command Tref, the DC power supply voltage Vdc detected by the voltage detector 15, and the DC power supply current Idc detected by the current detector 16,
Based on these, it is determined whether or not an abnormality has occurred in the rotation speed sensor 3, and when it is determined that an abnormality has occurred, an operation of generating an abnormality signal E is performed. As shown in FIG. It comprises units 21, 22, a subtractor 23, a comparator 24, and an error limit value generator 25.

Then, as shown in FIG.
The speed detection value Ndet output from the speed detector 6 and the torque command Tref output from the speed controller 8 are input to one multiplier 21, and the voltage detector 15 outputs to the other multiplier 22. The taken DC power supply voltage Vdc and the DC power supply current Idc taken by the current detector 16 are input.

At this time, the voltage and current of the DC power supply often include a high-frequency ripple. In such a case, the DC power supply voltage Vdc from the voltage detector 15 is used.
And the DC power supply current Id from the current detector 16
It is necessary to use a low-pass filter with a sufficient time constant to capture c, and to capture through c.

As a result, one multiplier 21 outputs a multiplication value Pnt of the detected speed value Ndet and the torque command Tref, and the other multiplier 22 outputs a multiplication value of the DC power supply voltage Vdc and the DC power supply current Idc. Pdc will be output. The multiplied value Pnt and the multiplied value Pdc are input to the subtractor 23.

The subtracter 23 is configured to output the absolute value of the difference between the multiplied value Pnt and the multiplied value Pdc as a deviation ΔP, and the thus output deviation ΔP is input to a comparator 24.

The error limit value EL generated from the error limit value generator 25 is also input to the comparator 24, whereby the comparator 24 sets the error limit value E
L is used as a threshold to determine the magnitude of the deviation ΔP, and when the magnitude of the deviation ΔP exceeds the error limit value LE, ie, (Δ
An output is generated when P> LE), and the output is an abnormal signal E indicating an abnormality of the rotational speed sensor 3.

Next, the sensor abnormality detector 14
The reason why the occurrence of an abnormality in the rotation speed sensor 3 can be determined including the occurrence of an abnormality in the signal transmission system therefrom will be described.
First, looking at the multiplied value Pnt, which is the output of one of the multipliers 21, this corresponds to the detected speed Ndet of the actual rotation speed n of the motor 2 detected by the rotation speed sensor 3 and the speed detection value Ndet detected by the rotation speed sensor 3. At this time, this is the product of the torque command Tref given to the motor 2, and therefore, unless the rotation speed sensor 3 and the signal fetching therefrom are abnormal, the motor 2 generates It should represent the power that would be generated, that is, the amount of energy generated by the motor 2.

Next, looking at the multiplied value Pvi, which is the output of the other multiplier 22, is the product of the DC power supply voltage Vdc and the DC power supply current Idc. It should represent the power that would be supplied to the motor 2, that is, the magnitude of the energy input to the motor 2.

Then, ignoring the loss in each part,
Although they should be equal, there are actually various losses. At this time, the multiplication value Pnt becomes smaller than the multiplication value Pvi because the loss in the motor 2 is also included, but the proportional relationship is lost. And the following relationship holds. Pnt = K · Pvi Here, K is a proportional constant, and is a numerical value less than 1 (0 <K <1) from the above-described loss and the like.

This proportional relationship is not related to the magnitude of the load on the motor 2, and the proportional constant K keeps a substantially constant value no matter how the load changes. This is because, if the load of the motor 2 fluctuates, it firstly appears as a fluctuation of the rotational speed n, but, as apparent from the configuration of FIG. This is because the torque command Tref is changed, and the DC power supply current Idc is proportionally changed accordingly.

As a result, when no abnormality occurs, the subtractor 23 outputs a deviation ΔP having a certain value determined by the magnitude of the proportionality constant K. Therefore, the value of the deviation ΔP at this time is assumed to be A, and an error limit value EL having a value (A + α) larger than this value A by a predetermined value α is always generated, that is, (EL = A + α). The error limit value generator 25 is configured as described above.

When setting the predetermined value α, the loss occurring in the wiring portion between the motor drive control device and the motor 2, the loss occurring in the motor itself, and the speed detection value Nde
It is necessary to consider an error between detection and calculation of each state quantity such as t, torque command value Tref, DC power supply voltage Vdc, and DC power supply current Idc.

Then, when no abnormality has occurred in either the rotation speed sensor 3 itself or the signal transmission system from now on, that is, when it is normal, the magnitude of the deviation ΔP is equal to or smaller than the error limit value EL, that is, ( Since ΔP ≦ EL), the comparator 24 does not generate any output, and the abnormal signal E is not generated.

However, now, the rotation speed sensor 3
To itself or at least one of the signal transmission systems in the future,
If an abnormality occurs for some reason, the multiplier 2
The speed detection value Ndet input to 1 is different from a normal value determined by the actual rotation speed n of the motor 2.

In this case, the proportional relationship between the above energies is broken, and as a result, the subtractor 2
The magnitude of the deviation ΔP, which is the output of No. 3, is equal to the error limit value EL.
, That is, (ΔP> EL). As a result, the comparator 24 outputs the abnormal signal E.

At this time, as described above, the motor 2
Since the above-mentioned proportional relationship between the energies is not affected by the load fluctuation, the abnormality of the rotation speed sensor 3 can be accurately determined, and a highly reliable abnormality determination can be obtained.

As described above, since the determination based on the abnormal signal E is accurately obtained, it is not necessary to take a long time to observe the situation from the time when the abnormal signal E is generated, and the abnormality occurs in the rotation speed sensor 3 immediately. And immediately proceed to the next abnormal process.

When the abnormal signal E is output in this manner, a predetermined abnormal process may be executed by means not shown. As the abnormality processing at this time, for example, a display indicating that an abnormality has occurred in the rotation speed sensor is performed,
There are processes such as stopping the supply of electric power to the motor to maintain safety, and any other processes can be executed as necessary.

Therefore, according to the above embodiment, the motor 2
Even if the load changes, the abnormality of the rotation speed sensor 3 can always be detected reliably, and as a result, accurate abnormality detection can be obtained with good responsiveness, and the motor drive control device can easily have high reliability. Can be given to.

In the above embodiment, the case where the motor 2 is a synchronous motor has been described. However, it is not necessary for those skilled in the art to explain that the present invention can be applied to the case of an induction motor. In addition, it is only obvious to those skilled in the art from the logical configuration of FIG. 2 that the present invention can be implemented by a software configuration. According to the embodiment having the software configuration, it is possible to greatly simplify hardware components.

[0046]

According to the present invention, it is possible to accurately detect a wide range of abnormalities, such as abnormalities of the rotational speed sensor itself attached to the motor, abnormalities of its output signal, and abnormalities between the sensor and the motor shaft. It is possible to obtain the effects of improving the reliability of motor speed control and reducing the time required for troubleshooting when an abnormality occurs.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a motor drive control device to which an embodiment of a rotation speed sensor abnormality determination device according to the present invention is applied.

FIG. 2 is a block diagram illustrating an embodiment of a rotation speed sensor abnormality determination device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inverter main circuit 2 Motor 3 Rotation speed sensor 4 Smoothing capacitor 5 Switching circuit 6 Speed detector 7 Subtractor 8 Speed controller 9 Current value / phase control circuit 10 Magnetic pole position calculator 11 Current controller 12, 13 Current detector 14 Sensor abnormality detector 15 Voltage detector 16 Current detector 21, 22 Multiplier 23 Subtractor 24 Comparator 25 Error limit value generator

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H576 BB06 BB07 CC01 CC05 DD02 DD04 DD05 GG02 GG04 HA04 HB01 JJ26 LL07 LL22 LL24 LL28 LL41 LL57

Claims (2)

[Claims] 1. A power converter for generating AC power of a variable frequency, an AC motor fed from the power converter, and sensor means for detecting a rotation speed of the AC motor, the detection being performed by the sensor means. Controlling the power conversion device in accordance with the rotation speed of the AC motor, thereby controlling the AC motor at a variable speed, based on the rotation speed of the AC motor detected by the sensor means. Means for calculating the power generated by the AC motor, and means for calculating the power input to the power converter, comparing the power and the power, and setting a difference between them in advance. A rotation speed sensor abnormality determination device configured to determine abnormality of the sensor based on whether a threshold value is exceeded. 2. The invention according to claim 1, wherein the power is provided as a product of a rotation speed detection value detected by the sensor means and a torque command value provided to the AC motor. An abnormality determination device for a rotation speed sensor.