JP3951934B2 - Electric motor system, motor system abnormality detection device and abnormality detection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric motor system, an abnormality detection device, and an abnormality detection method that can detect an abnormality in an electric motor and its peripheral circuits.
[0002]
[Prior art]
A technique of operating with high efficiency by connecting an electric motor to a circuit including an electric motor control circuit such as an inverter circuit is widely used. For example, as shown in FIG. 7, a plurality of electric motors M1, M2, and M3 are connected to a main circuit 10 that includes a plurality of inverter circuits INV1, INV2, and INV3, and each inverter circuit INV1, INV2, is connected from a control unit 14 that includes a computer. By outputting the frequency designation signals S _f1 , S _f2 , S _f3 that output alternating currents of different frequencies to the INV ₃ , control for operating the motors M 1, M 2, M 3 at different rotational frequencies is also performed. It is coming.
[0003]
As a method for detecting an abnormality of such an electric motor system, an abnormality diagnosis method disclosed in Japanese Patent Laid-Open No. 2002-189064 and an abnormality detection method disclosed in Japanese Patent Laid-Open No. 2001-78480 are known.
[0004]
[Patent Document 1]
JP 2002-189064 A [Patent Document 2]
Japanese Patent Laid-Open No. 2001-78480
[Problems to be solved by the invention]
In the electric motor system, for example, when an abnormality such as an increase in stray capacitance occurs, the common mode current flowing through the electric motor and the main circuit increases to cause abnormal heating of the electric motor and the main circuit. Further, as the stray capacitance increases, noise is likely to occur between the body portion of the motor and the main circuit, which may cause malfunction. Furthermore, when the stray capacitance increases, there is a risk of electric shock when a human body touches the motor or main circuit.
[0006]
In order to prevent these problems, it is necessary to detect abnormalities in the motor system at an early stage, but it is possible to directly detect electromagnetic abnormalities such as an increase in stray capacitance between the motor and the main circuit to which the motor is connected and the grounding point. There was no technology. In particular, when a plurality of electric motors are connected to one main circuit, there is a strong demand for a technique that can determine which motor has an abnormality.
[0007]
In view of the above problems, an object of the present invention is to provide an electric motor system, an abnormality detection device, and an abnormality detection method capable of detecting an abnormality such as an increase in stray capacitance in order to solve at least one of the above problems. To do.
[0008]
[Means for Solving the Problems]
The present invention capable of solving the above problems is an electric motor system comprising an electric motor, a main circuit connected to the electric motor, and a measurement circuit for measuring an electromagnetic physical quantity from a measurement point provided in the main circuit, It comprises an abnormality detecting means for detecting an abnormality based on a value of a frequency component corresponding to a rotation frequency of the electric motor in the physical quantity.
[0009]
Another aspect of the present invention that can solve the above-described problem is an abnormality detection device including a measurement circuit that measures an electromagnetic physical quantity from a measurement point provided in a main circuit connected to an electric motor, It includes an abnormality detecting means for detecting an abnormality based on a value of a frequency component corresponding to the rotation frequency of the electric motor.
[0010]
Here, when a plurality of electric motors are connected to the main circuit, it is preferable that the abnormality detecting unit detects an abnormality based on a value of a frequency component corresponding to a rotation frequency for each electric motor in the physical quantity. .
[0011]
It is also preferable to further include rotational frequency control means for operating the motors at different rotational frequencies when detecting an abnormality.
[0012]
Furthermore, it is also preferable that the abnormality detection unit specifies an abnormal motor based on a value of a frequency component corresponding to a rotation frequency for each electric motor in the physical quantity.
[0013]
Another aspect of the present invention that can solve the above problem is an abnormality detection method for measuring an electromagnetic physical quantity from a measurement point provided in a main circuit connected to an electric motor, and detecting an abnormality based on the physical quantity. And an abnormality detecting step of detecting an abnormality based on a value of a frequency component corresponding to a rotation frequency of the electric motor in the physical quantity.
[0014]
Here, when a plurality of electric motors are connected to the main circuit, it is preferable that the abnormality detection step detects an abnormality based on a value of a frequency component corresponding to a rotation frequency for each electric motor in the physical quantity. .
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings.
[0016]
As shown in FIG. 1, the electric motor system in the present embodiment basically includes electric motors M1, M2, and M3, a main circuit 10, a sensor circuit 12, and a control unit 14. The main circuit 10 includes a DC power supply 16 and inverter circuits INV1, INV2, and INV3.
[0017]
The inverter circuits INV1, INV2, and INV3 are connected to the motors M1, M2, and M3, the DC power source 16, and the control unit 14, respectively. In the present embodiment, the inverter circuit refers to all circuits that convert direct current into alternating current, and various inverter circuits using a bridge circuit or the like of a semiconductor switching element can be applied.
[0018]
The control unit 14 is a computer including a CPU, a memory, an analog / digital conversion circuit, and the like. In response to an external control command, the control unit 14 outputs frequency designation signals S _f1 , S _f2 , S _f3 to the inverter circuits INV1, INV2, INV3. The inverter circuits INV1, INV2, and INV3 receive the frequency designation signals S _f1 , S _f2 , and S _f3 , respectively, convert the DC current supplied from the DC power source into AC currents of the frequencies f1, f2, and f3 to convert the motor M1, Supply to M2 and M3. The electric motors M1, M2, and M3 receive the outputs from the inverter circuits INV1, INV2, and INV3, and rotate at the rotation frequencies f1, f2, and f3, respectively.
[0019]
A sensor circuit 12 is connected to the main circuit 10 including the inverter circuits INV1, INV2, and INV3. The sensor circuit 12 measures a potential difference between a voltage at one point in the main circuit 10 and the ground voltage. The measured potential difference is output to the control unit 14 as the measurement voltage V (f). The measurement voltage V (f) is superposed with an AC voltage having the fundamental frequencies of the rotation frequencies f1, f2, and f3 of the electric motors M1, M2, and M3.
[0020]
As shown in FIG. 2, the sensor circuit 12 includes a resistor R having a high resistance value between one end of the DC power source 16 of the main circuit 10 and a ground point (for example, the casing of the motor system is generally a ground point). And a potential difference between both ends of the resistor R can be output as a measurement voltage V (f). Further, as shown in FIG. 3, a detection coil L magnetically coupled from the wiring in the main circuit 10 may be provided, and a potential difference between both ends of the detection coil L may be output as a measurement voltage V (f). .
[0021]
The control unit 14 receives the measurement voltage V (f) and converts the measurement voltage V (f) into a digital signal by an analog / digital conversion circuit. The measurement voltage V (f) converted into a digital signal is converted into a frequency spectrum using an existing fast Fourier transform method or the like.
[0022]
FIG. 4 shows an example of a frequency spectrum obtained by performing Fourier transform on the measured voltage V (f). Since the measurement voltage V (f) is superimposed with an AC voltage having the fundamental frequencies of the rotation frequencies f1, f2, and f3 of the motors M1, M2, and M3, the voltage value is in the vicinity of the frequencies f1, f2, and f3 of the frequency spectrum. V _f1 , V _f2 , V _f3 appear. When the electric motors M1, M2, and M3 are operating normally, the voltage values V _f1 , V _f2 , and V _f3 are within the normal range indicated by the broken lines.
[0023]
However, when an abnormality such as an increase in the stray capacitance between the windings of the motors M1, M2, and M3 and the grounding point occurs, the values of the voltage values _Vf1 , _Vf2 , and _Vf3 change. For example, assuming that the stray capacitance of the motor M1 increases while the motors M1, M2, and M3 are operating at the rotation frequencies f1, f2, and f3, respectively, the frequency of the measurement voltage V (f) as shown in FIG. The voltage value V _{f1 at f1} becomes larger than the normal range. That is, when each voltage value of the measurement voltage V (f) is not in the normal range, it can be determined that an abnormality has occurred in the motor system.
[0024]
Therefore, the abnormality of the motor system can be detected based on the voltage value of the frequency component of the measurement voltage V (f) corresponding to the rotation frequency of the motor determined based on the frequency designation signal.
[0025]
Further, when a plurality of electric motors are connected to the main circuit 10, it can be determined which motor has an abnormality from the voltage value of the frequency component corresponding to the rotation frequency of each electric motor.
[0026]
At this time, if a plurality of electric motors are operated at the same rotation frequency, voltages from the plurality of electric motors are superimposed on a frequency component corresponding to the rotation frequency. As a result, it becomes impossible to accurately detect an abnormality.
[0027]
Therefore, when detecting an abnormality, it is also preferable to output a frequency designation signal for operating the motors at different rotational frequencies from the control unit 14, and then detect the abnormality. At this time, each voltage component from the motor superimposed on the measurement voltage V (f) has a spread around the rotation frequency, so that the voltage components of each motor can be clearly separated from the measurement voltage V (f). It is preferable to set the rotation frequency by opening.
[0028]
In the present embodiment, the measurement voltage V (f) converted into a digital signal is digitally processed and separated into frequency components. However, as shown in FIG. 6, a variable bandpass filter having a variable pass frequency. Can be used to separate the frequency component corresponding to the rotational frequency of the motor from the measured voltage V (f).
[0029]
In the present embodiment, the frequency component corresponding to the fundamental frequency (rotational frequency) of the motor of the measurement voltage V (f) is used. However, the harmonic component such as the second harmonic, the third harmonic, etc. of the fundamental frequency is used. An abnormality can also be detected using.
[0030]
In the present embodiment, the sensor circuit 12 measures the voltage between one point in the main circuit 10 and the ground potential, and detects an abnormality in the motors M1, M2, and M3 from the frequency component of the measured voltage. However, the present invention is not limited to this method, and an abnormality can be similarly detected from the electromagnetic physical quantity of the main circuit 10, for example, frequency components of measured values such as current, power, and magnetomotive force.
[0031]
【The invention's effect】
According to the present invention, it is possible to accurately detect abnormality of the electric motor. Further, in an electric motor system including a plurality of electric motors, it is possible to separately detect which motor is abnormal.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram showing a configuration of an electric motor system in an embodiment of the present invention.
FIG. 2 is a circuit diagram showing an example of a sensor circuit in the embodiment of the present invention.
FIG. 3 is a circuit diagram showing another example of the sensor circuit in the embodiment of the present invention.
FIG. 4 is a diagram showing a frequency spectrum of a measurement voltage in the embodiment of the present invention.
FIG. 5 is a diagram for explaining abnormality detection in the embodiment of the present invention.
FIG. 6 is a block diagram showing a frequency component separation circuit in the embodiment of the present invention.
FIG. 7 is a block circuit diagram showing a conventional electric motor system.
[Explanation of symbols]
10 main circuit, 12 sensor circuit, 14 control unit, 16 DC power supply, M1, M2, M3 motor, INV1, INV2, INV3 inverter circuit.

Claims (10)

An electric motor system comprising: an electric motor; a main circuit connected to the electric motor; and a measurement circuit that measures an electromagnetic physical quantity from a measurement point provided in the main circuit,
An electric motor system comprising an abnormality detecting means for detecting an abnormality based on a value of a frequency component corresponding to a rotation frequency of the electric motor in the physical quantity. The electric motor system according to claim 1,
A plurality of electric motors are connected to the main circuit,
The motor system according to claim 1, wherein the abnormality detection means detects an abnormality based on a value of a frequency component corresponding to a rotation frequency of each electric motor in the physical quantity. The electric motor system according to claim 2,
An electric motor system comprising a rotation frequency control means for operating each of the electric motors at a different rotation frequency when detecting an abnormality. In the electric motor system according to claim 2 or 3,
The motor system according to claim 1, wherein the abnormality detection means identifies a motor that is abnormal based on a value of a frequency component corresponding to a rotation frequency for each of the motors in the physical quantity. An abnormality detection device comprising a measurement circuit for measuring an electromagnetic physical quantity from a measurement point provided in a main circuit connected to an electric motor,
An abnormality detection device comprising abnormality detection means for detecting an abnormality based on a value of a frequency component corresponding to a rotation frequency of the electric motor in the physical quantity. In the abnormality detection device according to claim 5,
When a plurality of electric motors are connected to the main circuit, the abnormality detecting unit detects an abnormality based on a value of a frequency component corresponding to a rotation frequency for each electric motor in the physical quantity. . In the abnormality detection device according to claim 6,
An abnormality detection apparatus comprising: a rotation frequency control means for operating each electric motor at a different rotation frequency when detecting an abnormality. In the abnormality detection device according to claim 6 or 7,
The abnormality detection device, wherein the abnormality detection unit identifies an abnormal motor based on a value of a frequency component corresponding to a rotation frequency of each electric motor in the physical quantity. An abnormality detection method for measuring an electromagnetic physical quantity from a measurement point provided in a main circuit connected to an electric motor, and detecting an abnormality based on the physical quantity,
An abnormality detection method comprising an abnormality detection step of detecting an abnormality based on a value of a frequency component corresponding to a rotation frequency of the electric motor in the physical quantity. In the abnormality detection method according to claim 9,
When a plurality of electric motors are connected to the main circuit, the abnormality detecting step detects an abnormality based on a value of a frequency component corresponding to a rotation frequency for each electric motor in the physical quantity. .

Images