JP2002257622A - Device for detecting torsional natural frequency of rotor bar in induction motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To forestall such a problem that vibration and noise are increased because of resonance of a rotor bar in an induction motor being variably driven by an inverter. SOLUTION: The device for detecting torsional natural frequency of the rotor bar in the induction motor is composed of a vibration sensor 11 which measures the vibration occurring in the induction motor 200 and outputs a vibration signal, a rotation sensor 10 which measures the number of revolutions of a shaft 1 of the induction motor 200 and outputs a revolution signal, a calculating means which includes a revolution counter 30, a calculator 32 and a fast Fourier transform device 33, carries out a frequency analysis of the vibration signal on the basis of these signals and extracts a torque fluctuation frequency and a vibration level at the torque fluctuation frequency corresponding to the number of revolutions at the time when the vibration signal is measured, a memory 34 which stores the torque fluctuation frequency and the vibration level at the torque fluctuation frequency extracted by the calculating means, a displaying device which displays the relationship between the torque fluctuation frequency and the vibration level stored in the memory 34 as a torsional vibration characteristic of the rotor bar in the induction motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor driven at a variable speed by an inverter, and more particularly, to preventing an increase in vibration and noise accompanying a decrease in the torsional natural frequency of a rotor bar of the induction motor. Related technology.

[0002]

2. Description of the Related Art In a railway vehicle such as a Shinkansen, a system in which an induction motor is driven at a variable speed by an inverter is going to be mainly used. When an induction motor is driven by an inverter, the pulsation of the drive current is large and the torque fluctuation is large. Therefore, the torsional natural frequency of the rotor bar and the torque pulsation frequency (hereinafter referred to as the torque fluctuation frequency) resonate and resonate, causing vibration and noise in the vehicle. May increase.

[0003]

FIG. 5 is a partially broken perspective view of a rotor of an induction motor. The rotor bar 3 is inserted into a slot (groove) 36 of the rotor core 2 with a small gap, and is partially pressed against the surface of the rotor core 2 by crimping 35. A varnish 37 is filled in a gap between the rotor bar 3 and the rotor core 2. further,
Both ends in the axial direction of the rotor bar 3 are respectively joined to annular short-circuit rings 4 arranged concentrically with the shaft 1, and the rotor bars 3 arranged on the outer periphery of the rotor core 2 are connected at the ends by the short-circuit rings 4. Have been.

[0004] As a vibration model, the rotor bar 3 can be regarded as a cantilever in which the rotor core 2 side is fixed and a short-circuit ring 4 is added as a mass to a free end. In such a structure, if the varnish 37 falls off or the caulking 35 becomes loose, the rigidity of the fixed point as a cantilever decreases,
The natural frequency decreases. FIG. 6 shows an example of the torsional vibration mode of the rotor bar. The broken line in the figure shows the rotor bar 3 in a state where the induction motor is not rotating. In the torsion mode 1, the short-circuit ring 4 is twisted in the direction of arrow A. In the torsion mode 2, the short-circuit ring 4 is in the direction of arrow A. This shows a state in which the rotor core 2 is twisted and receives a rotational force in the direction of arrow B at the same time.

[0005] The torsional natural frequency of the rotor bar (hereinafter referred to as the natural frequency) has a natural frequency higher than the torque fluctuation frequency at the beginning of manufacture, and does not resonate with the torque fluctuation frequency. However, as the traveling distance increases, the natural frequency gradually decreases due to the secular change such as the varnish 37 falling off or the caulking 35 loosening, and may resonate with the torque fluctuation frequency. However, conventionally, it has been difficult to measure the torsional natural frequency of the rotor bar during traveling, and during periodic inspections, etc., when the vehicle is stopped (the motor is stopped) and the motor is hit, etc. The torsional natural frequency of the rotor bar was examined by vibrating by applying an impact. For this reason, the torsional natural frequency of the rotor bar decreases between the periodic inspections, and resonance occurs, and the vibration and noise in the vehicle may increase.

In the technique described in Japanese Patent Application Laid-Open No. Hei 9-117120, resonance is simultaneously performed on the drive shaft side and the non-drive shaft side by making the natural frequency different between the drive shaft side and the non-drive shaft side of the motor. It is proposed to eliminate noise and reduce noise. However, it is not considered that the natural frequency itself decreases due to aging. An object of the present invention is to prevent the rotor bar of an induction motor driven at a variable speed by an inverter from resonating and increasing vibration and noise.

[0007]

SUMMARY OF THE INVENTION The present inventors have found that when the rotational speed of an inverter-controlled induction motor changes, the torque fluctuation frequency changes accordingly, that is, the frequency of the exciting force applied to the rotor bar changes continuously. It is the rotor bar that vibrates due to the change and the torque fluctuation of the induction motor, and the other parts can be ignored. When the frequency of the exciting force changes continuously, the amplitude due to the exciting force also changes, and the amplitude becomes maximum when the natural frequency of the rotor bar matches the frequency of the exciting force. Therefore, when the rotation speed of the electric motor changes, if it is detected how the amplitude at the torque fluctuation frequency changes with the change of the torque fluctuation frequency, the frequency at which the amplitude becomes maximum, that is,
The natural frequency of the rotor bar can be known.

In order to achieve the above object, the present invention provides an apparatus for detecting a torsional natural frequency of an induction motor rotor bar, comprising: a vibration sensor for measuring a vibration generated in the induction motor to output a vibration signal; and a shaft of the induction motor. A rotation detector that measures the number of rotations and outputs a number of rotations signal, and based on these signals, analyzes the frequency of the vibration signal, and a torque fluctuation frequency corresponding to the number of rotations when the vibration signal is measured. Calculating means for extracting the vibration level at the torque fluctuation frequency; storage means for storing the torque fluctuation frequency and the vibration level at the torque fluctuation frequency extracted by the calculation means;
Display means for displaying the relationship between the torque fluctuation frequency and the vibration level stored in the storage means as torsional vibration characteristics of the rotor bar of the induction motor.

Preferably, the display means is configured to display a preset limit eigenvalue of the frequency of the natural vibration of the rotor bar of the induction motor in accordance with the torsional vibration characteristic. As the limit eigenvalue, for example, when there is a sixth or twelfth fluctuating torque frequency, it is preferable to set the fluctuating torque frequency of a higher order fluctuating torque at the upper limit rotational speed of the induction motor.

The above-mentioned torque fluctuation frequency can be calculated as motor shaft speed × [torque fluctuation order × motor pole number] / 2.

The vibration sensor may measure the vibration on the non-rotating body side including the bearing housing, the frame, and the bracket.

The storage means can store torsional vibration characteristics measured at a plurality of time points, and the display means can simultaneously display the torsional vibration characteristics measured at the plurality of time points. It is desirable to configure. The plurality of times are, for example, at the beginning of manufacture, that is, at the start of operation of the induction motor, and at any time after operation.

It is preferable that the display means has a screen having two orthogonal axes, and of the two axes, one axis is displayed with the magnitude of the vibration level and the other axis is displayed with the frequency.

The number of rotations of the induction motor and the torque fluctuation frequency are in a multiple relationship. In other words, the torque fluctuation frequency is not a specific frequency, but changes with a change in the number of revolutions of the electric motor while maintaining a multiplying relationship. The rotation speed of the motor and the torque fluctuation frequency are usually in a non-integer multiple, but are generally approximated to an integer multiple.
Explanation will be made using integers as follows. It should be noted that how many times the torque fluctuation frequency is related to the number of revolutions is determined by determining the inverter.

In the present invention configured as described above, for example, during a period from when the vehicle driven by the inverter-controlled induction motor reaches the maximum speed to when the vehicle reaches the maximum speed, or when the vehicle stops from the maximum speed, the torque fluctuation may occur. The relationship between the frequency and the vibration level can be grasped. Specifically, during a process in which the speed of the vehicle fluctuates, that is, in a process in which the rotational speed of the electric motor changes, the signal of the vibration sensor is repeatedly taken in a plurality of times for a certain period of time. The fetched data is subjected to Fourier transform by a calculation means and frequency analyzed. By performing the frequency analysis, the relationship between the vibration frequency and the vibration level at the time of data acquisition can be understood. Further, the motor rotation speed at that time is obtained from the rotation signal of the motor taken in at the same time. Since the rotation speed of the electric motor and the torque fluctuation frequency are in a multiplying relationship, the frequency obtained by multiplying the rotation speed, that is, the vibration level of the torque fluctuation frequency is extracted by the calculation means from the frequency analysis result and stored in the storage means together with the torque fluctuation frequency. I do.

The above-mentioned process from the capture of the vibration signal to the storage in the storage means is repeated during a predetermined time interval or at a predetermined rotation speed while the vehicle is accelerating or decelerating. The fluctuation curve of the vibration level with respect to the torque fluctuation frequency is stored in the storage means.

When the speed increase or the deceleration is completed, the display means displays the relationship between the torque fluctuation frequency and the vibration level stored in the storage means. When the torque fluctuation frequency matches the torsional natural frequency of the rotor bar, the vibration of the rotor bar increases due to resonance. Conversely, when the torque fluctuation frequency and the torsional natural frequency of the rotor bar are separated, the vibration decreases. That is, when the torque fluctuation frequency is plotted on the horizontal axis and the vibration level for the torque fluctuation frequency is plotted on the vertical axis, the relationship between the vibration level and the torque fluctuation frequency stored in the storage means is graphically displayed on the display means, and a convex resonance curve is obtained. Can be

Since the rotor bar resonates mainly with the torque fluctuation frequency, the convex resonance curve is the torsional vibration characteristic of the rotor bar, and the peak frequency of the convexity is the torsional natural frequency of the rotor bar. .
If the torsional natural frequency of the rotor bar at the start of use of the induction motor is confirmed by the above method, the torsional natural frequency of the rotor bar at the time of use of the induction motor during the use of the induction motor is determined. It is possible to easily confirm how the number has changed with respect to the number, and it is possible to prevent the vibration and noise from increasing due to the resonance of the rotor bar.

If the relationship between the vibration level and the torque fluctuation frequency at different points in time can be stored in the storage means, the relationship between the vibration level and the torque fluctuation frequency at the beginning of manufacture is stored, and the most recent By displaying the data alongside the data, even a person who has no knowledge of vibration can easily read the change in the natural frequency.

[0020]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 shows an external appearance of a torsional natural frequency detection device 100 for a rotor bar of an induction motor for a vehicle according to this embodiment.

In FIG. 1, the torsional natural frequency detecting device 100 of the induction motor rotor bar 3 for a vehicle is mounted on the measuring instrument body 16 and the induction motor 200 for the vehicle, measures the vibration of the induction motor 200 for the vehicle, and responds to the vibration. A vibration sensor 11 for outputting a signal, and an input terminal 14 of a measuring instrument body 16
A rotation sensor (rotation sensor) 10 for measuring the number of rotations by counting irregularities of an encoder 9 attached to the tip of the motor shaft 1; And a cable 13 for connecting to the input terminal 15 of the measuring instrument body 16.

As shown in FIGS. 1 and 2, the measuring instrument main body 16 includes an amplifier 29 connected to the input terminal 14 and an amplifier 29.
, An A / D converter 31 connected to the A / D converter 31, a fast Fourier converter 33 connected to the A / D converter 31, and a start switch 25 connected to the fast Fourier converter 33 to start measurement
And a stop switch 26 for terminating the measurement, an A / D converter 28 connected to the input terminal 15, and an A / D converter 28.
, A computing device 32 connected to the computing device 32, a motor pole number setting device 17 and a torque fluctuation order setting device 19 connected to the computing device 32, and also connected to the computing device 32. Memory 34, a memory selector 20 connected to the memory 34 and a display 23 as display means, a frequency range setting device 18 and a display order setting device 21 connected to the display 23, and a display 23, a limit eigenvalue setting unit 22, a reset switch 24, and a power switch 27.

The output side of the fast Fourier transformer 33 is connected to the computing unit 32, and the rotation number counter 30 and the computing unit 32
And a fast Fourier transformer 33 to form a calculation means.

The frequency range setting unit 18 roughly specifies the range of the natural frequency to be detected. Motor pole number setting device 17
Sets the number of poles of the motor 200 to be measured. The torque fluctuation order setting device 19 sets a torque fluctuation order which is an exciting force of the rotor bar, that is, a multiple of the motor rotation speed. The torque fluctuation order is determined by an inverter that drives the electric motor 200 to be measured at a variable speed. The memory selector 20 specifies a location where the measurement result is stored. The display order setting device 21 specifies a torque fluctuation order component to be displayed. The display 23 displays the measurement result. The limit eigenvalue setting unit 22 designates, as a limit eigenvalue, a limit natural frequency at which the rotor bar does not resonate with the torque fluctuation.

The electric motor 200 to be measured includes a stator 7 therein, a bracket 7 for supporting the shaft 1 via a bearing 5, a rotor core 2 fixed to the shaft 1, a rotor bar 3 attached to the rotor core 2, and a rotor bar. 3 and a short-circuit ring 4 attached to the axial end of the shaft 3.
The rotation detector 10 and the vibration sensor 11 include a bracket 7
Is mounted on the end face in the axial direction. The motor 200 to be measured is driven at a variable speed by an inverter.

The shaft 1 of the electric motor 200 to be measured shown in FIG. 1 is rotated by driving by an inverter. At this time, a fluctuation torque is applied to the rotor bar 3 due to the pulsation of the driving current, and vibration is generated. The vibration is transmitted from the rotor core 2 to the bearing 5 via the shaft 1 and further transmitted to the bracket 7. The vibration transmitted to the bracket 7 is detected by the vibration sensor 11,
Measuring instrument body 16 from input terminal 14 via cable 12
Is entered in

On the other hand, on the side opposite to the drive shaft of the shaft 1, an encoder 9 is provided.
The rotation detector 10 reads irregularities engraved on the peripheral edge of the encoder 9, and inputs the irregularities into the measuring device main body 16 from the input terminal 15 via the cable 13. FIG.
Is assumed to use a speed generator as a rotation sensor. When the rotation detector 10 reads and outputs irregularities engraved on the periphery of the encoder 9, the rotation detector 1
0 is a digital signal, the A / D converter 2
8 is unnecessary.

The calculation process until the vibration signal and the rotation signal input from the input terminals 14 and 15 into the measuring instrument main body 16 are displayed on the display 23 as a detection result will be described with reference to FIGS.
This will be described with reference to FIG.

FIG. 2 shows a signal flow in the measuring instrument main body 16.
Shown in

In the measuring instrument body 16, the input terminal 14
Is input to the A / D converter 31 after being amplified by the amplifier 29, and is converted into a digital value. The vibration signal converted into a digital quantity by the A / D converter 31 is Fourier-transformed by the fast Fourier transformer 33 and is converted into frequency domain data, that is, complex data having a real part and an imaginary part. Fast Fourier Transformer 33
Then, the amplitude is calculated by taking the square root of the sum of the squares of the real part and the imaginary part. That is,

[0031]

(Equation 1) Ai: the amplitude of the i-th frequency (Re) _i : the size of the real part of the i-th frequency (Im) _i : the size of the imaginary part of the i-th frequency

The sampling interval of the A / D converter 31 is Δt
(Seconds), assuming that the number of fetched data is N, N / 2 frequency data are obtained every 1 / Δt (Hz) from 0 Hz. Therefore, the maximum frequency is N / 2Δt (Hz)
Becomes The calculated N / 2 frequencies and amplitudes, ie, the results of the frequency analysis, are sent to the calculator 32.

On the other hand, the rotation signal is converted into a digital quantity by the A / D converter 28 in the measuring instrument main body 16, and
The rotation counter 30 counts the number of rotations. As described above, in the case of the rotation sensor using the encoder shown in FIG. 1, its output is directly input to the rotation counter 30, and the number of rotations is output. The obtained rotation speed is sent to the calculator 32.

The computing unit 32 uses the motor pole number P specified by the motor pole number setting unit 17 and the torque fluctuation order T specified by the torque fluctuation order setting unit 19 to determine which frequency of the frequency analysis results. Decide if data should be stored in memory. The frequency F (Hz) sent to the memory 34 is given by the following equation (2), where n (rotation / sec) is the number of rotations at that time.

F = n × T × P / 2 (2) Since the frequency analysis data is discrete data,
Although the frequency F to be sent to the frequency analysis data and the frequency analysis data hardly match each other, data of the closest frequency is adopted.
Further, the torque fluctuation order T is designated by an integer such as a sixth order or a twelfth order, but it is desirable to use a value (a non-integer) as close as possible to an accurate torque fluctuation order in an actual calculation.

Since a plurality of torque fluctuation orders can be designated, when a plurality of torque fluctuation orders are designated, a plurality of frequencies are sent to the memory 34.

FIG. 3 shows these relationships in a diagram. While the motor is accelerating (decelerating), N pieces of vibration data (time waveform) are captured at intervals of Δt seconds, and the fast Fourier transformer 33 performs a frequency analysis on the vibration data and obtains a result. Is output to the arithmetic unit 32. Each waveform shown in FIG. 3 schematically shows the result of the frequency analysis. The rotation number counter 30 calculates the rotation number of the electric motor from the rotation signal and outputs the calculated rotation number to the calculator 32. The arithmetic unit 32 stores the number of motor poles P, the order of torque fluctuation T and the number of rotations n in the memory 3.
The frequency F (Hz) to be sent to F.4 is calculated by the above equation (2), and the vibration level corresponding to the calculated frequency is extracted from the frequency analysis result input from the fast Fourier transformer 33. The retrieved vibration level is stored in memory 3 along with the corresponding frequency.
Sent to 4. When the data transfer to the memory 34 is completed, the next N pieces of vibration data are fetched, and the same operation as described above is repeated. In FIG. 3, the frequency F (Hz) sent to the memory 34 is shown.
Indicates that two torque fluctuation orders T are set (sixth and twelfth orders) for each rotation speed.

The memory 34 stores the transmitted frequency and amplitude data (vibration level) in combination. As shown in FIG. 4, the memory 34 is divided into two systems, a memory 1 and a memory 2, and the memory 1 can be overwritten and can be cleared by a reset switch. The memory 2 can be overwritten, but cannot be cleared by the reset switch. The memory selector 20 can select which of the transmitted data is to be stored.
It is preferable that the latest data be stored in the memory 1 and the data used for comparison, such as the data at the beginning of production, be stored in the memory 2.

When the start switch 25 is pressed, the measurement starts, and the processing from the capture of the vibration data to the storage in the memory 34 is continued until the stop switch 26 is pressed.

When the stop switch 26 is pressed, the data in the range specified by the frequency range setting unit 18 out of the data of the order specified by the display order setting unit 21 is displayed in the format shown in FIG. Will be displayed.

Further, the eigenvalue specified in the limit eigenvalue setting unit 22 is displayed together with the data as a limit value for preventing resonance.

All data displayed on the display 23 and data stored in the memory 1 can be erased by pressing the reset switch 24.

Next, the operation and effect of this embodiment will be described.

FIGS. 7 and 8 show an example of a torque variation as an exciting force. This torque fluctuation is caused by the pulsation of the driving current from the inverter, and there is a fluctuation torque at a frequency of about 6 times (sixth order) and about 12 times (12th order) with respect to the frequency of the driving basic torque. As shown in the figure, the sixth-order variable torque component is considerably larger than the twelfth-order variable torque component. In other words, when resonance occurs at the sixth torque fluctuation frequency, it means that the vibration increases. FIG. 8 shows the frequency range of the sixth and twelfth fluctuation torque in the case of the motor pole number 4 in comparison with the motor rotation speed. When the motor rotation speed increases to the upper limit, the frequency of the sixth fluctuation torque is considerably increased. It turns out that it becomes high. In the case of FIG.
In the case of zero rotation (RPM), the frequency of the sixth-order fluctuation torque is approximately 900 Hz. This means that when the natural frequency of the rotor bar of the induction motor decreases to 900 Hz (usually, the natural frequency of the rotor bar is higher than 900 Hz), the torque fluctuation frequency of the sixth order at the upper limit rotation speed of the induction motor is reduced. This means that they resonate and the vibration increases.

It should be noted that, for example, the motor rotation speed is 1000 RPM.
In this case, the sixth-order fluctuation torque frequency is 200 Hz when the torque fluctuation order T is calculated as 6 in the equation (2), whereas in FIG. 8, the value is lower than 200 Hz. As described above, the rotational speed and the torque fluctuation frequency are generally approximated to an integral multiple, but more precisely, are related to a non-integer multiple. In other words, even if it is called 6 times, it is exactly 5.8 times, so (2)
When the torque fluctuation frequency is calculated using the equation 6 as the torque fluctuation order T, a deviation occurs from the frequency obtained in the accurate relationship between the rotational speed and the torque fluctuation frequency shown in FIG.

Hereinafter, a procedure in which the operator monitors the torsional natural frequency of the rotor bar using the vehicle induction motor rotor bar torsional natural frequency detecting apparatus 100 of the present embodiment will be described.

The power switch 27 is turned ON, the motor pole number setting device 17 is set to, for example, 4 (for a four-pole motor), and the upper limit of the frequency range setting device 18 is set to 1200H.
z, the lower limit is set to 600 Hz, ch1 (channel 1) of the torque fluctuation order setting device 19 is set to 6th order, ch2 (channel 2) is set to 12th order, and the memory selector 20 is set to c
h1 (memory 1) is selected, 900 Hz is set as the limit eigenvalue in the limit eigenvalue setting device 22, and the 12th order is set in the display order setting device 21.

The reason why the limit eigenvalue is set to 900 Hz is that, as described above, when the motor rotation speed is the upper limit of 5000 rotations (RPM), the frequency of the sixth-order fluctuating torque is approximately 9 Hz.
00 Hz, because it is desired to avoid resonance with the sixth-order fluctuation torque. Also, the twelfth order is set in the display order setting unit 21 because the upper limit of the frequency of the sixth order fluctuation torque is 900 Hz when the motor upper limit rotational speed is 5000 RPM.
This is because data in a frequency region of 900 Hz or more, that is, in a frequency region where the natural frequency of the rotor bar exists, cannot be obtained, and the current natural frequency of the rotor bar cannot be confirmed. If the twelfth order is set in the display order setting device 21 and the vibration level at the twelfth torque fluctuation frequency is displayed on the screen, a change in the vibration level at a frequency of 900 Hz or more is displayed as illustrated in FIG. The position where the natural frequency of is currently located can be confirmed.

When the motor starts to rotate and the vehicle starts moving, the start switch 25 is pressed to start the measurement. When the vehicle has finished accelerating and has reached the maximum speed, when the stop switch 26 is pressed, the frequency stored in the memory 34 and the data of the vibration level corresponding to the frequency are read,
On the screen of the display 23, as shown in the upper part of FIG. 1, the relationship between the twelfth order torque fluctuation frequency and the vibration level is displayed by a solid line. At the same time, the relationship between the frequency and the vibration level measured at the beginning of the production or use of the induction motor and stored in the memory 2 is displayed on the screen by a dotted line, and the limit eigenvalue is displayed by a dashed line. The peak of the twelfth torque fluctuation frequency-vibration level curve is the rotor bar natural frequency, so that even an operator without knowledge of vibration can read the current natural frequency and go to the displayed limit natural value. It is easy to judge whether or not repair is necessary based on the degree of approach.

The upper limit rotation speed of the motor, the number of motor poles,
And the order of torque fluctuation (for example, 6), the above 9
Since the frequency corresponding to 00 Hz can be calculated, the limit eigenvalue does not necessarily have to be displayed.

In the above embodiment, the vibration of the induction motor is detected via the vibration sensor 11 mounted on the bracket 7 on the non-rotating body side of the induction motor. The detection may be performed via a vibration sensor mounted on a bearing box or frame on the non-rotating body side. Further, the vibration of the shaft 1 may be directly detected optically or magnetically in a non-contact manner.

According to the present embodiment, when the vehicle starts from the stop state and reaches the maximum speed, and when the vehicle decelerates from the maximum speed and enters the stop state, the torque fluctuation frequency and the vibration level curve of the induction motor are changed. Therefore, the latest natural frequency of the rotor bar can be known without waiting for the periodic inspection of the vehicle. Therefore, it is possible to accurately know the time of the repair, and it is possible to prevent the noise of the vehicle from increasing due to the resonance of the rotor bar.

Furthermore, the natural frequency clearly appears as a peak of the frequency-vibration level curve, and the limit frequency at which resonance with the fluctuating torque can be displayed together.
Even an operator without knowledge of vibration can easily make a diagnosis.

[0054]

According to the present invention, it is possible to prevent the rotor bar of the induction motor driven at variable speed by the inverter from resonating and increasing the vibration and noise.

[Brief description of the drawings]

FIG. 1 is an external view showing a configuration of a torsional natural frequency detecting device for a rotor bar of an induction motor for a vehicle according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an internal configuration and a signal flow of the measuring instrument main body shown in FIG.

FIG. 3 is a conceptual diagram showing an example of a frequency analysis result obtained by the measuring instrument main body shown in FIG.

FIG. 4 is a diagram illustrating an example of a configuration content of a memory illustrated in FIG. 2;

FIG. 5 is a partially broken sectional view showing a structural example of a rotor bar of the induction motor for a vehicle.

FIG. 6 is a diagram illustrating an example of a deformation pattern of a torsional vibration mode of a rotor bar.

FIG. 7 is a graph showing an example of the magnitude of a torque fluctuation order component of a vehicle induction motor.

FIG. 8 is a graph showing an example of a frequency range of a torque fluctuation order component of an induction motor for a vehicle.

[Explanation of symbols]

1 axis 3 Rotor bar 7 Bracket 9 Encoder 10 Rotation sensor 11 Vibration sensor 16 Measuring instrument body 17 Motor pole number setting device 18 Frequency range setting device 19 Torque fluctuation order setting device 20 Memory selection switch 21 Display order setting device 22 Limit eigenvalue setting device 23 Display 32 Arithmetic unit 33 Fast Fourier Transformer 34 Memory 100 Induction motor for vehicle Induction motor for detecting torsional natural frequency of rotor bar 200 Induction motor for vehicle

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G024 AD25 CA09 CA14 DA09 FA04 FA15 2G064 AA12 AB11 BA02 CC26 CC43 CC57 DD09 DD12

Claims (5)

[The claims] 1. A vibration sensor that measures vibration generated in an induction motor and outputs a vibration signal, a rotation detector that measures a rotation speed of a shaft of the induction motor and outputs a rotation speed signal, Calculating means for analyzing the frequency of the vibration signal and extracting a torque fluctuation frequency and a vibration level at the torque fluctuation frequency corresponding to the rotation speed at the time when the vibration signal is measured; and a torque extracted by the calculation means. Storage means for storing the vibration level at the fluctuation frequency and the torque fluctuation frequency, and display means for displaying the relationship between the torque fluctuation frequency and the vibration level stored in the storage means as torsional vibration characteristics of the rotor bar of the induction motor, A torsional natural frequency detection device for an induction motor rotor bar, comprising: 2. The torsional natural frequency detecting device according to claim 1, wherein said display means displays a preset limit natural value of a frequency of a natural vibration of a rotor bar of said induction motor in accordance with said torsional vibration characteristic. A torsion natural frequency detection device for an induction motor rotor bar, characterized in that the device is configured to be able to perform the operation. 3. The induction motor according to claim 1, wherein the torque fluctuation frequency is a motor shaft rotation speed × [torque fluctuation order × motor pole number] / 2. Rotor bar torsional natural frequency detector. 4. The torsional natural frequency detecting device according to claim 1, wherein the vibration sensor measures the vibration on a non-rotating body side including a bearing box, a frame, and a bracket. A torsional natural frequency detecting device for an induction motor rotor bar characterized by the following: 5. The torsional natural frequency detection device according to claim 1, wherein the storage unit can store torsional vibration characteristics measured at a plurality of time points, Further, the display means is configured to be able to simultaneously display the torsional vibration characteristics measured at the plurality of time points, wherein the torsional natural frequency of the induction motor rotor bar is detected.