JP5483960B2 - Resonance reducing method and resonance reducing apparatus for rotating machine - Google Patents

Description

  The present invention relates to a resonance reduction of torsional torque of a rotating machine using a variable speed induction motor as a driving machine through a speed increasing gear.

  Rotating machines driven by a variable speed induction motor have a range of operating rotational speeds rather than a single point, and therefore, in order to reduce machine vibration, a design that avoids not only axial vibration resonance but also torsional vibration resonance is designed. is necessary. For this reason, conventionally, the natural frequency of the torsional vibration system of a rotating machine has been designed to avoid the excitation torque in the actual operating range.In particular, the primary natural frequency of torsion with a high response magnification is set to the excitation torque. It is designed to be lower than the frequency of the rotational speed of the variable speed motor shaft, which is the cause, and the basic frequency of the input current of the variable speed induction motor.

  On the other hand, for example, in a reciprocating engine, it is known that a torsional excitation torque having a frequency equal to or lower than the rotational speed of the shaft is generated. There is an example in which a method of generating torque that reduces the vibration is taken (see Patent Document 1).

JP 10-169703 A

  However, in the method of generating the torque for reducing the torque at the time of resonance by control as in Patent Document 1, the optimal control parameter may be lost due to a change in the operating state, which may cause instability. In this case, conversely, torque vibration due to self-excited vibration may be increased.

  In the vibration reduction method of the rotating machine, it is ideal to avoid resonance between the natural frequency of the mechanical vibration system and the excitation frequency, and there are few problems. However, in practice, it has been found that it is difficult to avoid only the first-order torsional natural frequency of all excitation torques. It is known that among the excitation torque generated by the variable speed motor, a number of frequencies lower than the frequency of the rotational speed are generated based on a certain regularity and resonate with the torsional natural frequency of the machine.

  In addition, since the amplitude of the excitation torque according to the frequency is relatively small and few rotating machines are equipped with a device for measuring the torsional vibration itself, it is generally difficult to find. Even in a rotating machine equipped with a shaft vibration measuring device, the shaft of a gear speed increaser shaft that amplifies the excitation torque to some extent in a state close to resonance near the natural frequency of torsion and transmits power by the tangential force of the gear tooth surface. In many cases, the existence is finally confirmed by appearing predominantly in vibration, or the existence is not confirmed until the coupling having the lowest strength against torsion in a rotating mechanical system is broken by high cycle fatigue.

  Such a frequency is generated in the case of a sideband generated by amplitude modulation of a plurality of frequencies existing in the motor input current, or by a feedback of a virtual sideband frequency due to a sampling failure of the motor input current used for variable speed control. The case of sidebands can be considered.

In either case, the relationship is a linear expression (linear) relating to a multiple of the fundamental frequency f of the motor input current. Specifically, it is represented by a relationship such as (Equation 1).
f _t = | f _c -mf | (Formula 1)
Here, f _t is the frequency of the torque excitation of the possibility of resonance in the primary torsional natural frequency, due to the frequency of the sideband. f is the fundamental frequency of the motor input current and is approximately proportional to the motor shaft rotational speed. f _c is any frequency other than the fundamental frequency present in the motor input current. As described above, it is difficult to advance identifying f _c. m is an arbitrary integer, and there are many cases where this multiple m is present, and it is difficult to know in advance which multiple is dominant.

  In view of the above-mentioned conventional drawbacks, the present invention performs frequency analysis of vibration of a rotating machine, predicts a motor input current fundamental frequency that resonates with the primary torsional natural frequency of the rotating machine, and calculates the motor input current fundamental frequency including that frequency. It is an object of the present invention to provide a resonance reduction method and a resonance reduction device for a rotary machine that can effectively avoid resonance of torsional vibration by jumping.

The present invention relates to a method for reducing resonance of a rotary machine connected to a variable speed induction motor through a speed increaser.
Using the fact that the torque of the rotating machine is related to the gearbox vibration, frequency analysis is performed on the signal obtained by the gearbox vibration detector, and the frequency component with increased amplitude and the motor input current fundamental frequency at that time are obtained. Record two points each, predict the motor input current fundamental frequency that resonates with the primary torsional natural frequency of the rotating machine using the assumed linear regularity, and jump to the motor input current fundamental frequency including that frequency. It is sent to the variable speed control device to avoid torsional vibration resonance

The present invention also relates to a resonance reduction device for a rotary machine connected to a variable speed induction motor via a gear speed increaser.
A variable speed control device for controlling the variable speed induction motor at a fundamental frequency;
A vibration detector for detecting shaft vibration of the gearbox,
An analyzer for analyzing the vibration signal of the vibration detector and extracting the vibration frequency and its amplitude;
Based on the primary torsion natural frequency of the rotating machine, the fundamental frequency of the variable speed control device, the vibration frequency and amplitude detected by the analyzer at the time of this frequency output, and the frequency component having an increased amplitude, The motor input current basic frequency is recorded at two points, and the motor input current basic frequency that resonates with the primary torsional natural frequency of the rotating machine is predicted using the assumed linear regularity. An arithmetic unit for sending an instruction signal for jumping the frequency to the variable speed control device is provided .

  Further, the present invention performs frequency analysis of the shaft vibration signal obtained from the gearbox shaft vibration detector, and calculates the vibration in advance by changing the shaft rotational speed and the proportional change in the motor input current fundamental frequency. The obtained torsional primary natural frequency and the frequency of the shaft vibration frequency range set before and after the primary natural frequency and having an amplitude equal to or higher than a predetermined threshold value are extracted, The motor input current fundamental frequency at that time is collected from the variable speed control device to the calculator.

  When the shaft rotational speed changes within a preset range, the frequency component with the increased amplitude changes so as to approach the torsional primary natural frequency, and increases more than the amplitude at the original shaft rotational speed. In this case, the frequency of the frequency component is extracted, and the motor input current fundamental frequency at that time is collected from the variable speed control device to the computing unit.

  Calculate the regularity in which the relationship between the extracted frequency of the two amplitudes and the fundamental frequency of the motor input current when each is extracted is linear (linear), and the motor input where resonance is expected to occur Find the current fundamental frequency.

  In order to jump the motor input current fundamental frequency range having a preset width including the motor input current fundamental frequency at which resonance is expected to occur, a preset width is set on both sides of the obtained motor input current fundamental frequency. A signal indicating the motor input current fundamental frequency range (or the corresponding shaft rotational speed) is given to the variable speed drive device. A motor input current basic frequency range corresponding to a torsional excitation frequency range determined to have a sufficiently small torsional vibration response magnification is designated as a preset motor input current basic frequency range for jumping. As a result, it is possible to avoid an increase in amplitude in the vicinity of resonance where the response magnification of torsional vibration is high.

  According to the present invention, it is possible to effectively avoid resonance of torsional vibration of a rotating machine system by predicting the resonating motor input current fundamental frequency, and to obtain some signal from the variable speed control device and to obtain the original value. Therefore, there is almost no possibility of causing self-excited vibration by variable speed drive control.

BRIEF DESCRIPTION OF THE DRAWINGS The structure schematic diagram of the rotary machine with a variable speed induction motor drive speed increasing gear concerning Example 1 of this invention. The figure showing the response magnification of the forced vibration of the torsional vibration of a mechanical system. The cascade diagram which showed the frequency analysis of the gearbox shaft vibration amplitude for every shaft rotational speed. FIG. 4 is an explanatory diagram of resonance avoiding means when the shaft vibration frequency due to the sideband wave decreases due to an increase in shaft rotation speed in the enlarged view of FIG. 3. Explanatory drawing of the resonance avoidance means when the axial vibration frequency resulting from a sideband wave similarly increases by the decrease in shaft rotational speed. Explanatory drawing of the resonance avoidance means when the axial vibration frequency resulting from a sideband wave similarly increases by the increase in shaft rotational speed. Explanatory drawing of the resonance avoidance means when the axial vibration frequency resulting from a sideband wave similarly decreases by the reduction | decrease of an axial rotation speed.

  Hereinafter, a variable torsion torque reducing method for a rotary machine with a variable speed induction motor driven speed increasing gear according to a first embodiment of the present invention will be described.

  FIG. 1 is a schematic configuration diagram of a rotating machine with a variable speed induction motor driven speed increasing gear according to an embodiment of the present invention. The shaft 9 of the load rotating machine 4 that fulfills a certain purpose is connected to the high speed shaft 8 of the speed increasing gear 3 via the high speed shaft coupling 9. The gear high-speed shaft 8 and the gear low-speed shaft 7 transmit torque by exerting a tangential force via the gear meshing portion 14. When the transmitted torque fluctuates, the fluctuation appears in the shaft vibrations of the gear high-speed shaft 8 and the gear low-speed shaft 7. Therefore, detecting the frequency and amplitude of shaft vibrations of the gear high-speed shaft 8 and the gear low-speed shaft 7 detects the frequency of the torque twisting the shaft and the value related to the torque amplitude.

  The gear low speed shaft 7 is connected to the shaft 5 of the induction motor 2 via the low speed shaft coupling 6. The induction motor 2 is controlled by the variable speed drive control device 1 and is operated at a variable speed. A non-contact vibration detector 13 is directed to the gear low-speed shaft 7, and the shaft vibration of the gear low-speed shaft 7 is detected as a signal and sent to the shaft vibration signal frequency analyzer 11. In this embodiment, the vibration detector 13 is directed to the gear low-speed shaft 7 to detect the shaft vibration of the gear low-speed shaft 7. However, the vibration detector 13 is directed to the gear high-speed shaft 8 to detect the shaft vibration of the gear high-speed shaft 8. It is also possible to detect torque fluctuations by detection.

The shaft vibration signal frequency analyzer 11 performs frequency analysis on the shaft vibration obtained from the gear low-speed shaft 7 with a detection signal, and sends each frequency and its amplitude data to the storage device 12 for storage. The computing unit 15 obtains, from the variable speed drive control device 1, the fundamental frequency f during operation of the rotary machine output from the variable speed drive control device 1 related to the rotational speed N of the induction motor 2, and outputs the basic frequency f. Each frequency f _t (f) of the shaft vibration of the gear low-speed shaft 7 and the amplitude A ( _ft (f)) of the component are obtained from the memory 12.

The relationship between the rotational speed N of the induction motor shaft 5 and the basic frequency (motor input current basic frequency) f output by the variable speed drive control device 1 is (Expression 2).
f = N · P / (120 (1-s)) (Formula 2)
Here, P is the number of poles of the induction motor 2, and s is slip. In order to obtain the rotational speed N of the induction motor shaft 5 assuming that the number of poles P is fixed, the variable speed drive control device 1 determines and outputs f in consideration of the slip s. At the time of steady operation of the rotary machine, the slip s is considered to be constant at a value much smaller than 1, and the fundamental frequency f and the rotational speed N are considered to be in a proportional relationship.

FIG. 2 is a diagram showing the response magnification of the forced vibration of the torsional vibration of the mechanical system, with the torque of the gear low-speed shaft on the vertical axis and the excitation frequency on the horizontal axis. f _n1 is the primary torsional natural frequency of the rotary machine obtained in advance by calculation.

As described above, the calculator 15 receives the frequency _ft (f) and the amplitude A ( _ft (f)) of the shaft vibration of the low speed gear 7 during operation of the rotary machine from the storage device 12. Yes. The arithmetic unit 15, the shaft vibration of each frequency f _t of (f), 1-order torsional natural frequency f frequency difference preset to _n1 lower from Delta] f _s-1 apart frequency f _t (f) = When the amplitude A (f _t (f)) exceeds a preset threshold A ₋ at f _n1 −Δf _s−1 , the frequency of the shaft vibration is recorded as f _t−1 , and at that time Record the fundamental frequency as f ₋₁ .

Further, when the variable speed drive control device 1 changes the fundamental frequency f in order to change the rotational speed N of the induction motor shaft 5, the frequency difference Δf _s preset in advance from the primary torsional natural frequency f _{n1. -2} apart frequency _{f t (f) = f n1} -Δf amplitudes at _{s-2 a (f t (} f)) is, at the frequency _{f t (f) = f n1} -Δf s-1 described above When the amplitude A is larger than f _t (f ₋₁ ) = f _n1 −Δf _s−1 ), it is considered that the frequency component of the shaft vibration has approached the primary torsion natural frequency f _n1 , and the computing unit 15 determines the shaft vibration. Is recorded as f _t-2 , and the fundamental frequency at that time is recorded as f ₋₂ . The above is the description on the left side of the primary torsion natural frequency f _n1 in FIG.

As before, among the frequency f _t of the shaft vibration (f), 1-order torsional natural frequency f from _n1, only the frequency difference Delta] f s _{+ 1} set in advance in the higher distant frequency f _t (f) = in f _{n1 +} Δf s + _1, the amplitude a (f _t (f)) is, when exceeding the threshold value a ₊ a preset arithmetic unit 15 records the frequency of the axial vibration as f _{t + 1} In addition, the fundamental frequency at that time is recorded as f _{+ 1} .

Further, when the variable speed drive control device 1 changes the fundamental frequency f in order to change the rotational speed N of the induction motor shaft 5, a frequency difference Δf _{s +} set in advance from the primary torsional natural frequency f _n1 to the higher one. ₂ apart by the frequency _{f t (f) = f n1} + Δf s + 2 in the amplitude a (f _t (f)) is, at the frequency _{f t (f) = f n1} + Δf s + 1 described above, If the amplitude _{a (f t (f +1)} = f n1 + Δf s + 1) is greater than, regarded as the frequency components of the shaft vibration has approached the primary torsional natural frequency f _n1, calculator 15 that shaft vibration Is recorded as f _{t + 2} , and the basic frequency at that time is recorded as f ₊₂ . The above is the description on the right side of the primary torsion natural frequency f _n1 in FIG. 2.

The threshold value A ₋ and threshold value A ₊ to be set in advance should be selected to be small enough not to miss even if the frequency is relatively far from the primary torsional natural frequency f _n1. It is necessary to select large enough not to pick up a small amplitude, and an optimum value is determined in consideration of both.

The method of determining the frequency differences Δf _s−1 and Δf _{s + 1} set in advance relates to the torsional vibration system of the rotating machine. As shown in FIG. 2, the maximum response ratio at natural frequency f _n1, the response magnification as the difference from the natural frequency f _n1 increases decreases. The frequency component of the torsional vibration according to the embodiment of the present invention also increases in amplitude as it approaches the torsional natural frequency f _n1 , but the response magnification is small at frequencies far from the natural frequency f _n1, and the vibration amplitude is small and distinguished from noise. In some cases, this frequency cannot be detected. On the other hand, if the frequency is too close to the natural frequency f _n1 , the response magnification is large, and the vibration amplitude becomes too large. Therefore, optimum frequency differences Δf _s−1 and Δf _{s + 1} are determined in consideration of both.

In the case of the shaft vibration frequencies f _t-1 and f _t-2 and the fundamental frequencies f ₋₁ and f ₋₂ recorded in the calculator 15, and the shaft vibration frequencies f _{t + 1} and f _{t + 2} , the fundamental frequency f _+1, in the case of f _+2, the fundamental frequency f _r to be expected that frequency dominant axis vibration resonates to the primary torsional natural frequency f _n1 calculated by calculator 15. To do so, it is necessary to define a linear (linear) relational expression that represents regularity.

FIG. 3 shows a cascade diagram showing a frequency analysis of the speed-up gear shaft vibration amplitude for each shaft rotation speed in the case of an induction motor having two poles P. The vertical axis represents the rotation speed and vibration amplitude of the induction motor, and the horizontal axis represents the vibration frequency. FIG. 3 shows that the component of the shaft vibration frequency caused by the sideband wave changes linearly with respect to the change of the shaft rotation speed, and the amplitude of the component is the primary torsional natural frequency f _{n1 of} about 16 Hz. You can see how it increases in the vicinity. Further, as the shaft rotation speed is increased, there are cases where the shaft vibration frequency due to the sideband wave decreases and increases.

As the shaft rotation speed is increased, the relationship between the shaft vibration frequency f _t and the fundamental frequency f when the shaft vibration frequency due to the sideband wave decreases is as follows: It can be expressed as equation 3).
f _t = f _c -mf (Formula 3)
On the other hand, as the shaft rotational speed is increased, the relationship between the shaft vibration frequency f _t and the fundamental frequency f when the shaft vibration frequency due to the sideband wave increases is based on the case of the above (Equation 1). It can be expressed as (Equation 4).
f _t = mf−f _c (Formula 4)
Become a (Equation 3) is applied, as depicted in FIG. 4 an enlarged portion of FIG. 3, when the shaft rotational speed (the fundamental frequency) increases, the fundamental frequency (f _+2> f ₊₁₎ As shown in FIG. 5 where the frequency of shaft vibration is (f _{t + 1} > f _{t + 2} ) and another part of FIG. 3 is enlarged, it is fundamental when the shaft rotational speed (fundamental frequency) decreases. There are two cases where the frequency is (f _-1 > f _-2 ) and the frequency of the shaft vibration is (f _t-2 > f _t-1 ). As can be seen in FIGS. 4 and 5, Equation 3 is a straight line relationship with a downward slope.

On the other hand, (Equation 4) is applied when the shaft rotation speed (fundamental frequency) increases, as shown in FIG. 6 in which a certain part of FIG. 3 is enlarged, the fundamental frequency becomes (f ₋₂ > f _{− 1} ) and when the shaft rotation frequency (fundamental frequency) decreases as shown in FIG. 7 where the frequency of the shaft vibration is (f _t-2 > f _t-1 ) and another part of FIG. 3 is enlarged. The basic frequency is (f ₊₁ > f ₊₂ ) and the axial vibration frequency is (f _{t + 1} > f _{t + 2} ). As can be seen in FIGS. 6 and 7, (Equation 4) is a straight line relationship that rises to the right.

Since both (Equation 3) and (Equation 4) have a linear relationship, in any of the above four ways, the unknown frequency can be obtained by obtaining the values of the axial vibration frequency _ft and the fundamental frequency f at two points on the straight line. _Fc and m can be obtained.

If f _c and m are determined, Equation 3, it is possible to determine the fundamental frequency f _r which is expected to resonate in the primary torsional natural frequency f _n1 in relation to formula 4. That is, in the case of the relationship of (Formula 3), it becomes the following formula.
f _r = (f _c −f _n1 ) / m (Formula 5)
In the case of the relationship of Formula 4, it becomes the following formula.
f _r = (f _n1 + f _c ) / m (Formula 6)
As described above, the calculation signal from the calculation unit 15 is sent to the calculation signal of the basic frequency f _r expected to resonate with the primary torsional natural frequency f _n1 obtained by the calculation unit 15 and the frequency width Δf _j for jumping the preset basic frequency f. feed to the drive control device 1, variable speed drive control device 1 by jumping the scope of the fundamental frequency f of the upper and lower frequency width Delta] f _j around the fundamental frequency f _r, the input frequency (input current as a control signal to the induction motor 2 Basic frequency) and variable speed operation. Therefore, since the control signal avoiding the primary torsional natural frequency f _n1 is sent to the induction motor 2, the resonance can be avoided.

4 to 7, the jump is indicated by a dotted arrow. 4 jumps upward when the vibration amplitude A ( _{ft + 2} ) is detected, and jumps downward when the vibration amplitude A ( _ft-2 ) is detected in FIG. In FIG. 7, the jump is made upward when the vibration amplitude A ( _ft-2 ) is detected, and in FIG. 7, the jump is made downward when the vibration amplitude A ( _{ft + 2} ) is detected.

Even if a control signal that avoids the primary torsional natural frequency f _n1 is sent, the rotational speed of the rotating machine continuously changes, so that the primary torsional natural frequency f _n1 passes for a moment. However, since the primary torsion natural frequency f _n1 is not included in the drive signal, a large resonance does not occur.

The jump (avoidance) frequency width of the basic frequency f is Δf _j , and the shaft vibrations of the gear low-speed shaft 7 and the gear high-speed shaft 8 (and the torsional vibration of the rotating machine of the same frequency) and the primary torsion natural frequency f _n1 The avoidance frequency range is mΔf _{j above} and below.

As a method of determining the frequency width Δf _j for jumping the preset basic frequency f, it is first considered that the primary torsion natural frequency f _n1 is moved away to an excitation frequency at which it is determined that the response magnification of torsional vibration is sufficiently small. If the range becomes too wide, the possible operating rotation speed range is limited too much, which may cause operational problems. Therefore, the optimum frequency width Δf _j is determined in consideration of both.

  Most of the variable speed control devices generally have a frequency range (or shaft rotation speed range) jump function added in advance, and there is a high possibility that the variable speed control device can be implemented in combination with the method of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Variable speed drive control device, 2 ... Induction motor, 3 ... Speed increasing gear, 4 ... Load rotating machine, 5 ... Induction motor shaft, 6 ... Low speed shaft coupling, 7 ... Gear low speed shaft, 8 ... Gear high speed shaft, DESCRIPTION OF SYMBOLS 9 ... High-speed shaft coupling, 10 ... Load rotary machine shaft, 11 ... Shaft vibration signal frequency analyzer, 12 ... Memory | storage device, 13 ... Gear low-speed shaft vibration detector, 14 ... Gear meshing part, 15 ... Calculator.

Claims (2)

In a method for reducing resonance of a rotating machine connected to a variable speed induction motor via a speed increaser ,
Using the fact that the torque of the rotating machine is related to the gearbox vibration, frequency analysis is performed on the signal obtained by the gearbox vibration detector, and the frequency component with increased amplitude and the motor input current fundamental frequency at that time are obtained. Record two points each, predict the motor input current fundamental frequency that resonates with the primary torsional natural frequency of the rotating machine using the assumed linear regularity, and jump to the motor input current fundamental frequency including that frequency. A method for reducing resonance of a rotary machine, wherein the resonance is transmitted to a variable speed control device to avoid torsional resonance. In a resonance reducing device for a rotating machine connected to a variable speed induction motor via a gear speed increaser,
A variable speed control device for controlling the variable speed induction motor at a fundamental frequency;
A vibration detector for detecting shaft vibration of the gearbox,
An analyzer for analyzing the vibration signal of the vibration detector and extracting the vibration frequency and its amplitude;
Based on the primary torsion natural frequency of the rotating machine, the fundamental frequency of the variable speed control device, the vibration frequency and amplitude detected by the analyzer at the time of this frequency output, and the frequency component having an increased amplitude, The motor input current basic frequency is recorded at two points, and the motor input current basic frequency that resonates with the primary torsional natural frequency of the rotating machine is predicted using the assumed linear regularity. An apparatus for reducing resonance of a rotary machine, comprising: an arithmetic unit that sends an instruction signal for jumping a frequency to the variable speed control device.

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