JPH0732566B2 - Operation monitoring device for canned motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to a canned motor operation monitoring apparatus, in which a stator core of a radial air gap type canned motor is provided with two detection coils. In the operation monitoring device that monitors the abnormal operation by canceling out the fundamental voltage from each other among the voltages induced in both detection coils and detecting the instantaneous difference in harmonic voltage, the detection of the bearing wear of the canned motor is detected. It relates to an improved directivity of sensitivity.

(Prior art) Canned motors are mainly used for driving pumps, and because they handle liquids that may cause a large accident even with a small failure, high reliability is required, and operating conditions are monitored externally. There is a need to.

In response to this request, the present applicant has proposed a “rotary electric machine operation monitoring device” described in Japanese Patent Publication No. 58-54580.

This rotary electric machine operation monitoring device is provided with two detection coils on a stator core of a rotary electric machine, which are separated from each other by a substantially pole pitch or an integral multiple thereof, and the rotation of rotor cores facing each other with a magnetic gap therebetween. The number of the rotor grooves is determined so that the relative positions of the child grooves are almost the same in the radial air gap type rotating electric machine, and in the axial direction air gap type rotating electric machine, the groove pitch of the rotor groove is different by about 0.5. Regarding the harmonic voltage having the frequency determined by the number of rotor grooves and the fundamental wave voltage synchronized with the power supply frequency induced in the detection coils, the fundamental wave voltages are canceled each other, and in the radial air gap type rotary electric machine, The difference between the instantaneous values of the harmonic voltage is detected by connecting both detection coils in series so that the sum of the instantaneous values of the harmonic voltage is detected in the axial air gap type rotating electric machine. One in which you made to constitute a.

Next, this detection principle will be described with reference to FIGS. 8 to 15 for a two-pole radial gap type induction motor.

As shown in FIG. 8, the two detection coils 1a and 1b are separated from the stator core 2 of the two-pole radial air gap induction motor by a pole pitch, that is, 180 degrees apart by a space angle, and the teeth of the stator core 2 are separated. The position of the detection coil 1a, 1b and the rotor groove 6 of the rotor core 5 facing the detection coil 1a, 1b with the magnetic gap 4 therebetween are the same while surrounding and embedding around one part of the portion 3. The number of the rotor grooves 6 is set to an even number,
As shown in the figure, the detection unit 7 is configured by connecting the detection coils 1a and 1b in series so that the fundamental wave voltages induced in the detection coils 1a and 1b cancel each other, and an indicator such as a voltmeter is provided at the output end thereof. Connect 8.

In this configuration, when the rotor 9 is rotated by turning on the power, magnetic fluxes are linked to both the detection coils 1a and 1b, and a frequency determined by the number of the rotor grooves 6 is added to the fundamental wave voltage synchronized with the power supply frequency. Although a voltage with a harmonic voltage having a voltage of 10 dB is induced, during normal operation, the fundamental voltage and harmonic voltage induced in both detection coils 1a and 1b are almost in phase as shown in Figs. 10 and 11. Since it is a value, the detected voltage appearing at the output end of the detection unit 7 is almost zero as shown in FIG. 12, and during abnormal operation, for example, runout rotation due to bearing wear, as shown in FIGS. 13 and 14. Both detection coils 1a, 1
The fundamental wave voltage induced in b is almost the same as that in normal operation, but the harmonic voltage at each moment is such that the peak value increases as the corresponding magnetic air gap 4 decreases and the corresponding magnetic air gap 4 increases.
Since the peak value of the higher one decreases, the difference between the instantaneous values of the two harmonic voltages having the different peak values appears at the output end of the detection section 7 as a detection voltage, as shown in FIG.

As described above, the detected voltage of the detection unit 7 which has been substantially zero during normal operation changes in an increasing direction during abnormal operation. Therefore, by supporting this change as a voltage change amount on the indicator 8 such as a voltmeter, In the motor, abnormal operation such as eccentric rotation of the rotor due to bearing wear, runout operation, open-phase operation, short-circuit operation and deformed contact of the can can be detected.

(Problems to be Solved by the Invention) However, in the radial air gap type canned motor,
There is no problem in the case where the rotor swings and rotates due to bearing wear, but when the rotor rotates in a biased direction due to bearing wear, that is, when the rotor rotates eccentrically, both rotors are rotated as shown in FIG. When the detection coil is wound in the vertical direction in the figure, the detection sensitivity to bearing wear is maximum when bearing wear occurs in the vertical direction and the rotor rotates eccentrically in the vertical direction, and decreases as it deviates from the vertical direction. However, there is a drawback that the detection sensitivity greatly decreases and becomes minimum in the left-right direction, that is, the detection sensitivity has a strong directivity.

In order to deal with this, in addition to the detection unit composed of two detection coils wound in the vertical direction
It is conceivable to provide a detection unit composed of individual detection coils and connect separate indicators to each, but it is necessary to have two indicators and the height is divided, and most of them have an explosion-proof structure. There is a problem that a structural change for adding another indicator to the required canned motor causes a considerable cost increase.

Therefore, as another means for solving the problem of the directivity of the detection sensitivity to the wear of the bearing, as shown in FIG. 16 of Japanese Patent Publication No. 60-52654, the iron core 2 of the AC rotary electric machine in which the number of pole pairs is not triple The detection coils 1a, 1b, 1c are wound at a space angle of about 120 °, and these three detection coils 1a, 1b, 1c are wound.
Is connected in series so as to obtain a combined voltage, a bearing wear detecting device for an AC rotating electric machine, which is not shown, and an iron core of an AC rotating electric machine having a pole pair number of not a multiple of 3 and 12 There has been proposed a bearing wear detecting device for an AC rotating electric machine in which a detecting coil is wound at a space angle of about 90 ° and the four detecting coils are connected in series to obtain a combined voltage.

However, according to the former invention in which three detection coils are provided, FIG. 17 in which the drawing showing the relationship between the bearing wear amount (eccentricity amount) and the detection voltage described in the above publication is transcribed, and the aforementioned Japanese Patent Publication 58. −
It is clear from the comparison with FIG. 18 and FIG. 19 that the drawings showing the relationship between the radial bearing wear amount and the detection voltage and the relationship between the load current and the detection voltage by the two detection coils described in Japanese Patent No. 54580 are transcribed, respectively. Thus, the rate of change of the detection voltage with respect to the change in the amount of bearing wear (eccentricity) is considerably lower than in the case of two detection coils, that is, the detection sensitivity is considerably poor,
Also, when the motor load changes, the detection voltage, which changed only slightly in the case of the two detection coils, changes significantly, so it is difficult to determine whether the increase in the detection voltage is due to bearing wear or motor load change. In addition, it is almost impossible to apply to a canned motor agitator in which a 6-pole machine whose pole pair number is a multiple of 3 is the mainstream.

Further, according to the latter invention in which four detection coils are provided,
Since the number of pole pairs is limited to a multiple of 3 and not a multiple of 12, it can be applied only to a 6-pole machine among the commonly used 2-pole, 4-pole, 6-pole and 8-pole canned motors. It cannot be applied to 2-pole machines and 4-pole machines, which account for most of the production, especially for 2-pole machines.

The present invention has been made in view of the above problems, and solves the problem of directivity of detection sensitivity to bearing wear,
(EN) Provided is a canned motor operation monitoring device which can detect bearing wear almost without being affected by changes in the negative pressure of a motor and can be applied to radial gap type canned motors of all pole pairs.

[Structure of Invention]

(Means for Solving the Problems) In order to achieve the above object, the present inventors have provided two stator cores 2 of a radial air gap canned motor as shown in FIG. 8 and FIG. Detect coils 1a and 1b at spatial angle 1
In the operation monitoring device having a configuration of being separated by 80 degrees, when the rotor 9 is eccentrically rotated in a direction perpendicular to the stator center line l _S passing through both detection coils 1a and 1b, both detection coils 1
Rotor grooves 6 facing a and 1b with a magnetic gap 4 in between.
Since the relative positions of the two shift in directions opposite to each other with respect to the rotation direction of the rotor 9, the transfer of the harmonic voltage induced in the detection coils 1a and 1b is detected according to the amount of rotation eccentricity of the rotor 9. In coil 1a or 1b, the lead, and the other detection coil
In 1b or 1a, a phase difference is generated in the harmonic voltage with a delay, and it is found that the detected voltage is generated by this phase difference, and the rotor 9 is directed toward the stator center line l _S passing through both detection coils 1a and 1b. The detected voltage caused by the phase difference of the harmonic voltage when rotated eccentrically in the direction orthogonal to the detected voltage caused by the difference in the peak value of the harmonic voltage when rotated eccentrically to In addition, the technical idea that a detection sensitivity characteristic close to omnidirectionality can be obtained by appropriately selecting the design values of each part of the canned motor that determines the magnitude of the peak value difference and the phase difference of the harmonic voltage has been reached. .

Based on this technical idea, the operation monitoring device for a canned motor according to the present invention is provided with two detection coils separated by 180 degrees in space angle on the stator core of a radial air gap type canned motor.
The number of rotor grooves is set to an even number so that the relational positions of the rotor grooves of the rotor core facing each other with a magnetic gap between them are the same, and the power source frequency induced in both of the detection coils is With respect to a harmonic voltage having a frequency determined by the synchronized fundamental voltage and the number of rotor grooves, the both detections are performed so that the fundamental voltages cancel each other and the difference in the instantaneous value of the harmonic voltage is detected. A coil is connected in series to form a detection unit, and a regular magnetic gap length G between the stator core and the rotor core, an outer diameter D of the rotor core, the number of rotor grooves N ₂ and a rotor are provided. The maximum allowable rotational eccentricity gm of Are set so as to satisfy the relationship.

(Operation) According to the operation monitoring device for a canned motor of the present invention, when the canned motor is operated, both detection coils have a harmonic voltage having a frequency determined by the number of rotor grooves in the fundamental wave voltage synchronized with the power supply frequency. Is induced, the fundamental wave voltages cancel each other at the output end of the detection section in which both detection coils are connected in series, and the difference in the instantaneous value of the harmonic voltage appears as the detection voltage.

When the rotor rotates while maintaining the regular magnetic gap length G, the harmonic voltages induced in both detection coils have almost the same phase and the same value, so that the detection voltage hardly occurs and the rotor When eccentrically rotates in the direction of the center line of the stator that passes through both detection coils, the harmonic voltage induced in the detection coils remains the same and the peak value of one increases and the peak value of the other decreases. As the eccentricity increases, the detection voltage due to the difference in peak value increases, and when the rotor eccentrically rotates in the direction perpendicular to the stator center line passing through both detection coils, harmonics induced in both detection coils are generated. Since the voltage has the same peak value and one phase advances and the other phase lags, the detected voltage due to this phase difference increases as the amount of rotation eccentricity increases, and when the rotor eccentrically rotates in the other direction. , Harmonics induced in both detection coils The pressure increases with one peak value and decreases with the other peak value, and as one phase advances and the other phase lags, the detection voltage due to the difference between the peak values and the phase difference increases as the rotational eccentricity increases. However, the regular magnetic gap length G, the outer diameter D of the rotor core, the number of rotor grooves N ₂ and the maximum allowable rotational eccentricity of the rotor gm Since the setting is made so as to satisfy the above condition, the detection voltage when the rotor is eccentrically rotated with the maximum allowable rotation eccentricity gm is the direction of the eccentricity direction of the stator center line passing through both detection coils or the direction perpendicular to this. When either one of the above is given, the maximum value is shown, and when the other is given, it shows the minimum value that is 3/4 or more of the maximum value.Therefore, there is little difference due to the eccentric direction, and there is no bearing wear. Detection sensitivity characteristics close to directivity can be obtained.

(Example) Next, the Example of this invention is described based on drawing.

FIGS. 1 to 3 show an embodiment in which the present invention is applied to a canned motor pump, which is a canned motor pump in which an 11 pump 12 and a radial gap type canned motor 13 are liquid-tightly integrated and fixed. Stator winding in stator groove 15 of child core 14
A stator 17 formed by winding 16 is inserted into a stator frame 18, a thin cylindrical stator can 19 is closely inserted into the inner peripheral surface of the stator 17, and both ends of the stator can 18 are put into the stator frame 18. A rotor that is densely welded and has a rotor conductor 22 mounted in a rotor groove 21 of a rotor core 20.
A rotary shaft 24 is inserted into the rotor 23, a thin-walled cylindrical rotor can 25 is attached to the outer peripheral surface of the rotor 23, and the rotor 23 is attached to the stator 17 by a stator can 19 and a rotor can 25. Sliding bearings 28a, 28b, which are arranged opposite to each other with a gap 26 in between, and have a rotating shaft 24 mounted on bearing housings 27a, 27b, are provided with sleeves 29a, 29b and thrust collars.
The canned motor 13 is configured by being axially supported via 30a and 30b.

Further, two detection coils 31a and 31b are provided on the stator iron core 14 at a space angle of 180 degrees, and in this embodiment, each one is wound around one of the iron core tooth portions 32 and embedded in the stator groove 15. Then, a distance formed by the thickness of the stator can 19 and the rotor can 25 and the length of the can gap 26 in the detection coils 31a and 31b, that is, the magnetic gap between the stator core 14 and the rotor core 20.
The number of the rotor grooves 21 is set to an even number so that the relational positions with the rotor grooves 21 facing each other across the 33 are the same, and the fundamental wave that is cycled to the power supply frequency induced in both the detection coils 31a and 31b. With respect to the harmonic voltage having the frequency determined by the voltage and the number of the rotor grooves 21, the detection coils 31a and 31b are connected in series so that the fundamental voltages cancel each other and the difference between the instantaneous values of the harmonic voltages is detected. To form a detection unit 34, and an indicator 36 is connected to the output terminals 35, 35 of the detection unit 34.

The magnetic gap length of the normal between the stator core 14 and rotor core 20 when the rotor 23 rotates concentrically without eccentric to the center axis O _S of the stator 17 G, the rotor core 20 outer diameter D, and maximum allowable rotational eccentricity gm when rotor groove number N ₂ and the rotor 23 rotates eccentrically with respect to the central axis O _S of the stator 17, Set to satisfy the relationship of.

In the canned motor pump 11, generally, in order to improve the pump efficiency, the rotation gaps 39a, 39b between the impeller 37 of the pump 12 and the casing 38 are set to be narrower than the can gap 26, so that the sliding bearings 28a, 28b are worn. Then, the rotational eccentricity of the rotor 23 when the impeller 37 starts to contact the casing 38 may be the maximum allowable rotational eccentricity gm, but in most cases, even if the impeller 37 contacts the casing 38 and rotates. Since there is no problem in practical use, or the impeller 37 may be intentionally rotated by contact in order to further improve the pump efficiency, in the present embodiment, the slide bearings 28a, 28b are used.
Wear, the rotor 23 is eccentrically rotated, and the rotor can 25
The maximum allowable rotational eccentricity gm is set as the rotational eccentricity of the rotor 23 when the rotor starts contacting the stator can 19.

Next, the operation of this embodiment will be described.

When turning on the power and operating the canned motor pump 11,
Magnetic fluxes are linked to both detection coils 31a and 31b to induce a voltage.

This induced voltage is a harmonic voltage with a frequency determined by the number of rotor grooves N ₂ in the fundamental voltage synchronized with the power supply frequency.
For more information, It is a voltage in which a harmonic voltage having a frequency represented by is superimposed.

Then, of the voltages induced in both detection coils 31a, 31b, the fundamental wave voltage cancels each other because it becomes almost the same value even if the rotor 23 is eccentrically rotated. Depending on the amount of rotation eccentricity and the direction of eccentricity of 23, the peak value of one increases and the other decreases, and the phase of one advances and the other lags.Therefore, a difference occurs in the harmonic voltage induced in both detection coils 31a and 31b. The difference between the harmonic voltages appears as a detection voltage between the output terminals 35, 35 of the detection unit 34.

That is, the harmonic rotor 23 when rotating concentrically to the central axis O _S of the stator 17, which is誘押harmonic voltage V _H a and a lower detection coil 31b induced above the detection coil 31a The voltage V _H b is logically V _H a = A ₀ sin ωt V _H b = B ₀ sin ωt = A ₀ sin ωt Therefore, the detected voltage V _H d does not occur as V _H d = V _H a −V _H b = 0 because they have the same phase and the same value, but the sliding bearings 28a and 28b are worn and the rotor 23
In but the direction of the stator centerline l _S through both detection coils 31a, a 31b, for example, when rotating eccentrically downwards as shown in FIG. 4, both the harmonic voltage V _H a, V _H b is, V _{H a = a 1 sin ωt V H} b = B 1 sin ωt a 1 <A 0 ,B 1> and B ₀ = a _0, but the phase is not changed, the harmonic voltage V induced in the upper part of the detection coil 31a Since the peak value of _H a decreases and the peak value of the harmonic voltage V _H b induced in the lower detection coil 31b increases, V _H d = (A ₁ −B ₁ ) sin ωt and The detection voltage V _H d is generated.

By the way, in the canned motor 13, since the stator can 19 and the rotor can 25 are provided, and the radial wear of the slide bearings 28a, 28b is taken into consideration, the stator can 1
Since the can gap 26 between the 9 and the rotor can 25 is set to a large value, the regular magnetic gap length G between the stator core 14 and the rotor core 20 is about 3 times as large as that of a general-purpose motor in a small machine, or even in a large machine. It is about twice as strong, and the stator can 19
And the can gap 26 between the rotor can 25 and the rotor can 25, that is, the rotor 23
Since the maximum permissible rotational eccentricity gm of is about half of the regular magnetic gap length G, both detection coils 31a, 31a,
The peak values of the harmonic voltages V _H a and V _H b induced in 31 b are almost inversely proportional to the dimensional changes of the magnetic gap 33 between the stator core 14 and the rotor core 20.

Therefore, as shown in FIG. 4, the rotor 23 has a rotational eccentricity g
When eccentrically rotated downward at, the magnetic gap length corresponding to the upper detection coil 31a becomes G + g, and the magnetic gap length corresponding to the lower detection coil 31b becomes G-g.
V _H a, V _H b are And the detection voltage V _H d is Becomes

Next, when the rotor 23 has a rotational eccentricity g, both detection coils 31a, 31b
When rotated eccentrically to the left as shown in FIG. 5, for example, in the direction perpendicular to the stator center line l _S passing through, the magnetic air length directly to the right becomes G + g and the magnetic air gap length just to the left becomes G-g. However, since the magnetic gap lengths corresponding to both detection coils 31a and 31b hardly change from G, the peak values of both harmonic voltages V _H a and V _H b are almost equal, while both harmonic voltages V _H a As for the phase of V _H b, when the rotor 23 rotates in the counterclockwise direction indicated by the arrow in the figure, each rotor groove 21 has a stator center line passing through both detection coils 31a and 31b on the upper detection coil 31a side. passing through the rotor center line l _R parallel to the stator centerline l _S after passing the l _S, the stator center line l is below the detection coil 31b side after passing through the rotor center line l _R since passing through _S, downward as shown in the FIG. 4 and when the rotor 23 rotates concentrically to the stator central axis O _S as shown in the Figure 2 Than when rotating eccentrically, advances the phase of the harmonic voltage V _H a induced above the detection coils 31a, delays the phase of the harmonic voltage V _H b induced below the detection coil 31b, the two Harmonic voltage V _H a, V
_The detection voltage V _H d is generated by the phase difference of _H b.

That is, in this case, the position of the rotor center line l _R parallel to the stator center line l _S passing through the both detection coils 31a and 31b is moved leftward by g, so that the two detection coils 31a and 31b are The relative positions of the rotor grooves 21 facing each other across the magnetic gap 33 are shifted to the left by g.
23 groove pitch Therefore, with the groove pitch of the rotor groove 21, Pitch and in electrical angle Therefore, the harmonic voltage V _H a, V _H b is And the detection voltage V _H d is Becomes

Therefore, the detected voltage V _H d when the rotor 23 is eccentrically rotated by the maximum allowable rotational eccentricity amount gm in the direction of the stator center line l _S passing through both detection coils 31a and 31b and in the direction perpendicular thereto
To equalize, the peak value of the detection voltage V _H d in equation (2) And the peak value of the detection voltage V _H d in equation (3) To Equals, that is, The proper magnetic gap length G, the outer diameter D of the rotor iron core 20 and the number of rotor grooves N ₂ may be selected so that the value of K becomes 4/3. For example, rotor 23
In the direction of the stator center line l _S passing through both detection coils 31a and 31b.
The detected voltage V _H d when eccentrically rotated by gm becomes 3/4 with respect to the detected voltage V _H d when eccentrically rotated by gm.

Next, the detected voltage V _H d when the rotor 23 is eccentrically rotated in a direction other than the vertical and horizontal directions, that is, the stator center line l _S passing through both the detection coils 31a and 31b and the direction perpendicular thereto is generally expressed. The formula will be described.

As shown in FIG. 6, the rotor 23 has an amount of rotational eccentricity g in the counterclockwise direction α [rad] with respect to the stator center line l _H orthogonal to the stator center line l _S passing through the detection coils 31a and 31b. ] When eccentrically rotated in the away direction, the reduction amount ΔGa of the magnetic gap length corresponding to the upper detection coil 31a is as follows: ▲ ▼ = gsinα, ▲ ▼ = gcosα And the increase ΔGb in the magnetic gap length corresponding to the lower detection coil 31b is Becomes

Further, the relative position of the rotor groove 21 facing the detection coils 31a, 31b with the magnetic gap 33 therebetween is the central angle of the rotor 23, The deviation of the central angle β is caused by the central angle of one groove pitch of the rotor 23. Therefore, the center angle of this one groove pitch And, in electrical angle, Equivalent to.

Therefore, the harmonic voltage V induced in the upper detection coil 31a
Harmonic voltage V induced in _H a and the detection coil 31b below
_H b is And the detection voltage V _H b is Becomes

Here, the detection voltage V _H d when the rotor 23 is eccentrically rotated downward by the rotation eccentricity g as shown in FIG.
When calculated from the equation, α = 3 / 2π, so And the detection voltage V _H d is And becomes the same as the expression (2).

Further, as shown in FIG. 5, the rotor 23 has a rotational eccentricity g
When the detection voltage V _H d when eccentrically rotating to the left is calculated from equation (5), α = π, so However, in almost all canned motors, Therefore, And the dimensional ratio that is unlikely in the design of the canned motor. Even Therefore, ΔGa = ΔGb≈0, and But as mentioned above Since the value of is quite small, You can put And the detection voltage V _H d is And becomes the same as the expression (3).

Then, among various combinations of G, gm, D and N ₂ that can be applied to the canned motor, various combinations satisfying the relationship of the expression (1), when the rotational eccentricity g becomes the maximum allowable rotational eccentricity gm, As a result of calculating the detection voltage V _H d in each eccentric direction based on the equation (5), the detection voltage V _H d is the same as the direction of the stator center line l _{S in which} the rotor 23 passes through both detection coils 31a and 31b. It is shown that the maximum value is shown when eccentrically rotated in one of the right-angled directions, the minimum value is shown when eccentrically rotated in the other direction, and an intermediate value between the two is shown when eccentrically rotated in the other direction. It was. From this, the above G, g
In equation (4), which is determined by m, D and N ₂ , Is a kind of coefficient indicating the directivity of the detection sensitivity, and the detection voltage V _H d when the rotation eccentricity g is the maximum allowable rotation eccentricity gm is, for example, in the case of K = 1. It shows the minimum value when it is in the direction perpendicular to the stator center line l _S passing through 31a, 31b, and shows the maximum value which is 1.2 times the minimum value when it is in the direction of the stator center line l _S , and K = 0.8. In the case of, the maximum value is shown when the eccentric direction is perpendicular to the stator center l _S , and the minimum value is 0.8 times the maximum value when it is in the direction of the stator center line l _S. Becomes

By the way, the same applies to the present embodiment, the "rotary electric machine operation monitoring device" described in JP-B-58-54580.
In the canned motor operation monitoring device to which the invention of claim 9 is applied, the sliding bearing 28 is provided in order to smooth the rotation of the rotor 23.
A narrow rotating sliding gap of about 1/10 mm is provided between a, 28b and sleeves 29a, 29b, and the sliding bearings 28a, 28a, due to the stacking of the radial dimension tolerances of the members constituting the canned motor 13. The inner peripheral surface of 28b is not completely concentric with the central axis O _{S of the} stator, and is decentered by several tens of mm, and the fundamental wave voltage induced in both detection coils 31a and 31b is slightly different from that of the stator 17. The detection voltage V _H d does not become zero even in the initial state where there is no bearing wear due to the fact that it is not completely canceled due to electromagnetic imbalance, and the rotor 23 is
10% to several 10% of the detected voltage V _H d when eccentrically rotated with the maximum allowable rotational eccentricity gm in the direction of the stator center line l _S passing through 1a and 31b.
%, And because the detection voltage V _H d changes by several tens of percent as the load of the canned motor 13 changes, the rotation eccentricity g of the rotor 23 is detected by the value of the detection voltage V _H d. It is a device with the property of roughly grasping the degree of progress of bearing wear, rather than accurately grasping the amount of bearing wear,
In view of this, the detected voltage when the rotor 23 is eccentrically rotated by the maximum allowable rotational eccentricity amount gm in the direction of the stator center line l _S passing through both detection coils 31a and 31b and in the direction orthogonal thereto.
The ratio of V _H d to the lesser than the greater, ie Is desirable to be closer to 1, but it can be sufficiently put to practical use if it is about 3/4 or more.

Therefore, the regular magnetic gap length G, the outer diameter D of the rotor core 23,
By setting the number of rotor grooves N ₂ and the maximum allowable rotational eccentricity gm so as to satisfy the relationship of the equation (1), the rotor 23
The detection voltage V _H d in the eccentric rotation does not differ much depending on the eccentric direction, and the detection sensitivity characteristic close to omnidirectional with respect to bearing wear is obtained.

Next, FIG. 7 shows a sliding bearing 28a in a conventional canned motor operation monitoring device having the following specifications and dimensions which does not satisfy the relationship of the formula (1) although it has the configuration shown in FIGS. 1 to 3 above. , 28b and sleeves 29a, 29b are replaced by ball bearings (not shown) to rotatably support the rotary shaft 24, and the bearing boxes 27a, 28b fastened to the ball bearings are eccentrically attached to the stator frame 18 and attached. A graph in which the detection voltage V _H d of the detection unit 34 is measured by eccentrically rotating the rotor 23 is shown.

In this graph, the X mark connected by the solid line indicates that the eccentric direction represented by α in Fig. 6 changes from 0 to π / 4 [rad] when the rotational eccentricity g is 0.25 mm, 0.5 mm and 0.7 mm, respectively. shows the measured value of the detected voltage V _H d when is the dotted line, the maximum value of the measured value of the detected voltage V _H d in the case of maximum permissible rotational eccentricity gm = 0.7 mm and (5) the calculated value by an equation The peak value A _{0 of the} equation (5) is determined so that the maximum value matches with the maximum value, and the rotational eccentricity g
Detected voltage for the eccentric direction α calculated by
The characteristic curve of V _H d is shown.

In this measurement example, Although the relationship between the measured value and the calculated value by the equation (5) is almost the same, the characteristic by the rotational eccentricity amount g of the detected voltage V _H d and the eccentric direction α is (5) ) Is proved, and from this, and in the case of the eccentricity direction α = 3 / 2π, that is, the rotor 23 has both detection coils 3
In the case of eccentric rotation in the direction of the stator center line l _S passing through 1a and 31b (downward as shown in FIG. 4), the rotational eccentricity g
The measured value and the calculated value of the detected voltage V _H d at 0.25 mm and 0.5 mm are very close to each other, and the rotor can 25 is removed and the rotational eccentricity g is 3 / of the normal magnetic gap length. 5 is 0.9
mm when And the measured value of the detection voltage V _H d Since the measured value of the detection voltage V _H d shown in is quite close, the normal magnetic gap length G is 2 for a general-purpose motor.
In the canned motor 13 that is more than twice as large and the maximum allowable rotational eccentricity gm is about half of the regular magnetic gap length G, the rotor 23 has the stator center line l _S passing through both the detection coils 31a and 31b. Both detection coils 31a, 31 when eccentrically rotated in the direction
The peak value of the harmonic voltage V _H a, V _H b induced in b is the stator core.
It is proved that it is almost inversely proportional to the dimensional change of the magnetic gap 33 between the rotor 16 and the rotor core 20.

〔The invention's effect〕

According to the operation monitoring device for a canned motor of the present invention, the regular magnetic gap length G between the stator core and the rotor core, the outer diameter D of the rotor core, the number of rotor grooves N _2, and the maximum allowable rotation of the rotor are provided. Eccentricity gm, By considering the canned motor design in advance so that the relationship of
When the maximum value is set to 1, the minimum value of the detection voltage when eccentric rotation occurs is 3/4 or more, and there is not much difference due to the eccentric direction, and detection sensitivity characteristics close to omnidirectional with respect to bearing wear are obtained. As described in the above Japanese Patent Publication No. 60-52654, it is necessary to provide two indicators, especially those having an explosion-proof structure, as in the case of providing two sets of detecting sections each including two detecting coils. The invention is applied to the stator core of the canned motor and the three detection coils provided at a space angle of about 120 degrees are connected in series, and the number of pole pairs is not a multiple of three. The detection voltage does not change significantly due to a change in the load of the canned motor, which makes it difficult to detect, and by applying the invention described in Japanese Patent Publication No. 60-52654, the stator core of the canned motor has almost no space angle.
The number of pole pairs is not limited to a multiple of 3 and not a multiple of 12 as in the case where four detection coils provided at 90 degrees are connected in series, and almost no change occurs in the load of the canned motor. Bearing wear can be detected without being affected, and it can be applied to radial gap type canned motors with all pole pairs.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing an embodiment in which the canned motor operation monitoring device of the present invention is applied to a canned motor pump, and FIG. 2 is a cross-sectional view taken along the line I--I of FIG. FIG. 4 is a circuit diagram of the same as above, FIG. 4 is an explanatory view showing a state when the rotor is eccentric downward, and FIG. 5 is an explanatory view showing a state when eccentric to the left side of the same. Is an explanatory diagram showing a state when eccentric to the upper right of the same, FIG. 7 is an operation monitoring device of a radial air gap type canned motor of a conventional example,
FIG. 8 is a characteristic diagram showing measured values and calculated values showing the relationship between the detected voltage and the eccentric direction with the rotational eccentricity of the rotor as a parameter. FIG. FIG. 9 is a cross-sectional view showing a conventional example applied to the radial air gap induction motor of FIG. 9, FIG. 9 is a circuit diagram of the same as above, and FIGS. 10 to 15 are waveform diagrams for explaining the operation of the conventional example of the same as above.
The figure shows a block diagram of the principle of the conventional operation monitoring device in which the detection unit is composed of three detection coils. Fig. 17 shows the relationship between the bearing wear amount (eccentricity amount) and the detected voltage in the conventional example. Fig. 18, Fig. 18 and Fig. 19 show the relationship between the bearing wear amount and the detected voltage in the conventional example in which the detector is composed of the two detector coils shown in Fig. 8 and Fig. 9, and the motor load current and the detector. It is a characteristic view which shows the relationship with an electric current. 13 …… Radial air gap type canned motor, 14 …… Stator core, 20 …… Rotor core, 21 …… Rotor groove, 23 …… Rotor, 31a, 31b …… Detection coil, 33 …… Magnetic gap , 34 ……
Detection unit.

Claims (1)

[Claims] 1. A rotor core of a rotor of a radial air gap type canned motor, wherein two detection coils are provided at a space angle of 180 degrees, and the two detection coils are opposed to each other with a magnetic air gap therebetween. The number of the rotor grooves is set to an even number so that the relative positions of the grooves are the same, and a harmonic having a fundamental wave voltage synchronized with the power supply frequency induced in the detection coils and a frequency determined by the number of the rotor grooves. Regarding wave voltage,
A detection unit is configured by connecting the detection coils in series so that the fundamental voltage is canceled by each other and the difference in the instantaneous value of the harmonic voltage is detected, and the stator core and the rotor core are connected. Of the regular magnetic air gap length G, the outer diameter D of the rotor core, the number of rotor grooves N ₂ and the maximum allowable rotational eccentricity gm of the rotor, The operation monitoring device for the canned motor is characterized by being set so as to satisfy the relationship of