CN114325388B - Motor starting locked-rotor fault diagnosis method based on soft-start current characteristics - Google Patents
Motor starting locked-rotor fault diagnosis method based on soft-start current characteristics Download PDFInfo
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Abstract
The invention discloses a motor starting locked-rotor fault diagnosis method based on soft-start current characteristics. The motor starting locked-rotor judging method provided by the invention takes the current sequence in the specific time window of normal soft start when the operation condition of the motor changes as the reference sequence, and can effectively improve the capability of the algorithm in adapting to different condition environments and inhibiting parameter drift caused by motor aging.
Description
Technical Field
The invention relates to the technical field of motors, in particular to a motor starting locked-rotor fault diagnosis method based on soft-start current characteristics.
Background
The motor is widely used in various industries such as various machine tools, electric automobiles, high-speed rail locomotives, factory power equipment, water supply and drainage equipment, elevators, electric fans, air conditioners and the like as a power source. Due to the complex working conditions and imperfect protection measures of the motor, the motor rotor is often locked, for example, a transmission mechanism on the motor rotor is locked or a speed change gear is locked due to foreign matters or faults, an elevator transmission chain is locked, a belt of a transmission device is locked, a fluid medium of a water pump is frozen or silt is locked. Once the locked rotor happens, the current of the motor rises sharply, which is far larger than the rated working current and even can reach dozens of times of the rated current. Huge electric current leads to motor consumption sharply to increase, and the inside temperature of motor rises fast, and motor coil insulated paint damages, leads to the inside short circuit of motor, and the electric current of the motor of further increase can arouse the conflagration even when serious. At present, the locked rotor detection technology provided in the existing literature generally adopts schemes of detecting the rotating speed of a motor, the counter electromotive force of the motor, the internal temperature of the motor, the current of the motor and the like. The locked rotor scheme is detected by adopting the rotating speed of the motor and the internal temperature of the motor, and a detection element needs to be added in the motor or on a rotating shaft, so that the structure of the motor is complex, the design and the manufacturing process of the whole motor are influenced, and the cost and the complexity are increased. The locked rotor is detected by adopting a counter electromotive force scheme, and on one hand, the rotating speed is calculated by an accurate and reliable mathematical model through the counter electromotive force; on the other hand, when the rotating speed is low, the value of the back electromotive force is small, the signal to noise ratio of the sampled data is not high, the sampled data is easily interfered by noise, a complex signal processing method is needed, and therefore a software algorithm is complex and the cost is high. The current detection locked rotor is adopted, and the locked rotor is widely used without changing the structure due to the aspect of data acquisition. However, in the existing scheme, the current peak value is often detected to judge whether the locked rotor occurs, and the locked rotor is compared with a motor locked rotor current reference value obtained by testing before leaving a factory, so as to judge whether the water pump has the start locked rotor. The scheme mainly has the following problems: firstly, locked-rotor current drift is caused by motor aging, difference of working environments and other reasons; and secondly, the judgment is only carried out by depending on the starting current peak value single-point parameter, so that misjudgment and failure can be caused, and the reliability, robustness and interference suppression capability of the judgment are reduced.
Disclosure of Invention
The invention aims to provide a motor starting locked-rotor fault diagnosis method based on soft-start current characteristics. The invention has the advantages of accurate judgment, simple structure and low cost.
The technical scheme of the invention is as follows: a motor starting locked-rotor fault diagnosis method based on soft start current characteristics comprises the following steps:
step one, when the motor is normally soft started, sampling period T is used s For interval pair motor current effective value
Sampling, and constructing a current three-dimensional characteristic vector psi in a normal soft start stage by using sampling data ref ；
Step two, when the motor is started to rotate and is blocked to detect, the sampling period T is used in the same way s For interval to effective value I of motor current soft (t) sampling, and constructing a three-dimensional characteristic vector psi of the current in the detection stage by using sampling data;
step three, enabling the three-dimensional characteristic vector psi of the current in the detection stage and the three-dimensional characteristic vector psi of the current in the normal soft start stage ref Performing operation to obtain dimensionless vector psi σ And psi σ 2 norm | ψ of σ || 2 ；
Step four, judging | | | ψ σ || 2 And if the value is less than or equal to the threshold value theta, determining that the motor is in a starting locked-rotor fault.
In the motor starting locked rotor fault diagnosis method based on soft start current characteristics, the three-dimensional characteristic vector psi of current in the normal soft start stage in the step one ref Is constructed with a sampling period T s Sampling the soft-start current effective value sensor for the beginning of the interval, marking the first sampling value as
The current sampling frequency is k, and k =1;
establishing soft start current array composed of M elements
Wherein i = { k-M +1,k-M +2, …, k-1,k }, M is a preset positive integer greater than 2, and k is the current sampling frequency;
solving arrays using bubbling
Non-zero maximum value element of
Satisfies the following conditions:
judgment of
Whether the result is true or not; if yes, entering the next step; otherwise, returning to the previous step for recalculation;
the preset maximum value filtering interval is a positive even number P and satisfies the following conditions:
computing
And
obtaining [ (U + 1) T s ,(U+N)T s ]The current effective value data in time form an array
Calculating the mean value of the array
Degree of harmony
According to the average value of the array
Degree of harmony
Obtaining the current three-dimensional characteristic vector in the normal soft start stage
In the motor start locked rotor fault diagnosis method based on soft start current characteristics, the construction process of the three-dimensional characteristic vector psi of the phase current detected in the second step is a sampling period T s Sampling the soft-start current effective value sensor for the beginning of the interval, and marking the first sampling value as I soft (1) (ii) a The current sampling frequency is k, and k =1;
establishing a soft-start current array { I) composed of M elements soft (i) I = { k-M +1,k-M +2, …, k-1,k }, wherein M is a preset positive integer greater than 2, and k is the current sampling time; i is soft (i)| i≤0 ＝0；
Method for solving array { I by using bubbling method soft (i) Non-zero maximum value element I in soft (U) satisfying: i is soft (U)＝max{I soft (i)}＞0，U∈{k-M+1,k-M+2,…,k-1,k}；
Judgment of
Whether the result is true or not; if yes, entering the next step; otherwise, returning to the previous step for recalculation;
the preset maximum value filtering interval is a positive even number P and satisfies the following conditions:
calculating out
And
obtaining [ (U + 1) T s ,(U+N)T s ]The current effective value data in time form an array { I soft (U+1),I soft (U+2),…,I soft (U + N) }, calculating array average value
Degree of harmony
According to the average value of the array
Harmony kurtosis
Constructing three-dimensional characteristic vector of soft start current
According to the motor starting locked-rotor fault diagnosis method based on the soft-start current characteristics, when the motor is normally soft-started, whether the operation working condition of the motor changes or not is judged, and after the motor is confirmed not to be in abnormal conditions such as locked-rotor and other overload conditions, sampling work is executed, the controller accesses the soft-start impedance into the power line of the motor, and the motor starts soft-start.
According to the motor starting locked-rotor fault diagnosis method based on the soft starting current characteristics, when the motor is started to rotate and is blocked to be detected, the soft starting impedance is connected to the power line of the motor, and the current is guaranteed to be always in a safe range during locked-rotor.
The motor starting locked-rotor fault diagnosis method based on the soft start current characteristics is characterized in that: in the sixth step, judge | | | ψ σ || 2 Whether the value is less than or equal to the threshold value theta, if not, the motor is in a normal soft start state, whether the soft start timing is finished is judged, if so, the controller short-circuits the soft start impedance on the power line of the motor, and the water pump enters a normal working procedure; otherwise, wait.
Compared with the prior art, the method and the device have the advantages that the current sequence in the specific time window of the soft start of the motor is detected, the relevance degree analysis is carried out on the current sequence and the reference current sequence in the specific time window of the normal soft start, and whether the locked rotor fault exists in the motor is judged according to the obtained current three-dimensional characteristic vector. The motor starting locked-rotor judging method provided by the invention takes the current sequence in the specific time window of normal soft start when the motor running condition changes as the reference sequence, and can effectively improve the capability of the algorithm in adapting to different working condition environments and inhibiting parameter drift caused by motor aging. The hardware structure of the invention is simple, only the current data is sampled and analyzed, and the cost is low. In addition, the invention increases soft start impedance to effectively limit the start current, ensures that the current is always in a safe range during locked rotor, and ensures that the motor is safe and reliable; the method obtains the current three-dimensional characteristic vector in the soft start current window time as a judgment basis, has simple algorithm, can effectively reduce misjudgment, and improves the reliability and robustness of diagnosis and the capability of inhibiting interference. The invention obtains the soft starting current of the motor when the working condition changes (such as the working environment changes, the motor ages, and the like) as the reference of locked-rotor detection, and can be adaptive to the locked-rotor current drift caused by the motor working condition and parameter changes.
Drawings
FIG. 1 is a schematic diagram of a motor soft start circuit;
FIG. 2 is a graph of normal soft start current and speed time;
FIG. 3 is a graph of soft start current and time variation of speed at a locked rotor fault.
Detailed Description
The invention is further illustrated by the following figures and examples, which are not to be construed as limiting the invention.
Example (b): a motor starting locked rotor fault diagnosis method based on soft start current characteristics comprises a motor normal soft start current acquisition algorithm and a motor starting locked rotor detection algorithm, wherein the motor normal soft start current acquisition algorithm comprises the following steps:
(1) Determine whether the operating condition of the motor has changed (e.g., operating environment changes and motor operating time is too long, resulting in aging, etc.)? If yes, entering the step (2); otherwise, a new soft start current parameter is not required to be set, and the operation is quitted;
(2) After confirming that the motor is not in abnormal conditions such as locked rotor and other overload conditions, manually pressing a normal soft start current parameter acquisition mode key, executing a soft start current parameter acquisition program, and entering the step (3);
(3) The controller closes the three-phase power supply contactor contact, and the motor starts soft start. With a sampling period T s Sampling the soft start current effective value sensor for interval start, marking the first sampling value as
The current sampling frequency is k, and k =1;
(4) Establishing soft start current array composed of M elements
Wherein i = { k-M +1,k-M +2, …, k-1,k }, M is a preset positive integer greater than 2, and k is the current sampling frequency;
(5) Solving arrays using methods such as, but not limited to, bubbling
Non-zero maximum value element of
Satisfies the following conditions:
(6) Judgment of
Is there any? If yes, entering the step (7); otherwise, returning to the step (5); wherein: []Is an integer operator.
(7) The preset maximum value filtering interval is a positive even number P and satisfies the following conditions:
computing
And
(8) Obtaining [ (U + 1) T s ,(U+N)T s ]The current effective value data in time form an array
Calculating the mean value of the array
Degree of harmony
(9) Constructing a three-dimensional characteristic vector of current in a normal soft start stage
And storing the reference value into a memory as a reference value of a motor starting locked rotor diagnostic algorithm.
(10) The program indicates that the soft start current parameters are successfully updated and the contacts of the three-phase power supply contactor are disconnected through modes of sound, light, electricity and the like, and the motor is stopped;
(11) The program exits;
the motor starting locked-rotor fault diagnosis algorithm comprises the following steps:
(1) Entering a motor starting locked-rotor fault diagnosis program;
(2) The controller closes the three-phase power supply contactor contact, and the motor starts soft start. With a sampling period T s Sampling the soft-start current effective value sensor for the beginning of the interval, and marking the first sampling value as I soft (1) (ii) a The current sampling frequency is k, and k =1;
(3) Establishing a soft-start current array { I) composed of M elements soft (i) Where i = { k-M +1,k-M +2, …, k-1,k }, M is presetDetermining a positive integer greater than 2, wherein k is the current sampling frequency; i is soft (i)| i≤0 ＝0；
(4) Solving arrays { I } using methods such as, but not limited to, bubbling soft (i) Non-zero maximum value element I in soft (U) satisfying: i is soft (U)＝max{I soft (i)}＞0，U∈{k-M+1,k-M+2,…,k-1,k}；
(5) Judgment of
Is there any? If yes, entering the step (6); otherwise, returning to the step (4); wherein: []Is the operator of taking integer.
(6) The preset maximum value filtering interval is a positive even number P and satisfies the following conditions:
computing
And
(7) Obtaining [ (U + 1) T s ,(U+N)T s ]The current effective value data in time form an array { I soft (U+1),I soft (U+2),…,I soft (U + N) }, calculating array average value
Degree of harmony
(8) Constructing three-dimensional eigenvectors of soft-start current
And is combined with psi ref Operating to obtain dimensionless vector
And psi σ 2 norm | | | ψ of σ || 2 ；
(9) Judge | | | ψ σ || 2 Is θ ≦ θ (where θ is a small positive threshold, e.g., 0.05, 0.1)? If yes, entering the step (12); otherwise, entering the step (10);
(10) Is the motor in a normal soft start state, does the soft start timing end? If yes, entering the step (11); otherwise, waiting;
(11) The controller closes a normally open contact connected in parallel to the soft start impedance, the three-phase soft start impedance connected in series to the power supply incoming line is short-circuited, the motor enters a normal working procedure, and the step (13) is carried out;
(12) The controller disconnects the contacts of the three-phase power supply contactor, alarms to start a locked rotor fault, and enters the step (13);
(13) The locked rotor fault diagnosis program exits;
in order to further explain the technical scheme of the invention, fig. 1 is a schematic diagram of a motor soft start circuit, which mainly comprises a normally open contactor KM1, a current effective value detection circuit, a three-phase soft start impedance Z, a normally open contactor KM2, a motor, a controller, a key S1, a key S2, a key S3, a KM1 coil, a driving circuit, a KM2 coil and a driving circuit. The normally open contactor KM1 is used for connecting or disconnecting three-phase 380V alternating current, and a coil of the normally open contactor KM is controlled by a controller output port Out 1. When Out1 is high, the coil of KM1 is energized and the contact of KM1 is closed. When Out1 is low, the coil of KM1 is de-energized and the contact of KM1 is open. The normally open contactor KM2 is used for short-circuiting three-phase soft start impedance Z, and a coil of the normally open contactor KM is controlled by an output port Out2 of the controller. When Out2 is at a high level, the coil of KM2 is electrified, the contact of KM2 is closed, the three-phase soft start impedance Z is in short circuit, the motor finishes soft start and enters a full-voltage working state. When Out2 is at a low level, the KM2 coil is powered off, the KM2 contact is disconnected, the three-phase soft start impedance Z is connected into a power line, and the motor is in a soft start state. The current effective value detection circuit is used for detecting the motor current effective value. The three-phase soft start impedance Z is connected in series in a power line and is used for limiting the starting current of the motor and realizing the soft start of the motor. The switch S1 is a normal soft start current parameter acquisition mode key connected to the input port I of the controllerAnd (N1). When the operation condition of the motor changes (such as the change of working environment, the aging of the motor and the like), manually pressing S1, executing a normal soft start current parameter acquisition algorithm by a controller, and acquiring a feature vector of a current effective value of the motor in a normal soft start stage under the current condition
The switch S2 is a motor operation starting key, is connected to the input port IN2 of the controller and is used for starting the motor to operate. When the controller memory does not exist
The S2 function is masked. At this point, pressing switch S2, the system will prompt the user that psi is not stored in the system ref The user must first press S1 to execute the motor normal soft start current parameter acquisition algorithm. When the controller memory has psi ref In the case of (3), pressing S2 starts the motor normally. The switch S3 is a stop button and is connected to the controller input port IN3. When S3 is pressed, the output ports Out1 and Out2 of the controller are at low level, the coil KM1 and the coil KM2 are powered off, the contacts KM1 and KM2 are disconnected, and the water pump stops running. The KM1 coil driving circuit is used for driving the KM1 coil and is controlled by an output port Out1 of the controller. When Out1 is at high level, the coil KM1 is electrified; when Out1 is low, the KM1 coil is de-energized. The KM2 coil driving circuit is used for driving the KM2 coil and is controlled by the output port Out2 of the controller. When Out2 is at high level, the KM2 coil is electrified; when Out2 is low, the KM2 coil is de-energized. The controller executes different function programs by acquiring the switch states of the switches S1, S2 and S3. The controller executes a normal soft start current parameter acquisition algorithm when finding that the S1 is pressed down, and after the execution is finished, the controller displays that the soft start current parameter is successfully acquired and then automatically stops; when the pressing of S2 is found, the controller executes a normal motor running program under the condition that the soft start current parameters are acquired; when the pressing of S3 is found, the controller executes a stop operation.
The working principle of the soft start circuit of the motor shown in fig. 1 is as follows: when the system is in standby state during power-on, output ports Out1 and Out2 are both lowA level. The controller detects the state of the keys in real time through a keyboard scanning program, and executes a normal soft start current parameter acquisition algorithm after the fact that the key is pressed in S1 is found. At this time, the controller enables the soft start timer to run for setting the soft start time. Meanwhile, the output port Out1 of the controller is at a high level, the coil of KM1 is electrified, the three-phase contact of KM1 is closed, and 380V three-phase alternating current is connected to the motor. Because Out2 is low level, the KM2 contact keeps an off state, the three-phase soft start impedance Z is connected in series on a power line, and the motor is in a soft start state. The controller acquires the time-varying relation of the current at the soft start stage by sampling the value of the current effective value detection circuit in real time through the AD (analog-to-digital) circuit
Until the soft start timing is over. By applying current to the soft start phase
Analysis of, obtaining
Peak value of
Time of occurrence of
And window time
Inner part
Kurtosis of
Further obtaining the current three-dimensional characteristic vector in the normal soft start stage
And the vector value is used as the base of a motor starting locked rotor diagnostic algorithmThe quasi-reference value is stored in a memory of the processor. Secondly, in the benchmark reference value psi ref Under the condition of being stored in the memory of the processor, the controller executes the motor operation control algorithm after finding S2 pressing through the keyboard scanning program. The controller enables the soft start timer to run. Meanwhile, the output port Out1 of the controller is at a high level, the coil of KM1 is electrified, the three-phase contact of KM1 is closed, and 380V three-phase alternating current is connected to the motor. Because Out2 is low level, the KM2 contact keeps an off state, the three-phase soft start impedance Z is connected in series on a power line, and the motor is in a soft start state. The controller samples the output value I of the current effective value detection circuit in real time through AD soft (t) determining I by the maximum value algorithm soft Maximum value of (t)
And the moment of their occurrence
Calculating window time
Inner I soft (t) kurtosis X r Further obtaining the three-dimensional characteristic vector of the current in the soft start stage of the motor
Calculating psi and psi ref Dimensionless vector between
And psi σ 2 norm | | | ψ of σ || 2 . Wherein, | | ψ σ || 2 Satisfies the following conditions:
by judging | | ψ σ || 2 And a relation between the parameter theta and a set small positive threshold value (for example, theta is 0.05 or 0.1), and further diagnosing whether the motor runs in a starting locked-rotor fault state. When the | | | ψ is satisfied σ || 2 When theta is less than or equal to theta, the motor is considered to be in starting locked rotorWhen the fault occurs, the output port Out1 of the controller is at a low level, the coil of the KM1 is powered off, the three-phase contact of the KM1 is disconnected, and the motor is stopped and alarms to stop the rotation. When | | | ψ σ || 2 When theta is higher than theta, the motor is in a normal starting state, and the state of the motor is continued until the soft starting timing is finished. Once the soft start is finished, the output port Out2 of the controller is at a high level, the coil of the KM2 is electrified, the three-phase contact of the KM2 is closed, and the motor enters a full-voltage normal operation state after the soft start is finished. And thirdly, no matter the controller executes the normal soft-start current parameter acquisition algorithm or the motor operation control algorithm, as long as the S3 is found to be pressed down, the Out1 and the Out2 are at low levels, and the motor is stopped immediately.
Fig. 2 is a graph showing the normal soft start current and the time variation of the rotating speed, and the starting time of the motor is defined as zero time. The relevant parameters in the figure are illustrated as follows:
is a curve of the normal soft start current with the time t,
Is a curve of the normal soft start rotating speed with the time t,
Is a soft start current
Maximum value of,
Is composed of
Reaches the maximum value
Corresponding time, I N Rated current value of motor, NT s Observing window time for soft start data, N being the number of sampled data within the window time, T s To sampleThe period,
Is the soft start end time.
When the soft start is normal, the conditions of locked rotor and the like can not occur under the working condition of the motor. When the soft start is started, the soft start current rises from zero to zero rapidly due to the small electromagnetic inertia of the equivalent circuit of the motor
Although the current rises to within a short time
But can be controlled due to the current limiting effect of the three-phase impedance Z
Is of a size satisfying
Wherein: alpha is a number greater than zero, and the specific value can be determined by actual conditions. By controlling the value of alpha, the net starting torque of the motor can be ensured not to be too large or too small, and the motor can normally and softly start and run at a certain acceleration. Because the net torque of the motor is not very large, and the mechanical rotation inertia is far larger than the electromagnetic inertia of the circuit, the rotating speed acceleration of the motor is far smaller than the acceleration of the soft start current rising stage. Thus, in
The rotational speed is small and negligible. However, under the action of the net torque, the rotating speed of the motor is continuously increased, the counter electromotive force of the motor is also continuously increased, and the current is also continuously increased
In that
Is continuously reduced, but
Is always greater than I N . Due to the continuous increase of the rotation speed and the counter electromotive force, an
In that
Is continuously reduced, so
The degree of decline gradually decreases, and the curve gradually flattens. However, at observation window time
In the interior of said container body,
the curve changes significantly. Thus, the feature of normal soft start can be realized by
And with
Kurtosis of internal current
Data construction three-dimensional feature vector
To characterize.
Fig. 3 is a graph showing the soft start current and the time variation of the rotating speed in the locked rotor fault, and the starting time of the motor is defined as zero time. The relevant parameters in the figure are illustrated as follows: i is soft (t) is a relation curve of soft start current with time t during locked rotor fault, n soft (t) is a relation curve of the soft start rotating speed along with the time t during the locked rotor fault,
Is I soft (t) maximum value,
Is I soft (t) reaches a maximum value
The corresponding time,
A stable value of the locked-rotor fault current for soft start,
Is the maximum value of the normal soft start current, NT s Observing window time for soft start data, N being the number of sampled data within the window time, T s Is a sampling period,
Is the soft start end time.
When the motor is locked soft (t) coincides with the time axis, remains zero, and its back electromotive force is zero. Because the electromagnetic inertia of the equivalent circuit of the motor is small, the current rises rapidly from zero in soft start and
is timed to
Then slightly falls and quickly reaches the locked-rotor stable current
As can be known from the theory knowledge related to the electromechanics,
due to normal soft start
The motor speed is very low within timeTherefore, it is possible to
And
the difference is small. As known from the equivalent circuit model of the motor, the leakage inductance and the excitation inductance in the model are very small, and the peak current of the soft start is realized when the motor is locked
And
the gap is also small. So that the method has the advantages that,
the difference between the values of (A) and (B) is small, and can be considered as
Similarly, normal soft start current
Time of peak
And locked rotor soft start peak time
The difference is also small, and it can be considered that
However, the waveforms shown in FIGS. 2 and 3 are at observation window times
And
in the interior of said container body,
the curve changes significantly, and I soft (t) the variation is not significant. By definition and mathematical meaning of kurtosis, the kurtosis of the waveform with obvious change in a section is very large, and the kurtosis of the waveform with unobvious change is very small. Therefore, the first and second electrodes are formed on the substrate,
much greater than X r Is provided with
From the above analysis of fig. 1 and 2, it can be seen that the normal soft start current of the motor
And locked rotor fault soft start current I soft (t) there are distinct features: peak current of the first transistor
Is provided with
Versus time of peak current
Is provided with
The time window
And
the difference between the interior kurtosis is large, there are
Thus, the current three-dimensional eigenvector is constructed during the normal soft start phase
On the basis of serving as a reference vector, solving three-dimensional characteristic vectors of current in the soft start stage of actual working conditions
And dimensionless vector
By judging psi σ 2 norm | | | ψ of σ || 2 And a very small threshold value theta (wherein theta is very small, such as 0.05 and 0.1) which is larger than zero, so as to diagnose whether the actual working condition is locked rotor, realize the fast identification and protection of the locked rotor of the motor, and improve the service life and the safety of the motor.
In summary, the invention judges whether the motor has the locked-rotor fault according to the obtained current three-dimensional feature vector by detecting the current sequence in the specific time window of the soft start of the motor and analyzing the correlation degree with the reference current sequence in the specific time window of the normal soft start. The motor starting locked-rotor judging method provided by the invention takes the current sequence in the specific time window of normal soft start when the motor running condition changes as the reference sequence, and can effectively improve the capability of the algorithm in adapting to different working condition environments and inhibiting parameter drift caused by motor aging.
Claims (6)
1. A motor starting locked-rotor fault diagnosis method based on soft-start current characteristics is characterized by comprising the following steps: the method comprises the following steps:
step one, when the motor is normally soft started, sampling period T is used s For interval pair motor current effective value
Sampling, and constructing a current three-dimensional characteristic vector psi in a normal soft start stage by using sampling data ref ；
Step two, when the motor is started to rotate and block, the sampling period T is used s For interval to effective value I of motor current soft (t) sampling by the number of samplesConstructing a three-dimensional eigenvector psi of the current in the detection stage;
step three, comparing the three-dimensional eigenvector psi of the current in the detection stage with the three-dimensional eigenvector psi of the current in the normal soft start stage ref Performing operation to obtain dimensionless vector psi σ And psi σ 2 norm | ψ of σ || 2 ；
Step four, judging | | | ψ σ || 2 And if the value is less than or equal to the threshold value theta, determining that the motor is in a starting locked-rotor fault.
2. The motor start locked rotor fault diagnosis method based on the soft-start current characteristics according to claim 1, characterized in that: current three-dimensional characteristic vector psi in normal soft start stage in step one ref Is constructed with a sampling period T s Sampling the soft start current effective value sensor for interval start, marking the first sampling value as
The current sampling frequency is k, and k =1;
establishing soft start current array composed of M elements
Wherein i = { k-M +1,k-M +2, …, k-1,k }, M is a preset positive integer greater than 2, and k is the current sampling frequency;
solving arrays using bubbling
Non-zero maximum value element of
Satisfies the following conditions:
U∈{k-M+1,k-M+2,…,k-1,k}；
judgment of
Whether the result is true; if yes, entering the next step; otherwise, returning to the previous step for recalculation;
the preset maximum value filtering interval is a positive even number P and satisfies the following conditions:
computing
And
obtaining [ (U + 1) T s ,(U+N)T s ]The current effective value data in time form an array
Calculating an array average
Degree of harmony
According to the average value of the array
Degree of harmony
Obtaining the current three-dimensional characteristic vector in the normal soft start stage
3. The motor start locked rotor fault diagnosis method based on the soft-start current characteristics according to claim 2, characterized in that: the construction process of the three-dimensional eigenvector psi of the phase current detected in the step two is a sampling period T s Sampling the soft-start current effective value sensor for the beginning of the interval, and marking the first sampling value as I soft (1) (ii) a The current sampling frequency is k, and k =1;
establishing a soft-start current array { I) composed of M elements soft (i) I = { k-M +1,k-M +2, …, k-1,k }, wherein M is a preset positive integer greater than 2, and k is the current sampling time; i is soft (i)| i≤0 ＝0；
Method for solving array { I by using bubbling method soft (i) Non-zero maximum value element I in soft (U) satisfying: i is soft (U)＝max{I soft (i)}＞0，U∈{k-M+1,k-M+2,…,k-1,k}；
Judgment of
Whether the result is true or not; if yes, entering the next step; otherwise, returning to the previous step for recalculation;
the preset maximum value filtering interval is a positive even number P and satisfies the following conditions:
computing
And
obtaining [ (U + 1) T s ,(U+N)T s ]The current effective value data in time form an array { I soft (U+1),I soft (U+2),…,I soft (U + N) }, calculating array average value
Degree of harmony
According to the mean value of the array
Degree of harmony
Constructing three-dimensional eigenvectors of soft-start current
4. The motor start locked rotor fault diagnosis method based on the soft-start current characteristics according to claim 1, characterized in that: when the motor is normally and softly started, firstly judging whether the operation condition of the motor changes or not, and after confirming that the motor is not in the abnormal condition of locked rotor, executing sampling work, connecting the soft start impedance to a power line of the motor by using the controller, and starting the soft start of the motor.
5. The motor start locked rotor fault diagnosis method based on the soft-start current characteristics according to claim 1, characterized in that: when the motor is started to rotate and is blocked, the soft start impedance is connected to a power line of the motor, and the current is always in a safe range when the motor is blocked.
6. The motor start locked rotor fault diagnosis method based on the soft-start current characteristics according to claim 1, characterized in that: in the sixth step, judge | | | ψ σ || 2 Whether the value is less than or equal to the threshold value theta, if not, the motor is in a normal soft start state, whether the soft start timing is finished is judged, if so, the controller short-circuits the soft start impedance on the power line of the motor, and the water pump enters a normal working procedure; otherwise, wait.
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