RU2716172C2 - Diagnostics method of asynchronized synchronous motor with squirrel cage rotor - Google Patents

Abstract

FIELD: measurement.

SUBSTANCE: invention relates to measurement equipment and diagnostics of electric motors. Method for diagnosing asynchronous electric motors with a squirrel-cage rotor, involving obtaining reference parameters of a defect-free electric motor, taking working characteristics, determining technical state based on comparison results, wherein values, frequencies and shapes of distribution of external magnetic field of dissipation of asynchronous electric motors, angular velocity and value of mechanical vibrations are taken, evaluation of technical state is performed by deviation of obtained data from one of detectors of external magnetic field from reference or average value by more than 10 %.

EFFECT: technical result is possibility of diagnostics of electric and mechanical damages and forecasting of further condition of asynchronized synchronous motor with squirrel-cage rotor and equipment during engine operation without its decommissioning.

3 cl, 1 dwg

Description

The proposed device and method relates to the fields of measuring equipment and diagnostics of electric motors, is a multi-channel device and method for determining the faults of induction motors by measuring external magnetic fields, angular velocity of rotation and vibration, which can be used to build various diagrams. Nowadays, induction motors are the most common class of electrical machines. They are widely used in industry, in utilities and transport, acting as a drive for conveyors, various pumps, cooling systems, and are beginning to be used as the main traction drives in transport.

At the same time, the diagnosis of such an important link, failure, which can lead to a halt in the production cycle or to breakdown of the systems it provides, is poorly developed and represents mainly emergency shutdown measures or methods requiring the engine to be taken out of service, which not always possible. In this case, the most appropriate solution is to service the equipment according to its actual condition.

Therefore, the assessment of the technical condition of asynchronous electric motors is an important task, the solution of which will allow to detect incipient defects at an early stage and, thereby, prevent emergency situations that can lead to negative consequences.

A known method for the diagnosis of electrical and mechanical damage to an asynchronous squirrel-cage motor [RF patent No. 2479096 C2, H02K 15/00, G01R 31/34, publ. 04/10/2013], according to which diagnostics are performed during engine operation by measuring current values at two points of its short-circuit ring spaced relative to each other by the pole division value of asynchronous electric motors or a multiple thereof, for which two sensors are installed on the short-circuited rotor ring current. The magnitudes of the currents flowing in the short-circuit ring of the rotor indicate the presence or absence of damage to the motor.

The disadvantages of this method are the limited scope and the complexity of the technical implementation due to the installation of current sensors on the short-circuited rotor ring.

There is a device (Author's certificate No. SU 1684761 A1, G01R 33/06, publ. 10/15/1991) for measuring and topography of scattering magnetic fields near the surface of the object of study, in which one three-component Hall sensor is used, moving along a predetermined path using a measuring rod relative to object of measurement, by means of a block of mechanical displacements with a rotary table and movable carriages driven by stepper motors. The data recorded by the sensor are subjected to statistical processing in the measuring and computing unit. The disadvantage of this device is functional limitations, namely, the ability to obtain data for constructing magnetic field distributions that do not vary in time, in addition, when registering a field, considerable time is required to move the sensor along a given spatial path. A device is known for measuring a spatial inhomogeneous, constant or time-varying magnetic field (RF patent RU No. 2548931, G01R 33/00, publ. 04.20.2015). The objective of the device is to reduce the influence of interference when measuring the magnetic field through the use of optical communication, the use of autonomous power sources, as well as increasing the functionality of the measuring device due to the possibility of increasing the number of measuring channels to a predetermined one, based on the conditions of a particular task, with the possibility of placing measuring channels and setting individual values of the parameters of the magnetic field survey (frequency, number of samples, conversion accuracy) at specific points x the space where you want to measure the magnetic field.

Designed to reduce the influence of interference when measuring the magnetic field through the use of optical communication, the use of autonomous power sources, as well as increasing the functionality of the measuring device due to the possibility of increasing the number of measuring channels to a predetermined one based on the conditions of a specific task with the possibility of placing the measuring channels and setting individual values magnetic field polling parameters (frequency, number of samples, conversion accuracy) at specific points in space where you want to measure the magnetic field.

The disadvantage of this device is the difficulty of use in production, due to the need to remove data from induction motors during operation using an optical transceiver, which in some cases can be a gross violation of safety precautions. Also, in rooms where engines are installed, they can often be dusty, which will reduce the quality of communication. It should be noted that the presence of a memory unit, a microcontroller, and a power supply in the sensor makes it inconvenient for recording magnetic fields of small power motors due to their large dimensions.

The closest is the Model-based motor fault detection system, (RF patent No. RU 2155328 C1, G01M 15/00, publ. 27.08.2000). The invention is a method and device for monitoring the state and forecasting the service life a. The task of the system is to detect mechanical failures that can cause engine damage, before the actual catastrophic engine failure. The operation of the system includes the stages of developing a model of the engine on a computer connected to the engine using a variety of sensors, by measuring many working signals using sensors. During operation of the electric motor, based on the measurement of a plurality of working signals, a linear equation of state in discrete time is solved. Further, comparing the solutions of the equation of state with the solution proposed by the model, the remainder is calculated, the state of asynchronous motors is determined. If the engine is running with a detected malfunction, a message is displayed indicating the existence of a malfunction to prevent unexpected engine damage. Steps, measurements, solutions, and comparisons are repeated at selected time intervals during the operation of induction motors.

The disadvantage of this method is the need to obtain preliminary results of experimental modeling for the mathematical description of each individual engine. It should also be noted the high complexity and cost of the used technical equipment that implements this method.

The objective of the invention is to expand the functionality by diagnosing electrical and mechanical defects of an asynchronous squirrel-cage electric motor, by measuring, during operation, the parameters of the external magnetic field of the scattering at the locations of the phase windings in each pole, angular velocity and vibration.

The solution to the problem is:

A method for diagnosing squirrel-cage induction electric motors, including obtaining reference parameters of a defect-free motor, taking performance data and determining the technical condition from comparison results, characterized in that they record the magnitude, frequency and shape of the distribution of the external magnetic field of the scattering of asynchronous motors, angular velocity and mechanical oscillations in three directions: vertical, horizontal. The information obtained during measurement is transmitted to a computer for analysis and decision making. The technical condition is assessed according to the threshold value, which is the difference between the data obtained from one of the sensors for recording the external magnetic field and the average value or standard by more than 10% and 5% for the angular velocity sensor, which are established by finite element modeling and analysis of experimental data , for mechanical vibrations, the assessment is made according to GOST ISO 10816-1-97 and GOST ISO 133731-2009.

The method is provided by a diagnostic device for asynchronous motors with squirrel-cage motors, including sensors for taking characteristics and computers, the presence of an output signal of three types, for measuring the parameters of the external magnetic field of scattering, angular velocity and vibration, and the outputs of all sensors are connected to the measuring unit, providing collection data and computer transmission. Magnetic field parameters are measured by sensors based on Hall elements installed on the motor housing, the distance between which depends on the magnitude of the pole division. The angular velocity is measured using a single sensor and a disk with the risks applied to it, mounted on the shaft of asynchronous motors. Vibration is measured by a three-component sensor mounted on the motor housing.

Figure 1 - Structural diagram of a device providing the proposed method for the diagnosis of asynchronous squirrel-cage motors.

In FIG. 1 is a structural diagram of a device providing the proposed method for diagnosing asynchronous motors, which consists of three types of sensors: T1 - magnetic field sensor, T2 - angular velocity sensor, T3 - vibration sensor connected to the measuring unit 6 and the computer (7). Sensors of types T1, T2, T3 consist of Hall elements 1, an optical sensor 2, a three-component vibration sensor 3, respectively, each sensor has a buffer (4), ADC (5). Using sensors of the first type T1 containing a Hall element (1), the number of which is determined by the design of the electric motor mounted on the housing, at a distance of pole division from each other, the parameters of the external magnetic field of the scattering of the electric motor are recorded. The signal from each sensor enters the filter buffer (4), then comes to the ADC (5) where it is digitized. After the ADC, the signal from all sensors arrives at the measuring unit (6), which coordinates the signals from all sensors and transmits them to the computer (7). The angular velocity is measured by one optical sensor (2) mounted permanently and a disk with the risks applied to it, mounted on the motor shaft, the signal from which is processed in the same way as from magnetic field sensors. The vibration value is measured by a three-component sensor (3), which is mounted on the engine casing to register the tangential as well as normal and axial components of the oscillations, the signal from which undergoes the same processing as the signal from the magnetic field and angular velocity sensors.

After processing and transmitting data to a computer (7), the data is analyzed and the technical condition is determined according to the following criteria. For the distribution of the external magnetic field of the electric motor, this is the deviation of the received data from one sensor from the standard, or from the average value by more than 10%. For the angular speed of rotation, the deviation of the speed at one of the measured points from the average value is more than 5%.

The technical result achieved by using the present invention is to enable the diagnosis of electrical and mechanical damage and prediction of the further state of squirrel-cage induction motors and equipment, during operation of the motor, without taking it out of operation, by measuring the characteristics of the external magnetic field at points spaced relative to each other by the magnitude of the pole division of asynchronous motors or a multiple thereof, and t Also controls vibration and angular velocity. The number of magnetic field sensors is determined by the design of the engine. This allows you to more accurately determine and predict the technical condition of the engine.

Claims (3)

1. A method for diagnosing squirrel-cage asynchronous electric motors, including obtaining reference parameters of a defect-free electric motor, taking performance characteristics, determining the technical condition according to the comparison results, characterized in that the following indicators are taken: magnitude, frequency and distribution form of the external magnetic field of the scattering of asynchronous electric motors, angular velocity and the magnitude of mechanical vibrations, the assessment of the technical condition is made by the deviation of the obtained data from one of d tchikov registration of an external magnetic field from the standard or average value by more than 10%. 2. The method according to p. 1, characterized in that the vibration measurement is performed by a three-component sensor, while one of the components is oriented in the tangential direction. 3. The method according to p. 1, characterized in that the technical condition is assessed by a threshold value, which is the difference between the data obtained by the angular velocity sensor at any point from a reference or an average value of more than 5%.

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