CN204789434U - Asynchronous motor bearing damage monitoring system - Google Patents

Abstract

The utility model discloses a bearing damage monitoring system of an asynchronous motor, which comprises the following units: a thermoelectric signal acquisition unit, which is used to detect the heat generated by friction between the roller of the bearing and the inner and outer raceways when the bearing on the asynchronous motor is damaged The generated thermoelectric signal is converted into a thermoelectric potential signal; the conditioning amplifier unit filters and amplifies the thermoelectric potential signal; the fault diagnosis and alarm unit digitally processes the thermoelectric potential signal, and grades the failure degree of the bearing to issue an acousto-optic alarm; The on-line monitoring unit can display the thermoelectric potential signal sent by the fault diagnosis and alarm unit in real-time graphically and visually; the data storage unit can store the monitoring information according to certain rules so as to analyze the bearing damage state offline; the utility model has a simple structure , The monitoring is convenient, the accurate monitoring of the internal damage state of the bearing is realized, the maintenance time and maintenance cost of the asynchronous motor are saved, and the production efficiency is improved.

Description

A Monitoring System for Asynchronous Motor Bearing Damage

technical field

The utility model relates to the technical field of electric motor equipment, in particular to an asynchronous motor bearing damage monitoring system.

Background technique

As the key power output and transmission equipment in the production and circulation link, asynchronous motors have been widely used in the support fields of electric power, steel, petrochemical, transportation and national defense, etc., and ensuring the safe and stable operation of asynchronous motors is the top priority of maintenance work Heavy. Various statistics show that the faults of asynchronous motors are mainly bearing faults, winding faults and broken rotor bars, among which bearing faults have the highest incidence rate, accounting for 30-42% of the total faults of asynchronous motors. In the normal operation of the bearing of the asynchronous motor, there is a lubricant between the roller and the raceway of the bearing, which avoids direct contact between the two metals and reduces friction loss. Bearing damage is likely to occur when the lubricant in the bearing is deteriorated or lacking, the bearing mating surface is processed or installed improperly, resulting in inaccurate positioning, the asynchronous motor is overloaded for a long time, the bearing is over-charged, and the bearing is defective. Bearing failures of asynchronous motors are mainly manifested as surface damage of bearing components, such as inner and outer raceway damage, pitting corrosion, cage defects or quality problems of the bearing itself. Bearing faults make it difficult to start the asynchronous motor, the rotor is unstable, the temperature of the bearing side rises, the timing is serious, the rotor magnetic gap oscillates violently, scrapes each other, the winding is short-circuited, and the motor is even burned. The traditional detection method of asynchronous motor bearing fault is to determine the bearing fault by sensing the temperature and vibration of the bearing part and listening to the abnormal sound of the bearing. Due to individual sensory differences, it is difficult to quantitatively analyze bearing faults. This method requires inspectors to have rich on-site experience, making it difficult to promote.

At present, the methods for monitoring bearing faults of asynchronous motors mainly include temperature method, oil sample method, vibration method, stator current method and oil film thickness method (contact resistance method).

The temperature method is to diagnose the working state of the bearing by monitoring the temperature of the bearing seat or the adjacent box. It is more sensitive to the overload, overspeed and poor lubrication of the bearing, but it is basic to the micro-cumulative faults such as pitting corrosion, metal peeling and damage of the bearing. no response.

The oil sample method is a method of diagnosing the operating state of the bearing by regularly taking oil samples from the lubricant used by the bearing and analyzing the size and content of specific metal particles in the oil sample. The oil sample method can be used for early failure analysis of bearings, but it is difficult to take samples during the working process of the motor, and the real-time performance is not strong. The oil samples are also easily mixed with particles that are not damaged by the bearing and affect the analysis results.

The vibration method is to measure the time-domain signal generated by the vibration of the bearing, and then transform the time-domain signal into a frequency-domain signal and compare it with the natural frequency characteristics of the bearing vibration to determine whether there is a fault in the bearing. The vibration method is not limited by the type of bearing, and the signal processing is convenient and intuitive, so it is the most widely used at present. However, the asynchronous motor has many vibration excitation sources, low signal-to-noise ratio, and it is difficult to accurately extract the characteristic information of the fault. It is inconvenient to install vibration sensors in many occasions, thus reducing the engineering practicability of the vibration method.

The stator current method is a method of testing and recording the motor stator current signal, and analyzing and processing the signal to determine whether the bearing is faulty. Because the faulty bearing will cause the vibration of the shaft, the vibration of the shaft will cause the vibration of the air gap between the stator and the rotor of the asynchronous motor. The air gap vibration modulates its magnetic flux, and the modulated magnetic flux induces a harmonic current in the stator winding. The frequency spectrum is used to extract the harmonic components induced by the vibration of the rotating shaft, and the fault detection of the bearing can be realized. Compared with the vibration method, the stator current method is simpler and more practical, but the magnitude of the fault frequency component corresponding to the stator current is small, which is easily covered by noise and fundamental frequency components, and it is difficult to extract fault eigenvalues.

The oil film thickness method judges the lubrication state of the bearing by measuring the contact resistance between the bearing surfaces. The resistance value reflects the oil film thickness of the bearing; the smaller the oil film thickness, the greater the probability of failure. The oil film thickness method is sensitive to damage and corrosion faults, and has poor applicability to faults such as surface peeling and cracks, and is not suitable for low-speed, multi-bearing coaxial, etc., and has little practical engineering application.

For this reason, a new method of monitoring asynchronous motor bearing faults has been developed, online monitoring of asynchronous motor bearing operating status, timely early warning and quantitative analysis of faults, avoiding major losses caused by bearing faults, and improving the operation reliability of asynchronous motors It has very important engineering practical value.

Contents of the invention

The purpose of this utility model is to solve the above-mentioned problems existing in the temperature method, oil sample method, vibration method, stator current method and oil film thickness method currently used for monitoring asynchronous motor bearing faults, and to provide a simple and convenient operation that can It is an asynchronous motor bearing damage monitoring system that accurately detects the damage state of the bearing in real time and ensures the stable and efficient operation of the asynchronous motor.

The specific solution of the utility model is: a bearing damage monitoring system for asynchronous motors, which is characterized in that it includes the following units:

The thermoelectric signal acquisition unit is used to convert the thermoelectric signal generated by the frictional heat between the roller of the bearing and the inner and outer raceways of the bearing when the bearing on the asynchronous motor is damaged into a thermoelectric potential signal that can be collected. The thermoelectric signal acquisition unit It includes a rotating shaft adapter installed on the non-power output shaft end of the asynchronous motor. The other end of the rotating shaft adapter is sequentially installed with a coaxially arranged connecting shaft, a conductive coupling, a relay rod and a conductive ring. The non-rotating end of the conductive ring serves as Signal output terminal, the signal output terminal is connected with the sampling resistor, and the other end of the sampling resistor is connected with the casing of the asynchronous motor; the casing, bearing and rotating shaft of the asynchronous motor are connected with the rotating shaft adapter, connecting shaft, conductive coupling , relay rod, conductive ring, and sampling resistor form a series circuit;

The conditioning amplifier unit is used to receive the thermoelectric potential signal transmitted from the signal output terminal, and filter and amplify the thermoelectric potential signal;

The fault diagnosis and alarm unit digitally processes the thermoelectric potential signal transmitted by the conditioning amplifier unit, performs real-time diagnosis to grade the fault degree of the bearing and sends out a corresponding sound and light alarm, and at the same time relays the main fault output, according to a certain Delay shutting down the asynchronous motor to ensure the safe operation of the asynchronous motor;

The online monitoring unit can display the thermoelectric potential signal sent by the fault diagnosis and alarm unit to represent the damage state of the bearing in real-time and graphically;

The data storage unit stores the monitoring information of the online monitoring unit according to certain rules, so as to conduct offline analysis of the bearing damage state.

In the utility model, the rotating shaft adapter and the non-power output shaft end of the asynchronous motor adopt clearance fit, and are fastened with the aid of conductive glue, and the rotating shaft adapter and the rotating shaft of the asynchronous motor are arranged on the same axis.

The conductive coupling described in the utility model is a spiral elastic coupling; the conductive ring is a mercury slip ring whose model is A1M; the relay rod is used to connect the conductive coupling and the conductive ring, and a There are mounting openings that match the swivel ends of the conductive rings.

The on-line monitoring unit in the utility model performs real-time graphical and visual display of the thermoelectric potential signal used to represent the damage state of the bearing, including display of time domain, frequency domain, time-frequency domain, three-dimensional graphics, and real-time display of the rotor speed of the asynchronous motor. show.

The data storage unit in the utility model continuously or intermittently stores the monitoring information used to represent the damage state of the bearing, and at the same time systematically records related parameters such as the bearing model, specification, damage form, and pyroelectric signal intensity for offline analysis.

The working principle of the utility model is as follows:

Rotating machinery usually includes a friction pair that carries relative motion. The friction pair needs a lubricating oil film to reduce its wear and tear consumption. Different motion forms of the lubricating oil film cause different lubrication states of the friction pair. The five common basic types of lubrication states are: ( a) Hydrodynamic lubrication; (b) Hydrostatic lubrication; (c) Elastohydrodynamic lubrication; (d) Boundary lubrication; (e) Dry friction state. In the actual working process, the friction pair is usually in a mixed lubrication state in which several of the above lubrication states coexist. The different oil film thicknesses of the bearings used by the asynchronous motor to support the rotating shaft cause different friction strengths, which in turn cause different mechanical energy losses, and the loss of mechanical energy is converted into heat energy, resulting in an increase in the temperature of the friction pair. According to Seebeck's thermoelectric effect theory, the temperature difference between the hot and cold ends of a metal will cause its internal charges to move, thereby generating a potential difference between its cold and hot ends. The change of the thermoelectric potential difference intensity reflects the change of the temperature of the friction pair, and the temperature of the friction pair indicates the intensity level of the friction. The damage degree of the asynchronous motor bearing can be accurately inferred from the change law of the thermoelectric potential difference.

As shown in Figure 2, in order to analyze the thermoelectric potential generated by the thermoelectric effect of the bearing, it may be assumed that two metal materials A and B form a closed loop, the hot end is T, and the cold end is T ₁ , T>T ₁ . According to Seebeck thermoelectric effect theory, it can be known that contact potential U _AB (T), U _AB (T ₁ ) and thermoelectric potential will be generated in the loop The algebraic sum is the total thermoelectric potential of the closed loop, and the current direction is shown in Figure 2. An external heat source acts as an energy source to maintain the circuit constant.

Assume that the free electron densities of two metals A and B at temperature T are N _A (T) and N _B (T) respectively, and N _A (T)>N _B (T). When A and B are in close contact, due to the unbalanced diffusion of free electrons, the number of free electrons from A to B is more than that from B to A, which forms an electric field that hinders the continuous diffusion and forms a drift. As the electrons continue to diffuse, the electric field strength continues to increase until the diffusion and drift reach a dynamic balance, the electric field strength tends to be stable, and a contact potential is generated at the contact between the two metals. Assuming that the temperature at the contact point of the two metal conductors is T, according to the force balance relationship and the theory of electron physics, the electric field electromotive force within an infinitely small step is:

$\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; T</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

k is Boltzmann's constant, k=1.38×10 ^-23 J/K; T is Kelvin temperature, unit K; e is electron charge, e=1.6×10 ^-19 C.

The electric field electromotive force at equilibrium is obtained by integrating along the contact surface from B to A:

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; T</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}\mathrm{<span\; class="notranslate">\; ln</span>}\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

The total electromotive force (that is, the contact potential) caused by the difference between the free electron density and the work function when metals A and B are in close contact is:

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&Phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&Phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; A</span>}}}{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 12</span>}\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; B</span>}}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; A</span>}}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; T</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; T</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}\mathrm{<span\; class="notranslate">\; ln</span>}\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

The contact potential is also called the Peltier potential. Assuming that the temperature of the contact point at the other end of the two conductors is T ₁ , the total contact potential of the closed circuit is:

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; \&lsqb;</span>\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; l</span>}\mathrm{<span\; class="notranslate">\; no</span>}\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; l</span>}\mathrm{<span\; class="notranslate">\; no</span>}\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&rsqb;</span><span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 12</span>}\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; B</span>}}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; A</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

For the same metal A, when there is a temperature difference between its two ends (the hot end is T, the cold end is T ₁ , T>T ₁ ), a thermoelectric potential will be generated The magnitude of the thermoelectric potential in conductor A is from T ₁ to T versus dU _A , resulting in:

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\overset{\mathrm{<span\; class="notranslate">\; T</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\frac{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; T</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; \&lsqb;</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

In the formula, U _A (T, T ₁ ) is the temperature difference potential at both ends of conductor A when the temperature at both ends is T, T ₁ . Respective orders for conductors A and B

${\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; \&lsqb;</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>}{{\mathrm{<span\; class="notranslate">\; n</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; \&lsqb;</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>}{{\mathrm{<span\; class="notranslate">\; n</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}$

σ _A , σ _B are Thomson coefficients. Then in the closed circuit formed by two conductors A and B, the temperature difference potential is:

$\underset{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\overset{\mathrm{<span\; class="notranslate">\; T</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; \&lsqb;</span>\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; l</span>}\mathrm{<span\; class="notranslate">\; no</span>}\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; l</span>}\mathrm{<span\; class="notranslate">\; no</span>}\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&rsqb;</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}\underset{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\overset{\mathrm{<span\; class="notranslate">\; T</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\mathrm{<span\; class="notranslate">\; l</span>}\mathrm{<span\; class="notranslate">\; no</span>}\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

The total thermoelectric potential U ^AB (T,T ₁ ) of the closed loop is:

${\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}\underset{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\overset{\mathrm{<span\; class="notranslate">\; T</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\mathrm{<span\; class="notranslate">\; ln</span>}\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 12</span>}\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; B</span>}}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; A</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

It can be seen from formula (7) that not only temperature difference and free electron density difference constitute thermoelectric potential, but also work function difference or Fermi level energy difference. Formula (7) can be shortened as:

U ^AB (T,T ₁ )＝A ₁ (TT ₁ )+A ₂ (T ² -T ₁ ² )(8)

or:

u(t,0)＝a ₁ t+a ₂ t ² (9)

This is the expression of the thermoelectric potential and temperature of the general thermocouple circuit. The size of the thermoelectric potential is related to the materials of the two electrodes of the thermocouple and the temperatures T and T _of the hot and cold ends. When the electrode material is determined, the thermoelectric potential depends _on the temperature T and T1. Practice has proved that the micro-change of thermoelectric potential dU ^AB (T,T ₁ ) is proportional to the micro-change of temperature dT:

dU ^AB (T,T ₁ )＝S _AB (T)dT(10)

Among them, S _AB (T) is the thermoelectric potential rate of the thermocouple composed of metal A and B, that is, the Seebeck coefficient. Assuming the inner and outer raceways of the bearing as metals A and B, according to the material properties and temperature difference of the inner and outer raceways of the bearing, it is possible to calculate the temperature rise caused by the damage of the inner and outer raceways of the bearing and then the thermoelectric effect. thermoelectric potential.

The utility model has simple structure and convenient monitoring. By extracting the thermoelectric signal generated by the frictional heat between the roller of the asynchronous motor bearing and the inner and outer raceways, the purpose of monitoring the damage degree of the relative moving parts inside the bearing is achieved. It is used to monitor the internal damage degree of ball bearings, sliding bearings, roller bearings and needle bearings. Moreover, the change of the bearing wear degree causes the temperature change, and the temperature change causes the thermoelectric potential change, so the law of the thermoelectric potential change can accurately reflect the damage state of the bearing, which provides a strong guarantee for the stable and efficient operation of the asynchronous motor. In this way, this practical The new type improves the monitoring efficiency, saves the maintenance time of the asynchronous motor and the corresponding labor cost, improves the production efficiency and creates social benefits.

Description of drawings

Fig. 1 is the installation structure schematic diagram of the present utility model;

Fig. 2 is the thermoelectric potential distribution schematic diagram that metal conductor A, B constitute closed conductor loop in the utility model;

FIG. 3 is a partially enlarged schematic diagram at K in FIG. 1 .

In the figure: 1—machine base, 2—front end cover, 3—rear end cover, 4—stator, 5—rotor, 6—rotating shaft, 7—rotor core assembly, 8—ball bearing, 801—roller (ball ), 802—inner raceway, 803—outer raceway, 9—thermoelectric signal acquisition unit, 10—conditioning amplification unit, 11—fault diagnosis and alarm unit, 12—online monitoring unit, 13—data storage unit, 14—shaft adapter , 15—connecting shaft, 16—conductive coupling, 17—relay rod, 18—conductive ring, 19—sampling resistor, 20—installation port, 21—voltmeter.

Detailed ways

Referring to FIGS. 1-3 , this embodiment specifically takes the monitoring of the damage state of the ball bearing in the asynchronous motor as an example.

Known according to the prior art, the asynchronous motor has a frame 1, and the front and rear ends of the frame 1 are correspondingly equipped with front and rear end covers 2, 3 (the frame 1 of the asynchronous motor and the front and rear end covers 2, 3 constitute the frame of the asynchronous motor. The casing) is equipped with a stator 4 and a rotor 5 correspondingly arranged in the casing, wherein the rotor 5 includes a rotating shaft 6 and a rotor core assembly 7, and ball bearings 8 are respectively set at the front and rear ends of the rotating shaft 6, and the front and rear The ball bearings 8 are correspondingly installed in the bearing holes of the front and rear end covers 2,3.

It can be seen from the above that the front and rear ball bearings 8 are generally made of alloy, and the front and rear ball bearings 8 are used as the gravity support of the rotating shaft 6, and the rotating shaft 6 is calibrated horizontally and vertically. The front and rear ball bearings 8 all have rollers (balls) 801 and inner and outer raceways 802, 803, the rollers (balls) 801 are evenly distributed in the inner and outer raceways 802, 803, and the inner and outer raceways 802 , 803 are filled with grease. And, the inner raceways 802 of the front and rear ball bearings 8 are in close contact with the rotating shaft 6, and the outer raceways 803 of the front and rear ball bearings 8 are in close contact with the front and rear end covers 2 and 3, so that the front and rear ball bearings 8 and the The casing of the asynchronous motor constitutes an equipotential body. When the asynchronous motor is working, the casing is grounded. When the lubricating oil film in the front and rear ball bearings 8 is partially damaged, the lubrication state between the rollers (balls) 801 and the inner and outer raceways 802, 803 becomes poor, causing friction and releasing a large amount of heat, which causes the balls A temperature difference is generated between the inner raceway 802 and the outer raceway 803 of the bearing 8 . According to the Seebeck thermoelectric effect theory, when there is a temperature difference inside the same metal conductor, a thermoelectric effect will occur, that is, a potential difference will be generated between the hot end and the cold end of the metal conductor, regardless of how many conductors are connected, this is the same metal conductor. The thermoelectric potential caused by its own temperature gradient. Therefore, the front and rear ball bearings 8 can be regarded as a power supply, the inner and outer raceways 802, 803 of the ball bearing 8 are used as positive and negative poles of the power supply, and the heat energy generated by the friction of the bearing damage inside the ball bearing 8 is used as the energy source of the power supply. The front and rear ball bearings 8 are used as power sources to form a complete circuit, and the internal damage of the bearings can be indirectly monitored by monitoring the potential change between the inner and outer raceways 802 and 803 of the front and rear ball bearings 8 (due to The casing is grounded, and the potential of the outer raceway 803 of the inner and outer ball bearings 8 is zero).

According to the above principles, a monitoring system for bearing damage of asynchronous motors can be constructed, which includes the following units:

The thermoelectric signal acquisition unit 9 is used to detect the frictional heat generated between the roller (ball) 801 of the ball bearing 8 and the inner and outer raceways 802, 803 of the ball bearing 8 when the ball bearing 8 on the asynchronous motor is damaged. The thermoelectric signal is converted into a thermoelectric potential signal that can be collected. The thermoelectric signal acquisition unit 9 includes a shaft adapter 14 installed on the non-power output shaft end of the asynchronous motor. Coupling 16, relay rod 17 and conductive ring 18, wherein the non-rotating end of the conductive ring 18 is used as the signal output end, the signal output end is connected with the sampling resistor 19, and the other end of the sampling resistor 19 is connected to the casing of the asynchronous motor connection (because the casing is grounded, the signal collected from the signal output end is a thermoelectric potential signal); the casing of the asynchronous motor, the ball bearing 8 and the rotating shaft 6 are sequentially connected with the rotating shaft adapter 14, the connecting shaft 15, and the conductive coupling 16 , a relay rod 17, a conductive ring 18, and a sampling resistor 19 form a series circuit;

Conditioning amplifying unit 10, used to receive the thermoelectric potential signal transmitted from the signal output terminal, and filter and amplify the thermoelectric potential signal;

The fault diagnosis and alarm unit 11 digitally processes the thermoelectric potential signal transmitted from the conditioning amplifier unit 10, performs real-time diagnosis to rate the fault degree of the ball bearing 8 and sends out a corresponding sound and light alarm, and at the same time relays the main fault output, Turn off the asynchronous motor at a certain time delay to ensure the safe operation of the asynchronous motor;

The on-line monitoring unit 12 performs real-time graphical and visual display of the thermoelectric potential signal used to represent the damage state of the bearing transmitted from the fault diagnosis and alarm unit 11;

The data storage unit 13 stores the monitoring information of the online monitoring unit 12 according to certain rules, so as to conduct offline analysis on the damage state of the bearing.

In this embodiment, the rotating shaft adapter 14 and the non-power output shaft end of the asynchronous motor adopt a clearance fit, and are fastened with the aid of conductive glue. The rotating shaft adapter 14 and the rotating shaft 6 of the asynchronous motor are arranged on the same axis.

The conductive coupling 16 in this embodiment is a spiral elastic coupling, and the conductive coupling 16 acts as a vibration damper, and transmits the thermoelectric signal collected by the rotating shaft adapter 14 from the rotating shaft 6 to the conductive shaft through the relay rod 17. Ring 18; the conductive ring 18 is a mercury slip ring whose model is A1M; the relay rod 17 is used to connect the conductive coupling 16 and the conductive ring 18, and the front end of the relay rod 17 is provided with a Matching mounting port 20.

In the present embodiment, a voltmeter 21 is also installed between the conditioning amplifying unit 10 and the fault diagnosis alarm unit 11, and the other end of the voltmeter 21 is connected (grounded) to the casing, and the sampling resistance can be read intuitively by the voltmeter 21 19 The magnitude of the voltage across the terminal.

The on-line monitoring unit 12 in this embodiment performs real-time graphical and visual display of the thermoelectric potential signal used to represent the damage state of the bearing, including the display of time domain, frequency domain, time-frequency domain, three-dimensional graphics, and the rotor 5 of the asynchronous motor. Real-time display of speed.

The data storage unit 13 described in this embodiment continuously or intermittently stores the monitoring information used to represent the damage state of the bearing, and at the same time systematically records the relevant parameters such as the model, specification, damage form, and pyroelectric signal intensity of the ball bearing 8 for future use. Offline analysis.

Claims (3)

1. an asynchronous motor bearing damage monitoring system, is characterized in that: include with lower unit:

Pyroelectric signal collecting unit, during for being there is damage in asynchronous motor head bearing, in the roller of bearing and bearing, the pyroelectric signal that between outer raceway, frictional heat produces is converted to collectable thermoelectrical potential signal, pyroelectric signal collecting unit includes the shaft adapter of the non-powered output shaft end being arranged on asynchronous motor, the other end of shaft adapter is provided with coaxially arranged coupling shaft successively, conduction shaft coupling, relaying bar and conducting ring, wherein the non-rotating end of conducting ring is as signal output part, signal output part is connected with sampling resistor, the other end of sampling resistor is connected with the casing of asynchronous motor, the casing of described asynchronous motor, bearing and rotating shaft form series loop with shaft adapter, coupling shaft, conduction shaft coupling, relaying bar, conducting ring, sampling resistor successively,

Conditioning amplifying unit, for the thermoelectrical potential signal that Received signal strength output terminal transmits, and carries out filtering to thermoelectrical potential signal and amplifies process;

Fault diagnosis alarm unit, digitized processing is carried out to the thermoelectrical potential signal that conditioning amplifying unit transmits, carry out real-time diagnosis to grade to the fault degree of bearing and to send corresponding sound and light alarm, relay output is carried out to major failure simultaneously, by at certain time-delay closing asynchronous motor, to ensure the security of operation of asynchronous motor;

On-line monitoring unit, what send fault diagnosis alarm unit carries out real time graphical for the thermoelectrical potential signal characterizing damage of the bearing state and intuitively shows;

Data storage cell, stores according to the monitoring information of certain rule to on-line monitoring unit, to carry out off-line analysis to damage of the bearing state.

2. a kind of asynchronous motor bearing damage monitoring system according to claim 1, it is characterized in that: the non-powered output shaft end of described shaft adapter and asynchronous motor adopts clearance fit, and assisted fastening by conducting resinl, the rotating shaft of shaft adapter and asynchronous motor is in arranging with axis.

3. a kind of asynchronous motor bearing damage monitoring system according to claim 1, is characterized in that: spiral elasticity shaft coupling selected by described conduction shaft coupling; Conducting ring selects model to be the mercury slip ring of A1M; Relaying bar for connecting conduction shaft coupling and conducting ring, and offers the installing port matched with the round end of conducting ring in the front end of relaying bar.