Operation of electric motors in unacceptable condition leads to material loses connected with unpredictable failure of the equipment and technological process breakdown produced by this failure, and also considerable expenditures of electrical energy, caused by increased power consumption.
One of these methods is based on that fact that the auxiliary machine systems of each section are independent in terms of ranked measured values. It allows to mark out sections with current references deviation from train`s average values, thereby it points out the section with developing malfunction in the supporting machine system.
It is perspective to develop method for condition diagnostics of electric trains based on spectral analysis of consumption/ generated current. This analysis allows to specify the condition of machine`s different elements and detect specific types of malfunctions.
Physical principle lying in the basis of this method is that any disturbance in the operation of electric and mechanical parts of the machine leads to change of magnetic flux in air gap and, consequently, to a change of a momentary electric current value. Accordingly, the presence of particular frequencies of fixed value in a current of a spectrum of three-phase feed system of auxiliary machines testifies the development of particular malfunctions of a unit.
Thus, for the continuous monitoring of auxiliary machine system it is enough to install three current sensors to the corresponded line conductors of transformation generator.
Tsurpal A.E. Selection of method for diagnostics of auxiliary machine system of electric trains // Nauka, obrazovanie, biznes (Science, education, business). - 2012. - pp. 202-205
The operation of the electric motors, which are in poor health, leads to the direct financial losses, connected with an unpredictable failure of the equipment and, as a result, the violation of flow, and also the considerable cost of electricity, due to the high power consumption.
The diagnostics of the rotary equipment is usually made by the vibration parameter. However, the diagnostics of the equipment by the power consumption parameter has a great potential, since that allows to increase the depth of the diagnostics of the so-called electrical defects, i.e. defects and failures, connected with the electromagnetic forces disbalance. For instance, if the resistance to shaft movement occurs, so it would be reflected in the change of the respective current signal, and in the increasing of power consumption.
The physics principle in the basis of diagnostic complex operation is that any perturbations in the operation of the electric or mechanic part of an electric motor and equipment, connected with it, lead to the changes of the magnetic flux in the gap of the electric machine and, as a result, to the consumption current modulation.
Tkachenko A.A., Naumenko A.P. Research on the dependence of the parameters of the electric motor current consumption on its health // Science, education, business (“Nauka, obrazovanie, biznes”). - 2011. - pp. 217-219
Piston compressors are the indispensable equipment of oil-refining enterprises, the failure of which may lead to a significant decrease of production, and costly repairs, increasing the danger to life and health of workers.
One of the problems, arising from the operation of piston compressors and requiring an immediate detection, is a hydraulic impact. The hydraulic shock is a phenomenon, which is accompanied by an abrupt pressure increase in the decreasing space. The hydraulic impacts can cause the destructions of cylinder-piston group details and emergency situation occurrence.
The implementation of the automatic vibroacoustic condition monitoring and diagnostics of piston compressors COMPACS® allows to successfully prevent downtimes and accidents caused by hydraulic impacts. Diagnostics and monitoring are based on the control of the level of vibroacoustic sensor signal, axially proceeding from the cylinder cover at the moment of approach of the piston to the top dead center and the level of condensate in the separator. However, the diagnosis reliability increasing will always be an urgent task.
Sidorenko I.S., Naumenko A.P. Assessment of the possibility of using the characteristic function for hydraulic impacts diagnostics // Science, education, business (“Nauka, obrazovanie, biznes”). - 2011. - pp. 215-217
Actual situation, when the rolling stock is maintained for appropriate condition due to the schedule-based preventive repair, suggests large resources costs on carrying out the planned repairs irrespectively of the actual condition of any MDRS-section unit. At the same time, the covert nature of defect nucleation and fault development leads to MDRS sections unscheduled decommissioning and additional costs.
An above-mentioned problems solving can be reached by means of an on-board condition monitoring system, making a real-time assessment of the each unit condition and giving information about the expediency of further operation. The efficiency of such a system consists in its continuous operation, i.e. the period of diagnosis, which is much smaller than fault development period in critical (emergency) condition, which gives an opportunity to carry out a condition-monitored operation of the machinery, avoiding the resource-intensive schedule-based preventive repair system.
The failures distribution analysis by the main groups of MDRS equipment shows a relatively high percentage of auxiliary machines faults in operation, it is about 10% and 20% of the detections during the repair and maintenance. The continuous condition monitoring of the auxiliary machines allows to minimize the costs for carrying out the schedule-based repair arrangement and to maximize its resource. In this case, the repair should be conducted only on those units, which are really in need of it in the required amount.
Tsurpal A.E. Failure analysis of supporting machines of motor driven rolling stock (MDRS) for its diagnostics // Science, education, business (“Nauka, obrazovanie, biznes”). - 2011. - pp.222-223
Statistical data about the traction motors failures, constituting more than 20% of the service failures total number, demonstrate the repair quality and motors testing at the repair enterprises. Thus, 65% of the motor failures occur for reasons of an electrical nature, such as: electrical breakdowns and turn-to-turn fault of armature winding, the main and additional poles, compensating windings. That testifies availability of factors, adversely affecting the dielectric resistance of the windings insulation. The suggestions for significant simplification of the traction electric motor testing process after repair, especially in the current repair № 3 process, are wrong.
Long-term experience in traction electric motors testing shows, that every month during the testing the 10-15 % of traction electric motors are identified with significant deviations in after-repair switching conditions at the Zheldorremmash plants.
On the assumption of the above-mentioned problems we suggest to tighten the control of testing and diagnostics of traction electric motors and fully automate the diagnostic complexes.
Melk V.V. Diagnostics of electric-driven rolling stock traction motors. Methods, types and main faults // Science, education, business (“Nauka, obrazovanie, biznes”). - 2011. - p. 184
A mathematical description for structure of a vibro-acoustic signal, obtained from a piston compressor specific assemblies with regard to the channel of vibro-acoustic oscillations formation and propagation, is a diagnostic model. This model allows to select the informative diagnostic features of the assembly malfunctions and defects.
One of the piston compressor most "problematic" assemblies is its valve. Number of valves per one cylinder usually ranges from four to eight and more. The report considers the model of vibro-acoustic oscillations, which have been converted into an electrical signal by dint of a sensor, mounted directly on the piston compressor valve or next to the valves group.
When considering the model, it was found that with an appropriate choice of locations for the vibro-acoustic signals sensors (on the piston compressor appropriate assemblies) one can diagnose the malfunctions occurrence in a double-acting piston compressor assemblies according to correlation of the second and more high-and low-frequency harmonics levels in an envelope spectrum of vibro-acoustic signals. Taking into account a modulation degree high sensitivity to changes in a modulating signal parameters, compared with a direct spectrum signal, it is advisable to use the frequency range that corresponds to a carrier frequency in vibro-acoustic oscillations, generated by gas flow.
Thus, the presented model of the vibro-acoustic signal allows to determine the most informative vibro-acoustic components, which can be used as the diagnostic features parameters for malfunctions in valves and other piston compressor components and parts.
Naumenko A.P. Patterns for vibro-acoustic signals of piston machines // Science, education, business (“Nauka, obrazovanie, biznes”). - 2011. - pp. 114-120
Synthesis of diagnostic features, appropriate to the piston machines technical condition types, main failures and operation modes, arising both separately and simultaneously, and invariant to the machine construction - is an important issue. One step for this problem solution is to create the diagnostic signal model for the unit under test.
The most common model of the known is a batch action generalized model of a quasi-periodic vibroacoustic signal, proposed by V.N. Kostyukov.
This model shows that the frequency content of the low-frequency vibration spectrum and the vibroacoustic signal envelope, obtained by filtering in the high-frequency field and subsequent detection, are approximately equal. These spectra can be represented by an expansion in the characteristic frequencies, which can be divided into three groups. To evaluate the unit technical condition it is necessary to select and measure the components energy characteristics for each group.
This model describes large classes of the units under test failures. The model further development is the model, which describes the vibroacoustic signals with respect to their sources interaction, thus increasing the diagnosing accuracy and depth, but its use for developing the diagnostic algorithms is not obvious.
Therefore, it is advisable to consider a few examples of the vibroacoustic signal models when specific defects and failures occur, thus forming the piston compressors diagnostic features.
Naumenko A.P. Vibroacoustic model of the piston compressor diagnostic signal // Dynamics of systems, mechanisms and machines. - 2009. - pp. 39-44
The necessary completeness and depth of electric circuits diagnostics can be provided by means of resistance assessment of control circuits loops under consideration and high-voltage power and auxiliary circuits sections. Obviously, the current sensors mounting at each loop of control circuits is inexpedient, as in that case the diagnostic complex complication exceeds the diagnosed object complication in several times.
To determine the specified parameters with the minimal number of sensors and the diagnostic complex flow lines, a principle of control circuits functional-test diagnostics has been developed. The principle consists in determining of each branch diagnostic features through timely inclusion of the branch in the operational process. This inclusion is carried out by means of test impacts injection to the main and auxiliary inputs. The specific sequence of impacts makes them identical to working ones.
At the same time the high-voltage circuits switching units fulfill the assigned functions in the whole range of possible combinations. The use of additional inputs (impacts injection has not been foreseen by the operation working algorithm for these impacts) for test impacts injection even with functional impairment in the branches of control circuits, corresponding to the main inputs, allows to ensure the impact transfer to the actuator, thus performing their primary function.
Kostyukov Al.V., Kazarin D.V. The choice of diagnostic features for electric trains circuits // Nauka, obrazovanie, biznes (Science, education, business). - 2009. - pp. 189-194
Diagnostics of the rolling stock wheel-motor units is an urgent matter of today. Bearing assemblies of wheel-sets and wheel-motor units (WMUs) undergo enormous impact forces and their technical condition largely influences a train performance safety.
It is customary to use 6 vibration sensors which are mounted on the general bearing assemblies (axle bearings, reducer, traction motor). Nevertheless there is an opinion that such a number of sensors is abundant and only increases diagnostic operations time.
In order to determine capability of vibration sensors number reduction while diagnosing of an electric train wheel-motor units, studies on the mutual impact between different subjects diagnostic features have been carried out.
Zaycev А.V., Lagaev А.А., Kostyukov V.N. Capability determination of vibration sensors number reduction while diagnosing of an electric train wheel-motor units // Nauka, obrazovanie, biznes (Science, education, business). - 2009. - pp. 154-157
Operating safety level of units with piston compressors is determined by reliability of their technical condition monitoring, timeliness and accuracy of malfunctions and their causes detection. Nowadays there are numerous technical tools designed for piston compressors monitoring and diagnostics, which are developed and manufactured in different countries by various companies. However, it remains a pending issue if the measurements are adequate to the actual technical condition of piston compressors and to the risk magnitude of their safe operation. Although there is a document that defines the general requirements for critical industrial facilities monitoring systems, nevertheless even experts find it rather difficult to sort out the advertised systems capabilities. In this connection there is an urgent necessity to systematize the condition diagnosing and monitoring methods and means for piston compressors.
Almost all monitoring and diagnostic systems are characterized by:
determination methodology for technical condition of piston compressors units and components is based on measurement of direct structural and technological parameters (relative displacement, pressure, temperature) and implements an online technology;
expert systems use the values of direct structural and technological parameters;
parameters of indirect processes (vibroacoustic oscillations) are used to assess these parameters values without a diagnosis-making and detection of malfunctions and defects causes.
In the equipment vibration analysis system COMPACS® the methodology for real-time monitoring and diagnostics is based not only on the measurement of direct structural and technological parameters, but on the use of vibroacoustic oscillation parameters as well, there have been implemented algorithms of the expert decision support system with an autodetection (in the rate of diagnostic signals measurement) of more than 20 units malfunctions and defects and the degree of their danger.
Naumenko A.P. Analysis of modern methods and means of piston compressors condition monitoring and diagnostics // Nauka, obrazovanie, biznes (Science, education, business). - 2009. - pp. 107-115