The main type of electric motors used in the electric drive of technological processes are induction motors with a squirrel-cage rotor. With proper operation, they have a higher MTBF (Mean Time Between Failures). It was found that one of the common causes of engine failure is bearing wear and, as a result, increased rotor eccentricity. We used the oscillating amplitude of the rotor speed in the transient state as a diagnostic parameter. The paper presents a method for this troubleshooting, a block scheme and appearance of the experimental installation, and a single-line diagram of the transmitter for measuring rpm. The experience has established the optimal ADC sampling frequency for experimentation to be carried out. The results of studies of changes in the rotor speed oscillating from time to time under load at rotor eccentricity have been given.
Mechanical drives have become the most widely used in design of agricultural machinery. In comparison to drives of machinery applied in other sectors of national economy, they are distinguished by their design features, performance, and cost-performance ratio. In this regard, diagnostics of mechanically driven parts of agricultural machinery is a key to the overall harvester diagnostics. In practice, health of drives is tested with subjective assessment methods, as a rule. The authors suggest application of a kinematic method for diagnostics of agricultural machinery drive trains during their operation; this method implies analysis of position changes and movement of mating parts: wear of parts and backlash of mating drive parts may be assessed by establishment of geometric parameters of diagnostics (linear and angular movements). The total transmission backlash may be established by dynamic torque appearing in transient states of mechanism operation; such total backlash characterizes dynamic errors in movement of an outlet member, which is a result of dependence of equivalent moment of inertia and drag torque from the velocity transmission error. Such diagnostics of potato harvester transmission allows checking of backlashes in separate sections of the chain, as well as assessment of quality of its components adjustment and maintenance. The research data were used for evaluation of overall engineering state of the harvester and determination of dynamic parameters of its components drives.
Squirrel-cage induction motors are the main type of electric motors used for the electric motor drive of the working mechanism of industrial processes. The task of the electrical service of the enterprise is to control the engine power during operation and to prevent overloads or inefficient operations. In order to do that a non-contact method for determining the power of squirrel-cage induction motors is proposed. The method is based on the property of the mechanical characteristics of an induction motor, when with increasing the moment of resistance on the drive shaft, the rotor speed decreases in proportion to the load. Therefore, by measuring the rotor speed of the engine, it is possible to judge the degree of its load. To confirm this, experimental studies of axial fans were carried out. Linear supply voltage, winding current, active power, power factor and engine speed were used as the analyzed parameters of the motors. For more information about the state of the motor, in addition to analyzing the stator current, an analysis of the frequency of the supply voltage, as well as the input power, which is directly related to the current and supply voltage, was made. In the course of the experiments, a number of functional dependences of engine performance on its speed were obtained. It was established that tests are necessary for not only repaired engines, but also new ones to determine the optimal modes of its operation and identify production defects.
The biochemical properties of the grain depend significantly on the effects of heat and moisture. By regulating the external conditions, it is possible to influence the biochemical processes in grain, to change its biochemical characteristics. The analysis of temperature dependence of electrophysical properties in fine-dispersed non-equilibrium heterogeneous medium has been carried out on the example of mechanically activated wheat. It is shown that the disordering of fine-dispersed grain structure and change of temperature condition have a significant influence on its dielectric properties. The value of the real component of the dielectric constant depends on the degree of samples dispersity, temperature and humidity conditions and the frequency of the external electric field. The study of the dielectric constant spectra showed that the maximum growth of the dielectric parameters corresponds to a temperature close to 100°C and its value increases for wheat samples with lower particles dispersity. The frequency of the external electric field has a significant influence on the dielectric parameters of wheat samples with different degrees of dispersity, which is associated with changes in the structure of the non-equilibrium system as a result of mechanical activation.
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