V. P. Metelkov

Toward the evaluation of the influence of temperature fluctuations on the durability of the stator winding insulation of asynchronous motors in random mode loading

The influence of the stator winding temperature oscillation on the insulation-aging rate of the asynchronous motors stator winding in random mode loading is discussed. It is shown that under certain parameters of the random mode insulation durability can significantly decrease, wherein the widely used average loss method gives the evaluation of the motor thermal state with a substantial error.

Some aspects of the reliability increasing of the transport electric drives

The problem of the increasing reliability of the electric drives of transport vehicles which are characterized by random load duties is discussed. It is noted that in such modes of operation the temperature oscillations substantially influence on the insulation aging rate of the motor winding. It is shown that under certain parameters of the random load the insulation durability can significantly decrease, and the well known average loss method gives the evaluation of the motor thermal state with a substantial error. It is offered the method of motor selection and verifying on the stage of the electric drive design which allows to take into account influence of the temperature oscillations on the durability of the motor winding insulation. The necessity the evaluation of the average insulation aging rate and of residual thermal resource with the aim of the reliability increasing and longevity of the motor is substantiated.

On an estimate of the rotor winding temperature at start-up of high-voltage induction motors

This paper is devoted to research of start-up modes of high-voltage induction motors. To reduce a voltage dips during start of such motors, soft starters based on thyristor voltage converters are widely used. Acceleration of high inertia drives with a long start-up mode can be accompanied by rotor winding overheating. The authors analyze possibilities for estimate of rotor winding overheating during start-up. Analytical expressions for energy dissipated in the rotor winding at start-up are obtained. Having solved the Fredholm integral equation, the authors derive expressions allowing estimate of heat dissipation from the rotor during start-up. Calculation results of analytical expressions are tested with an integrated model that includes all elements of the power network. The adiabatic approach to the assessment of the maximum winding temperature at starting modes excluding heat transfer into the environment is proved to result in a substantial error. Analytical expressions allowing an approximate account of an uneven temperature distribution along the winding rotor are obtained.

Some peculiarities of the simulation of electric drives with random mode loading

The paper considers some features reflected by simulation of electric drives operated in the random load modes. It is shown that the distribution laws for losses and the torque are essentially different. I.e., when modeling random modes of electric drive it is impossible to transfer the distribution law of the motor load, which is characterized by the motor torque, to the motor loss distribution. It is also shown that the value of the standard process deviation can significantly differ from the standard deviation of the amplitudes of this process; the difference can be either downwards or upwards depending on the cyclic duration factor and mathematical expectation of the amplitude. The influence of the torque limitation on probability density functions of load and losses was considered. The distribution law in the absence of the torque limitation and with regard to the impact of these limitations can result in different values of mathematical expectations and variances.

Evaluation of dynamic properties of the TEFC induction motors thermal models

Paper is devoted to research the dynamics of thermodynamic models for Totally Enclosed Fan-Cooled (TEFC) induction motors on the basis of the thermal lumped circuits. Clusterization a series of TEFC motors motors for general industrial application was performed. It allowed to group motors into clusters with consimilar parameter vectors of 5-node thermodynamic model. With using a method of genetic algorithms was carried out determination of the parameters of generalized 5-node thermal models corresponding to different clusters. An approach is proposed which allowing carry out a general analysis of the dynamic properties TEFC motors. With the use of frequency response for thermal models was revealed the actual area for gain values over a channel from the motor torque to the stator winding temperature for typical TEFC motors with mesh windings. The possibility of using the obtained thermal models to evaluate the influence of temperature fluctuations on the insulation resource expenditure acceleration was shown.

Research of the start-up modes of multi-stage blower asynchronous drive

Paper is devoted to research of start-up modes of high-voltage asynchronous motor multi-stage blower. To reduce a voltage dips during starting of such motors are widely used soft starters based on a thyristor voltage converters. For high inertia drives with a long start-up mode an acceleration can be accompanied by overheating of the motor windings. In this paper we evaluated the possibility of reducing the rotor winding overheating. Research was carried out with the help of an integrated model that includes all the elements from the electric power network to the operating mechanism. The paper presents the description of this integrated model. It has been shown that by adjusting the value of the current limit setting during starting with thyristor voltage converters the problem with the overheating of rotor winding in the considered drive as a whole cannot be solved. It is also shown that there may be some reduction in the impact of thermal effects on the rotor winding by means of choosing the duration of the interval between repeated starts of the drive with the help of the integrated mathematical model.