International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Paper deals with testing of a specific centrifugal fan under different conditions – changes in supply voltage and flow rate regulation by throttling, as well as the application of frequency control. A digital portable multifunctional device has been used for measuring and analyzing three-phase electrical circuits. Some intrinsic electrical variables have been measured and recorded, and others have been subsequently calculated. Comments, conclusions and recommendations have been done. The results obtained would be interesting for specialists dealing with this technical equipment.

Paper deals with determining the possible savings of electrical energy in a passenger elevator. After carrying out calculations with a set number of floors of an administrative building and number of passengers according to a proven and widely used methodology in Bulgaria, an appropriate three-phase squirrel-cage induction motor has been selected to drive the considered elevator system. Calculations have been also carried out on the possible recovery, i.e. returning electrical energy back to the supply power grid when the driving rotating electrical machine is switched to generator mode. Variants with different number of passengers and movement of the cabin in upward and downward directions were theoretically studied. The active power, time to work in recovery mode and the active energy returned to the power grid are defined for each specific case. Calculations of possible electrical energy return in generator mode would be of interest to specialists dealing with these technical facilities.

Paper deals with determining the permissible number of switches on per hour depending on the load and operating mode parameters – starting and stopping times, pause duration, etc. The criterion is that the overheating of the stator winding does not exceed the overheating at nominal mode and load. The basis of the chosen method is the assumption that the electric motor is assumed to be a conditionally uniform body, i.e. a body made of the same material with an infinitely large thermal conductivity and therefore having the same temperature throughout its volume under all possible modes and loads. The results of the calculations with a computer program
implemented are presented in tabular form.

Paper deals with a newly designed three-phase asynchronous electric motor with an application as a traction motor for driving compact battery-powered electric vehicles mainly in urban environments. The main characteristics of the motor are presented. The problems and solutions related to the sizing and optimization of the motor in the design according to various criteria and conditions are analyzed, with energy efficiency being the main determining factor.

The paper deals with the problems in the operation of non-linear loads, causing distortions in the sinewaves of voltages and currents. There is currently increasing use of variable frequency drives (frequency inverters) that drive electric motors and are such loads. The experimental results cover multiple measurements of voltages and currents harmonic components and the calculated values of the total harmonic distortion coefficients of voltage and current for each of the phases, supplying different loads. An analysis of the results obtained has been done and specific conclusions have been pointed out on the basis of the measurements carried out.

Paper deals with specifics of converting a conventional car into an electric one. The main stages of the conversion process are dealt concise but thorough. The findings are the basis for launching a large scale project with the necessary duration and financing, as a result of carrying out the necessary development activities and experiments will proceed to the development of a prototype, which will ultimately be realized. The overall focus is on research and application in the students’ learning process.

In the case of energy-efficient drives with induction motors, the tendency to implement optimally designed motors, combined with intelligent control, incorporating an integrated monitoring and diagnostics system, is becoming increasingly important. Induction motors in industrial systems operate with frequent starting, dynamic loads and sometimes unbalance of supply voltage. In order to maintain an optimal operating condition, reduce the number of failures and build up an optimal repair and maintenance system, it is important to have an advanced monitoring system coupled with fault identification techniques. The behavior of optimally designed three-phase induction motors designed to operate integrated into hydraulic units with continuous duty operating mode is considered

Paper deals with the dynamic behavior of pump unit electric drive. The electric motor, subject of development, is a new standard efficiency induction motor with squirrel cage rotor, designed to operate in continuous operation. The determination of operating characteristics of induction motor in dynamic modes is necessary to establish the properties of the machine in specific conditions. In some industrial areas can occur very often sags with a depth of between 10% and 15% of the rated voltage as a result of switching electrical loads on systems of users. As a result of simulation studies the influences of the supply voltage and total torque of inertia of the electric drive have been assessed on arising impact torques and currents and electric energy losses of electric drive for pump unit. The results obtained are in addition to experimental studies of the same motor. Some of the study results have been presented graphically. An analysis and conclusions from the results obtained have been done