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.

This paper presents a design proposal for an electronic throttle control system intended for the experimental light hybridelectric vehicle. This vehicle was made in the scope of ongoing student project of developing and creating a light hybrid-electric vehicle as a platform for educational and research work. In the present case, ATV/quad-vehicle engine is used, where the throttle command of IC engine was originally realized using mechanical linkages and cable. In order to fully exploit hybrid drive potentials, control of both IC engine and electric hub motors had to be exerted by using single accelerator pedal. For this purpose, the original IC engine control system had to be replaced by an electric motor actuator that uses control signal from accelerator pedal used for electric motors control. The prototype of mechanism that converts rotation of electric motor actuator output shaft into linear displacement of the needle valve was also designed and produced applying 3D printing technique.

Research on electrical drives in agricultural machines rose in the last 20 years and is still continuing. Electric drives have the potential of better controllability and higher degree of efficiency compared to hydraulic and mechanical drives. However, power density is a disadvantage and needs to be compensated with additional functionality and higher reliability in the systems approach seeking for an overall advantage compared to current drive trains for propulsion and functional elements of mobile machines. Electric drives allow a high degree of integrating of the drive into a functional element, which would allow freeing up space needed for the combine working channel. At the chair of Agricultural Systems and Technology was developed an electric drive integrated in a tangential threshing cylinder as an example of an alternative drive solution for future combines. Following, tests with grain in the laboratory under field conditions were completed.