Practical Platform for Open and Closed Loop Speed Control of an Inverter Driven Asynchronous Machine Used for Teaching Purposes

The paper presents a laboratory setup based on a SIMOVERT MASTER- DRIVES MC Inverter from SIEMENS used for open and closed loop speed control of an induction machine. The platform allows four quadrant operation of the machine using both the classical V/Hz scalar principle and field oriented vector control principle. The rectifier unit consists of a classical three phase diode bridge and two high voltage capacitors in order to obtain a voltage source behavior of the converter. In order to obtain the four quadrant operation of the drive, several methods are investigated out of which one is proposed and implemented. The theoretical aspects of V/Hz scalar principle and field oriented vector control principle are better explained using the proposed experimental platform

Optimal Design of the Vertical Earthing with Electrodes Arranged in Line

The design methods of earthing from standards recommend the choice of electrode lengths and propose that the distances between electrodes to be 1–3 times larger than their length. The number of electrodes is determined from the condition of achieving the design earth resistance, while the design ends with the choice of one of the variants. This paper presents the methodology for calculating the earthing system with cylindrical, vertical electrodes arranged in a line. The main variables are the length and the number of earth electrodes, as well as the distance between adjacent ones. Firstly, a set of technologically advantageous values for the earth electrode length is established (e.g., 10 values). For each value of the electrode length and different numbers of electrodes (e.g., 11 values), the distance between adjacent electrodes is determined (e.g., for 110 cases), which leads to the design value resistance. Finally, optimal solutions are identified based on the five optimal applied criteria. The proposed optimal criteria for earthing design are the footprint area, the total earthing volume, the total dispersion surface, the total metal mass, and the investment costs. Comparing the optimal solutions with other technically possible solutions clearly highlights substantial savings concerning space, material, and cost