Group items tagged

In this work, some fundamental aspects concerning the efficiency of induction machines are treated. The standards and the therein prescribed methods for the determination of the energy efficiency of induction machines are discussed. A detailed comparison of the four most relevant and recent methods identifies the differences. By means of measurement results of different machines, the differences between and the shortcomings of certain methods is confirmed. In that context, special attention is paid to the new, so-called ‘Eh-Y’ method. A concise overview of the most important points of attention for an increased efficiency of motor drives en the role of the induction motor (efficiency) in this context is completed with some examples. The difference between motor and generator mode is discussed and explained based on measurement results of machines of different size and efficiency class. Special attention is paid to the behaviour and performance of induction machines supplied by unbalanced voltages. More specifically it is investigated if and how the susceptibility to voltage asymmetry is influenced by material choice, in which the main focus lies on copper rotor technology. Therefore, the different standards for the description and quantification of voltage unbalance are studied first. The theoretical discussion is backed-up with experimental results of several machines.

The paper discusses the use of a dual energy storage system based on batteries and supercapacitors in hybrid electric vehicles (HEV). The battery has a large energy density, enabling an all-electric driving range of 100 km, while the supercapacitor has a large power density and provides peak power during acceleration and regenerative breaking. The paper discusses the benefits and drawbacks of both storage systems and the specific requirements imposed by the hybrid drive train. Coupling such a HEV to the grid allows interaction between grid and HEV, providing the grid with a controllable load. Depending on the communication between the hybrid fleet and the grid, this load can be controlled by adjusting the electricity price in order to allow a higher penetration of intermittent renewable energy sources such as wind parks in the grid and if the communication allows the transmission system operator to reduce the load imposed on the grid by the hybrid fleet, the hybrid fleet can become part of the secondary frequency control reserve. In case of sudden demand or supply fluctuations, the hybrid fleet can assist in primary control of the grid. Due to the dual energy storage system the HEVs can also provide fast load tracking to keep the voltage in microgrids at the desired set point. An experimental setup with a battery, grid coupling and induction machine proves the feasibility of the concept.