Recent Developments of Electrical Drives - Part 23. The book stating the recent developments of electrical drives, can be useful for engineers and researchers investigating and designing electrical and electronic devices as well as for students and young researchers dealing with electrical and electronic engineering, computer sciences (advanced computer modelling, sophisticated control systems with artificial intelligence tools applied, optimal design bye use of classical and genetic algorithms employed), applied mathematics and all the topics where electromagnetic, thermal, mechanical phenomena occur | 212 Schlensok and Henneberger Table 1. Cases for different force excitations Type of excitation Rotational direction Stator-teeth Left-hand Rotor-teeth Right-hand Stator-teeth Right-hand Rotor- and stator-teeth Right-hand values are positioned on the side of the mounting-plate. Left-hand rotation results in maximal excitation locations on the opposite side of the machine. For this both directions are computed and the audible acoustic-noise radiation is compared. Fig. 1 defines the rotational direction. Usually it is sufficient to simply take the force excitation of the stator in to consideration to make good predictions of the radiated noise. The stator of the regarded machine is weakly coupled to the casing mechanically spoken by hard rubber rings around the casing caps and steel-spring pins in the notches of the stator and casing. The rotor on the other hand is strongly coupled to the casing caps by the bearings. For this the rotor excitation has to be taken into account as well for comparison reasons. Electromagnetic simulation The first step of the computational process is the electromagnetic simulation. The induction machine is simulated with a three-dimensional magnetostatic model which uses stator and rotor currents as excitations. Due to computational timesaving reasons the rotor-bar currents are derived from a two-dimensional transient computation 5 . The 2D model consists of 6 882 first order triangular elements and the computation of one time step in 2D takes Figure 1. Definition of rotational direction location of the mounting plate the mounting notches the screw holes and the rubber rings. II-7. Comparison of Stator-and Rotor-Force Excitation 213 t2D s. A 3D time-step simulation takes t3D 494 min due to 288 782 first order tetrahedral elements in the 3D model. The duration of the transient phenomenon ttp equals the rotor-time constant tr ttp tr 1 Depending on the time step At At3D qs the number of time steps lost Nlost for analysis is .
