On the Influence of Eccentricities on Flux Linkages of Permanent Magnet Synchronous Machines

The noise behavior of electrical machines is influenced by tolerances. Eccentricities in particular lead to poorer noise behavior. However, the measurement of NVH quantities is usually very complex. Therefore, it is of interest to be able to detect such tolerances also by other measurands. In this paper, the influence of eccentricities on the flux linkages is investigated. For this purpose, detailed investigations were carried out using FEA. In a further step, these are compared with the results obtained from a test rig measurement. Prior to this, a methodology is presented with which the angle-dependent flux linkages can be determined. It is shown that eccentricities cause only slight changes in the harmonic components of the flux linkages. Due to the symmetry properties of the investigated machine, the changes in the flux linkage caused by the different air gap lengths cancel each other out. This could also be confirmed in the experiment

Determination and emulation of motor-like flux conditions for loss characterization by means of a single tooth geometry

High quantities and a demand on low costs in automotive drives result in new production methods of electrical machines. Besides, the electric drive train efficiency is improved to offer long ranges. Referring to this relationship the loss models of electrical machines are improved more and more. Focusing on iron losses, remarkable influences on the loss characteristics are attributed to the manufacturing processes. In this publication, a new approach of measuring the losses of a single stator tooth of an electrical machine considering motor-like flux conditions is introduced. Derivation of motor-like flux conditions is described, transfer to the test bench is defined and measurements are shown - concluding with a comparison of simulation and measurement as well as the identified tooth losses of the investigated machine. This gives the possibility to improve iron loss models in case of additional losses due to manufacturing influences

The chemistry of AlF and CaF production in buffer gas sources

In this work, we explore the role of chemical reactions on the properties of buffer gas cooled molecular beams. In particular, we focus on scenarios relevant to the formation of AlF and CaF via chemical reactions between the Ca and Al atoms ablated from a solid target in an atmosphere of a fluorine-containing gas, in this case, SF6 and NF3. Reactions are studied following an ab initio molecular dynamics approach, and the results are rationalized following a tree-shaped reaction model based on Bayesian inference. We find that NF3 reacts more efficiently with hot metal atoms to form monofluoride molecules than SF6. In addition, when using NF3, the reaction products have lower kinetic energy, requiring fewer collisions to thermalize with the cryogenic helium. Furthermore, we find that the reaction probability for AlF formation is much higher than for CaF across a broad range of kinetic temperatures

Spectroscopic characterization of the a³Π state of aluminum monofluoride

Spectroscopic studies of aluminum monofluoride (AlF) have revealed its highly favorable properties for direct laser cooling. All Q lines of the strong A1Π ← X1Σ+ transition around 227 nm are rotationally closed and thereby suitable for the main cooling cycle. The same holds for the narrow, spin-forbidden a3Π ← X1Σ+ transition around 367 nm, which has a recoil limit in the µK range. We here report on the spectroscopic characterization of the lowest rotational levels in the a3Π state of AlF for v = 0–8 using a jet-cooled, pulsed molecular beam. An accidental AC Stark shift is observed on the a3Π0, v = 4 ← X1Σ+, v = 4 band. By using time-delayed ionization for state-selective detection of the molecules in the metastable a3Π state at different points along the molecular beam, the radiative lifetime of the a3Π1, v = 0, J = 1 level is experimentally determined as τ = 1.89 ± 0.15 ms. A laser/radio frequency multiple resonance ionization scheme is employed to determine the hyperfine splittings in the a3Π1, v = 5 level. The experimentally derived hyperfine parameters are compared to the outcome of quantum chemistry calculations. A spectral line with a width of 1.27 kHz is recorded between hyperfine levels in the a3Π, v = 0 state. These measurements benchmark the electronic potential of the a3Π state and yield accurate values for the photon scattering rate and for the elements of the Franck–Condon matrix of the a3Π–X1Σ+ system

Using a direct simulation Monte Carlo approach to model collisions in a buffer gas cell

A direct simulation Monte Carlo (DSMC) method is applied to model collisions between He buffer gas atoms and ammonia molecules within a buffer gas cell. State-tostate cross sections, calculated as a function of collision energy, enable the inelastic collisions between He and NH3 to be considered explicitly. The inclusion of rotationalstate-changing collisions affects the translational temperature of the beam, indicating that elastic and inelastic processes should not be considered in isolation. The properties of the cold molecular beam exiting the cell are examined as a function of the cell parameters and operating conditions; the rotational and translational energy distributions and are in accord with experimental measurements. The DSMC calculations show that thermalisation occurs well within the typical 10-20 mm length of many buffer gas cells, suggesting that shorter cells could be employed in many instances – yielding a higher flux of cold molecules

Spectroscopic characterization of aluminum monofluoride with relevance to laser cooling and trapping

Here we report on spectroscopic measurements of the aluminum monofluoride molecule (AlF) that are relevant to laser cooling and trapping experiments. We measure the detailed energy level structure of AlF in the X$^1\Sigma^+$ electronic ground state, in the A$^1\Pi$ state, and in the metastable a$^3\Pi$ state. We determine the rotational, vibrational and electronic branching ratios from the A$^1\Pi$ state. We also study how the rotational levels split and shift in external electric and magnetic fields. We find that AlF is an excellent candidate for laser cooling on any Q-line of the A$^1\Pi$ - X$^1\Sigma^+$ transition and for trapping at high densities

Using a direct simulation Monte Carlo approach to model collisions in a buffer gas cell - supporting material

The dataset includes results from our direct simulation Monte Carlo (DSMC) modelling of the collisions between buffer gas atoms and ammonia molecules within a buffer gas cell. Both elastic and inelastic collisions are considered, through the inclusion of energy-dependent state-to-state collision cross sections. The properties of the resulting molecular beam are examined as a function of cell parameters and operating conditions – yielding good agreement with available experimental measurements. This study represents an important extension of previous investigations into buffer-gas cooling. We demonstrate that thermalisation occurs well within the typical 10-20mm length of typical experimental buffer gas cells, suggesting that a shorter cell could be employed in many applications. Our DSMC calculations indicate that shorter cells would achieve comparable molecular beam properties (translational and rotational temperature) with the benefit of significantly increased molecular density. The data were created from 2015-2016 and are discussed in detail in the accompanying publication. The labelling of each data file corresponds to the labelling adopted for the associated figure in the publicatio