Calculation of rotor losses in PM machines with retaining sleeves using transfer matrices

Abstract

Accurate calculation of rotor losses in PM synchronous machines can be critical because these losses tend to be very small relative to others in the machine. Numerical methods, such as finite element analysis (FEA), can now provide accurate estimates of these losses, but they, especially 3D FEA, can be time consuming. Analytical methods therefore remain very useful as quick tools for estimating losses at the early design stages. This paper presents a new improved analytical method for the calculations of rotor eddy current losses in PM machines using a reformulation of the current sheet model into transfer matrices to solve Helmholtz's diffusion equation. Such methodology reduces the complexity of the problem significantly, particularly in machines with retaining sleeves, and simplifies the numerical evaluation of the resulting equations. A high speed PM machine with a retaining sleeve is presented as a case study. The analytical results are verified using FEA.

Eddy current loss estimation for direct drive wind turbine generators with superconducting excitation winding by numerical and analytical models

“…The model involves 9 regions and is shown in Figure 2. A generalisation to less/more regions is straight‐forward as shown by Anglada et al 5 The constituting field equations are solved for each region separately, whilst the continuity relations for the normal component of the flux density B r and the tangential component of the magnetic field strength H γ fix the remaining degrees of freedom. The low frequencies in the order of f ∼ 5 Hz (fundamental)…150 Hz (relevant harmonics) allow to neglect any displacement currents.…”

A study on reducing eddy current loss of sleeve and improving torque density using ferrofluid of a surface permanent magnet synchronous motor

“…This is because when the rotation speed gets faster, the torque required gets smaller. Recently, many studies have been conducted on the surfaceattached type [5][6][7][8][9][10][11] and interior PM rotor configuration [12][13][14][15][16] for the mechanical design of the rotor structure for high-speed PM machines. High-speed PM motors are characterised to have the advantage of high-power density.…”