Extraction of Rotor Eddy-Current Harmonic Losses in High-Speed Solid-Rotor Induction Machines by an Improved Virtual Permanent Magnet Harmonic Machine Model

Abstract

High-speed induction machines equipped with a solid steel rotor are capable of achieving a high-rotating speed than other types of machines, because of their simpler and more robust rotor structure. At the same time, however, the eddy-current losses in the solid rotor may be critical, because of the high conductivity of the rotor material, which makes it easy for axial eddy currents to travel in the solid rotor. To efficiently mitigate the rotor eddy-current losses, it is important to accurately determine the rotor eddycurrent losses induced by a particular harmonic in advance. In this paper, an improved virtual permanent magnet harmonic machine (VPMHM) model equipped with a sinusoidally magnetized virtual magnet based on the finite element method (FEM) is proposed for determination of the rotor eddy-current harmonic losses. The 2-D fast Fourier transform was used to accurately analyze the time-spatial air-gap flux density harmonics. The VPMHM model was enhanced to ensure that it was able to exactly produce the required flux density harmonics in the air gap. Two algorithms for the improved VPMHM models with different hybrid excitations were proposed to determine the harmonic losses together with the other important harmonic behavior. The model was further investigated to separate the electromagnetic transients from different harmonics. Finally, the simulation time for the harmonic losses required by the enhanced VPMHM model was significantly reduced by separating the harmonic transients. All the results and conclusions presented in this paper are based on the FEM analysis. INDEX TERMS Solid-rotor high-speed induction machine (IM), finite element method (FEM), 2-D fast Fourier transform, eddy-current losses, improved virtual permanent magnet harmonic machine (VPMHM).

Influence of Magnetic and Nonmagnetic Layers in an Axially Laminated Anisotropic Rotor of a High-Speed Synchronous Reluctance Motor Including Manufacturing Aspects

“…The fundamental of the flux density decreases with thicker layers because of the decrease in the d-axis inductance. The separation of the stator and rotor harmonics was implemented by the 2D Fourier analysis presented in [25]. The stator winding and slot harmonics are produced by the fundamental frequency fsyn.…”

Accelerating the Time-Stepping Finite-Element Analysis of Induction Machines in Transient-Magnetic Solutions

“…Furthermore, if the machine is equipped with an end ring, the end ring resistance R ring has to be increased to R ring /s. A virtual permanent magnet harmonic machine (VPMHM) model described in [29], [30] is used to comfirm the validity of (2). The main idea of the VPMHM model is to replace a stator of the IM with a purely sinusoidal magnetic source in the air gap to excite the machine (the rotor).…”

“…currents and torques) can be obtained from the TH solution. For example, the three-phase average line currents (RMS values) given by the TH and TM solutions are 2716 A and 2717 A, respectively, at per-unit slip s = 0.005 for a 660 V, 2-pole, 2 MW, 12000 r/min high-speed IM with a solid rotor as reported in [29]. Nevertheless, in steady state the magnetic field distribution given by the TH solution is still far from that given by the TM solution.…”

Design of a High-Speed Solid-Rotor Induction Machine With an Asymmetric Winding and Suppression of the Current Unbalance by Special Coil Arrangements

“…The machine studied is a 660 V, 2 MW, 200 Hz, 12000 r/min high-speed slitted-solid-rotor IM. Its initial design is reported in detail in [26], [27]. The more specific dimensions of the high-speed solid-rotor IM are listed in Table 1.…”