An Analytical Approach to Magnet Eddy-Current Losses for Interior Permanent-Magnet Synchronous Machines During Flux Weakening

Abstract

This paper presents an analytical approach for evaluating the magnet eddy-current losses of interior permanent-magnet synchronous machines (IPMSMs) during flux weakening. To investigate the magnet eddy-current losses, an analytical method of the time-varying magnetic flux density in the magnet is proposed based on the armature reaction magnetic field analysis. According to the time-varying magnetic flux density, a coefficient is used to evaluate the magnet eddy-current losses during flux weakening. The coefficient can indicate how the major design parameters in an IPMSM affect magnet eddy-current losses during flux-weakening operation. Finite-element analysis was used to validate the proposed model and calculate the magnet eddy-current losses of IPMSM with different design parameters.

Impact of Machine Magnetization State on Permanent Magnet Losses in Permanent Magnet Synchronous Machines

“…It is observed from (3) that the losses are proportional to the square of the magnetic field amplitude (Bmn) and frequency (fn) and inversely proportional to the resistivity of the material (ρ), which changes with the magnetic field due to MR effect (1)- (2). Joule losses can also be expressed as a function of the induced n th current harmonic In and magnet resistance at that frequency Rn.…”

“…Estimation of the PM losses due to Eddy currents in PMSMs can be extremely difficult once it is assembled, due to the large number of design parameters that can affect [2].…”

“…High speed operation in conventional PMSMs, i.e. interior PMSMs (IPMSMs) and surface PMSMs (SPMSMs), requires injection of negative current in the d-axis [1]- [2] to produce flux weakening d-axis current is also used below rated speed in IPMSMs to achieve maximum torque per ampere (MTPA) [1]. In addition to weaken the stator flux linkage, daxis current also increases the air-gap flux harmonic content, which increase Eddy current losses in the stator/rotor cores and PMs [1]- [3].…”

“…to nonsinusoidal currents, confinement of the stator windings into the stator slots, etc. Eddy current losses can significantly contribute to the overall temperature raise in PMSMs, increasing the risk of PM demagnetization [2]- [3], [8]. Hysteresis losses are typically less relevant since the magnetic materials in PMSMs always operate in the second quadrant of B-H curve [8].…”

Investigation of Permanent Magnet Demagnetization in Synchronous Machines during Multiple Short-Circuit Fault Conditions

“…Eddy current losses have been studied in electrical machines with two-dimensional as well as more accurate three-dimensional simulations [13][14][15]. For some applications, especially in high-speed machines, they could become a problem [16].…”