Abstract
The common analytical models for the no-load iron loss of permanent magnet(PM) motors usually neglect the iron loss caused by the rotating magnetic field in the tooth tips and the harmonics of the magnetic fields in the teeth and yokes. This paper presents an analytical model for no-load iron loss of a fractional-slot surface-mounted permanent magnet motor. According to the existing analytical model of the magnetic field distribution in the slotted air gap, the magnetic flux densities considering the harmonics of the stator tooth and yoke are both derived based on the continuity of magnetic flux. Due to the complexity of the magnetic field in the tooth tip, the tangential flux density of the tooth tip is approximated by an equivalent sine wave and the radial component is regarded to be the same as that of the corresponding tooth. After obtaining the magnetic fields in stator different regions, the analytical iron loss is calculated by using the Bertotti model and the orthogonal decomposition model. A 20-pole/24-slot PM synchronous motor is taken as an example. The maximum error between the analytical model and finite element model(FEM) is 5.46%, which verifies the validity of the proposed method.
Highlights
Iron loss is a main component of the total loss of the PM motors
Most analytical models only consider the iron loss caused by the radial magnetic field in the teeth, while the loss caused by the tangential magnetic field in the tooth tips is neglected
Due to the irregular shape of the tooth tip, the tangential flux density of the tooth tip is approximated by an equivalent sine wave and the radial component is regarded to be the same as that of the corresponding tooth
Summary
Iron loss is a main component of the total loss of the PM motors. Accurate prediction of the iron loss is the premise of optimizing motor efficiency and temperature rise. Using either the FEM or the analytical model to calculate the iron loss, the premise is to obtain the magnetic fields in the stator core. There are usually two ways to obtain the magnetic fields in the stator core. Most analytical models only consider the iron loss caused by the radial magnetic field in the teeth, while the loss caused by the tangential magnetic field in the tooth tips is neglected. In this paper, based on the existing analytical model of the magnetic field distribution in the slotted air gap, the specific expressions of the magnetic flux densities considering the harmonics in the stator teeth and yokes are both given according to the continuity of magnetic flux. An FEM of a 20-pole/24-slot PM synchronous motor is simulated to verify the validity of the proposed method
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