Salient Stator Research Articles

Novel Salient Stator Pole-shoe Structure for Reducing Shaft-to-Frame Voltage of the PMSM

Novel Salient Stator Pole-shoe Structure for Reducing Shaft-to-Frame Voltage of the PMSM

Metal Amorphous Nanocomposite Soft Magnetic Material-Enabled High Power Density, Rare Earth Free Rotational Machines

Metal amorphous nanocomposites (MANCs) are promising soft magnetic materials (SMMs) for power electronic applications offering low power loss at high frequency and maintaining a relatively high flux density. While applications in certain motor designs have been recently modeled, their widespread application awaits scaled manufacturing of MANC materials and proliferation of new higher speed motor designs. A hybrid motor design based on permanent magnets and doubly salient stator and rotor is reported here to develop a compact (a factor of 10 smaller than currently possible in Si steels), high-speed (>1 kHz, electrical), high-power (>2.5 kW) motor by incorporating low loss ( $2.2 \times 10^{5}$ A/m sustainable, for example, with a high-grade hard ferrite magnet.

Comparative study of synchronous machines having permanent magnets in stator

Stator permanent magnet synchronous machines (SPMSMs) with doubly salient stator and rotor structure and non-overlapping winding are investigated in this paper. The PMs can be located on the surface or in the stator pole and even in the stator yoke with alternative polarities. The selection of rotor pole number is flexible, which can be any integers except the phase number and its multiples. When the numbers of stator and rotor poles (Ns/Nr) are differed by one, 6-stator pole SPMSMs have bipolar phase flux-linkages and symmetric phase back-EMFs as well as high torques. Further, three typical PM locations are chosen to compare and analyze the influence of PM locations on electromagnetic performances under 6/7 Ns/Nr combination. The results show that SPMSM with PMs mounted on the surface of stator pole has the highest PM utilization efficiency and the most sinusoidal phase back-EMF but the largest cogging torque. The SPMSM with PMs mounted on the stator yoke exhibits the largest average torque as well as the lowest torque ripple and cogging torque but the lowest PM utilization efficiency. The analyses are experimentally validated on several prototype machines.

Hybrid-Excited Doubly Salient Synchronous Machine With Permanent Magnets Between Adjacent Salient Stator Poles

A novel stator hybrid-excited, parallel flux path, synchronous machine of doubly salient topology is proposed. It has the novel features of: 1) hybrid dc field and permanent magnet (PM) excitation in the stator; 2) magnets placed in the slots between adjacent salient stator poles; and 3) the magnetic poles of PMs arranged, such that the flux premagnetizes the stator, but it is in a direction to oppose the dc excitation flux. The electromagnetic characteristics of the machine are analyzed on open-circuit and load. Since the new machine topology is developed from the variable-flux machine (VFM), a comparison of their electromagnetic torque and machine losses is conducted. The average electromagnetic torque of the hybrid-excited machine can be increased by 18% for fixed copper loss in comparison with the VFM due to the reduction of magnetic saturation in the stator. It is also shown that at high temperatures some risk of PM demagnetization exists when excited with dc and armature currents due to fringing flux that exists between the stator and the rotor poles. However, this affects only a very small area of the PMs. The performance of the hybrid-excited machine is predicted by a 2-D finite-element analysis and experimentally validated.

Analysis of Novel Multi-Tooth Variable Flux Reluctance Machines With Different Stator and Rotor Pole Combinations

Novel multi-tooth variable flux reluctance machines (VFRMs), which adopt doubly salient stator and rotor structure with nonoverlapping stator ac armature and dc field windings, are investigated in this paper. The rotor pole number can be any integer except the phase number and its multiples. Meanwhile, to obtain symmetrical bipolar phase flux-linkage and back electromotive force waveforms, the ratio of stator pole number to the greatest common divisor of stator- and rotor-pole numbers should be even integers. Furthermore, under the same rated copper loss and stator outer radius as well as 6-pole stator, 4-tooth per stator pole VFRMs in which the stator and rotor pole number determined by N r = nN s ± 1 (n is the number of small teeth per stator pole) exhibit the highest average torque. Moreover, compared with the optimal 6/7 stator/rotor pole single-tooth VFRM, the 6/25 stator/rotor pole 4-tooth VFRM has more sinusoidal and larger back EMF, negligible cogging torque, lower torque ripple, and higher torque capability at relatively low copper loss. Similar to single-tooth VFRMs, 4-tooth VFRMs with N r = nN s ± 1 exhibit more sinusoidal back EMF and larger torque than that of VFRMs with N r = nN s ± 2. The analyses are experimentally validated by several prototype machines.

Analysis of a Novel Transverse Flux Type Permanent Magnet Reluctance Generator

This paper proposes a novel transverse flux type permanent magnet reluctance generator (TFPMRG), which contains a permanent magnet (PM) in its U-shaped salient stator pole. A U-shaped stator core is designed with the short flux path to reduce the mutual effect between phases. Moreover, the proposed TFPMRG shape is designed for using PM instead of an excitation circuit to provide the field excitation, which increases the output power and efficiency. Both the transverse flux type switched reluctance generator (TFSRG) and the TFPMRG are designed using 3-D finite-element analysis (FEA) and a torque equation called the D-2L method. Finally, the design results of the TFSRG and TFPMRG are confirmed with 3-D FEA. According to the results, the output power and efficiency of TFPMRG are higher than those of TFSRG.

Investigation into Characteristics of Switched Reluctance Motors Made of Permendur

A switched reluctance (SR) motor has salient stator and rotor poles. Concentrated windings individually turn around all stator poles, while the rotor pole has no windings or magnets. Therefore, the SR motor has the following features: a simple and robust structure, large thermal resistance, faster rotation, and low-cost construction. To improve the output power and efficiency of rotating machines, investigations into various materials have recently been conducted to replace conventional non-oriented silicon steel such as grain-oriented silicon steel and soft magnetic composites (SMCs). This paper investigates the possibility of utilizing SR motors made of permendur. We estimated the torque-current characteristics, iron-loss characteristics, and the efficiency of an SR motor using the finite element method (FEM). Furthermore, a suitable structure for SR motors made of permendur is proposed.

A design technique to improve the performance of flux-reversal machines

Flux-reversal machine (FRM) is a doubly salient stator permanent magnet (PM) machine with flux linkage reversal in the stator concentrated windings. It can operate in both motoring and generating modes. In this paper, a design technique to improve the performance of FRM is proposed. The proposed techniques have a stator winding and a magnet arrangement method. The stator and rotor shapes of concave-type and a flux barrier are also proposed. According to the experimental results, it is shown that the proposed FRM has improved the performance.