In this paper, a novel flux-assisted spoke type permanent magnet synchronous motor with an unconventional 9-phase stator structure is presented. The proposed 9-phase motor has two additional flux-assisted magnets between the main spoke magnets. Initial design, detailed magnetic simulations, parametric analyses are completed. A comparison between the proposed motor and unconventional 9-phase surface magnet motor are also performed and the benefits of the novel 9-phase structure is presented. It is revealed that the novel 9-phase motor has certain benefits for applications requiring more power density and wide constant power region.

In this study, six promising interior permanent magnet (IPM) motors are designed as a spindle motor for computer numerical control (CNC) milling machine application. An existing surface-mounted permanent magnet (SPM) motor in a CNC is selected for a baseline motor. In order to reach more high speeds as to SPM motor, six different IPM rotor topologies are investigated while keeping the exact stator structure and windings of the reference motor. A comprehensive comparison of the IPM rotor topologies is performed, and the benefits and drawbacks of the designs are highlighted. The best performance design is selected and manufactured for experimental studies. No-load and on-load tests are performed by a motor test system, and the obtained results are compared with the finite element analysis (FEA) results. It is observed that the results are in good agreement. It is shown that it is possible to have an optimized IPM motor for such high speed spindle application by using same stator and winding structure with reference SPM motor.

Hybrid 3-phase stepper motors remain the preferred solution for many applications in robotics and aerospace industries as they can provide accurate position and speed control in open loop systems. On the other hand, they are rarely used in oil and gas industry. In this paper, potential use of this motor technology to oil and gas industry specifically downhole applications is investigated. For this purpose, design and analyses of a 3-phase hybrid stepper motor are carried out with the detailed investigation on the impact of airgap on the motor performance. The difficulty of the design comes from extremely large L/D ratio of the stepper motor due to the application requirements. Fundamental design-based equations are used for the initial design of the motor and detailed 3D finite element analysis (FEA) models are carried out to check the motor performance. Finally, modelling and design of two 3-phase hybrid stepper motors with different airgaps are presented to illustrate the effect of the airgap length on motor performance.

In this study, an investigation of winding structures is performed for 3-phase unbalanced and asymmetric winding permanent magnet (PM) machines including different slot-pole combinations. There are two different cases for unbalanced winding (UBW) structure: 1) Stator slot number of the machine is divisible by three, 2) Stator slot number of the machine is not divisible by three. Only the first case is examined in this paper. The unbalanced winding layouts are created for minimum unbalance and maximum winding factor. Total magneto motive force (MMF) distributions for nine different slot-pole combinations and their harmonic contents are presented. Variation of the amount of unbalance for different slot-pole combinations is also provided in the paper. A prototype motor with 39-slots and 12-poles has been manufactured for experimental verification. A comparison between the finite element analysis (FEA) results and experimental results is presented for the prototype motor for both no-load and on-load conditions.

This paper presents magnetic equivalent circuit (MEC) modeling approaches for an unbalanced and asymmetric winding 39-slot 12-pole permanent magnet (PM) motor. Such unconventional slot-pole configuration has certain benefits over conventional integral slot PM motors such as low cogging and torque ripple, and low rotor manufacturing cost. This slot-pole combination leads difficulty in analytical modeling since the motor symmetry is different from conventional PM motors. Simpler MEC modeling approaches would be useful in designing such motors with unconventional combinations. Four different MEC modeling approaches are investigated in this paper for an experimentally verified 39-slot 12-pole motor. Benefits and drawbacks of each approach are presented. No-load and on-load results obtained from MEC modeling approaches are compared with the finite element analysis (FEA) and test data to illustrate the benefits of the modeling approaches.

In this paper, two different winding configurations and phase angle displacements of an unconventional nine-phase permanent magnet (PM) motor have been investigated in terms of flux weakening capabilities. The focus has been on a 117-slot 36-pole unbalanced and asymmetric winding motor since these motors have certain benefits. In addition, it is not possible to create a balanced winding structure for this motor due to the selected slot-pole combination. Performance of the designed motors have been verified experimentally and flux weakening capabilities have been investigated using 2 Dimensional finite element analysis (2D FEA) and test results. It is shown that the flux weakening capabilities of the proposed 9-phase PM motors with two winding options yield similar results compared to a conventional balanced multi-phase PM motors.

Permanent magnet (PM) synchronous motors have found numerous applications over the last two decades due to their high torque to weight ratio and efficiency. However, one of the main drawbacks of the PM motors is the magnet corrosion. This paper investigates the influence of magnet corrosion on the performance of surface mounted permanent magnet motors. Un-corroded and corroded magnet rotors are used to investigate the motor performance including voltage and torque constants. It has been found out that the corroded rotor does not degrade the motor performance even after the intense corrosion tests if good quality NdFeB magnets are used.