Two-part Rotor Research Articles

Using and enhancing the cogging torque of PM machines in valve positioning applications

In this study, it is aimed to use the cogging torque of permanent magnet (PM) machines for providing the load torque in the valve positioning applications. The policy is to use the machine cogging torque to overcome the load torque at the steady-state condition (fixed valve position). Therefore, there is no excitation, and no armature Joule losses at the steady-state condition and consequently lower thermal stress for the machine. To have a more compact actuator, it is tried to increase the machine cogging torque. Two well-known types of PM machines, i.e. surface-mounted PM (SPM) and flux-switching PM (FSPM) machines are studied to be applied in this application. Some techniques such as applying auxiliary slots and PM segmentation (for the SPM machine) and two-part rotor topology (for both SPM and FSPM machines) are proposed to increase the machine cogging torque. The impact of each technique on the developed cogging torque is studied by means of finite element analysis. Finally, the SPM and FSPM machines are compared together in the terms of the torque density. The validity of the proposed concept of providing the load torque by the cogging torque is investigated by experimental tests.

A Hybrid Interior Permanent Magnet Variable Flux Memory Machine Using Two-Part Rotor

In this paper, a novel hybrid permanent magnet variable flux memory machine using two-part rotor is proposed whose rotor comprises an AlNiCo part and a NdFeB part adjacent to each other on the same shaft. With the proposed topology, flexible flux controllability can be achieved since the magnetization state of AlNiCo can be adjusted by a temporary current pulse. The detailed operating principles are described, and the split ratio and some key design parameters are optimized. Then, the electromagnetic performance of the proposed machine with emphases on back electromotive force, flux density, flux-weakening performance, and torque characteristics is investigated. Finally, 3-D finite-element validation is implemented and a machine prototype has been manufactured and tested to validate the analyses.

A New Hybrid Permanent Magnet Synchronous Motor With Two Different Rotor Sections

In this paper, a new hybrid permanent magnet (PM) synchronous motor with two-part rotor is proposed. The new motor is composed of surface mounted and interior magnet rotor segments on a stepped skewed shaft. The hybrid topology has wider constant power speed ratio than conventional surface mounted PM motors with relatively the same torque density. No-load and on-load finite-element analyses (FEA) are performed independently for both surface PM and interior PM synchronous motor. Superposition of the results is gathered to obtain the actual performance of the hybrid motor. The 2-D FEA results with skewed models are also performed at the final stage of the design. A prototype motor is manufactured and experimental results are obtained. Good agreement is observed between the simulations and test data for the proposed motor.

Design and field-weakening performance of permanent-magnet/reluctance motor with two-part rotor

A synchronous motor with two-part rotor is described whose rotor comprises a surface-magnet part and a reluctance part mounted adjacent to each other on the same axis. An axially laminated construction is used in the reluctance part to achieve a high saliency ratio. Machine parameters and physical design details are selected to obtain constant-power characteristics over a 3:1 speed range by field-weakening. Test results demonstrate the achievement of the desired characteristics, in good agreement with computed predictions. The two-part rotor construction is thus a candidate for applications such as electric vehicles.

New approach to longitudinal magnetic field in drum type machine

Without 3D analysis, the longitudinal distribution of the magnetic field in a drum-type electric machine can be determined two-dimensionally, provided that radial results, fundamental components of the air gap flux density related to each axially-separated part, are obtained in advance by any conventional 2D numerical method. Details on the new approach, including how to bound the domain, how to represent the problem and how to solve it, are presented. As an application, a new type of synchronous machine with a two-part rotor, having a surface permanent magnet part and an axially-laminated anisotropic reluctance part axially-separated on the same shaft, is investigated, with obvious high computational economy and improved accuracy.

Variable-frequency synchronous motor drives for electric vehicles

The performance capability envelope of a variable-frequency, permanent-magnet synchronous motor drive with field weakening is dependent upon the product of maximum current and direct-axis inductance. To obtain a performance characteristic suitable for a typical electric vehicle drive, in which short-term increase of current is applied, it is necessary to design an optimum value of direct-axis inductance. The paper presents an analysis of a hybrid motor design which uses a two-part rotor construction comprising a surface-magnet part and an axially laminated reluctance part. This arrangement combines the properties of all other types of synchronous motor and offers a greater choice of design variables. It is shown that the desired form of performance may be achieved when the high-inductance axis of the reluctance part is arranged to lead the magnet axis by 90/spl deg/ (elec.).