Multipolar SPM machines for direct drive application: a general design approach

A closed-form, per-unit formulation for the design of surface mounted permanent magnet motors having high numbers of poles is hereby proposed. The analytical expression of machine inductances is presented, covering distributed and concentrated windings configurations. The paper addresses how the slot/pole combination, the geometric variables and the number of poles are related to average torque, the Joule loss and the power factor. The performance of distributed and concentrated windings machines is compared analytically, in normalized quantities. Last, the design approach is tested on four design examples, including all winding types and validated by finite element analysis

Position-sensorless control of permanent-magnet-assisted synchronous reluctance motor

The sensorless control of permanent-magnet-assisted synchronous reluctance (PMASR) motors is investigated, in order to conjugate the advantages of the sensorless control with full exploitation of the allowed operating area, for a given inverter. An additional pulsating flux is injected in the d-axis direction at low and zero speed, while it is dropped out, at large speed, to save voltage and additional loss. A flux-observer-based control scheme is used, which includes an accurate knowledge of the motor magnetic behavior. This leads, in general, to good robustness against load variations, by counteracting the magnetic cross saturation effect. Moreover, it allows an easy and effective correspondence between the wanted torque and flux and the set values of the chosen control variables, that is d-axis flux and q-axis current. Experimental verification of the proposed method is given, both steady-state and dynamic performance are outlined. A prototype PMASR motor will be used to this aim, as part of a purposely assembled prototype drive, for light traction application (electric scooter

Improved modelling of a distributed anisotropy synchronous reluctance machine

The mathematical modeling of a d.a. synchronous reluctance machine is considered. The model refers to the more general case, taking the presence of slots in the stator structure into account. The resulting linear second order differential equation with periodic coefficients gives the rotor magnetic potential distribution on the rotor surface, once the static MMF is given. The induction value in the rotor iron is also calculated, in order to account for the additional rotor iron losses enhanced by stator slots. An approximated analytical solution is found, in a particular case, and the calculated results are compared with experimental ones. Practical suggestions are given to overcome the rotor losses problem