The synchronous reactances of permanent magnet (PM) motors have been determined using: 1) analytical method, i.e., form factors of the stator field (armature reaction factors), 2) finite element method (FEM), and 3) experimental tests on a special machine set. The analytical method is widely used in calculations of synchronous reactances of salient pole synchronous machines with electromagnetic excitation. Rotors of PM synchronous machines have more complicated structures, hence it is more difficult to predict accurately the magnetic field distribution in their airgaps in order to find the form factors of the stator field. Numerical methods of field analysis can easily solve this problem. The FEM can predict both the synchronous and mutual (armature reaction) reactances in the d and q axes. The leakage reactance can then be evaluated as a difference between synchronous and mutual reactances. As an example, a small, three-phase, four-pole motor with SmCo surface mounted PM's (three parallel magnets per pole), and mild-steel pole shoes has been investigated. Such a complicated rotor structure has been intentionally designed in order to be able to compare the advantages and disadvantages of the analytical method and the FEM. In the FEM, the reactances have been calculated using both the flux linkage and current/energy perturbation method. Synchronous reactances as functions of the stator current and load angle obtained analytically from the FEM modeling and from measurements have been compared.

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The transient performance of permanent magnet dc commutator motors has been simulated using a two dimensional finite element model. The simulations of start‐up characteristics and braking conditions are concentrated on. The finite element approach in simulating transients of dc motors is discussed with a proposed solution to the problem A finite element solution that ignores the induced eddy current losses in the small volume rotor is shown as a quick solution that gives fair accuracy. The results are compared against experimental data obtained for a 370 W permanent magnet dc motor using a data acquisition system.

A new high performance brushless permanent magnet (PM) motor operating both as a synchronous and d.c. shunt motor has been presented. The motor has been designed using a classical approach with synchronous teacLances obtained from the finite element method (FEM). For the load angle close to 90' the motor can be switched automatically from a.c. to d.c. mode. The complete integrated drive system consists of two parts: (1) motor with position sensors and (2) IGBT inverter together with control circuitry. The mode switching control strategy, operation, and performance have been discussed.h'eywmdsPermanent magnet motors. High performance universal motors. Integrated drives. r, '

The increased use of permanent magnet synchronous motors in small to medium power applications has made it imperative that these motors' performance can be modelled successfully. The accuracy of calculating the synchronous reactances determines the success of the modelling technique. An analytical method and the finite element method are used to calculate the synchronous reactances of two prototype synchronous motors. The calculations are compared with measurement for both motors. The results show that the finite element method is more reliable in obtaining synchronous reactances than the analytical method for rotor designs that are very intricate, although both methods show reasonable accuracy.

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