Permanent-magnet fields for synchronous machines — II

MOST OF THE PROCEDURES and formulas for the electrical design calculations of synchronous machines with electromagnetic field poles may be adapted also to machines with permanent-magnet fields, but without quite the same close degree of conformity between prediction and actual performance. The main reasons for this discrepancy are: magnetic tolerances in the hard magnetic material, assumptions in practical leakage calculations, uncertainty in locating exactly the position of the minor hysteresis loop when the magnets have been stabilized by short circuit, and difficulties in magnetizing closely spaced poles to full saturation.