Magnetic flux density measurement in permanent magnet synchronous machines

This paper describes two measurement techniques of the air gap flux density in a small permanent magnet synchronous machine. The first method is based of the harmonic analysis of the induced voltage in a search coil placed on the inner periphery of the stator, while the second relies on the analysis of the induced voltage in the stator windings. Accurate results can be achieved since the measurement procedure relies only on well defined electrical quantities regardless of the dimensions of the machine. A further appreciation of the accuracy of the proposed measurement procedures can be confirmed by the reconstruction of the stator induced voltages. Although each method has its own merit in terms of field sensing, they are basically identical; nonetheless they enable a cross comparison of the measured results.