Research Engineer Bowers & Wilkins Group Ltd Southwater, United Kingdom
In this work COMSOL Multiphysics is used to simulate the current distortion produced in a blocked coil loudspeaker using the sweep method. First, the normal magnetisation curve and hysteresis loops of the soft magnetic material involved are identified. Then, current distortion measurements are performed on the loudspeaker motor under test. Finally, time domain models are developed first using a lossless soft magnetic material (BH curve model) and then using a widely used hysteretic model (Jiles-Atherton model). The simulations are then compared to the measurements and the results discussed. The use of lossless magnetic material models strongly underestimates odd harmonics, proving that if a correct prediction of current distortion is desired it is necessary to accurately model minor hysteresis loops.
Authors: Marco Baratelli (Bowers & Wilkins Group Ltd) and Oliver Munroe (Laboratoire d’Acoustique de l’Université du Mans)