Experimental research on iron loss of high-speed spindle motor under variable frequency drive power supply

Measuring magnetic flux density in actual motor systems and understanding the influence of power harmonics on iron loss are urgent challenges under variable frequency drive (VFD) power supply conditions, and this research is studied based on the classical Bertotti's three constant coefficient model. An iron loss model incorporating various harmonic voltages is established by substituting the amplitude and frequency of voltage for magnetic density amplitude and considering the effects of output harmonic voltage by the VFD. The voltage waveform was measured under a VFD power supply and decomposed via Fourier analysis to determine the amplitude of each harmonic voltage. The iron loss coefficients are solved using the least squares method. The iron loss and harmonic iron loss are calculated and analyzed with and without filtering under different frequencies and voltage conditions. Experimental results indicated that iron loss increases with the increase of voltage, frequency, and magnetic flux. The harmonic iron loss increased with the voltage and magnetic flux at low frequencies. While the harmonic iron loss decreased as voltage and magnetic flux increased at high frequencies. The iron loss is significantly higher than in sine-driven ones in pulse width modulation VFD-driven spindle motors, and harmonic iron loss took up a proportion of at least 20% of the total iron loss. This research not only offers a precise method to predict the iron loss of high-speed spindle motors but also reveals the pattern of iron loss variation, providing a theoretical basis for motor design and optimization.