The method of multiple reference frames is employed in the development of a
state variable model for brushless DC drives with non-sinusoidal back emf
waveforms. This model has the desirable features of being valid for transie
nt and steady-state analysis as well as having state variables that are con
stant in the steady-state. The model facilitates both nonlinear and linear
system analysis and control design. Computer simulation and experimental da
ta are included to validate the analysis.