A novel and accurate estimation method of the steady state electromagnetic torque reduction in a brushless motor drive system with inverter dead time

摘要

A novel method for determining the steady-state torque reduction in industrial brushless motor drive systems, due to pulsewidth modulated (PWM) inverter dead time, is presented. Estimation is based on the single Fourier series representation of the three-phase stator winding delayed PWM voltages using d-q coordinates fixed in the rotor frame. This simplified approach eliminates the need for very small time steps (/spl sim/0.5% T/sub s/) in the search of the PWM pulse edge transitions within a switching period T/sub s/ for accurate model simulation with a beneficial saving in computational (CPU) resources. Model integrity is validated when simulation results, based on a fixed amplitude frequency modulated current feedback step response, are checked for coherence against those for an actual drive system. Subsequent simulations show the effect of inverter delay on the reduction of generated torque with rotor speed.