Electric machine drive system analysis by strong coupling magnetic field with the nonlinear external circuit and control algorithm is increasingly drawing attentions from both the academic researchers and industrial designers. The steady and transient performances of the drive system can be accordingly obtained with credible computation convergence and accuracy by taking into account the space harmonics, time harmonics, and their interactions between. However, the pulse-width modulation techniques commonly employed in the electric machine drives will normally result in numeric analysis with extensive computational time. A novel time-step method, namely trigger method, is proposed in order to reduce the computational load in this paper. The comparisons between the results from the conventional and new methods have revealed that the proposed method could significantly reduce the simulation time without notable compromise on the accuracy. Experimental tests of a permanent magnet synchronous machine drive system with the space vector pulse width modulation technique are carried out to validate the simulation results from the proposed method. Besides, the validity of the proposed trigger method has been further underpinned by the corresponding estimated and experimental results of a practical servo-drive system based on the synchronous reluctance machine.