Co-existing attractor of PWM controlled DC drives

We report the observation of co-existing attractor with fractal basin boundaries in PWM controlled dc series drives. This type of drive is extensibly used in electric traction and other applications. The dc drive shows different bifurcation behavior when different types of input voltage and switching elements are used. The bifurcation diagram of the motor drawn with different initial conditions shows the existence of co-existing attractor. These phenomena may have serious technological implication.