This paper experimentally examines effects of stable nonlinear normal modes on self-synchronized phenomena by using oscillators that are excited by intermittent electromagnetic power. The oscillator behaves as a pendulum-type oscillator when the applied voltage is low whereas as a rotor-type oscillator when the voltage is high. Stable nonlinear normal modes are obtained numerically by modified shooting method. Experimental and analytical results demonstrate that self-synchronized phenomena of pendulum-type oscillators as well as rotor-type oscillators can be explained well by using stable nonlinear normal modes of the system.