Self-exciting capacitor circuit for a low-power, lowspeed single-phase induction generator

It is not easy to generate voltage in a low-power, low-speed induction generator without initial voltage on its excitation capacitor. A special circuit needs to be designed to create an initial charging of capacitor if it is to be used for pico/microhydro power generation in remote area. During start-up process, the resulted waveform of capacitor current is almost always of damped sinusoid because the energy transferred between capacitor and inductor is continuously decreasing and becoming heat losses in the resistor. Highly damped of current is not desired as there will be no enough charges remaining to initiate the voltage and power generation. Experiment results indicate that it needs at least the amplitude reduction up to about 20% after five cycles - being equivalent to 0.1 second for a 50-Hz system frequency - to obtain a successful starting-up of the low-power, low-speed single-phase induction generator considered in this paper.