Recently, the AC motor which has a simple structure and needs less maintenance has become to be used frequently as a servomotor for position control in the automatic control field. This paper concerns with a method to improve the current and power waveforms of an AC motor, and the current waveforms and 3$phi$ power waveforms are analyzed by FFT under verious running conditions. The system is composed of a digital bridge inverter, low pass LC filter, and 3$phi$ AC motor. Through the computer simulations and experiments, it is confirmed that current waveforms and $phi$ power waveforms con by improved by utilizing the high order low pass LC filter than that of lower order.