In present daily life, many facilities almost use motor inside such as for residents, department stores, or in production line for many industries. The motors must be a part of the machines such as water pumps, air compressors, cranes, industrial fans, conveyers and etc. In industries, motors are often required to be controlled theirs speed and torque for serving needs of production lines or support works. To control the speed and torque of motor, variable speed drive (VSD) is widely applied. These applications are not only useful for mechanical control by electrical but also useful for energy saving job. When apply VSD to control the motor, speed and torque can be stabilized or input power of VSD can be large reduced resulting low energy consumption. However, by using VSD for controlling speed and torque of motors, some problem of power quality appears. This problem is harmonic distortion on input voltage and current of VSD. Input sinusoidal voltage and current waveform are distorted to nonsinusoidal by application of six pulse three phase diode rectifier circuit as shown in Fig. 1.