Ambition had been always oriented to replace the DC link AC Frequency changers used as drives, due to it's severe dv/dt effect on motor winding mean life time caused by high frequency PWM switching in addition to its DC link stage(s) requirement. This converter is to be replaced by a direct AC-to-AC power frequency changer. This work is proposed to achieve two major important trends. First is to design and implement a 3-phase fully precise controlled cycloconverter based on integral half cycle selection with minimum harmonic distortion, near sinusoidal output waveforms, and phase balancing capabilities. The second trend is the investigation of applying Pulse Width Modulation PWM for cycloconverter output voltage control and compare its performance with the phase-angle control triggering mode of thyristors mostly used in conventional cycloconverters. The switching frequency used for PWM is much lower than that used in inverter type frequency changers to achieve minimum dv/dt effect. A proposal of new PWM techniques oriented for harmonic reduction and elimination of undesired harmonic components that have sever effects on a 3-phase induction machine operation is also presented. A prototype power frequency changer employing various techniques such as PWM harmonic reduction (HRT and HRVCT), equal area PWM, Half cycle omission (HCO and PHCO), comb filter, and integral-cycle based cycloconverter techniques enhanced by PWM is designed and implemented in the laboratory. The system is tested with three-phase resistive, single-phase and three-phase induction motor loads. The design of the three-phase system is simple, inexpensive, and can be assembled using commercially available components. Satisfactory agreements are achieved between the theoretical and experimental results. Mathematical analysis and MATLAB 6.5 simulation programs are used to investigate the effect and advantages of the proposed techniques. Major harmonic reduction and supply frequency elimination are made through most techniques. HCO is found to work in addition to harmonic reduction as a phase balancing technique. Comb filter is found to be a novel technique for undesired harmonic component elimination. This technique is used for the first time in power frequency changing applications.