A digital control method for a six-pulse bridge cyclo-converter using a microprocessor is designed and implemented to replace the conventional analog control circuitry. As a result, much of the complex analog control circuity is eliminated and several outstanding benefits which come from the use of a microprocessor are obtained. Selfdiagnosis feature is one of the. The microprocessor tests all the inputs and RAM, etc. If any error is found, the panel lights will flicker. This yields tremendous benefits from the maintenance and backup units point of view. Another outstanding benefit is that it is easy to change the control software to satisfy an entirely different control sequence with different parameter values. In conclusion, a conventional cycloconverter system is redesigned into a programmable low-frequency, three-phase power converter in a manner of digitalization.