The paper considers the issues of effective direct start of high-voltage asynchronous motors of high power with the help of "thyristor voltage regulator -asynchronous motor" (TVR-AM) system. To increase the voltage and power of TVR in the work it is proposed to use series-parallel connected groups of thyristors (TG) instead of one thyristor TVR. The requirements to TG control signals, providing fail-safe thyristor commutation, have been scientifically proved and experimentally verified. In the proposed work a microprocessor device is used to monitor and control the simultaneous opening and closing of thyristors in each phase. Thyristors opening and closing instructions into microprocessor memory were compiled into C++ program.