BASIC CONCEPTS The technology used to regulate the speed of electric motors first consisted of electronic speed drives consisting of thyristor bridge rectifiers and direct current motors with mechanical switching based on collectors and brushes. This technology is still proving itself useful. Although new vector-controlled technologies with asynchronous motors are taking over the market for low-power applications, the combined costs of motor + drive are still extremely advantageous for power ratings above 50 kW and ensure outstanding performance and speed regulation