FREQUENCY-CONTROLLED AC DRIVE Russian patent published in 1999 - IPC

FIELD: power voltage and frequency changers for controlling general-purpose ac squirrel- cage motors. SUBSTANCE: drive has three-phase power rectifier and secondary three-phase bridge converter whose control inputs are connected to outputs of microprocessor controller; drive motor is connected to converter output. Introduced in addition are balanced resistive bridge circuit, integrating capacitor, differential standardizing amplifier, and analog-to-digital converter. Diagonally opposite input pair of terminals of balanced resistive bridge circuit is connected to output leads of three-phase bridge rectifier; integrating circuit is connected to one of sides of diagonally opposite output pair of terminals of balanced resistive bridge circuit; diagonally opposite output pair of terminals of bridge circuit is connected to differential inputs of standardizing amplifier whose output is connected to analog- to-digital converter input. Output of the latter is connected to fifth input of microprocessor controller. EFFECT: improved reliability, reduced size and mass, reduced manufacturing cost of drive. 1 dwg