| 摘要 |
PURPOSE:To simply and freely vary the rotating speed of a motor by altering by a frequency generator the drive period of a power transistor, and controlling the ON period of the transistor with the voltage applied to a comparator. CONSTITUTION:The base terminals 1-6 of transistors TR1-TR6 for controlling the rotating speed of a 3-phase motor IM are not connected to the output terminals 1-6 of base drive circuits 7-12. A frequency generator 13 outputs a rectangular pulse which is inputted to a counter 14 and a triangular pulse which is inputted to the positive input of a comparator 15, the frequency is varied by the input voltage which is given by a variable resistor 16n thereby altering the drive periods of the transistors TR1-TR6. The periods that the transistors TR1-TR6 become ON are varied by altering the voltage which is given to the negative input of the comparator 15 via transistors 35, 37 and resistors 38, 39. |
