| 摘要 |
PURPOSE:To enable running frequency to be changed by the external command by calculating a correction value on the basis of quantity of state in a compressor drive system, applying modulation to the sine wave of an inverter control circuit to enable the stable running and controlling an unstabe phenomenon restraining function. CONSTITUTION:A correction value phi(t) in the occurrence of unstable phenomenon is figured out by a calculating circuit 9 on the basis of a value detected by a detecting circuit 8 with respect to the deviation of current wave form from sine wave. And by applying phase modulation to the reference sine wave Vcostheta of an inverter circuit 5 according to said correction value theta(t) can be eliminated abnormal current pulsation to permit the stable running of a compressor. Further, when the running frequency is changed by the external command, a switch 22 in an unstable phenomenon restraining function turning on-off section 20 is connected to the positive voltage side to change the running frequency under the condition of removing said function and thereafter again give said function. Thus, the abrupt change in the running frequency can be attained and the occurrence of excessive current, breakage of control elements or the like can be prevented. |
