DRIVE DEVICE FOR COMPRESSOR

摘要

PURPOSE:To obviate unstable running by detecting only low frequency components of about a half rotational frequency from the quantity of state of a compressor drive system with a extracting means and applying phase modulation to the reference sine wave on the basis of a correction value calculated by the detected data. CONSTITUTION:In the occurrence of unstable phenomenon, the cycle of current vector becomes two times the cycle of torque fluctuation, i.e. the frequency is halved so that a correction value phi(t) is figured out by a calculating circuit 9 on the basis of the value extracted from this half frequency component by a extracting circuit 8. And the correction value is added to or subtracted from a signal theta from a theta generator 12 to obtain theta+ or -phi(t) to generate sine wave Vcos( - or + + or -phi(t)) subjected to phase modulation by said correction value phi(t) with respect to the reference sine wave Vcostheta. A switch signal subjected to pulse modulation to be approximated to the sine wave by this sine wave and an carrier wave is supplied to an inverter circuit 5 to eliminate abnormal current pulsation causing the unstable phenomenon and permit a compressor 7 to be driven under the condition without the unstable phenomenon.