Acceleration/deceleration control apparatus using slip speed

Claim 1

An acceleration/deceleration control apparatus for controlling the speed of an induction motor using a slip speed thereof, comprising: detector means for detecting an actual speed of the induction motor to provide an actual speed signal ωr corresponding thereto; a vector controller for generating a slip speed signal ωs* as a function of a secondary flux registered previously corresponding to said actual speed signal ωr, of said actual speed signal ωr, and of a command speed signal ωr* derived as a result of the control of said apparatus; slip feedback means connected to said vector controller for feeding back the slip speed signal ωs* in the form of the absolute value signal ωs of said slip speed signal ωs*; comparing means connected to said slip feedback means for comparing a predetermined allowable slip speed signal ωs' corresponding to said actual speed signal ωr with said slip speed signal ωs; first means for generating a first pulse train Pωc for specifying the speed of the induction motor; responsive means connected to said comparing means and said first means for forcing said first means to continue the generation of said first pulse train Pωc when the slip speed signal ωs is equal to or less than said allowable slip speed signal ωs' as a result of the comparison in said comparing means or forcing the same to moderate the generation of said first pulse train Pωc when the slip speed signal ωs is greater than said allowable slip speed signal ωs' until the slip speed signal ωs becomes less than the allowable slip speed signal ωs', whereby the angular frequency of the rotating magnetic field of the induction motor is inhibited from changing excessively, to prevent stalling of the induction motor; second means connected to said detector means, and to said vector controller and said comparing means for receiving said actual speed signal ωr detected by said detector means, and for generating both of a second pulse train Pωr corresponding to said actual speed signal ωr and of the absolute value of the actual speed signal ωr, and applying the latter to said comparing means and said vector controller; a droop counter connected to said first means, second means, and vector controller for generating said command speed signal ωr* correspondingly to a difference between the accumulation of said first pulse train Pωc and the accumulation of said second pulse train Pωr, said command speed signal ωr* so generated being supplied to said vector controller together with said absolute value of the actual speed signal ωr from said second means for controlling the torque of the induction motor connected to said vector controller.