Method and apparatus for controlling an AC motor

Claim 2

A control apparatus for an AC motor comprising: (a) an AC motor (3, 6) driven by a power converter (2); (b) current command means (11, 19, 51) for producing a current command signal to instruct the magnitude of a motor current to be supplied to said AC motor; (c) current pattern calculating means (14, 21, 24) for obtaining a current pattern signal based on a sinusoidal signal which determines a phase of said motor current; (d) current control means (33, 17) for controlling said power converter so as to cause said motor current to agree with said current pattern signal; (e) current detecting means (16, 23, 20, 45) for detecting said motor current to produce a current detecting signal; in which said apparatus further comprises; (f) current correction control means (32, 12, 13, 121, 122, 131, 132) for obtaining a current deviation of said current detecting signal from said current command signal so as to produce a current correction signal proportional to said current deviation and adding said current correction signal to said current command signal so as to apply the sum to said current pattern calculating means.

Claim 3

A control apparatus for an AC motor according to claim 1, characterized in that - said current correction control means (32, 12, 13, 18) produce the current correction signal proportional to said current deviation and said current command signal.

Claim 4

A control apparatus for an AC motor according to claim 1, characterized in that - a current command signal produced by said current command means (11, 19) instructs the magnitude of a component parallel to field magnetic flux of said motor and another component perpendicular to said parallel component; - said current pattern signal obtained by said current pattern calculation means (21) is based on a sinusoidal signal which determines thephase of said motor current and said current command signal includes the parallel component and perpendicular component command; - said current detecting means (16, 23, 20). detect the respective magnitudes of said parallel'and perpendicular components of said motor current; - current correction control means (321, 322, 121, 122, 131, 132) obtain a first current deviation of the detected magnitudes of said parallel component of said motor from said parallel component current command and a second current deviation of the detected magnitude of said perpendicular component of said motor from said perpendicular component current command and said first and second deviations are added to said parallel and perpendicular component current commands, respectively, so as to apply the respective sums to said current. pattern calculation means.

Claim 5

A control method for an AC motor of claim 1, characterized by following steps: A) driving an AC motor by a power convertor; B) procuding a current command signal to instruct the magnitude of a motor current to be supplied to said AC motor; C) obtaining a current pattern signal based on a sinusoidal signal which determines a phase of said motor current; D) controlling said power converter to cause said motor current to agree with said current pattern signal; E) detecting said motor current to produce a current detecting signal; F) obtaining a current deviation of said current detecting signal from said current command signal so as to produce a current correction signal proportional to said current deviation and adding said current correction signal to said current command signal so as to apply the sum to said current pattern calculation means.

Claim 6

A control method according to claim 4 characterized in that - in step F said current correction signal is produced proportional to said current deviation and said current command signal.

Claim 7

A control method according to claim 4, characterized in that in step B said current command signal instructs the magnitude of a component parallel to field magnetic flux of said motor and another component perpendicular to said parallel component; said current pattern signal of step C is based on a sinusoidal signal which determines a phase of said motor current and said current command signal includes the parallel component command and perpendicular component command; in step E the respective magnitudes of said parallel and perpendicular components of said motor current are detected; in step F a first current deviation of the detected magnitudesof said parallel component of said motor from said parallel component current command and a second current deviation of the detected magnitude of said perpendicular component of said motor from said perpendicular component current command are detected and said first and second deviations are added to said parallel and perpendicular component current commands, respectively, and the respective sums are applied to current pattern calculating means (21) for obtaining said current pattern signal of step C.