To attain high-speed response control for positioning by obtaining a switching signal with the first switching command signal selected, when a position deviation is within a prescribed range or the second switching signal, when it is out of a prescribed range.
When a positional deviation is within a prescribed range, a first discriminating means permits a selecting signal generating means 17 to select the first switching command signal PU1, PV1, PW1 as a selecting signal 'L' for outputting switching signals PU, PV, PW into a main circuit power element group 4. An average control means 13 forms a current control system, which permits a current deviation value to be amplified by a gain restricted to some extent, so that the voltage based on a voltage command from it is applied to the drive winding of a three-phase electric motor 1. When a position deviation is out of a prescribed range, the first discriminating means permits the selecting signal generating means 17 to select the second switching signals PU2, PV2, PW2 as a selecting signal 'H' for outputting switching signals PU, PV, PW. It is thus possible to form a current control system by an instantaneous value current control means.
YASOHARA MASAHIRO
TAKADA KAZUYUKI
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