Patent ID: 9248539
Filing Date: 2016-02-02
CPC Classification: B23Q,H02P

Claim Text:
1. A control device for a machine tool including a feed shaft motor for driving a feed shaft and a main shaft motor for driving a main shaft, the control device comprising: a converter mutually converting power between AC power on an AC power supply side and DC power of a DC link at a DC side; a feed shaft motor inverter connected to the DC link, and mutually converting power between DC power of the DC link and AC power which is driving electric power or regenerative electric power of the feed shaft motor; a main shaft motor inverter connected to the DC link, and mutually converting power between DC power of the DC link and AC power which is driving electric power or regenerative electric power of the main shaft motor; a power failure detection unit detecting presence or absence of power failure on the AC power supply side of the converter; a feed shaft motor deceleration command unit outputting a feed shaft motor deceleration command to control power interconversion by the feed shaft motor inverter so as to decelerate the feed shaft motor, when the power failure detection unit detects power failure; a determination unit determining whether an operation of the feed shaft motor satisfies a predetermined determination condition; and an excitation command unit outputting an excitation current command to output excitation current larger than excitation current instructed by a master control unit from the main shaft motor inverter to the main shaft motor, when the determination unit determines that the predetermined determination condition is satisfied, wherein the predetermined determination condition is at least one of a condition in which the feed shaft is being moved in a rapid traverse mode, a condition in which a speed of the feed shaft is not smaller than a predetermined value, and a condition in which a sum of kinetic energies of all feed shafts is not smaller than a predetermined value.