Patents by Inventor Yoichiro Arakawa

Yoichiro Arakawa has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 8710781
    Abstract: In a power conversion device that includes a PWM converting means for generating a PWM pulse by comparing three-phase voltage commands with a triangular wave carrier signal, a power converter for converting between a DC voltage and a three-phase AC voltage by driving a switching element according to the PWM pulse, a current detecting means for detecting a pulsed current flowing through a DC bus conductor of a main circuit, and a voltage command correcting means for correcting three-phase voltage commands, which corrects the three-phase voltage commands so that a line voltage value between the maximum phase and an intermediate phase and a line voltage value between the intermediate phase and the minimum phase are each equal to or larger than a predetermined value, the maximum phase, intermediate phase, and minimum phase being determined in correspondence to momentary values of the three-phase voltage commands arranged in descending order, if the voltage command is outside an allowable upper limit or lower limi
    Type: Grant
    Filed: February 17, 2010
    Date of Patent: April 29, 2014
    Assignee: Hitachi Industrial Equipment Systems Co., Ltd.
    Inventors: Yoichiro Arakawa, Koichiro Nagata, Yuusuke Arao, Shigehisa Aoyagi
  • Publication number: 20110292700
    Abstract: In a power conversion device that includes a PWM converting means for generating a PWM pulse by comparing three-phase voltage commands with a triangular wave carrier signal, a power converter for converting between a DC voltage and a three-phase AC voltage by driving a switching element according to the PWM pulse, a current detecting means for detecting a pulsed current flowing through a DC bus conductor of a main circuit, and a voltage command correcting means for correcting three-phase voltage commands, which corrects the three-phase voltage commands so that a line voltage value between the maximum phase and an intermediate phase and a line voltage value between the intermediate phase and the minimum phase are each equal to or larger than a predetermined value, the maximum phase, intermediate phase, and minimum phase being determined in correspondence to momentary values of the three-phase voltage commands arranged in descending order, if the voltage command is outside an allowable upper limit or lower limi
    Type: Application
    Filed: February 17, 2010
    Publication date: December 1, 2011
    Inventors: Yoichiro Arakawa, Koichiro Nagata, Yuusuke Arao, Shigehisa Aoyagi
  • Patent number: 7902790
    Abstract: A slip frequency is estimated from a current instruction or detected currents in an induction motor. Acceleration impossibility in an induction motor drive unit is determined, when the slip frequency exceeds the maximum torque generating slip frequency for the predetermined interval or the time integrating result exceeds a predetermined value; when the q-axis magnetic flux exceeds the maximum torque generating q-axis magnetic flux or exceeds for a predetermined interval; when the estimated rotational speed is under a predetermined value; when the rotational speed variation rate is negative; and when the rotational speed instruction value or the estimated rotational speed is equal to or smaller than a predetermined value. An induction motor drive system and an elevating system including the induction motor drive unit are also disclosed.
    Type: Grant
    Filed: June 19, 2008
    Date of Patent: March 8, 2011
    Assignee: Hitachi Industrial Equipment Systems Co., Ltd.
    Inventors: Yoichiro Arakawa, Koichiro Nagata, Hiroyuki Tomita
  • Publication number: 20080315824
    Abstract: A slip frequency is estimated from a current instruction or detected currents in an induction motor. Acceleration impossibility in an induction motor drive unit is determined, when the slip frequency exceeds the maximum torque generating slip frequency for the predetermined interval or the time integrating result exceeds a predetermined value; when the q-axis magnetic flux exceeds the maximum torque generating q-axis magnetic flux or exceeds for a predetermined interval; when the estimated rotational speed is under a predetermined value; when the rotational speed variation rate is negative; and when the rotational speed instruction value or the estimated rotational speed is equal to or smaller than a predetermined value. An induction motor drive system and an elevating system including the induction motor drive unit are also disclosed.
    Type: Application
    Filed: June 19, 2008
    Publication date: December 25, 2008
    Inventors: Yoichiro ARAKAWA, Koichiro NAGATA, Hiroyuki TOMITA