Patents by Inventor Tomohiro Kawachi
Tomohiro Kawachi 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).
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Patent number: 9231514Abstract: A winding switching signal generator is configured to obtain information indicating a degree of field weakening from at least one of a current command calculator and a constant output controller, and to generate a winding switching signal for switching from a low speed rotation state to a high speed rotation state when the degree of the field weakening exceeds a predetermined condition in the low speed rotation state.Type: GrantFiled: May 16, 2013Date of Patent: January 5, 2016Assignee: KABUSHIKI KAISHA YASKAWA DENKIInventors: Zhenning Chen, Tomohiro Kawachi, Kenji Tomohara, Koji Higashikawa, Masashi Takenouchi
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Patent number: 9184688Abstract: An inverter device according to an embodiment includes a constant power controller. The constant power controller computes and outputs, when a value of a voltage reference to an AC motor exceeds a predetermined threshold value, a d-axis current reference correction value on the basis of the value of the voltage reference and the predetermined threshold value. Moreover, the constant power controller generates the d-axis current reference correction value by using a constant power model determined by a torque reference or a speed reference and a supplied direct voltage at an output switching timing determined based on a winding switching signal and outputs the d-axis current reference correction value for a predetermined time.Type: GrantFiled: June 28, 2012Date of Patent: November 10, 2015Assignee: KABUSHIKI KAISHA YASKAWA DENKIInventors: Zhenning Chen, Tomohiro Kawachi, Mitsunori Kuzushima
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Patent number: 9166513Abstract: Provided is an inverter apparatus 20 configured to switch a current winding to an optimal winding when a rotation speed of a rotor of an AC electric motor 40 is within a hysteresis region defined by first and second switch timings for switching a state of an armature winding between a first winding and a second winding and when the current winding differs from the optimal winding.Type: GrantFiled: May 16, 2013Date of Patent: October 20, 2015Assignee: KABUSHIKI KAISHA YASKAWA DENKIInventors: Masashi Takenouchi, Tomohiro Kawachi, Kenji Tomohara, Koji Higashikawa
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Publication number: 20140210397Abstract: Provided is an inverter apparatus 20 configured to switch a current winding to an optimal winding when a rotation speed of a rotor of an AC electric motor 40 is within a hysteresis region defined by first and second switch timings for switching a state of an armature winding between a first winding and a second winding and when the current winding differs from the optimal winding.Type: ApplicationFiled: May 16, 2013Publication date: July 31, 2014Applicant: KABUSHIKI KAISHA YASKAWA DENKIInventors: Masashi TAKENOUCHI, Tomohiro KAWACHI, Kenji TOMOHARA, Koji HIGASHIKAWA
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Publication number: 20140197771Abstract: A winding switching signal generator is configured to obtain information indicating a degree of field weakening from at least one of a current command calculator and a constant output controller, and to generate a winding switching signal for switching from a low speed rotation state to a high speed rotation state when the degree of the field weakening exceeds a predetermined condition in the low speed rotation state.Type: ApplicationFiled: May 16, 2013Publication date: July 17, 2014Applicant: KABUSHIKI KAISHA YASKAWA DENKIInventors: Zhenning CHEN, Tomohiro KAWACHI, Kenji TOMOHARA, Koji HIGASHIKAWA, Masashi TAKENOUCHI
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Publication number: 20130009586Abstract: An inverter device according to an embodiment includes a constant power controller. The constant power controller computes and outputs, when a value of a voltage reference to an AC motor exceeds a predetermined threshold value, a d-axis current reference correction value on the basis of the value of the voltage reference and the predetermined threshold value. Moreover, the constant power controller generates the d-axis current reference correction value by using a constant power model determined by a torque reference or a speed reference and a supplied direct voltage at an output switching timing determined based on a winding switching signal and outputs the d-axis current reference correction value for a predetermined time.Type: ApplicationFiled: June 28, 2012Publication date: January 10, 2013Applicant: KABUSHIKI KAISHA YASKAWA DENKIInventors: Zhenning CHEN, Tomohiro KAWACHI, Mitsunori KUZUSHIMA
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Patent number: 6965338Abstract: A cascade A/D converter that has shorter settling time and enables high-speed operation is provided. A cascade A/D converter comprises fundamental constituent elements cascaded in plural stages, each fundamental constituent element comprising a first comparator for inputting an analog input signal, a D/A converter for converting an output of the first comparator to an analog signal again, and a subtractor for subtracting an output of the D/A converter from the analog input signal, the fundamental constituent elements comprising: a second comparator for inputting the analog input signal every least significant bit near a transition point of the first comparator; and an arithmetic operating unit for generating upper bits based on an output of the first comparator and interpolating lower bits based on an output of the second comparator.Type: GrantFiled: November 19, 2004Date of Patent: November 15, 2005Assignee: Yokogawa Electric CorporationInventors: Koichi Irie, Tomohiro Kawachi, Tatsuro Akiyama
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Publication number: 20050162300Abstract: A cascade A/D converter that has shorter settling time and enables high-speed operation is provided. A cascade A/D converter comprises fundamental constituent elements cascaded in plural stages, each fundamental constituent element comprising a first comparator for inputting an analog input signal, a D/A converter for converting an output of the first comparator to an analog signal again, and a subtractor for subtracting an output of the D/A converter from the analog input signal, the fundamental constituent elements comprising: a second comparator for inputting the analog input signal every least significant bit near a transition point of the first comparator; and an arithmetic operating unit for generating upper bits based on an output of the first comparator and interpolating lower bits based on an output of the second comparator.Type: ApplicationFiled: November 19, 2004Publication date: July 28, 2005Applicant: YOKOGAWA ELECTRIC CORPORATIONInventors: Koichi Irie, Tomohiro Kawachi, Tatsuro Akiyama
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Patent number: 6815924Abstract: A technique for controlling an AC motor. An electric power is output to the AC motor. The output current of an electric power converter is controlled based on a difference signal of an output current detection signal and a current command signal of the electric power converter. When the AC motor is in a free run condition, current control is conducted by forcing the current command signal to be zero so that a current in the AC motor is made zero. The amplitude and phase and angular velocity of a residual voltage of the AC motor are found based on a calculated output voltage command.Type: GrantFiled: March 19, 2002Date of Patent: November 9, 2004Assignee: Kabushiki Kaisha Yaskawa DenkiInventors: Hideaki Iura, Yoichi Yamamoto, Tomohiro Kawachi