Patents by Inventor Tetsuo Ugawa

Tetsuo Ugawa 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).

  • Field ground fault detector and field ground fault relay for detecting ground corresponding to DC component extracted ground fault current
    Patent number: 5764462
    Abstract: According to a field ground fault detector, a predetermined resistor is connected in series to a predetermined DC voltage. A DC voltage is applied between an N electrode side field circuit of a generator and a ground through the resistor. A voltage applied between terminals of the resistor is input to a low-pass filter. A voltage applied between the N electrode side field circuit and the ground is input to another low-pass filter. Output voltages of the low-pass filters are input to a level ratio determining circuit. The level ratio determining circuit outputs the determined result of the ground fault to the outside of the field ground fault detector corresponding to these voltages. Thus, even if the DC voltage varies or a higher harmonic voltage takes place in a generator of a thyristor exciting type, it does not affect the detecting sensitivity of the ground fault.
    Type: Grant
    Filed: April 24, 1997
    Date of Patent: June 9, 1998
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Toshio Tanaka, Yoshinori Takei, Tetsuo Ugawa
  • Field ground fault detector and field ground fault relay for detecting ground fault corresponding to DC component extracted from ground fault current
    Patent number: 5675465
    Abstract: According to a field ground fault detector, a predetermined resistor is connected in series to a predetermined DC voltage. A DC voltage is applied between an N electrode side field circuit of a generator and a ground through the resistor. A voltage applied between terminals of the resistor is input to a low-pass filter. A voltage applied between the N electrode side field circuit and the ground is input to another low-pass filter. Output voltages of the low-pass filters are input to a level ratio determining circuit. The level ratio determining circuit outputs the determined result of the ground fault to the outside of the field ground fault detector corresponding to these voltages. Thus, even if the DC voltage varies or a higher harmonic voltage takes place in a generator of a thyristor exciting type, it does not affect the detecting sensitivity of the ground fault.
    Type: Grant
    Filed: February 23, 1995
    Date of Patent: October 7, 1997
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Toshio Tanaka, Yoshinori Takei, Tetsuo Ugawa