Electricity: motive power systems – Induction motor systems – Power-factor control
Patent
1986-10-29
1988-07-19
Shoop, Jr., William M.
Electricity: motive power systems
Induction motor systems
Power-factor control
318807, 318427, 318800, 363 37, 363 64, H02P 736
Patent
active
047587717
ABSTRACT:
This invention relates to an apparatus for driving an ac motor that includes a current controlled type power converter which produces an ac current or power having an arbitrary frequency at its output, a first switch provided to connect the power converter and the ac motor, and a second switch provided to connect an independent ac power supply and the ac motor. The apparatus operates in two switching modes, namely, switching from the ac power supply to the power converter and switching from the power converter to the ac power supply. To perform such a switching operation smoothly, the apparatus of the invention a voltage phase detector circuit for detecting the voltage phase of the ac power supply, detector circuit for detecting a value proportional to the power factor of the ac motor, a holding circuit for holding the value proportional to the power factor for a predetermined time, a current phase detector for detecting the current phase of the ac motor on the basis of the voltage phase of the ac power supply and the value proportional to the power factor, and a switching circuit for causing the first and second switches to be operative in synchronism with the phase detection signal.
REFERENCES:
patent: 4249120 (1981-02-01), Earle
patent: 4409533 (1983-10-01), Kawabata
patent: 4641042 (1987-02-01), Miyazawa
Ando Yasuhiro
Saito Suzuo
Kabushiki Kaisha Toshiba
Shoop Jr. William M.
Young Brian
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