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Control apparatus for induction motor

  • US 5,304,912 A
  • Filed: 09/21/1992
  • Issued: 04/19/1994
  • Est. Priority Date: 09/21/1991
  • Status: Expired due to Fees
First Claim
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1. A control apparatus for an induction motor, comprising:

  • an inverter for supplying a drive current to said induction motor on the basis of a predetermined control signal;

    a rotational speed sensor for detecting a rotational speed of said induction motor;

    a V/f control circuit for generating a control signal for said inverter in response to a predetermined speed command inputted to said V/f control circuit;

    a vector control circuit for generating a control signal for said inverter on the basis of said speed command signal and a rotational speed signal supplied from said rotational speed sensor;

    an abnormality detecting circuit having an input supplied with an output signal of said rotational speed sensor for detecting abnormality of said rotational speed sensor; and

    a change-over circuit having inputs supplied with the output signals of said V/f control circuit and said vector control circuit, respectively, for selecting the control signal from said V/f control circuit when abnormality of said rotational speed sensor is detected by said abnormality detection circuit, while selecting the control signal from said vector control circuit when no abnormality is detected in said rotational speed sensor, said selected control signal being output to said inverter.

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