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Inverter control apparatus

  • US 4,663,578 A
  • Filed: 05/20/1985
  • Issued: 05/05/1987
  • Est. Priority Date: 05/21/1984
  • Status: Expired due to Fees
First Claim
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1. An inverter control apparatus comprising:

  • an inverter circuit for converting a direct current to an alternating current and feeding the latter to a motor;

    a cushion circuit functioning in response to the output of a frequency setting circuit and producing a frequency command which is free from inducing any abrupt change in the running speed of said inverter circuit;

    a voltage-frequency ratio circuit for deciding, in response to said frequency command, an output voltage at a predetermined voltage-frequency ratio;

    a current detector for detecting the current inputted to said motor;

    a current-value preset circuit for presetting no-load current value relative to said motor;

    a subtracter circuit for subtracting the detected current value of said current detector from the current value preset by said current-value preset circuit;

    a corrective voltage output circuit for producing an output voltage corresponding to a current variation caused by the load of said motor and obtained from said subtracter circuit; and

    a PWM generator circuit for determining the timing to switch said inverter circuit in response to the result of adding the respective output voltages of said corrective voltage output circuit and said voltage-frequency ratio circuit and also in response to the frequency command based on the output frequency of said frequency setting circuit;

    said inverter circuit being equipped with a mode discriminator to discriminate between a power running mode and a regenerative running mode; and

    when said inverter circuit is judged to be in a power running mode by said mode discriminator, a voltage command substantially proportional to the output of said subtracter circuit is added to the output of said voltage-frequency ratio circuit; and

    when said inverter circuit is judged to be in a regenerative running mode by said mode discriminator, a voltage command substantially proportional to the output of said subtracter circuit is subtracted from the output of said voltage-frequency ratio circuit.

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