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Motor control method and apparatus therefor

  • US 4,641,067 A
  • Filed: 09/11/1985
  • Issued: 02/03/1987
  • Est. Priority Date: 09/13/1984
  • Status: Expired due to Term
First Claim
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1. The method of controlling operation of an electric motor to change an operating condition of said motor upon the occurrence of an abnormal load condition comprising the steps of:

  • (a) initiating a timing means during periods of operation of said motor to establish a series of predetermined time periods Δ

    T;

    (b) measuring current I applied to said motor during said periods of operation as a measure of load condition thereof;

    (c) deriving an initial value Imin representative of load current at the beginning of each said time period Δ

    T;

    (d) Adding a predetermined value Δ

    X to said value Imin to set a reference value Ir representative of said abnormal load condition;

    (e) periodically measuring sucessive values of I at successive time intervals substantially shorter than time period Δ

    T;

    (f) comparing said sucessive measured values of I with Ir and with said value Imin;

    (g) if within a time period Δ

    T the value of I should decrease below said value Imin and then begin to increase, resetting said timing means to begin a new time period Δ

    T and setting a new reference value Ir; and

    (h) if within a time period Δ

    T the measure value I should increase to equal or exceed the value Ir, recognizing such increase as said abnormal load condition and initiating a change in operating condition of said motor in response thereto.

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