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System and method for saving energy when driving masses having periodic load variations

  • US 9,240,745 B2
  • Filed: 02/27/2014
  • Issued: 01/19/2016
  • Est. Priority Date: 09/08/2009
  • Status: Active Grant
First Claim
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1. A method of saving energy for an electric motor having periodic load variations, the method comprising the steps of:

  • detecting a supply voltage and a current applied to said motor;

    observing a phase angle between the supply voltage and the current;

    obtaining a time segment value corresponding to a duration of the periodic load variations;

    comparing the observed phase angle with a threshold phase angle;

    adjusting the supply voltage when the observed phase angle approaches the threshold phase angle, the supply voltage being adjusted by changing a firing angle of a switching device that electrically couples the supply voltage and the motor, the supply voltage being adjusted to maintain the observed phase angle at a value corresponding to a target phase angle;

    applying the supply voltage to said motor when the firing angle falls below a threshold firing angle;

    identifying at least one off-time period during the time segment value, the at least one off-time time period corresponding to when the adjusted supply voltage is applied to the motor;

    decoupling the supply voltage to the motor during the at least one off-time period; and

    coupling the supply voltage to the motor during a remainder of the time segment value, the remainder of the time segment value including at least one turn-on time period.

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