SYSTEM AND METHOD FOR SAVING ENERGY WHEN DRIVING MASSES HAVING PERIODIC LOAD VARIATIONS

摘要

A system and method are described for conserving energy by decoupling a supply voltage to an electric motor operating under periodic load variations. A time segment value corresponding to a duration of periodic load variations is obtained and the supply voltage is adjusted to maintain an observed phase angle for a supply voltage and current at a value corresponding to a target phase angle. At least one off-time period is identified during the time segment value that corresponds to when the adjusted supply voltage is applied to the motor. During a remainder of the time segment value, at least one turn-on time period is provided when the supply voltage is coupled to the motor. The system may enter to a closed-loop control process after a predetermined period of time to adjust to any changes in the periodic load variations.

主权项

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.