Energy conserving electric motor power control method and apparatus
First Claim
1. Energy conserving method comprising the steps of:
- providing a source of alternating current power;
operating an a.c. subsynchronous electric motor from the source of a.c. power;
driving a substantially inconstant mechanical load with the motor;
coupling a reactor substantially between the source of a.c. power and at least a main run winding of the electric motor;
determining the reactor to have a first impedance producing a first voltage drop when the motor is driving a minimum level of mechanical load;
determining changes in motor loading; and
,shunting the reactor with an ON-state semiconductor switch during at least a portion of the period of a.c. power flow when the determined motor loading exceeds a predetermined value thereby reducing the level of the first voltage drop.
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Accused Products
Abstract
An energy conserving device which reduces excess level of alternating current power fed to RUN windings of an a.c. electric induction motor whenever the motor is less than fully loaded. A voltage dropping reactor coupled between an a.c. power source and the motor produces about 10-30% reduction in applied motor terminal voltage under reduced motor load running conditions, while a semiconductor switch acts to instantly shunt out the voltage dropping effect of the reactor and couple an increased portion, or full level of a.c. terminal voltage to the motor whenever the motor load increases. Changes in instantaneous levels of motor loading may be determined by changes in motor speed slip, determined from the motor'"'"'s operating power factor, or preprogrammed. As a result of less a.c. power being applied to the motor under all but full-load conditions, a considerable reduction in eddy current and winding resistance losses is obtained which may save 20% or more in electrical energy usage in refrigerators, air conditioners, and other major appliances and as a result considerably lessen power demand from utility lines.
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Citations
20 Claims
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1. Energy conserving method comprising the steps of:
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providing a source of alternating current power; operating an a.c. subsynchronous electric motor from the source of a.c. power; driving a substantially inconstant mechanical load with the motor; coupling a reactor substantially between the source of a.c. power and at least a main run winding of the electric motor; determining the reactor to have a first impedance producing a first voltage drop when the motor is driving a minimum level of mechanical load; determining changes in motor loading; and
,shunting the reactor with an ON-state semiconductor switch during at least a portion of the period of a.c. power flow when the determined motor loading exceeds a predetermined value thereby reducing the level of the first voltage drop. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. Energy conserving means comprising:
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source of alternating current power; induction motor means coupled with the a.c. power source; reactor means for producing a reactive a.c. voltage drop coupled between the source and the motor means; means for producing substantially inconstant mechanical loading of the motor means; means for determining the motor loading produced by the mechanical load producing means; semiconductor switch means coupled with the reactor means and the motor load determining means; means for turning the switch means ON and reducing the voltage drop produced across the reactor means during at least a portion of the period of a.c. power flow when the motor loading is determined to exceed a minimum value. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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17. Energy conserving means comprising:
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source of alternating current power; induction motor means coupled with the a.c. power source; means for producing a reactive voltage drop between the source and the motor means; means for producing substantially inconstant mechanical loading of the motor means; means for determining the motor loading produced by the mechanical load producing means; and
,means for reducing the reactive voltage drop in response to a determined increase in motor loading above a predetermined level. - View Dependent Claims (18, 19, 20)
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Specification