Energy conserving electric induction motor field control method and apparatus
First Claim
1. Induction motor field excitation method comprising steps of:
- winding a motor RUN field comprising a major winding portion and at least one minor winding portion;
determining a motor loading signal;
energizing the major winding portion when level of the determined motor loading signal is about that of a fully loaded said motor; and
,energizing a seriate connection of the major winding portion and at least one said minor winding portion when the level of the determined motor loading signal is about a predetermined level less than that of a fully loaded said motor.
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Abstract
An alternating current induction motor having a tapped RUN winding for developing different levels of stator field excitation which induces rotational torque into a rotor having an output member that drives various levels of mechanical load. Instant motor loading is sensed as a change in power factor or subsynchronous slip speed and the level of RUN winding excitation, together with the resulting magnetic field strength, is immediately changed to compensate for the sensed load changes. The change in RUN winding excitation is brought about by having a RUN winding the full extent of which may be coupled with a.c. power to produce magnetic field strength and resulting output member torque at least sufficient to operate the motor under minimum load conditions, and at least one tapped portion of the RUN winding which may be alternatively coupled with the a.c. power to produce an increased level of magnetic field strength necessary for operating the motor under maximal, or at least an increased level of motor loading.
60 Citations
20 Claims
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1. Induction motor field excitation method comprising steps of:
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winding a motor RUN field comprising a major winding portion and at least one minor winding portion; determining a motor loading signal; energizing the major winding portion when level of the determined motor loading signal is about that of a fully loaded said motor; and
,energizing a seriate connection of the major winding portion and at least one said minor winding portion when the level of the determined motor loading signal is about a predetermined level less than that of a fully loaded said motor. - View Dependent Claims (2, 3, 4)
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5. Induction motor field excitation method comprising the steps of:
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producing the field excitation with RUN windings comprising seriately wound major and minor portions; producing output member rotational torque in response to instant level of the field excitation; coupling the output member with a mechanical load; determining changes in torque demand level of the mechanical load; seriatim coupling of a.c. power with the major and minor portions of the RUN winding effective to produce a moderate said level of field excitation when the determined said torque demand level is less than a predetermined value; and
,coupling the a.c. power preferably with the major portion of the RUN winding effective to produce an increased said level of field excitation when the determined said torque demand level is at least the predetermined value. - View Dependent Claims (6, 7, 8, 9, 10)
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11. Induction motor means comprising:
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means for producing magnetic flux field excitation including RUN winding means comprising a seriately coupled plurality of RUN winding portions; means for producing a level of rotational torque at an output member in proportion to the field excitation; means for producing fluctuant mechanical loading of the output member; means for producing a load level signal value proportional to changes in level of the rotational torque coupled between the output member and the mechanical loading means; means for coupling a source of a.c. power with the plurality of RUN winding portions when the load level signal value is less than a predetermined value; and
,means for coupling the source of a.c. power with a predetermined fewer number of the RUN winding portions when the load level signal value is at least the predetermined value. - View Dependent Claims (12, 13, 14, 15)
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16. Induction motor means comprising:
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stator means; RUN winding means comprising at least a seriately coupled first portion and second portion effective for producing magnetic field flux excitation in the stator means; rotor means coupled with the magnetic field excitation and effective to produce rotational torque in an output member; load means coupled with the output member; means for determining a motor load level signal value; means for seriately coupling the first portion and second portion of the RUN winding means with a source of a.c. power when the determined value of the motor load level signal is less than a predetermined value; means for seriately coupling the source of a.c. power ordinarily with only the first portion RUN winding means when the determined level of the motor loading is at least the predetermined value. - View Dependent Claims (17, 18, 19, 20)
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Specification