Emergency power system for capacitor start motors
First Claim
1. An emergency power circuit for an induction motor having at least first and second windings, said motor normally operating at a normal speed determined by connection to a commercial frequency power line subject to failure, comprising, in combination:
- an emergency power DC storage battery;
inverter means supplied by said battery and having output terminals connectable to said motor;
a control circuit for said inverter means; and
said control circuit establishing a run frequency to run said motor at a running speed considerably less than said normal speed.
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Accused Products
Abstract
An emergency power circuit powers an induction motor which has at least first and second windings. The motor is normally operating at a normal speed determined by connection to commercial frequency power line, but which is subject to failure. During failure the emergency power circuit is used to supply emergency power from a DC storage battery. An inverter is supplied by the battery and has an output connectable to the motor. A control circuit for the inverter establishes a first frequency to run the motor at a running speed which is considerably less than the normal speed. Single, two-phase and three-phase systems are disclosed as well as a soft start system to start the motor at about one-fourth speed and run it at one-half speed. Preferably a high frequency oscillator is used with the frequency divided dozen to operate the motor at a speed below normal 60 Hz energization speed. The foregoing Abstract is merely a resume of general applications, it is not a complete discussion of all principles of operation or applications, and is not to be construed limitation on the scope of the claimed subject matter.
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Citations
23 Claims
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1. An emergency power circuit for an induction motor having at least first and second windings, said motor normally operating at a normal speed determined by connection to a commercial frequency power line subject to failure, comprising, in combination:
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an emergency power DC storage battery; inverter means supplied by said battery and having output terminals connectable to said motor; a control circuit for said inverter means; and said control circuit establishing a run frequency to run said motor at a running speed considerably less than said normal speed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method of operating an induction motor having a starting capacitance connectable across a winding of the motor comprising the steps of:
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providing a first power source to the motor at a normal frequency; providing a second power source at an emergency frequency substantially lower than said normal frequency; connecting the second power source to the motor upon a failure of the first power source and a request for motor action; and changing the starting capacitance of the motor to correspond to whichever of the first and second power sources is connected to the motor.
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Specification