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AssigneeOtis Elevator Company
InventorsRichard E. Peruggi, Thomas M. McHugh, Edward E. Ahigian, Jerome F. Jaminet, Thomas He, Thomas M. Kowalczyk, Richard E. Kulak, David W. Barrett
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An elevator car door is moved by a variable voltage, variable frequency linear induction motor which is driven open current loop to achieve a desired velocity profile indicated by an incremental linear encoder, with washed out proportional and integral gain. A magnetizing current insufficient to overcome the weight of the door is added in quadrature with the linear force current, and frequency is determined open loop in a predetermined fashion. Pulse width modulation voltage control signals are utilized to apply fixed voltages of correct polarity through a low pass three phase filter to the windings of the motor for correct intervals of time so as to synthesize desired sinusoidal winding currents. A boost of current is provided following each zero crossing of the sinusoidal winding currents to overcome lags therein. A ramp down of voltage avoids dropping the door at the end of door opening and door closing.
A method of operating a linear induction motor for opening and closing an elevator car door to which it is connected, comprising:
In a method of operating a variable voltage, variable frequency linear induction motor which is connected to an elevator car door, for opening and closing the car door, in which a magnetizing current component is added in quadrature to a force inducing current component so as to provide the vector summation thereof, the improvement which comprises limiting the amplitude of the magnetizing current component to an amplitude which insufficient to provide sufficient normal force between the primary and secondary of the linear induction motor to overcome the weight of the elevator car door.
Dependencies are inferred from the claim text.