Smooth and quiet linear induction motor elevator door operation
Number of patents in Portfolio can not be more than 2000
United States of America Patent
Stats
-
Mar 5, 1996
Grant Date -
N/A
app pub date -
Apr 6, 1994
filing date -
Apr 6, 1994
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
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.
First Claim
Other Claims data not available