Maintaining open loop current drive to linear induction motor
US5503248A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 6, 1994 |
| Grant date | Apr 2, 1996 |
| Priority date | — |
| Expiry date | Apr 6, 2014 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE05Y2900/104
- WIPO fieldHandling
- WIPO sectorMechanical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.