Variable speed drive for induction motor
US3991354A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 29, 1975 |
| Grant date | Nov 9, 1976 |
| Priority date | — |
| Expiry date | May 29, 1995 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02P27/045
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A variable speed drive is provided for a polyphase induction motor. The motor is connected through a contactor to a constant frequency polyphase alternating current power source for starting and for full speed operation but is supplied by a variable frequency source in a single phase operating mode when reduced speed levels are desired. In the single phase operating mode, low speed operation is provided by driving the motor with a cycloconverter which converts power from the polyphase source to single phase alternating current of a predetermined lower frequency. The motor speed decreases from a higher level to a lower level by coasting, with gate signals of the cycloconverter suppressed until a desired lower speed is reached. Initiation of contactor and cycloconverter operation is coordinated by motor speed sensing means.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.