Speed reducing control system for a polyphase electric motor
US4791341A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 19, 1988 |
| Grant date | Dec 13, 1988 |
| Priority date | — |
| Expiry date | Jan 19, 2008 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02T10/7072
- WIPO fieldTransport
- WIPO sectorMechanical engineering
Abstract
A variable speed 3-phase a-c motor is connected to a 3-phase source of alternating voltage via a plurality of controllable solid state electric valves which are so arranged and controlled that motor speed can be reduced by skipping selected cycles of the source voltage. For half speed operation 12 valves are arranged to interconnect the source and motor phases, and over two consecutive periods of the source voltage six separate, uniformly spaced "firing windows" are selected during which the conducting states of different pairs of these valves are initiated in a predetermined pattern that results, in each phase of the motor, in a double-pulse current waveform having one-half the fundamental frequency of the source voltage.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.