Electric motor speed control apparatus and method
US4996470A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 14, 1989 |
| Grant date | Feb 26, 1991 |
| Priority date | — |
| Expiry date | Jul 14, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02P3/18
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
The speed of an induction motor is reduced by initially using dynamic electrical braking to slow the motor to a speed at which it will not remain synchronized to the A.C. supply frequency. At this point, A.C. cycle skipping is employed to apply current to the motor at an effective frequency which is a fundamental frequency component of the A.C. supply line frequency. The motor becomes synchronized at this fundamental frequency component. If desired, the motor can be brought to a complete stop by discontinuing the cycle skipping and using the dynamic braking again for a given period of time. This technique provides a very controlled stopping of the motor enabling equipment driven by the motor to be accurately positioned.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.