Speed control for electric motor
US4230977A · kind A · utility
Inventor
Key dates
| Filing date | Jul 3, 1978 |
| Grant date | Oct 28, 1980 |
| Priority date | — |
| Expiry date | Jul 3, 1998 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02P7/288
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A speed control system for an electric motor is provided for use, for example, in dental offices to control dental drill motors, and the like, which in one embodiment provides speed control from either a foot-operated potentiometer or a panel hand-operated potentiometer. The system includes a negative resistance generating circuit which maintains constant speed of the motor for any particular speed setting in the presence of variations in the mechanical load on the motor. The circuit also provides dynamic braking which immediately slows the motor and brings the motor to an almost immediate stop when the speed control potentiometers are returned to their neutral positions. A guardian circuit is also provided in the system which prevents motor burn-up in the presence of a sustained overload condition.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.