Motor stoppage detection using back emf voltage
US5003241A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 15, 1989 |
| Grant date | Mar 26, 1991 |
| Priority date | — |
| Expiry date | Feb 15, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02P3/18
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An AC electric motor can be braked by applying current pulses to the motor when the polarity of the supply voltage is opposed to the polarity of the back electromotive force (emf) voltage across a stator coil of the motor. This current application continues until the motor has stopped. The stoppage is detected by sensing when the current is being applied during every cycle of the supply voltage. Thereafter, the polarity pattern of back emf voltage induced across each of the motor stator coils is sensed. The occurrence of a back emf voltage polarity pattern that remains unchanged for a given number of cycles is detected. Thereafter, a change in this pattern is sensed and the braking current application either ceases or continues for an additional predetermined interval.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.