Circuit and method for detecting deceleration rates of a polyphase DC motor
US5294877A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 30, 1992 |
| Grant date | Mar 15, 1994 |
| Priority date | — |
| Expiry date | Apr 30, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02P6/182
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A circuit for operating a polyphase dc motor includes first circuitry for determining when the back emf of the floating driving coils crosses zero. A first counter counts a time period between a first set of zero crossings, and a second counter is loaded with the count reached by the first counter. The second counter counts a time period between a subsequently occurring set of zero crossings. If the second counter reaches zero before the occurrence of a third zero crossing, a warning signal is generated. A method for determining if a deceleration rate of a polyphase dc motor exceeds a predetermined threshold includes measuring a first period between a first set of zero crossings of the back emf of the floating driving coils, and comparing the measurement of the first period with a subsequent period between a subsequent set of zero crossings. If the subsequent period is larger than the first period by a predetermined amount a warning signal is produced. The first period is measured by counting up from zero at a first predetermined rate from a first zero crossing until a second zero crossing occurs. The comparison of the measurement of the first period with a subsequent period is don…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.