Starting a brushless DC motor
US5198733A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 13, 1990 |
| Grant date | Mar 30, 1993 |
| Priority date | — |
| Expiry date | Nov 13, 2010 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02P6/22
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A brushless DC motor is started by initially specifying an arbitrary rotor position and applying such drive currents to the three motor phase inputs that the rotor moves to the predetermined position and thereafter applying a current pulse to the appropriate winding to cause the rotor to move in the desired rotational direction. After the motor has begun to turn, the current supply to the motor phase inputs is interrupted. The current in the motor is allowed to decay to a level where the I and R voltage drops in the windings are substantially less than the back EMFs at the speed at which the motor is turning. The small back EMFs generated in the windings are sampled and monitored to detect whether the rotor has moved to a position requiring a change in commutation. Drive current is supplied to the three motor phase inputs in accordance with whether or not a need for a change in commutation was detected by the sample so that the rotor will continue to turn in the required direction. The current interruption and sampling are repeated at a rate greater then the commutation rate (i.e. more frequently as the motor speed increases) and at a rate directly proportional to the speed of the …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.