Commutation of a universal motor operating in brake mode
US5677586A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 25, 1994 |
| Grant date | Oct 14, 1997 |
| Priority date | — |
| Expiry date | Aug 25, 2014 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S388/932
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A universal motor (18) for a power tool (10) has a stator assembly (22) and an armature (24). The stator assembly includes a plurality of interconnected field windings (28-34) to which current is supplied to run the motor. The armature has a commutator (36) including brushes (40a, 40b) for circulating current through the armature. To quickly and safely brake the motor, without excessively damaging the brushes, a switch (16) is interposed between an AC power source for the motor and the armature. In one embodiment, the switch shorts the armature during braking. In this embodiment, the switch includes sets (56, 58, 60) of electrical contacts by which the inner field windings (28, 30) are connected in series with the outer filed windings (32, 34); and the field windings are series connected with the armature. When the motor is braked, the switch is moved to a position opening the electrical connection between the power source and the outer field winding, while maintaining the electrical connection with the inner field windings. The switch includes electrical contacts across which the armature is connected when the motor is braked. The armature is shorted across these electrical contac…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.