Electricity: motive power systems – Synchronous motor systems
Reexamination Certificate
2000-03-13
2001-06-19
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Synchronous motor systems
C318S430000, C318S724000
Reexamination Certificate
active
06249103
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a driver circuit for a synchronous alternating-current motor.
More specifically, the subject of the invention is a driver circuit for a synchronous motor comprising a stator with at least one winding arranged around a substantially U- or C-shaped pack of magnetic plates between the pole ends of which a permanent-magnet rotor is mounted for rotation.
Alternating-current synchronous motors of this type are used, for example, for driving pumps such as pumps for aquariums or for household appliances.
A problem with these motors is that, upon starting, they typically develop a very low torque which is generally insufficient to overcome the resisting torque offered by the load, for example, the resisting torque of a pump rotor immersed in a liquid.
Various solutions, mostly of a mechanical nature, have been proposed for addressing this problem. For example, in one known solution, the rotor of the motor is disconnected from the load upon starting and is then connected thereto only after a certain angular displacement has been performed.
A coupling for achieving a mechanical connection of this type between the rotor and the load of a synchronous alternating-current motor is described, for example. in European patent application No. 0 207 430.
Couplings of this type, however, have the disadvantage of being quite noisy in operation.
The object of the present invention is to provide a driver circuit for a synchronous, alternating-current motor of the type specified above which addresses shortcomings associated with the prior art.
SUMMARY OF THE INVENTION
In one aspect of the present invention, a driver circuit is presented for a synchronous, alternating-current motor comprising a stator with at least one winding arranged around a substantially U- or C-shaped pack of magnetic plates between pole ends of which a permanent-magnet rotor is mounted for rotating. The driver circuit includes a first triac connected in series with the winding between a terminal of an alternating-current voltage supply. The first triac has a gate connected to an intermediate point of the stator winding of the motor. A second triac is connected between the intermediate point of the winding of the motor and the terminal of the voltage supply to which the first triac is connected. A control circuit is connected to the gate of the second triac that is operable to, each time the motor is connected to the voltage supply, initially make the second triac conductive and consequently cut off the first triac for a predetermined initial period of time, and cut off the second triac and allow the first triac to become conductive after the predetermined initial period of time, so that, during the predetermined initial period of time, only a portion of the winding of the motor is connected to the voltage supply by via the second triac and, after the predetermined initial period of time, the whole winding of the motor is connected to the voltage supply.
REFERENCES:
patent: 3761792 (1973-09-01), Whitney et al.
patent: 3792324 (1974-02-01), Suarez et al.
patent: 4896105 (1990-01-01), Engel et al.
patent: 5483139 (1996-01-01), Welles, II
patent: 0574823 A2 (1993-12-01), None
Acquaviva Sebastiano
Alvaro Nicolino
Howrey Simon Arnold & White , LLP
Plaset Spa
Ro Bentsu
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