Electricity: motive power systems – Synchronous motor systems
Reexamination Certificate
1999-02-01
2001-01-23
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Synchronous motor systems
C318S707000, C318S711000, C318S476000, C318S566000
Reexamination Certificate
active
06177777
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an actuation and control method and to the corresponding device, particularly for permanent-magnet synchronous motors.
BACKGROUND ART
Synchronous motors are AC motors which rotate at a fixed rate, known as synchronous rate, which depends on the frequency of the supply voltage and on the number of poles of the motor.
Synchronous motors are generally substantially constituted by a rotor, having a ring of magnetic poles excited with direct current (inductor), and by a stator, constituted by a laminated magnetic core; the armature winding is located in the internal peripheral region of said core, within grooves formed therein, and is connected to the AC supply line by means of terminals.
In the particular case of permanent-magnet motors, the inductor is constituted by a permanent magnet, generally made of alnico or magnetized ferrite, instead of by poles excited with DC current.
Small permanent-magnet synchronous motors are currently in widespread use owing to their simplicity and low cost and are usually used for low power levels.
The synchronous motor, however, entails some drawbacks. First of all, it is not possible to predict the starting rotation direction; moreover, the static torque offered is substantially weak, making startup sometimes difficult even in the presence of relatively small loads.
Various devices have been devised in order to obviate this drawback, but they are particularly complicated and expensive and therefore cannot be used conveniently in motors which must have a modest cost, such as for example those designed for pumps or similar devices.
In many cases, the use of these systems entails structural modifications to the motor, making their use impossible in normal mass-production.
DISCLOSURE OF THE INVENTION
A principal aim of the present invention is to allow the startup of a synchronous motor so as to select the preferred rotation direction and provide a high static torque. These characteristics can be achieved by means of an electronic device which is particularly simple and economical and uses an appropriately programmed microcontroller. This solution allows to minimize the use of discrete external components, to the full advantage of circuit simplicity, reliability, and costs.
The following characteristics are among the advantages of the present invention and are listed by way of non-limitative example.
With the method and corresponding device according to the present invention it is possible to vary the rotation rate of a synchronous motor through a frequency variation, gradually passing from the motor rotation rate to a preset rotation rate. This is achieved by means of a ramp time which is calibrated (according to the characteristics of the motor) so as to maintain synchronism.
It is possible to correct the induction on the stator by means of a curve which is preset in the EPROM of the microcontroller (also referenced to as &mgr;controller hereinafter).
It is possible to implement various curves, which are selected automatically by the microcontroller by means of dedicated software, according to the operating conditions of the motor, for example as a function of the load, of the time required to reach a certain rotation rate, and other parameters.
In other words, the &mgr;controller contains software which contains the information required to define the curve which is most adapted to the operating conditions of the motor.
The stator current is controlled in order to correct the induction curve and to protect the permanent magnet.
There is provided a launching procedure and a presetting operation by using DC current which is modulated so as to avoid demagnetizing the rotor magnet.
The rotation direction and the position of the motor are also controlled by means of sensors.
REFERENCES:
patent: 3903463 (1975-09-01), Kanamori
patent: 4347464 (1982-08-01), Park et al.
patent: 4661756 (1987-04-01), Murphy et al.
patent: 5315225 (1994-05-01), Heinrich et al.
patent: 5373223 (1994-12-01), Akagi et al.
patent: 5569994 (1996-10-01), Taylor et al.
patent: 5675226 (1997-10-01), Riola′
patent: 5701065 (1997-12-01), Ishizaki
patent: 0574823 (1993-12-01), None
patent: 0666639 (1995-08-01), None
patent: 0682404 (1995-11-01), None
Josif Albert
Martin Edgardo San
Modiano Guido
Nappi Robert E.
O'Byrne Daniel
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