Synchronous electric motor

Details Synchronous electric motor Synchronous electric motor

1999-10-01

2001-05-01

Nappi, Robert E. (Department: 2837)

Electricity: motive power systems

Induction motor systems

C318S700000

Reexamination Certificate

active

06225775

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a synchronous electric motor.
More specifically, the subject of the invention is a single-phase synchronous electric motor comprising:
a rotor or inductor with permanent magnets, with at least one pair of poles,
a stator or armature having a winding wound around a magnetic circuit,
position-detecting means associated with the rotor for providing driving signals in dependence on the angular position of the rotor, and
a driver circuit connected to the detecting means and to the stator winding and having a pair of terminals for connection to an alternating voltage supply, the driver circuit being arranged to control the flow of current in the stator winding in dependence on the signals supplied by the position-detecting means.
Synchronous motors of this type are characterized in that, during steady-state operation, the angular velocity &ohgr; (in revolutions/minute) is related to the frequency f of the alternating supply voltage (in Hz) and to the number p of pairs of poles by the known equation:
&ohgr;=
f·
60
/p
Thus, for example, a single-phase synchronous motor with two poles (p=1) supplied with a 50 Hz alternating voltage rotates, during steady-state operation, at an angular velocity &ohgr;=3000 revolutions/minute.
A synchronous electric motor with 4 poles (p=2), also supplied with a 50 Hz alternating voltage, rotates, during steady-state operation, at an angular velocity of 1500 revolutions/minute.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a synchronous electric motor of the type specified above having, in general p (p=1, 2 . . . ) pairs of poles but having, during steady-state operation, a synchronism rate of revolution equal to that of a motor with 2p poles.
This and other objects are achieved, according to the invention, by a synchronous electric motor, the main characteristics of which are defined in appended claim
1
.


REFERENCES:
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patent: 4678972 (1987-07-01), Lehnhoff et al.
patent: 4698562 (1987-10-01), Gale et al.
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patent: 4791341 (1988-12-01), Brown et al.
patent: 4818922 (1989-04-01), Sears et al.
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patent: 5764019 (1998-06-01), Webster
patent: 0574823A2 (1993-06-01), None
patent: 0682404A2 (1995-04-01), None
patent: 0851570A1 (1997-12-01), None

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