SYNCHRONOUS ELECTRIC MACHINE

• US 3,743,873 A
• Filed: 12/20/1971
• Issued: 07/03/1973
• Est. Priority Date: 01/22/1971
• Status: Expired due to Term

• Current Assignee: Henricus Cornelis Johannes De Jong
• Original Assignee: Henricus Cornelis Johannes De Jong
• Inventors: de Jong, Henricus Cornelis Johannes
• Primary Examiner(s): Skudy, R.
• Application Number:
  US05/209,614
• Time in Patent Office: 561 Days
• Field of Search: 310/45,162,163,164,165,156,113,114
• US Class Current: 310/165
• CPC Class Codes: H02K 19/103 Motors having windings on the stator and a variable reluctance soft-iron rotor without windings
• CPC Class Codes: H02K 19/20 with variable-reluctance soft-iron rotors without winding
• CPC Class Codes: H02K 21/046 with rotating permanent magnets and stationary field winding
• CPC Class Codes: H02K 21/46 Motors having additional short-circuited winding for starting as an asynchronous motor

Abstract

A synchronous electric machine having a stator is provided with a polyphase winding producing a rotating magnetic filed and an annular D.C. winding to produce a coaxial steady field. Sets of rotor poles are disposed in axially spaced transverse planes and permanent magnets consisting of ceramic material of high coercivity and having radially inner and outer faces of opposite polarity are disposed in each transverse plane between the poles, the polarity of the radially outer faces of the permanent magnets being opposed to that induced in adjacent poles by the D.C. winding.

Claims

1. A synchronous A.C. motor comprising, in combination:

a housing having a pair of axially spaced core members disposed therein;

D.C. winding means disposed between said core members for establishing a closed D.C. magnetic field extending axially within said housing and passing radially through said core members;

A.C. winding means extending through said core members and circumferentially of said housing for establishing a rotating magnetic field within said housing;

a rotor journalled in said housing concentrically of said core members and said winding means, said rotor including a shaft having opposite end portions formed of non-magnetizable material and an intermediate portion joining said opposite end portions which is of magnetizable material, said intermediate portion of the shaft being surrounded by said core members and being of an axial length to extend therebeyond, said rotor also including a pair of squirrel cage winding means fixed to said intermediate portion of the shaft, each said squirrel cage winding means including circumferentially spaced electrically conducting bars and axially spaced end rings between which said bars extend and which end rings are disposed in planes substantially straddling a respective core member and a pole piece disposed between said end rings, each pole piece presenting a plurality of radially projecting poles through which some of said conducting bars extend and said poles being separated by circumferentially equidistant radially recessed portions whereby said D.C. winding means induces said D.C. magnetic field to pass axially through said intermediate portion of the shaft and radially through said said poles to said core members; and

a plurality of permanent magnets disposed within each squirrel cage winding, one of said permanent magnets being disposed in each of said radially recessed portions of said pole pieces and presenting radially inner and outer surfaces of opposite polarity in which the radially outer surface of each permanent magnet is of polarity opposite to that induced by said D.C. winding means in the poles of that squirrel cage winding with which such permanent magnet is associated.

2. A synchronous electric machine according to claim 1, characterized in that the permanent magnets are in the form of segments of a circle.

3. A synchronous electric machine according to claim 1, characterized in that the permanent magnets are plate-shaped and are each bounded by a soft-iron pole shoe having the shape of a segment of a circle.

4. A synchronous electric machine according to claim 1, characterized in that the axial length of the permanent magnet is greater than that of the squirrel cage winding means.

5. A synchronous electric machine according to claim 1, characterized in that the permanent magnets consist of ceramic material of high coercivity.

6. A synchronous electric machine according to claim 3 characterized in that axially extending openings are formed in each pole piece adjacent the end regions of said radially recessed portions.

7. A synchronous electric motor comprising, in combination:

a housing having a pair of axially spaced annular core members therein;

annular D.C. winding means disposed between said core members for establishing a closed D.C. magnetic field extending axially within said housing and passing radially through said core members;

A.C. winding means extending through said core members and circumferentially of said housing for establishing a rotating magnetic field within said housing;

a rotor journalled in said housing cOncentrically of said core members and of said winding means, said rotor including a pair of axially spaced squirrel cage winding means disposed in registry respectively with said core members and each including an annular pole piece having circumferentially spaced radially projecting poles defining recessed regions therebetween, the poles of one squirrel cage winding means being disposed in axial alignment with the recessed regions of the other squirrel cage winding means, said rotor also including a shaft intermediate portion of magnetizable material projecting through both said squirrel cage winding means and upon which said annular pole pieces are engaged; and

a permanent magnet associated with each of said recessed regions, each permanent magnet having radially spaced inner and outer surfaces of opposite polarity in which the inner surface is disposed in close proximity to said shaft intermediate portion and the outer surface is of polarity opposite to that induced in the associated pole piece by said D.C. magnetic field.