Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-12-16
2002-10-15
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S179000, C310S184000
Reexamination Certificate
active
06465923
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a magnetically journalled electrical drive.
Magnetic journalling technology opens up fields of application of machine and apparatus construction with extremely high requirements on the speed of rotation region, the lifetime, the purity and the sealing tightness of the drive system—thus substantially fields of application which cannot or can only with difficulty be realised using conventional journalling techniques. Various embodiments, such as for example high speed milling and grinding spindles, turbocompressors, vacuum pumps, or pumps for chemical or medical products of high purity, are already being equipped with magnetic bearings.
In the art, loops are alternatively known as phases. Thus the term loop, single loop or multiple loop can alternatively mean phase, single phase or multiple phase.
A conventional magnetically journalled electrical machine (
FIG. 1
) requires, in addition to a machine unit
1
, two radial magnetic bearings
2
and
3
respectively, an axial magnetic bearing
4
, two mechanical interception bearings
5
and
6
respectively, and a total of thirteen power controllers
7
,
8
,
9
and
10
for the excitation of the motoric and magnetic bearing loops.
There are proposals (
FIG. 2
) in the literature for integrating machines and radial magnetic bearings in a magnetic stator unit. Two separate winding systems
11
and
12
for the torque and suspension force winding are inserted multiply layered into grooves in a stator. Both winding systems are three-looped and differ by one in the number of pole pairs. The coils are distributed over a plurality of grooves. The example of
FIG. 2
shows:
a four-pole machine winding
11
(outside): first loop
13
, second loop
14
, third loop
15
a two-pole suspension winding
12
(inside): first loop
16
, second loop
17
, third loop
18
.
The arrows (without reference symbols) from the rotor in the direction towards the stator or from the stator in the direction towards the rotor stand for the direction of the magnetization of the four magnetic rotor segments (e.g. radial or diametral magnetization).
In applications which require no rigid-axis rotor guidance, such as for example in ventilators, fans, pumps or mixers, the axial magnetic bearing and the second radial magnetic bearing can be omitted from the integrated machine-magnetic-bearing embodiment. A prerequisite for this is a disc-shaped embodiment of the rotor with a length dimension (
FIG. 3
) which is small with respect to the rotor diameter. Thus a passive stabilization of the rotor position in the axial direction and the tilt directions can be achieved via the magnetic traction
41
between the stator
39
and the rotor
40
.
In many cases, however the complicated and expensive system construction and therewith the higher manufacturing costs stand in the way of the technical use of magnetic journalling.
SUMMARY OF THE INVENTION
It is therefore an object of the invention simplify the mechanical construction of the machine and magnetic bearing unit, taking into consideration the electronic excitation which is suitable for this.
Preferred embodiments of the invention embodiment are characterised by a considerably simplified stator or rotor construction respectively, the winding construction of the magnetically journalled machine with respect to previously known solutions, as well as the saving of power controllers. Thus, for example, only three loops and six coils are required for a magnetically journalled single phase motor.
Exemplary embodiments of the invention are explained in the following with reference to the drawings.
REFERENCES:
patent: 3572854 (1971-03-01), Danby
patent: 5036235 (1991-07-01), Kleckner
patent: 0726638 (1996-08-01), None
patent: 0768750 (1997-04-01), None
patent: WO 97/15978 (1997-05-01), None
Yohji Okada et al.: “Levitation and Torque Control of Internal Permanent Magnet Type Bearingless Motor”IEEE Transactions on Control Systems Technology4(5) 565-571 (Sep. 5, 1996).
A. Chiba et al.: “An Analysis of Bearingless AC Motors”IEEE Transactions on Energy Conversion9(1) 61-68 (Mar. 1, 1994).
Lam Thanh
Ramirez Nestor
Sulzer Electronics AG
Townsend and Townsend / and Crew LLP
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