Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-08-26
2001-10-02
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S06800R, C310S168000, C318S798000, C318S800000, C318S801000, C318S806000
Reexamination Certificate
active
06297574
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a magnetic bearing apparatus for the journalling of a body, in particular of a rotor, in accordance with the preamble of the independent patent claim.
Magnetic bearing apparatuses for the non-contact journalling of bodies, such as for example rotors of electric motors, rotating shafts, pump rotors or non-rotating bodies, are increasingly gaining in importance. Bearing apparatuses of this kind typically comprise a stator, which is provided with at least one electrical winding by means of which a magnetic control field can be produced and regulated. By means of this regulatable control field, magnetic forces are exerted on the rotating or levitating body to be journalled which hold the latter without contact in a desired position relative to the stator.
A magnetic bearing is disclosed in WO-A-97/07340, the stator of which comprises a three-phase rotary current winding for the production of the magnetic control field. The radial magnetic bearing forces are produced through the superposition of a unipolar magnetic field on this rotary field.
In WO-A-95/18925 a special form of a magnetic bearing apparatus is disclosed, namely a so-called bearing-free motor. A bearing-free motor is an electromagnetic rotary drive in which the rotor is journalled with respect to the stator without contact by means of magnetic forces. The characteristic to which the bearing-free motor owes its name is that the stator is designed as a bearing and drive stator and the rotor both as a bearing and drive stator and as a drive rotor. This means that in a bearing-free motor the magnetic bearing and the drive device form an inseparable physical unit. Separate magnetic bearings or separate drive apparatuses for the rotor are not provided. As a consequence, the so-called bearing-free motor is also a magnetic bearing apparatus with an integrated rotary drive.
The bearing and drive stator of a bearing-free motor is designed or, respectively, provided with windings in such a manner that it produces an electromagnetic rotary field which, on the one hand, exerts a torque on the rotor which drives its rotation about the axis of rotation, and which, on the other hand, exerts a transverse force on the rotor which can be set as desired so that its radial position relative to a plane perpendicular to the axis of rotation can be predetermined or actively regulated respectively. For this the electrical windings of the stator—as for example has already been disclosed in the already cited WO-A-95/18925—comprises a drive winding with the number of pole pairs p and a control winding with the number of pole pairs p±1 for the production of a magnetic control field. An electromagnetic rotary field can be produced with these two windings which exerts both a driving torque and also a transverse force which can be set as desired on the rotor. The rotor can thus be actively controlled or regulated respectively with respect to three degrees of freedom, namely the rotation about the axis of rotation A and its radial position relative to a plane perpendicular to the axis of rotation (two degrees of freedom). With respect to three further degrees of freedom, namely its axial deflection in the direction of the axis of rotation and tiltings relative to the plane perpendicular to the axis of rotation A (two degrees of freedom) the rotor is passively magnetically, that is, not controllably, stabilized by reluctance forces.
The term “bearing-free motor” is to be understood in this sense for the following explanations. Reference is made here to WO-A-95/18925 for further details of the design and especially the control or regulation respectively of the bearing-free motor.
In the bearing-free motor in accordance with WO-A-95/18925 the control winding for the production of the magnetic control field by means of which the radial position of the rotor is regulated can also be designed as a three-phase winding in a manner similar to that disclosed in WO-A-97/07340 for the magnetic bearing. In the last named publication several reasons are also mentioned why it is advantageous to design the control winding as a three-phase rotary current winding.
A problem with known magnetic bearing apparatuses is that when faults arise, such as for example the failure of an amplifier stage or the breakage of an electrical line in one of the phases of the control winding, a correct functioning of the bearing apparatus is no longer given. This can represent a safety hazard in particular in very sensitive applications, e.g. in blood pumps.
SUMMARY OF THE INVENTION
An object of the invention is thus to provide a magnetic bearing apparatus which still enables a correct operation even when faults arise, which means in particular a reliable magnetic journalling of the body to be journalled.
The magnetic bearing apparatus of the invention thus comprises a stator with a control winding having at least three loops for the production of a magnetic control field by means of which the position of the body relative to the stator can be regulated, with each loop belonging to a different electrical phase, as well as a control device which in a first operating mode supplies each loop with in each case a phase current or in each case a phase voltage as a control parameter. Means are provided in order to regulate the control parameter for each loop independently of the control parameter for the other loops. Furthermore, a monitoring unit is provided which can switch the bearing apparatus into a second operating mode in which a reduced number of phases, which is at least two, produces the magnetic control field.
The bearing apparatus in accordance with the invention can thus be operated in two operating modes. In the first operating mode the magnetic control field is generated by all three phases of the three or higher phase control winding, that is, by all their loops. In the second operating mode the magnetic control field is only produced with a reduced number of phases, which amounts to at least two however.
Thus all the loops of the control winding are no longer used; one or more loops of the control winding are “switched off” in this second operating mode. A two-phase control winding is namely sufficient in order to generate the control field which is required for the regulation of the radial position of the body relative to the stator. For this it is however necessary that the two phase currents or phase voltages can be regulated independently of one another.
Through the two operating modes it is possible to operate the bearing apparatus with a reduced number of phases when a fault arises in one of the phases, for example in the event of the failure of a winding loop as a result of a break in the line or of a short circuit or in the event of the failure of the amplifier which supplies this phase, without concessions on the correct functioning of the magnetic bearing being necessary. This error tolerance, namely that of ensuring a reliable operation of the magnetic journalling even in the event of the failure of one phase, represents an enormous increase in the operating safety in comparison with other magnetic bearings.
The monitoring unit preferably monitors the functioning of each individual phase and, in the event of a failure in one phase, switches the bearing apparatus over into the second operating mode in which only the phases without faults still produce the magnetic control field.
As has already been mentioned it is necessary for the case that the control winding is operated in only two phases any longer that the phase current or the phase voltage can be regulated in the two loops of the control winding independently of one another. Usually the phase currents or the phase voltages for the individual phases are provided by an amplifier unit which is contained in the device.
In a first preferred embodiment the means for the independent regulation of the control parameter (phase current or phase voltage) comprise a star point which is capable of loading, to which each phase is connected and which is placed at a
Jenckel Peter
Reiter Hans-Georg
Schob Reto
Dinh Le Dang
Lust Antriebstechnik GmbH
Ramirez Nestor
Townsend and Townsend / and Crew LLP
LandOfFree
Magnetic bearing apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic bearing apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic bearing apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2573515