Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-04-28
2002-02-26
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S06800R, C318S721000
Reexamination Certificate
active
06351048
ABSTRACT:
The invention relates to an electrical rotary drive in accordance with the preamble of independent claim
1
, and to a blood pump with a rotary drive of this kind.
Blood pumps, which are usually designed as axial or as centrifugal pumps, serve for the forwarding of blood and are used for example in the framework of operations on the heart for maintaining the blood circulation. Furthermore, implantable blood pumps are known which are implanted into the body of the patient for the temporary or chronic support of the heart activity.
In blood pumps it must be ensured that no contamination of the forwarded blood occurs. Therefore in blood pumps the rotor of the electromagnetic drive and/or the pump rotor is/are preferably magnetically journalled without contact. This magnetic journalling of the rotor can be realized either through separate magnetic bearings, that is, bearings which are different from the drive; or the magnetic journalling is realized by the stator of the drive.
In WO-A-96/31934 for example a rotation pump is disclosed which is suitable as a blood pump and which is designed as a so-called bearingless motor. This is an electromagnetic rotary drive in which the rotor is journalled without contact with respect to the stator by means of magnetic forces, with no separate magnetic bearings being present for the rotor. For this the stator is designed as a bearing and drive stator comprising a drive winding and a control winding. With these two windings a magnetic rotary field can be produced which on the one hand exerts a torque on the rotor which causes it to rotate, and which on the other hand exerts any desired settable transverse force on the rotor, so that its radial position can be actively controlled or regulated respectively. Thus three degrees of freedom of the rotor can be actively regulated. With respect to three further degrees of freedom, namely its axial deflection in the direction of the axis of rotation and tiltings with respect to the plane which is perpendicular to the axis of rotation (two degrees of freedom) the rotor is passively magnetically, which means not controllably, stabilized through reluctance forces.
The term “bearingless motor” is to be understood in this sense for the following explanations. With respect to the further details of the design and especially of the control or regulation respectively of the bearingless motor, reference is made here, in addition to the already cited WO-A-96/31934, to WO-95/18925.
Furthermore, blood pumps should be compact and space saving, in particular in the case of an implantation in the body, but nevertheless be able to achieve a pumping performance which corresponds at least to that of the heart. For this it is proposed e.g. in WO-A-96/31934 to provide the rotor of the bearingless motor with vanes, so that the rotor of the rotary drive is identical to the pump rotor, and thus forms an integral rotor. This rotor thus serves as a drive rotor, a bearing rotor and a pump rotor, through which a very compact and high performance blood pump can be realized.
A problem in known bearingless motors is to be seen in that when faults arise, such as for example the failure of an amplifier stage or the breaking of an electrical line in one of the phases of the stator, a correct functioning of the drive and/or of the magnetic journalling of the rotor is no longer ensured. This represents an enormous safety hazard in particular in very sensitive uses, e.g. in implanted blood pumps. A failure of the rotor drive or of the magnetic rotor journalling can namely have very severe, possibly even fatal consequences. The invention is thus dedicated to the task of significantly reducing this safety hazard.
The object of the invention is therefore to provide an electrical rotary drive which is designed as a bearingless motor and which is fault tolerant both with respect to the magnetic journalling of the rotor and with respect to the driving of the rotor, which means that a correct operation of the bearingless motor with reliable magnetic journalling of the rotor and reliable driving of the rotor should still be possible when faults arise.
The electrical rotary drive which satisfies this object is characterized by the features of the independent claim
1
.
The electrical rotary drive in accordance with the invention, designed as a bearingless motor, thus has a magnetically journalled rotor and a stator which comprises a drive winding having at least two loops for producing a magnetic drive field which produces a torque on the rotor, and a control winding having at least three loops for producing a magnetic control field by means of which the position of the rotor with respect to the stator can be regulated, with each loop of the drive winding belonging to a different electrical drive phase, and with each loop of the control winding belonging to a different electrical control phase, as well as a setting device which provides each loop of the drive winding and each loop of the control winding with a phase current or a phase voltage as a setting parameter, with the setting device being designed in such a manner that the setting parameter for each loop of the drive winding and for each loop of the control winding can be regulated independently of the setting parameters for the other loops.
For this the setting device preferably comprises for each loop of the drive winding and for each loop of the control winding a separate bipolar power amplifier, which is integrated into a control apparatus for the rotary drive.
The rotary drive in accordance with the invention, which is designed as a bearingless motor, operates in fault-free normal operation with at least two drive phases and at least three control phases. The terms “drive phase” and “control phase” respectively are used in each case to mean a loop of the drive winding or of the control winding respectively and the part of the setting device which supplies it. Since the setting parameters, that is, the phase voltage or the phase current, can be regulated for each loop of the drive winding and for each loop of the control winding completely independently of the setting parameters for the other loops, each drive phase and each control phase can be operated independently of the remaining electrical phases. Thus the rotary drive can continue to be operated with a reduced number of drive phases and/or control phases respectively when a fault arises in a drive phase and/or a control phase, e.g. in the event of a failure of a complete phase, without concessions regarding the correct functioning either of the magnetic journalling or of the driving of the rotor of the rotary drive being necessary.
The minimum requirement for an enduring correct operation is that one drive phase and two control phases of the rotary drive are still fault-free, which means that at least one drive phase and at least one control phase can fail completely without the reliable operation of the rotary drive being endangered. Depending on how many drive and control phases the rotary drive in accordance with the invention is equipped with, it can still continue to be operated even after a failure of a plurality of drive and/or control phases.
Since the rotary drive in accordance with the invention can be operated with a reduced number of phases, it is in principle irrelevant where a fault arises in a drive phase or in a control phase. Thus for example a power amplifier can fail, or a break can occur in a line in one loop of the drive winding or of the control winding respectively, or a short circuit can arise in a power amplifier or in a winding loop of the drive or the control winding; and in spite of such a fault a further reliable operation of the rotary drive is possible. As a result of this high fault tolerance the rotary drive in accordance with the invention brings about a considerable increase in the operating reliability.
The rotary drive in accordance with the invention with its at least two-phase design of the drive winding in the fault-free normal case is preferably a permanent-magnetically excited rotary fie
Gempp Thomas
Schob Reto
Levitronix LLC
Mullins Burton S.
Townsend and Townsend / and Crew LLP
LandOfFree
Electrical rotary drive does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrical rotary drive, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrical rotary drive will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2972889