WO2009147550A1

WO2009147550A1 - Scalable power transfer device for providing electrical power for a computer tomography device

Info

Publication number: WO2009147550A1
Application number: PCT/IB2009/052031
Authority: WO
Inventors: Peter-Christian E. H. H.-J. Leymann; Max C. Urban
Original assignee: Philips Intellectual Property and Standards GmbH; Koninklijke Philips Electronics NV
Current assignee: Philips Intellectual Property and Standards GmbH; Koninklijke Philips NV
Priority date: 2008-06-02
Filing date: 2009-05-15
Publication date: 2009-12-10
Anticipated expiration: 2010-12-02

Abstract

The invention provides for a scalable power transfer device for providing electrical energy for a computer tomography gantry. The power transfer device (301) comprises two E-core pairs (311, 313) which might be provided with windings (319, 321, 323) depending on a power transfer requirement. The E-cores have a size and geometry which provides winding windows (325, 327) having sufficient volume to accommodate enough windings for power transfer even for the most power consuming applications. However, for less power consuming applications, the number and/or geometry of windings can be easily reduced thereby adapting the power transfer capabilities of the device.

Description

Scalable power transfer device for providing electrical power for a computer tomography device

FIELD OF THE INVENTION

The present invention relates a power transfer device for providing electrical power for a computer tomography (CT) device. Particularly, the invention relates to a power transfer device such as a rotary transformer for transferring electrical power from a stationary part to a rotary part of a computer tomography gantry. Finally, the invention furthermore relates to a computer tomography device comprising such power transfer device.

BACKGROUND OF THE INVENTION

In a computer tomography device, electrical energy is usually transferred from a stationary part of a gantry connected to a power supply device to a rotary part of the gantry in order to supply power to consumer devices such as an X-ray tube or an X- ray detector mounted on the rotary part. Therein, the requirements with respect to the amount of power to be supplied by a power source and to be transferred to the rotary part of the gantry may significantly vary depending on a specific application. For example, high quality applications such as cardiac computer tomography may require high power supply of up to 15OkW whereas simple applications may require e.g. only 6OkW.

The power may be transferred from the stationary part to the rotary part using e.g. a rotary power transformer which transfers energy contactlessly using magnetical inductance.

Former systems need components for generating an output power which exactly fit to the required power of the consumers of the gantry such as the X-ray tube. Furthermore, also the transfer device for transferring energy from the stationary part to the rotary part of the gantry is usually specifically pre-established for transferring a specific maximum power. In case of a change of the required power of the consumers at the gantry, extensive reconstructions or structural changes to the power transfer device may be necessary.

SUMMARY OF THE INVENTION

There may be a need to provide improved devices which enable the possibility to adjust the supply of electrical energy to the requirements of a computer tomography gantry device. According to a first aspect of the present invention, a power transfer device for contactlessly transferring electrical power from a stationary part to a rotary part of a computer tomography gantry is proposed. The power transfer device comprises: two primary E-cores comprising first and second primary windings and being arranged on the stationary part of the computer tomography gantry; and two secondary E-cores comprising first and second secondary windings and being arranged on the rotary part of the computer tomography gantry. Therein, one of the primary E- cores and one of the secondary E-cores, respectively, form an E-core pair for inductively transferring electrical energy from the primary to the secondary E-core. Furthermore, the primary windings are to be connected to a power supply source on the stationary part and the secondary windings are to be connected to a power consumer on the rotary part such that overall power may be transferred from the power supply source to the power consumer distributedly via the first and second E-core pairs.

According to a second aspect of the present invention, a computer tomography device with a gantry comprising a power transfer device of the fourth aspect, a power supply connected to the power transfer device at a stationary part of the gantry, and a power consumer connected to the power transfer device at a rotary part of the gantry is proposed. Therein, the power supply may be a high frequency high power supply providing power in a range of e.g. 30 - 20OkW as an AC current with a frequency of e.g. 30 - 300kHz. The power consumer may be e.g. a unipolar or bipolar X-ray source. It may be seen as a gist of the present invention according to the above aspects to provide a scaleable power transfer mechanism for a computer tomography gantry. Herein, the scalability may be reached by providing two separate pairs of E- cores wherein each pair of E-cores is adapted for transferring electrical energy from a primary side to a secondary side. Accordingly, a first portion of power to be transferred from the stationary part of the gantry to the rotary part of the gantry may be inductively transferred within the first E-core pair whereas a second portion may be transferred within the second E-core pair. The partition or distribution to two separate E-core may be advantageous in that each of the single E-cores may be smaller thereby e.g. reducing the mechanical load onto each E-core. Furthermore, for example in CT devices comprising a bipolar X-ray tube in which the anode is held at a positive voltage and the cathode is held at a negative voltage, the power, e.g. 5OkW, for the anode may be transferred via the first E-core pair whereas the power, e.g. 5OkW, for the cathode may be transferred via the second E-core pair. Alternatively, in CT devices comprising a unipolar X-ray tube in which the anode is held at ground potential and the cathode is held at a strongly negative voltage, the overall power for the cathode, e.g. 10OkW, may be partly transferred via the first E-core pair and partly via the second E-core pair.

Further details and possible advantages of embodiments of the invention according to the first aspect will be described in the following. The power transfer device for contactlessly transferring electrical power from a stationary part to a rotary part of a computer tomography gantry may also be referred to as rotary transformer. Therein, electrical energy is inductively transferred from a primary core being fixed to a stationary part of a CT gantry to a secondary core being fixed to a rotary part of the gantry. Therein, an AC current flowing through the primary windings in the primary core creates an alternating magnetic field which then induces an electric current in the secondary windings in the secondary core. Accordingly, electrical energy can be transformed into magnetical energy at the primary core and can be re-transformed into electrical energy at the secondary core such that energy can be contactlessly transferred thereby reducing any friction or wear between stationary and rotary parts. The E-cores have an "E"-shape including two winding windows in the two halves of the "E" in which windings are implemented. The E-cores may comprise a magnetically conductive material, preferably a ferro-magnetical material such as iron or ferrite. The windings may comprise litz strands including an electrically conductive material. The windings may be wound into the winding windows of the cores and may completely or partly fill the winding windows. The windings can be arranged in the two winding windows of an E-core in opposing winding directions in order to focus the magnetic field generated by the electric current flowing through the windings.

According to an embodiment of the invention, the primary and secondary E-cores are arranged symmetrically. For example, the E-cores may be arranged in mirror symmetry to each other wherein a symmetry plane may be arranged in an air gap between both E-cores. Due to symmetry effects, both, the mechanical loads and the magnetic fields may be distributed advantageously. For example, the magnetic fields created in the primary cores may be effectively coupled into symmetrically arranged secondary cores and e.g. leakage losses may be reduced. Furthermore, due to symmetry effects, cross-talking may be reduced or even completely depressed.

According to a further embodiment of the invention, the secondary E- cores are enclosed between the primary E-cores or, equivalently, the primary E-cores are enclosed between the secondary E-cores. In other words, a laterally outer pair of cores of a first type, i.e. primary or secondary core, may encompass a laterally inner pair of cores of a second type, i.e. secondary or primary core. In both configurations, the secondary cores being attached to the rotary part of the gantry may be rotatably guided along the stationary primary cores.

According to a further embodiment of the invention, the size of the primary and secondary E-cores is selected in accordance with a maximum power supply requirement and an arrangement of primary and secondary windings in the E-cores is scalably adapted for a specific power supply requirement. In other words, the E-cores may be provided with a size which is sufficient to enclose enough windings such as to transfer enough electrical power even for the most power consuming envisaged applications. For example, the size of the E-cores may be adapted for transferring rates of up to 20OkW by providing enough volume in the winding windows. However, the winding windows of the E-cores are not necessarily completely filled with windings. Instead, the number and size of windings incorporated into the E-cores may be selected depending on the actual power transfer requirements. Accordingly, while the size and shape of the E-cores cannot be easily changed during manufacture and therefore one "standard" E-core may be provided for all requirements, the size and arrangement of the windings within the cores may be easily changed and may therefore be adapted to the specific application requirements.

According to a further embodiment of the invention, the power transfer device further comprises third primary windings arranged on at least one of the primary E-cores and third secondary windings arranged on at least one of the secondary E-cores, wherein the pair of third windings is adapted to transfer auxiliary power from the stationary part to the rotary part.

For example, whereas the main power transferred through the first and second E-core pair may be used for the X-ray source of the CT gantry, the auxiliary power may be used e.g. for supplying an X-ray detector. The third windings may be placed in winding windows of at least one of the E-core pairs at regions not occupied by the first and second primary and secondary windings. Accordingly, auxiliary power may be transferred without the need for additional E-cores. Depending on the remaining space which is left free in the winding windows adjacent to the first and second windings, additional fourth windings may be arranged in the winding window in order to transfer power for further auxiliary power consumers. The additional windings may be arranged in the winding windows in a way such that a symmetry of the windings in the E-cores is maintained. In this way it may be prevented that neighbouring windings negatively influence each other e.g. by cross-talking.

It should be noted that the above features may also be combined, possibly even if described with respect to different subject matters. The combination of the above features may also lead to synergetic effects, even if not explicitly described in detail. These and other aspects of the present invention will become apparent from and elucidated with reference to the embodiments described hereinafter, to which the invention is not limited.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described in the following with reference to the following drawings.

Fig. 1 shows a power transfer device according to an embodiment of the present invention; Fig. 2 shows scalable system comprising a power supply device and a power transfer device according to a further embodiment of the present invention; Fig. 3 shows a CT gantry device according to a further embodiment of the present invention.

All figures are only schematically and not to scale.

DETAILED DESCRIPTION OF EMBODIMENTS

Fig. 1 schematically shows a power transfer device 301 according to another embodiment of the present invention. The device 301 can be used to contactlessly transfer electrical power from a stationary power source to e.g. a high power bipolar X-ray source mounted on a rotary part of a CT gantry.

The device 301 comprises two primary E-cores 303, 305 and two secondary E-cores 307, 309. One of the primary E-cores 303, 305 is symmectrically arranged with respect to a respective one of the secondary E-cores 307, 309 with an intermediate air gap 308, 310 and two E-core pairs 311, 313 are formed thereby. The primary E-cores 303, 305 are arranged at laterally outer positions and are mounted on a stationary frame 315 which may be connected to a stationary part of a CT gantry. The secondary E-cores 307, 309 are arranged at laterally inner positions in-between the primary E-cores 303, 305 and are mounted on a rotary frame 317 which may be connected to a rotary part of a CT gantry.

A plurality of primary and secondary windings 319, 321, 323 are arranged in winding windows 325, 327 of the E-core pairs 311, 313 for transferring energy from a primary E-core connected to a stationary power source to a secondary E- core connected to a rotary power consumer. The power consumer may be e.g. a bipolar X-ray tube. Therein, windings 319 on a first E-core pair 311 may be part of a first power transfer circuit (A) and may transfer the power for a negative cathode of the X- ray tube and windings on a second E-core pair 313 may be part of a second power transfer circuit (B) and may transfer the power for a positive anode. Both power portions may be in the range of e.g. 50 - 10OkW.

In a remaining space in the winding windows 325, 327, additional windings 323 may be arranged which may be part of a third power transfer circuit (C) (and, optionally, further power transfer circuits (not shown in the figure)) and which may transfer the auxiliary power e.g. for an other consumers such as an X-ray detector mounted on the rotary part of the CT gantry.

At the lower part of the rotary frame 317 a data transmission link 329 for transmission of data, e.g. from the X-ray detector mounted at the rotary part of the CT gantry to a stationary analyzing unit, is provided. Furthermore, a protective earth connection 331 is provided.

In the following, details of Fig. 1 are explained in other words: Double E- core framework and winding outline is shown. Each two E-cores are used for bipolar tube (+) and (-) power line, the lower part of the E-core is moreover used for the auxiliary power line. In case of an Unipolar tube is used, both E-Core rings can be used for one power line (indicated by A+B (scalable: use one for small systems, two for large systems). Combination C is used for auxiliary power. It is also possible to use one E- core couple for Unipolar tube power and one for auxiliary power (i.e.: use A for Unipolar tube power and B for aux. Power). Fig. 2 schematically shows a scalable power supply and transfer system

401 according to a further embodiment of the present invention. The system 401 comprises a plurality of power supply modules 403, 405, 407, 409 which may be coupled within a common power supply device 411. The power supply device 411 is coupled to a power transfer device 413 including two pairs of E-cores 415, 417 which may transfer the power provided by the stationary power supply device 411 to consumers mounted at a rotary part of a CT gantry. Such consumers may be e.g. a uni- or bipolar high voltage unit 419 for power supply of an X-ray source 421.

Due to the possibility of modularly coupling a plurality of power supply modules 403, 405, 407, 409 to a common power supply device 411 and due to the possibility of adapting the power transfer device 413 to the amount of power to be transferred by incorporating more or less windings into the E-core pairs, the power supply and transfer system 401 may be scalably adapted to the power requirements of a specific application. For example, for high power cardiac CT applications, a plurality of power supply modules 403 - 409 may be coupled and the entire winding windows in the E-cores 415, 417 may be filled with windings. Alternatively, for low power X-ray applications, only one power supply module and only a few windings in the E-core may suffice. Accordingly, the system 401 may be easily adapted to different requirements using same components which may therefore be produced at high scale and low cost. Finally, ideas and details of embodiments of the power transfer device, an example of which is shown in figure 1, and of the scalable power supply and transfer system, an example of which is shown in figure 2, are explained in other words:

CT systems require X-ray tubes and power electronics on a rotating frame. Due to different applicational needs different tube types (power level, bipolar type for mid-tier systems, unipolar type for top-tier systems) are used which have different power requirements. Traditionally, these configurations require several different building blocks for the entire power chain (mains switches, rectifiers, inverters, isolation transformers, high voltage cascades etc.). In standard CT system, sliprings transfer the power from the stationary to the rotating part.

New concepts include rotary transformers to transfer the power. RT are built with ferrite material and litzwires made of copper. These materials lead to a high material related costprice compared to standard sliprings. All parts of the power chain are highly sophisticated electronics and must be produced and tested properly to guarantee high reliability of CT systems. Up to now field scalable power units are not implemented due to this restriction.

The invention in an embodiment shows a scalable power chain architecture including a rotary transformer. For the whole power range and the different configurations of X-ray tubes the same electronic building blocks can be used. All units can be pre-mounted and tested. The final configuration can be determined during final assembly and during field upgrades. No quality or reliability issues are foreseen due to the new scalable architecture. The material cost-price is always optimized and adapted to the actual power requirements.

Essential features of the invention may be seen in Field Scalability of a x-ray system

Rotary transformer can be used either for unipolar and bipolar tubes - Windings of auxiliary power can be placed in double E-cores without needing a third E-core ring.

Mech. alignment of double E-cores can easily be used to mount and place control data link cost effective in same framework.

According to embodiments of the invention the scalable power architecture is based on the overview of building blocks. The dotted lines define the different configurations and applications. This means only cabling and clamping has to be modified during assembly. The material costprice and the testing amount of work is minimized and fulfils the overall costprice requirements and supply chain demands.

Fig. 3 shows an exemplary embodiment of a computer tomography gantry (91) arrangement. The gantry (91) comprises a stationary part (92) connected to a high frequency power source (98) and a rotary part (93) adapted to rotate relative to the stationary part (92). An X-ray source (94) and an X-ray detector (95) are attached to the rotary part (93) at opposing locations such as to be rotatable around a patient positioned on a table 97. The X-ray detector (95) and the X-ray source (94) are connected to a control and analysing unit (99) adapted to control same and to evaluate the detection results of the X-ray detector (95). Ideas of the present invention may be summarized as follows: The invention provides for a scalable power transfer device for providing electrical energy for a computer tomography gantry. The power transfer device (301) comprises two E- core pairs (311, 313) which might be provided with windings (319, 321, 323) depending on a power transfer requirement. The E-cores have a size and geometry which provides winding windows (325, 327) having sufficient volume to accommodate enough windings for power transfer even for the most power consuming applications. However, for less power consuming applications, the number and/or geometry of windings can be easily reduced thereby adapting the power transfer capabilities of the device. It should be noted that the term 'comprising' does not exclude other elements or steps and the 'a' or 'an' does not exclude a plurality. Also elements described in association with the different embodiments may be combined. It should be noted that the reference signs in the claims shall not be construed as limiting the scope of the claims.

LIST OF REFERENCE SIGNS

301 power supply device

303 primary E-core 305 primary E-core

307 secondary E-core

308 air gap

309 secondary E-core

310 air gap 311 E-core pair

313 E-core pair

315 stationary frame

317 rotary frame

319 windings 321 windings

323 windings

325 winding window

327 winding window

329 data transmission link 331 protective earth connection

401 power supply and transfer system

403 power supply module

405 power supply module

407 power supply module 409 power supply module

411 power supply device

413 power transfer device

415 E-core

417 E-core 419 high vo ltage unit

421 X-ray source 91 computer tomography gantry

92 stationary part

93 rotary part

94 X-ray source

95 X-ray detector

97 table

98 high frequency power source

99 control and analysing unit

Claims

CLAIMS:

1. A power transfer device (301) for contactlessly transferring electrical power from a stationary part (92) to a rotary part (93) of a computer tomography gantry (91), the device comprising: - two primary E-cores (303, 305) comprising first and second primary windings (319) and being arranged on the stationary part of the computer tomography gantry;

- two secondary E-cores (307, 309) comprising first and second secondary windings (321) and being arranged on the rotary part of the computer tomography gantry; wherein one of the primary E-cores and one of the secondary E-cores, respectively, form an E-core pair (311, 313) for inductively transferring electrical energy from the primary to the secondary E-core; wherein the primary windings are connected to a power supply source on the stationary part and the secondary windings are connected to a power consumer on the rotary part such that overall power may be transferred from the power supply source to the power consumer distributedly via the first and second E-cores pairs.

2. The power transfer device of claim 1, wherein the primary and secondary E-cores (303, 305, 307, 309) are arranged symmetrically.

3. The power transfer device of claim 1 or 2, wherein the secondary E-cores (307, 309) are enclosed between the primary E-cores (303, 305).

4. The power transfer device of one of claims 1 to 3, wherein the size of the primary and secondary E-cores (303, 305, 307, 309) is selected in accordance with a maximum power supply requirement and where an arrangement of primary and secondary windings (319, 321) in the E-cores (303, 305, 307, 309) is scalably adapted for a specific power supply requirement.

5. The power transfer device of one of claims 1 to 4, further comprising third primary windings (323) arranged on at least one of the primary E-cores (303, 305) and third secondary windings (323) arranged on at least one of the secondary E-cores (307, 309), wherein the pair of third windings is adapted to transfer auxiliary power from the stationary part to the rotary part.

6. A computer tomography device comprising

- a gantry comprising a power transfer device of one of claims 1 to 5.

- a power supply connected to the power transfer device at a stationary part of the gantry;

- a power consumer connected to the power transfer device at a rotary part of the gantry.