Method for compensating for system tolerances in inductive couplers

Technical field

p0001The invention relates to inductive coupler for contactless power transfer especially for computer tomography. By this the predominantly required to operate the X-ray tube electrical power from the stationary side to the rotary side of the gantry is transmitted a computer tomograph. The transmission takes place here without contact by means of an inductive rotary transducer, which similar to a transformer is constructed in which the primary side and secondary side are rotated against each other.

State of the art

p0002When mutually movable units such as radars or computed tomography, as with linearly movable units such as crane systems or conveyors, it is often necessary to transmit electrical energy between mobile units. To transfer this energy without contact, inductive couplers are preferably used. These have to mechanical slip rings or slip rings the advantage that abrasion, wear, mechanical force for moving the coupler and also the maintenance is much lower. The notion of an inductive coupler refers to a circuit for generating an alternating voltage with an inductive transformer or rotating transformer for power transmission between two mutually moveable and in particular rotating parts.

p0003Inductive rotary joint, as described for example in the <patcit id="pcit0001" dnum="US7197113B"><text>US 7,197,113</text></patcit> disclosed, have magnetic cores of iron or ferrite and at least one winding on each side of the relatively rotating units. In a first winding an alternating current is fed and picked up via a second, opposite the movable coil again.

p0004The <patcit id="pcit0002" dnum="US7054411B"><text>US 7,054,411</text></patcit> shows a complete circuit of an inductive power transfer system for computed tomography with the associated power electronics.

p0005When electrically coupled slip rings, it is easy to transfer a predetermined voltage from the stator to the rotor side. It must be taken into account only the relatively low ohmic losses. With inductive rotary joints, the leakage inductance of the rotary transformer plays an essential role. It represents a frequency-dependent impedance that substantially affect the transmission characteristics of the resolver. This stray inductance depends on various factors such as the inductance of the windings of the stator and the rotor side and from the magnetic assembly. In order to transmit electrical energy through such a rotary transformer is now, a series capacitance is connected in series with the compensation. This results in a series resonant circuit. This has zero impedance at its resonant frequency and allows here the transmitting large forces. To control the power flow, the operating frequency can be selected in deviation from the resonant frequency.

p0006Instead of a series resonant circuit can be constructed by connecting a capacitor and a parallel resonant circuit. The characteristics described below take well to a parallel resonant circuit. The resonant circuit has an impedance of almost zero at its resonant frequency and allows here the transmitting large forces. Through a change in impedance, which is brought about by a change in the switching frequency, the output voltage can be controlled.

p0007The inductors in a resonant circuit represent frequency dependent impedances, which significantly influence the transmission characteristics of the rotary joint. These inductances are dependent upon various factors such as the structure and permeability of the magnetic circuit, the design of the winding and in particular the air gap between the stator and the rotor side. These factors are in mass production is not constant but subject to certain tolerances. To the output voltage on the rotating side for all occurring in set values ​​of the relevant components involved - particularly the resonant capacitor, the adapting transformer and the inductive rotary transducer - to keep within allowable limits are known various measures. One way is to measure the output voltage and attributed this metric to the stationary side. For this purpose, however, a rotary joint is required, causing the additional cost and space required.

p0008Another possibility is, on the rotating side an additional converter stage, usually a DC-DC converter, installed between the secondary side of the rotary transformer and output. For these converter stages gravure or boost converters are often used, but other converters, such as zeta or Cuk converter are possible. The input voltage of this downstream converter stage can vary within a wide range, the output voltage is kept constant. This solution requires but on the rotating side an additional transformer, which increases the costs and weight and volume of the assembly.

Summary of the Invention

p0009The invention has the object of providing an inductive coupler, in particular an inductive rotary transformer embodying such that the output voltage can be kept approximately constant regardless of mechanical and electrical tolerances of the electrical components by a primary-side control. Another aspect of the invention is a method to maintain the output voltage of an inductive coupler independent of the mechanical and electrical tolerances of the electrical components constant. Furthermore, to be necessary in accordance with the invention, no rotary joint for transmitting Rückkopplung- or control signals from the secondary side to the primary side for the transmission of measured values ​​of the output voltage on the secondary side.

p0010This object is achieved by a device according to Claim first Advantageous embodiments of the invention are specified in the subclaims.

p0011The inventive method is used in an inductive coupling device, preferably an inductive rotary transformer. The inductive coupling means includes a power generator for generating a pulsed DC voltage or an AC voltage. Furthermore, it comprises an inductive power transformer, wherein the primary side and the secondary side are mutually movable. This power transformer has a primary side having at least a primary winding and a secondary side having at least one secondary winding. Further, in series with the primary winding of a capacitor, preferably connected in the form of a resonance capacitor, so that there is a series resonant circuit. The pulsed DC voltage or AC voltage of the power generator is fed to the power transfer in this series resonance circuit, so that in the primary winding an alternating magnetic field is produced. This induced in the secondary winding in turn, a current which is fed to a load. For a better coupling between the primary winding and secondary winding are provided with components soft magnetic materials, preferably iron or ferrite components. Optionally may be provided between the power generator and the inductive power transformer nor a matching transformer. To carry out and control of the process control means is preferably present.

p0012The method according to the invention comprises three portions, which can be, g each subdivided into a plurality of steps a, b, c, d, e, f. The first two sections relate to different measurements of resonance frequencies, while the third section deals with the evaluation of the measurement results. The first two sections can be interchanged in their order even to today, without that this will change the process in its fundamentals. This results in the sequence of steps: d, e, f, a, b, c, g.

p0013The first section includes the steps of:<ol><li>a) generating a short sequence of at least one pulse of a DC voltage or a period of an AC voltage;</li><li>b) shorting the series resonant circuit;</li><li>c) measuring the frequency of the series resonant circuit in the resultant wave having a first frequency;</li></ol>

p0014The second section comprises the steps of:<ul><li>d) generation of a longer sequence with several pulses of a DC voltage or a plurality of periods of an AC voltage so that at the load (12) a predetermined small voltage is built up;</li><li>e) shorting the series resonant circuit; </li><li>f) measuring the frequency of the series resonant circuit in the resultant wave having a second frequency;</li></ul>

p0015The third section comprises the step of:<ul><li>g) determining a control parameter for controlling the power generator by calculation, estimation or using a table of values ​​from the in steps c and f measured frequencies.</li></ul>

p0016In the first portion, a short sequence is fed from at least one pulse of a DC voltage or of at least one period of an alternating voltage in the resonant circuit by the power generator. The sequence preferably comprises less than 10, particularly preferably only one pulse or a period. In the next step of the series resonant circuit is short-circuited. Characterized that vibrates at a first resonant frequency. In a third step, this resonant frequency is measured. This first resonant frequency is determined by the resonant capacitor and the active in this series resonant inductors. According to the equivalent circuit diagram according to<figref idrefs="f0001">figure 2</figref> these are primarily the first series inductor and the second series inductance of the inductive rotary transducer. In the event that between the power generator and the inductive power transformer a matching transformer is still connected, still flow its first series inductance and second series inductance in the resonance frequency using.

p0017In a second portion of a longer sequence is generated with a plurality of pulses of a DC voltage or with a plurality of periods of an AC voltage by the power generator. By this longer sequence, a certain amount of energy is delivered to the secondary side, in which a corresponding charging capacitor is charged behind a rectifier circuit. The charging capacitor is preferably less than the known voltage charged with a voltage, so that the circuit is not yet activated at the load, for example an X-ray source. Then turn the series resonant circuit is shorted. It is measured a second resonance frequency in the next step. This second resonance frequency is now determined by other components than the first resonance frequency. By the charging of the charging capacitor, the rectifying diodes are now reverse biased as long as the series resonance circuit has only a small amplitude of vibration. Characterized the current circuit to the load from the rest of the circuit is decoupled. Thus contributes, as in<figref idrefs="f0001">figure 3</figref> shown at the secondary side of the inductive power transmitter not to series resonance. This is determined solely by the first series inductor and the first parallel inductance of the rotary transformer and optionally through the first series inductor and the second series inductance of adapting transformer. Since in principle, the first parallel inductor of the primary winding of the rotary transformer is substantially greater than the second series inductor, now resulting from the sum of said first series inductance and said first shunt inductance of the rotary transformer a substantially higher inductance as in the first section from the sum of said first series inductance and the second series inductance of the rotary joint. Consequently, the second resonant frequency is significantly lower than the first resonance frequency. The inductances of the inductive rotary transducer are highly dependent on the air gap of the rotating rotary transformer and vary considerably already at relatively small air gap tolerances.

p0018In a third section, the determination will now be at least a value for a control variable for controlling the primary side, with which the output voltage can be adjusted. This can be done by calculation, estimation or by reading out a table of values. the operating frequency of the power generator is preferably used as a control variable determined. Alternatively or additionally, an input voltage of the power generator (an intermediate circuit voltage) can be set as, for example, generated by a featured converter or a power factor correction circuit. In principle, a correction factor can be used for an internal command value of a control circuit in place of the control variable. In particular, can thus be corrected, for example by correcting size a default value for a generator frequency or output voltage.

p0019Since two different measurements were carried out in the first and second portion having different resonant frequencies, in which different components of the power transformer were involved, can now be the inductance of the primary side of the power and / or the leakage inductance of the power transformer to calculate, if the other component values, such as the capacity of the resonance capacitor and, optionally, the inductances of the adapting transformer are known or defined as constant values. This inductance can now also be an optimum operating point or an optimal operating frequency of the power generator for transmitting a predetermined power or for achieving a sound output voltage or an output current at the output side to determine.

p0020To create the table of values ​​or a formula for calculating the control amount, a multi-dimensional table of values, such as, in a calibration phase in <figref idrefs="f0004">Fig. 8</figref> shown, are incorporated by reference. This is done by deliberately varying the parameters such as air gap and resonant capacitance, thus different resonant frequencies can be set for both measurements. By adjusting the air gap is the resonant frequency, the results of the measurement in accordance with Section 2, varies with variation of the resonant capacitance or leakage inductance is the resonant frequency, the results for the measurement according to section 1, varies. For each measured frequency pair is the value for the control variable - in<figref idrefs="f0004">Fig. 8</figref> for example, the switching frequency of the inverter-determined, which is necessary to adjust the output voltage to the desired value. This multi-dimensional characteristic field is for example stored in the memory of the control or regulation controller, which can be part of the power generator. After both measurements have been performed in the serial device and the two measured frequencies are present, an appropriate value for the control variable may for example be determined from an interpolation for an arbitrary measured frequency pair. Alternatively can be used instead of the characteristic curves a formula describing the functional relationship between the control variable and the two resonant frequencies, stored and used to determine the appropriate value of the control variable.

p0021The inventive method described can now apply for different positions between the moving parts of the power transformer, especially at different angular positions of a rotary joint. As can be found in the case of a rotary transducer is a function of inductance and the optimum operating frequency in dependence on the angular position. Advantageously, during the commissioning of a CT scanner is an initialization or a measurement sequence, in which the inventive method is carried out angular position depending on at least one rotation of the rotating part of the gantry of the computed tomography.

p0022For verification of a measurement or for increasing the accuracy of the measurement, several measurements can be carried out successively advantageous. The respective measured frequencies can be checked for plausibility. So faulty measurements can be screened. By arithmetic averaging, the accuracy of the overall measurement can be increased.

p0023Logically, it is expected that the measured values ​​are in a pre-determined region of. This allowable range results from the maximum allowable tolerances. Now If the measured values ​​for one of the two measurement methods outside the allowable range, it may cause a malfunction of the device, such as a too low or too high output voltage, which is measured not itself directly. With the described method the malfunction can be detected, and an error signal is output. As a result, the device will shut down and as a corresponding service warning can be signaled. In this way, impermissibly large tolerances of mechanics or electrical components are detected. These tolerances can be, for example, during the life, change in the operation within the specified range in the specification or material defects and be greater than the permissible limits.

p0024In a further embodiment, an auxiliary generator is used in place of the power generator for the generation of the sequences of at least one pulse of a DC voltage or a period of an AC voltage. This has in comparison with the generator that can power the load of the X-ray tube, make a comparatively low power and can be correspondingly simple dimensioned. Can also be provided to short-circuit the series resonant circuit, a suitable auxiliary switch.

p0025Advantageously, the measurements can be performed even under load. Optionally, the history of the loading conditions can be evaluated in order to determine an appropriate time of measurement. During the operation or in short intervals, in which no X-ray radiation is emitted, the effects of the operation such as thermal expansion can be detected and thus compensated due to temperature increase.

p0026The method according to the invention is also applicable for inductive rotary transducer with multiple primary windings and / or more secondary windings.

p0027Another object of the invention is an inductive coupling means with a control device for carrying out the method described above.

p0028Another object of the invention is a computer tomograph with a previously described inductive coupling device.

p0029The statements made in this document refer to the sake of clarity on inductive rotary transformer for energy transfer between the relatively rotating units. This is the essential object of the invention. However, it is apparent to those skilled in the art that the same principles can also be used for contactless energy transfer between any mutually movable units, in particular between the linearly movable units. It must be made here only an adaptation of the geometry of the rotary transformer to the web and the type of movement. The measuring method according to the invention is just as advantageously used here.

DESCRIPTION OF THE DRAWINGS

p0030The invention is described below, without restricting the general inventive idea, by exemplary embodiments with reference to the drawings.<dl id="dl0001"><dt>figure 1</dt><dd>schematically shows the equivalent circuit of an inductive rotary transducer according to the invention.</dd><dt>figure 2</dt><dd>shows the current profile of the first measuring process in the circuit.</dd><dt>figure 3</dt><dd>shows the current profile of the second measuring process in the circuit.</dd><dt>figure 4</dt><dd>shows the waveform of the output current of the power generator during the first measurement. </dd><dt>figure 5</dt><dd>shows the waveform of the output current of the power generator during the second measurement.</dd><dt>figure 6</dt><dd>shows schematically the structure of an inductive power transformer according to the invention.</dd><dt>figure 7</dt><dd>schematically shows a computer tomograph.</dd><dt>figure 8</dt><dd>exemplifies a 3D characteristic field with which of the two measurements, the correct value for the manipulated variable (here switching frequency) is determined.</dd></dl>

p0031In <figref idrefs="f0001">figure 1</figref> is shown according to the invention schematically the equivalent circuit of an inductive rotary transducer. The power generator 50 includes a power switch 51, which generates from an input DC voltage, not shown here a clocked direct voltage or an alternating voltage. This switch may for example be a half bridge or a full bridge. Here power transistors such as FETs or IGBTs are used. At the output of the switch there is a resonance capacitor 52 forming a series resonant circuit with the other inductances of the circuit. The power generator 50 supplies an output current 54 at an output voltage 55 to the matching transformer 60. This in turn is represented by an equivalent circuit. It comprises the two magnetically coupled with each other first parallel inductor 62 and the second parallel inductor 63 and the first series inductor 61 and the second series inductor 64. This matching transformer is used to adjust the impedance or the voltage level of the power generator to the subsequent inductive rotary transformer 70 and the load circuit 80th The inductive rotary transducer 70 is represented here by an equivalent circuit diagram. The transformer itself has a primary inductance (first parallel inductor) 72 and a secondary inductance (second parallel inductor) 73rd These two are so separated by the rotation gap 75 shown here schematically an air gap between rotor and stator from each other. Again, the first series inductor 71 and second series inductance 74 exists. On the rotor side of the rotary joint, the load circuit 80 is connected. This comprises a rectifier 81 and a charge capacitor 82 and a load, here symbolized through the load resistor 83. The rectifier 81 may be in accordance with the prior art, a half-wave rectifier, a bridge rectifier, or preferably a synchronous rectifier. The circuit illustrated here is a preferred embodiment. An inventive inductive rotary transformer or an inventive method also works without a matching transformer 60. This is not mandatory, however, increases the flexibility in the dimensioning of the entire assembly significantly. In addition, can be realized by this further isolation. Further, the resonance capacitor 52 may be arranged at other locations of the circuit, so that there is a series resonant circuit.

p0032<figref idrefs="f0001">figure 2</figref> shows the first measurement process according to the invention. There a short voltage or current pulse or a short pulse sequence is delivered to the circuit via the resonance capacitor 52 by means of the circuit breaker 51st After being pinched by the circuit breaker or an auxiliary switch the output of the circuit breaker, so that the resonant circuit itself can vibrate at its natural frequency. The result is here a series resonant circuit consisting of the resonant capacitor 52 and the series inductors 61, 64,71 and 74, which feeds the load resistor 84th This load resistance usually does not match the load resistance 83 at rated load by the X-ray tube, since the X-ray tube can not be put into operation by the low transmitted power. This load resistance results from the fact that introduced by the rectifier 81, a current in the charging capacitor 82 and the latter is thereby charged. The energy required to charge the charging capacitor is removed from the resonant circuit. The result here is a decaying oscillation with a first resonant frequency, as in the<figref idrefs="f0002">figure 4</figref> is shown.

p0033In <figref idrefs="f0001">figure 3</figref> is shown according to the invention, the current course of the second measurement process. In preparation for the measurement, a pulse sequence defined length is generated through the power switch 51 and fed into the resonant circuit of the rotary transformer. Thereby, the charging capacitor 82 receives a certain charge, and thus a certain voltage. In a second step, the output of the power switch 51 is short-circuited by a short-circuit 53 again. The circuit also resonates here on a natural frequency. Since it has been charged by the previous pulse packet, the charging capacitor 82 to a predetermined voltage, the rectifier 81 is only brought into a conducting state when the maximum amplitude of voltage at the anode of a rectifier diode exceeds the voltage on the cathode. In a measuring voltage in the resonant circuit is less than the voltage at the charging capacitor 82 is one or more rectifier diodes of the rectifier 81 permanently locked in a state. Thus, no resonant current the resonant frequency to flow through the output-side circuit from the secondary winding of the inductive rotary transformer and the inductor 74. Referring now to the resonant capacitor 52 through the inductors 61, 64, 71 and in particular by the relatively high inductance of the primary winding of the rotary transformer 72 determines , Since this inductance is significantly higher than the inductance 74 in the normal case, this results in a significantly lower resonance frequency as described in the<figref idrefs="f0002">figure 4</figref> is shown. From this resonance frequency can now be closed on the first parallel inductor 72 of the primary winding of the rotary transformer.

p0034<figref idrefs="f0002">figure 4</figref> again shows the waveform of the output current 54 of the power generator during the first measuring process, as a function of time in an exemplary arrangement. The lower horizontal axis indicate here the time in microseconds and is scaled from 0 microseconds to the left to 1000 microseconds on the right side. The vertical axis indicates the current with a scaling of - 50 amperes at the lower side to + 50 amperes at the upper side of the diagram. It is here very well the ringing recognizable. Here we see not a disease caused by an ohmic load deadbeat. Rather, the current decreases linearly with the number of periods, suggesting that with each cycle of the oscillation, a constant amount of energy is removed from the resonant circuit. With this amount of power of the charging capacitor 82 is gradually charged.

p0035<figref idrefs="f0002">figure 5</figref> shows the variation of the output current of the power generator 54 in the second measurement. Again, the time as in<figref idrefs="f0002">figure 4</figref> 0-1000 microseconds plotted on the horizontal axis. On the vertical axis of the current scaled by the resonant circuit of 10 amperes at the lower end is applied to +15 amperes at the upper end. The result is here a vibration having a significantly lower frequency than in the previously measured first curve.

p0036<figref idrefs="f0003">figure 6</figref> shows schematically the structure of an inductive power transformer according to the invention, which is preferably constructed as a rotary transformer. This power transformer has a mostly stationary Inappropriate primary side 20 and a usually movable or rotating Inappropriate secondary side 10th Of course, the primary side and secondary side can be reversed, so that energy can be transferred from the movable side on the fixed or stationary side. On the mobile here secondary side there is a secondary winding of the inductive power transmitter which transmits its power to a load 12th This load may be a computer tomograph, for example the X-ray tube. The primary side comprises a primary side of the power transformer 21, which is powered by a power generator 23 via a matching 22nd The power generator 23 has an inverter 25 and a resonance capacitor 24. There may also be one or more capacitors arranged at the output of the inverter in series with any inductance of the circuit in place of the resonance capacitor.

p0037<figref idrefs="f0003">figure 7</figref> schematically shows the structure of a further inventive inductive power transformer, which is designed for parallel resonant operation. The resonant capacitor 24 is exemplary parallel to the primary side of the power transformer 21 connected here. In principle, a resonance capacitor may be connected in parallel for generating parallel resonances at any other inductor. It could also be provided a plurality of resonant capacitors. For a combined operation with series or parallel resonances could also at least one further resonance capacitor may be connected in series, as shown for example in the previous figure.

p0038In <figref idrefs="f0004">figure 8</figref> is still schematically, the construction of a computer tomograph shown with an inductive rotary transformer according to the invention. The stationary part of the rotary joint is suspended in a solid frame 110th The rotating part of the gantry 109 is mounted for rotation relative thereto and rotates in the direction of rotation 108. There is an X-ray tube 101, the x-ray beam 102 generated, which radiates through the lying on a couch 107 patients 104 and collected by a detector 103 and into electrical signals is converted. For the transmission of electrical energy from a power supply unit 111, an inductive power transmission line 100, and inductive coupler is provided with an inductive rotary transformer. The primary side here arranged on the stationary part and the secondary side of the rotating part. The data obtained by the detector 103 are transmitted to an evaluation 106th This purpose, a control bus 105 to the well by the evaluation unit, the gantry itself can be controlled.

p0039In <figref idrefs="f0005">figure 9</figref> is an example of a 3D characteristic diagram shown, with which of the two resonant frequency measurements, the correct value for the manipulated variable (here switching frequency) is determined. The characteristic field is determined once at a reference system by targeted variation of the inductances and capacitances. It may be for example, stored in a nonvolatile memory such as a flash memory of a DSP or microcontroller. Lying measured by a standard set values ​​for the resonant frequencies between two points, so is suitable interpolated to achieve the smallest possible error. The axis 94 (pulse frequency) shows the measured frequency in the first section in a range from 34 to 44 kilohertz. The shaft 93 (resonant frequency) shows the measured frequency in the second section in a range from 15 to 30 kilohertz. The axis 95 (adjusting frequency) shows the output, here by way of example, the generator frequency in a range of 30 to 50 kilohertz.

p0040In <figref idrefs="f0006">figure 10</figref> is an example of a 3D-characteristics field illustrated showing the relationship between air gap width 91, resonant capacitor 90 and the first frequency determined therefrom 92. The axis 91 is the width of the air gap in a range from 0.4 mm to 2.0 mm. The axis 90 shows the resonant capacitance in the range 72-88 Nanofarad. The axis 92 shows the measured in the first section first frequency in a range from 34 to 46 kilohertz.

LIST OF REFERENCE NUMBERS

p0041<dl id="dl0002"><dt>10</dt><dd>Movable side</dd><dt>11</dt><dd>Secondary side of the power</dd><dt>12</dt><dd>load</dd><dt>20</dt><dd>Stationary side</dd><dt>21</dt><dd>Primary side of the power</dd><dt>22</dt><dd>matching transformer</dd><dt>23</dt><dd>power generator</dd><dt>24</dt><dd>resonant capacitor</dd><dt>25</dt><dd>inverter</dd><dt>50</dt><dd>power generator</dd><dt>51</dt><dd>breaker</dd><dt>52</dt><dd>resonant capacitor</dd><dt>53</dt><dd>short circuit</dd><dt>54</dt><dd>Output current of the power generator</dd><dt>55</dt><dd>Output voltage of the power generator</dd><dt>60</dt><dd>Equivalent circuit diagram of adapting transformer</dd><dt>61</dt><dd>First series inductance of the equivalent circuit of adapting transformer</dd><dt>62</dt><dd>First parallel inductance of the equivalent circuit of adapting transformer</dd><dt>63</dt><dd>Second parallel inductance of the equivalent circuit of adapting transformer</dd><dt>64</dt><dd>Second series inductance of the equivalent circuit of adapting transformer</dd><dt>70</dt><dd>Equivalent circuit diagram of the inductive rotary transducer</dd><dt>71</dt><dd>First series inductance of the equivalent circuit of the inductive rotary transducer</dd><dt>72</dt><dd>First parallel inductance of the equivalent circuit of the inductive rotary transducer</dd><dt>73</dt><dd>Second parallel inductance of the equivalent circuit of the inductive rotary transducer</dd><dt>74</dt><dd>Second series inductance of the equivalent circuit of the inductive rotary transducer</dd><dt>75</dt><dd>splitting </dd><dt>80</dt><dd>Powershift</dd><dt>81</dt><dd>rectifier</dd><dt>82</dt><dd>charging capacitor</dd><dt>83</dt><dd>Load resistor at rated load</dd><dt>84</dt><dd>Load resistor for measuring</dd><dt>90</dt><dd>resonant capacitance</dd><dt>91</dt><dd>Air gap width</dd><dt>92</dt><dd>pulse frequency</dd><dt>93</dt><dd>oscillating frequency</dd><dt>94</dt><dd>pulse frequency</dd><dt>95</dt><dd>adjusting frequency</dd><dt>100</dt><dd>Inductive Power Transformers</dd><dt>101</dt><dd>X-ray tube</dd><dt>102</dt><dd>X-ray beam</dd><dt>103</dt><dd>detector</dd><dt>104</dt><dd>patient</dd><dt>105</dt><dd>control bus</dd><dt>106</dt><dd>evaluation</dd><dt>107</dt><dd>couch</dd><dt>108</dt><dd>direction of rotation</dd><dt>109</dt><dd>Rotating part of the gantry</dd><dt>110</dt><dd>Stationary frame of the gantry</dd></dl>