MXPA93005484A - A system of distribution of energy of no conta - Google Patents

Abstract

An inductively coupled power distribution system for vehicles in motion, in which primary resonant circuits distribute energy, which is collected by resonant secondary circuits and used in optimized form. For all circuits to be largely resonating at the same frequency means are used to detect and adjust the resonant components, for example, circuit 700 illustrates a compensator that corrects the drift of the frequency, which is applicable to several embodiments in where the elements 702 to 709 compare the current frequency to a reference voltage and cause the trigger 711 to be activated or deactivated accordingly. Switches 712 and 713 are thus driven to connect or disconnect respectively, and when disconnected, supplementary capacitors 714 and 715 are included with main capacitor 716 in the primary resonant circuit. Control by oscillation of small amplitude ["dithering"] or by impulses provides a continuous control of the resonance since the system takes a few milliseconds in response

Description

A SYSTEM DS DISTRIBUTION OF NON-CONTACT ENERGY OWNER: AUCKLAND UNISERVICE3 LIMITED, a New Zealand company, resident in: Uniservices House, 58 Symonds Street, Auckland 1001, New Zealand, DAIFUKU CO LIMITED, a company from Japan, resident in: 2-11, 3- Chome Mitejima, Nishiyodoga a-Ku, Osaka 555, Japan.

INVENTOR: JOHN TALBOT BOYS, a New Zealand citizen, residing at: 15A Island Bay Road, Birkdale, Auckland 1310, New Zealand, ^ SHUZO NISHINO, a Japanese citizen, residing at: 2-11, 3-Chome Mitejima, Nishiyodogawa- Ku, Osaka 555, Japan.

E X T R A C T O An inductively coupled power distribution system for vehicles in motion, in which primary resonant circuits distribute energy, which is collected by resonant secondary circuits and used in optimized form. For all circuits to be largely resonating at the same frequency means are used to detect and adjust the resonant components; for example, circuit 700 illustrates a compensator that corrects the drift of the frequency, which is applicable to several embodiments wherein elements 702 to 709 compare the current frequency to a reference voltage and cause the trigger 711 to be activated or deactivated. as it matches. The switches 712 and 713 are thus driven to connect or disconnect respectively, and when disconnected, the supplementary capacitors 714 and 715 are included with the main capacitor 716 in the primary resonant circuit. Control by oscillation of small amplitude ["dithering"] or by impulses provides a continuous control of the resonance since the system takes a few milliseconds to respond.

MOOIP? .t »FIELD This invention relates to the provision of inductively coupled electrical energy through a space to mobile or portable energy consuming apparatuses such as vehicles. More particularly it relates to those inductively coupled systems employing resonant circuits, and even more particularly to ways to maintain mutually consistent resonance frequencies in both primary and secondary circuits.

BACKGROUND Modern advances in semiconductors have made feasible the provision of inductively coupled energy to vehicles in motion, and have allowed the use of LC resonant circuits in the primary circuit or secondary circuits or both. Among other advantages the resonance provides - (a) high circulating currents despite relatively small energy supplies, (b) relatively low emission of electromagnetic fields in harmonics of the operating frequency, (c) small ferromagnetic cores, if any, and (d) novel means for the control of electromagnetic coupling through spaces. Obviously the system will have its highest efficiency when all the resonant circuits are resonating naturally to a large extent the same frequency, and largely in phase. Despite the careful tuning at the time of installation, effects on the inductance and also on the operating parameters of switches caused by variable loads can cause operating frequencies to change. This variability owes in part to the combined use of the track conductor in the preferred embodiments of the invention, both as the resonant inductor and as the emitter of changing magnetic fields. In fact, the resonant inductor is the distributed inductance of the pathway and is inherently susceptible to induced currents in adjacent secondary coils, which vary according to consumption. He "400SF? .M1 preferred prior art switch power supply simply detects each zero pass within the current in the resonant circuit and causes immediate commutation transitions. It has no means to determine the true frequency of operation - apart from a start oscillator that is applied momentarily. The rigidity of the primary-secondary coupling can generate more than one condition where the entire system seems to be in resonance but usually only one of these conditions correlates to a frequency at which an optimal energy transfer can be made. Since it will decrease the efficiency of the energy transfer if the resonance frequencies are not well matchedIt is therefore convenient to maintain a relatively constant operating frequency during any reasonable condition of use.

OBJECT It is an object of the present invention to provide an improved system for the maintenance of consistent resonance frequencies within an inductively coupled power transfer system, or one that will at least provide the public with a useful choice.

DETAILED DESCRIPTION OF THE INVENTION In one aspect, the invention provides a non-contact energy distribution system for causing electrical energy to be transferred from a primary resonant circuit capable of generating an alternating magnetic field to at least one movable object having at least one secondary resonant circuit that incorporates an inductive coil to intercept said magnetic field and therefore generate an electromotive force, characterized in that said energy distribution system includes means for maintaining the resonant frequency of the primary resonant circuit and of the resonant circuits secondary to, or close to, a consistent frequency. In another aspect the invention provides a non-contact power supply to cause i «oosp?.« m electrical energy is transferred from a primary resonant circuit to at least one movable object that has at least one secondary resonant circuit that incorporates an inductive coil to intercept a magnetic field and therefore generate an electromotive force, said power supply comprising a supply of switching power that generates a high frequency resonant current, characterized in that there are means for maintaining the frequency of the resonant current at or near a predetermined frequency.

DRAWINGS The following is a description of several preferred forms of the invention, given by way of example or only, with reference to the accompanying drawings. These examples relate in particular to a system for distributing energy to moving carriages traveling on rails adjacent to primary conductors, although the system can also be applied naturally to other energy consumers such as lamps or battery chargers.

Fig 1: is a circuit diagram illustrating an induction line that can be tuned by means of a tuning capacitor.

Fig 2: is a circuit diagram of an induction line that can be tuned by means of adjustable coils.

Fig 3: is an illustration of a solution that uses switched inductors to vary the resonant inductance in small increments.

Fig 4: is an i lust rac i on of a system that provides a stable frequency source for the primary energy supply instead of letting the frequency drift.

Fig 5: is an indication of a means for tuning (or frequency tracking) within secondary circuits - such as «400SP? .I» in the cheeks themselves. ig 6: is an illustration of a "false carriage" or artificial secondary resonant circuit, in or near the power supply, used to perform control and, optionally, serve as a parameter sensor for the induction line.

Fig 7: is a circuit that tests the current operating frequency and continuously adjusts the tuning of the power supply. It is based on an integral-proportional controller and employs capacitors and switches in parallel with the main resonant capacitor.

Fig 8a-c: show schematic graphs of the phase angle (Y axis) against the frequency (X axis) in circuits that are sub-coupled (8a), critically coupled (8b), and over-coupled (8c) Fig 9a-c: show in principle the use of zero inductance cables (9a), and in practice (9b and 9c), to join spaced nodes of a circuit having multiple resonant elements, and therefore to restrict modes of oscillation.

PREFERRED EMBODIMENTS All these embodiments have in common the purpose of providing a consistent resonance frequency throughout the energy distribution system. The advantages associated with the provision of a resonance frequency throughout the system include the following: 1. All resonant circuits have a largely zero power factor - they act as pure resistors. 2. The Q of the system is increased. 3. Aberrant modes of oscillation are inhibited. 4. Coupling is improved. 5. The energy transfer is improved. "400SF?." 3 Some of a number of possible solutions to the problem of ensuring that there is a consistent resonance frequency throughout the entire system are illustrated in the preferred embodiments described herein. In summary, the embodiments to be described are: 1. The tuning of the primary circuit by means of a small capacitor switched through the main resonant capacitor. This method tries to keep the resonance frequency of the system constant (Fig 1, Fig 7). 2. The tuning of the primary circuit by means of a pair of variable inductances; each one in series with one side of the primary circuit. This method also tries to keep the resonance frequency of the system constant (Fig 2). 3. The use of switched inductors (for example SCR devices), to vary the resonant inductance in small increments. This solution tries to keep the resonance frequency of the system constant (Fig 3). 4. Make the primary energy supply a stable frequency source determined by the parameters of the path inductance, instead of letting the frequency drift. This strategy will keep the resonance frequency of the system constant (Fig 4). 5. Include means of tuning (or frequency tracking) in the secondary circuits - the cheeks themselves. This system has a variable global frequency (Fig 5). 6. Use a "fake cheek" or artificial secondary resonant circuit to the side, or near the power supply to perform control. This system also has a variable global frequency (Fig 6). 7. Use switched capacitance within the power supply to vary the resonant capacitance in small increments. (Control by oscillation of small amplitude ["dithering"] or by impulses provides a more precise control) (Fig 7). 8. Use zero inductance cables to join spaced nodes of a circuit, which have similar amplitude and phase, usually where the capacitors, and so on Í400SP? .I9J restrict the oscillation modes (Fig 9a-c). The embodiments, illustrated in Figures 1, 2, 3, and 6 presume the presence of a master controller, not illustrated therein, to check the frequency of the resonant current in the primary circuit and take appropriate measures to alter specific parameters of circuits of concentrated components (one or both of L and C), in the event that the frequency drifts away from acceptable values. This controller can be a type of fixed phase circuit [PLL = "phase-locked loop"], but a preferred form would be a proportional controller of the type shown in Figure 7.

Embodiment 1 - see Figure 1. An induction line 100 is provided by a pair of wire leads 101 and 102, together with a coil 103 and a main capacitor 104. (The power supply is not shown, but it would be connected through the inductor 103). In this example, an auxiliary capacitor 116 is provided in parallel with the main capacitor, which can be connected and disconnected from the circuit by means of an appropriate switch 117, to vary the frequency of the induction line. . By providing an auxiliary capacitor 116, it is possible to tune the resonance frequency of the induction line to accommodate the changes in frequency that result from the number and / or movement of moving bodies (typically electrically driven carriages) in the induction line. The change in frequency results from a change in inductance, and therefore there is a change in the resonance frequency. If a largely constant primary frequency is maintained, no secondary circuit must be restored. It will be appreciated that the capacitor 116 may be in series, rather than in parallel with the main capacitor (where a switch would pass it through the side), and could comprise one or more variable condensers, so that it could be tuned the resonance of the line by varying the capacitance of the auxiliary capacitor 116. In another version, the two capacitors can be replaced by a H00SP ?. I9J only variable capacitor.

EMBODIMENT 2 Figure 2 shows a similar induction line 200, having a pair of wire leads 201 and 202 forming a circuit, a main coil 203, and a main capacitor 204. An array of tuning coils 205 is provided and 206, so that the resonance frequency of the induction line can be tuned by varying the mutual inductance of the coils 205 and 206. This can be achieved in several ways; when using electrical or mechanical adjustments. The simplest solution is to place one of the coils inside the other, each wound around a cylindrical former (preferably plastic), with the inner coil capable of being moved in relation to the outer coil. This can be achieved in several ways. For example, the inner coil can be telescoped inside or out with respect to the outer coil, such that there is a different degree of overlap, and consequently, that there is a different resulting frequency in the induction line as the inductance of the coils. Alternatively, it is possible to tune the resonance frequency by rotating the inner coil with respect to the outer coil. This is the preferred arrangement, in which the length of the inner coil is smaller than the inner diameter of the outer coil, such that the inner coil can be rotated about its centric point relative to the position of the outer coil. In this way maximum inductance can be achieved when the inner coil has its longitudinal axis aligned with the longitudinal axis of the outer coil, and minimum inductance can be achieved when the inner coil has its longitudinal axis at right angles to the longitudinal axis of the coil Exterior. In this way, the resonance frequency of the induction line 201-202 can be varied, to take into account an increase or a reduction in the number of vehicles in the induction line, and the amount of energy that the or each vehicle Take the induction line. (400S7A.IM REALIZATION 3 Figure 3 illustrates the principles of this modification, in which part of the main resonant conductor is illustrated as 301, which has a set of discrete inductances (302, 302 ', 302"etc.) placed Each inductor has a short circuit interrupter, such as a solid state switch (303, 303 ', 303"etc.), in series with it, showing the use of SCR devices placed back to back as solid-state switches, although other devices are usable, such as TRIAC or MOSFET devices (preferable due to their low resistance when turned on and consequently their low losses by I2R) .A door power supply (304, 304 ', 304" etc.) is provided for each SCR device and isolated exciter input is used to connect a control signal.Preferably the values of the inductances will be graduated in a growing series, but with small increments, such that a g Widest mains of compensatory inductance is available. Preferably, the symmetry of the track is maintained by making changes equal to the inductance of both sides of the track. In use, a stable gate current is caused to flow through a particular SCR apparatus of the series 303 at any time that a particular incremental inductance of the series 302 is not required, as determined by a frequency controlling apparatus.

REALIZATION 4, The prior art method of letting the resonant energy supply detect zero crossing points of the resonant current in the primary circuit, and to be switched at that moment, resulting in a resonant energy supply whose frequency The actual operation is set by instantaneous values of L and C and therefore can drift, it can be replaced by a method in which the switching points are determined by an external, independent, and stable clock. Although the resonant circuit could no longer emulate a pure resistance each time the operating frequency is not the same as its frequency 44003PA.I93, and that is why a power factor component can arise, this is minimal when measured in switching devices based on a single cycle. To compensate for possible problematic power factor effects, switched inductances or capacitances may also be introduced into the circuit as the embodiments of FIGS. 3 or 7 above. This method does not require any retuning in the individual cheeks part, and is insensitive to the effects of the over-critical damping in the power factor around resonance (see Figure 8). It also has the advantage for airports and the like that any radiated electromagnetic interference is of a constant frequency, which can be placed somewhere where it will not interfere with identified devices. In more detail, Figure 4 shows a simplified diagram 400 of a constant frequency resonant energy supply, with two solid state switches 401, 401 'which alternately connect each side of the resonant line 402 to a conductor 403; while a return of c.c. it is provided by means of the center bypass choke type inductor 404. A capacitor 405 is the resonant capacitor. A crystal-controlled oscillator with an optional 406 divider chain (crystal: 409) generates complementary 10 KHz pulse pulses and sends them to solid-state switches (10 KHz is a preferred frequency, but another frequency can also be used). Optionally, for example to take into account thermal effects in resonant components, a frequency can be generated which in the short time is stable but which varies according to, for example, local or ambient temperatures.

EMBODIMENT 5 In this embodiment the resonance frequency of the primary circuit is allowed to find its own stable level, while each of the consuming devices has to individually track that frequency by causing its own parameters of secondary resonant circuit to change in this way. equal it The advantages of this approach include (a) «4 0IPA.I93 that minor currents are involved, (b) the system is more robust because it has inherent redundancy, (c) the sensor process is located within the apparatuses responsible for variations in the load and, ( d) it is less likely that the possible voltage limits will be exceeded - especially by momentary oscillations - since the secondary resonant circuit will tend to minimize the maximum amplitude of any momentary oscillation generated by switching capacitors. Figure 5 shows a secondary sounding circuit 500, together with a frequency monitor 510 (which can be understood as: a fixed phase circuit [PLL = "phase-locked loop"), a circuit like the one shown in Figure 7, or a preprogrammed series of cause / effect combinations), a series of incremental capacitors 502, 502 ', 502"etc, and series switches 504, 504', 504" et c, the Those in use are switched by the controller in such a way as to cause the resonance frequency of the entire circuit 500 to closely track the operating frequency of the primary circuit 501.

REALIZATION 6 The real iz ac l ion of the specialized secondary or "false cheek" shown in Figure 6 is a hybrid in the sense that it is similar to a frequency switch on board the cheek as in the previous realization, but, being located adjacent to the switching power supply, it could be under the control of a master controller and could also be used as an apparatus to verify the operation of the line. While secondary circuits are normally provided around a resonant inductive energy transfer system as mobile consumers, a dedicated and fixed secondary circuit, preferably located in or within the main switching power supply and inductively coupled to the power supply output , can be used to (a) verify the proper functioning of the system, and (b) modify the characteristics of the primary circuit for a relatively low cost. < 400.PA. t9.

Figure 6 shows a typical specialized secondary resonant circuit or "false carriage" (611-613) coupled to an inductively driven 600 track system. (603 is the main resonant capacitor, 604 is the central bypass inductor, while the inductor 605 provides a constant current supply from the DC source 606. 607 and 608, the switching apparatuses are controlled by a controller 609). The secondary inductor 611 is coupled by the primary inductor 610 to the primary resonant circuit 601, and the tuning capacitor 612 completes the resonant circuit in this secondary resonant circuit. The capacitor 612 is shown as a variable apparatus; a master controller could vary this capacitor as in embodiments 1, 5 and 7, to tune the "false carriage" and thus affect the resonance in the primary circuit. Since this circuit is electrically isolated from the primary, one side of it can be connected to or refer to a ground system, and a test point 613 can be used to provide signals proportional to the current of the resonant circuit. Means may be provided to cause the input power to the resonant or switching power supply to be cut off if the circulating resonant current rises too high. The preferred percentage of turns of the inductance 611 compared to the inductance 600 will preferably be more than 1, to allow relatively low current switching in the "false carriage" to effect a variant capacitance 612, by, for example, adding or removing increments of capacitance by commutation. This coupling mode can give a relatively high voltage induced resonant current which is rather responsive to control in a low loss mode by solid state switches such as MOSFET devices or high voltage bipolar transistors. The I of the losses by I2R is reduced by a given power. Because these active devices are incorporated into a secondary resonant circuit, they are better protected, relatively speaking, against momentary oscillations in the primary resonant circuit. This method is generally preferred over those that modify the frequency per share «400SFA.I» directly inside the primary circuit. It also has the advantage with this method - which involves a resonant circuit adjacent to, and under the direct control of the master frequency controller - that changes can be made quickly so as to immediately compensate for changes in the primary frequency as a result of the circuit resonant slave is inside or near the resonant energy supply and its controller.

Calculations on the "effective capacitance" that can provide a "false cheek".

By way of a realistic example (see Figure 5) in which the secondary inductance 611 of the "false cheek" is 300μH, tuned to resonance by a 612 capacitor of 0.9μF, the mutual inductance M is 10μH,? (frequency) is 2 * p * 104, and in which a switch 614 can convert the resonant circuit into an open circuit ....

The impedance reflected on the track is: Z2 '- (? 2m2) / Z2 where Z2 = j (? L2 - l /? C2) In the case where C2 (612) is disconnected from the circuit (open circuit) ....

Z2 '- -j. 20.9 x 10"3 = > C2 '= 759μF In comparison to the case where C2 is connected to the circuit ....

Z2 '= -j. 1,165 = > C2 '= 46.9μF Thus, a 0.9 microfarad capacitor can simulate a Í400-PA.I93 much larger capacitor to the primary path, EMBODIMENT 7 A frequency control embodiment includes a plurality of pairs of capacitors placed through the solid state switches of the switching power supply. These capacitors are provided with values in an arithmetic series, in such a way that a digital approximation can be created and maintained at a given value. Surprisingly it has been discovered that, since the frequency of the resonant system takes time to adjust to a new frequency, it is possible to use only an additional pair of capacitors through the solid state switches, and to vary the duty cycle over which the torque is connected to the circuit, to achieve precise control over frequency. The duration of the frequency change, as a result of a step alteration imposed in L or C in this type of resonant inductive energy distribution system, is relatively long - at least a few and up to 10 milliseconds - especially when one or more secondary resonant circuits carry resonant current to a primary frequency, which will tend to continue resonating at that primary frequency. To achieve a more accurate and continuous control of the frequency than could be provided by the long-term introduction of relatively large increases in inductance or capacitance, these increments can be repetitively added to the system, or removed from the system by switching, for durations of even a single cycle, after which the average frequency will assume an intermediate value. Figure 7 illustrates at 701 a resonant energy supply similar to that of Figure 6 in which an additional pair of semiconductor switches 712, 713, are connected or disconnected by means of the gate control buffer circuit 711 (eg, of the type integrated circuit ICL 7667) to insert the capacitors 714 and 715 into the resonant circuit. The control section is illustrated in 700. A (5400SPA.I93 square wave version of the resonant voltage which has been taken from capacitor 716 (typically converted by limitation and a circuit with hysteresis of the Schmitt type, ["Schmitt trigger"] as is well known to those skilled in the art) applies to the input current, this will be approximately 10 KHz for preferred systems.The signal is fed to a frequency to voltage converter 702, preferably having a time constant of about 10 mS.The frequency output dependent on this The stage is connected to an integral proportional controller section 703 for which real-size components 704 determine their response characteristics.A stable voltage is set at 721 to provide a reference for the circuit.The output is fed to a converter from voltage to frequency 705, the output of which 722 is nominally 1.28 MHz and which is fed to an 8 bit binary divider 706 to give a division of 256. A reset input 709 to this divider is created from the rising edges of the square wave input signal as a short pulse (preferably less than 0.5 s within a single action device ["one shot device" "] 708. Therefore the divider 706 creates a square wave signal of a nominally 5 KHz frequency. This is fed to the D input of a flip flop 707, while the original signal is fed to the clock input. Thus, the Q output of the "flip-flop" jogger will be either high (when the frequency of the signal is too low or it is necessary to remove capacitance) or low (when the frequency of the path it is too high and extra capacitance is required). This signal 710 is fed to the buffer circuit 711 and then to both MOSFET or IGBT transistors 712 and 713, and therefore causes the connection to the circuit, or disconnection of the circuit from the capacitors 714 and 715. There are of course many other ways by the which frequency control could be implemented. Figures 8a, b and c illustrate measurements of the relationship between phase angle (Y axis) and frequency (X axis) for a resonant energy distribution system having primary and secondary resonant circuits. The «400SPA.« M nominal resonance frequency is 10 KHz. The points at which the zero phase angle line intersects represent true or false resonant modes. Computerized measurements and models of an inductive energy transfer system show that while the coupling between primary and secondary circuits rises (for example from that shown in Figure 8a to that of Figure 8b) towards a critical value (Figure 8b), the phase angle plot against frequency develops a twisting, tending to the horizontal. In the case of over-critical coupling, the phase graph (Y) versus frequency (X) will show a brief directional retraction at the zero point location (Figure 8c) if the circuit under test is quickly precipitated by resonance. The critical coupling is defined as the condition in which the trace passes horizontally through the resonance point, while in the subcritical coupling the trace crosses the zero phase line once. With critical coupling conditions the switching resonant power supply may show an instability in the operating frequency since the conditions of "pure resistance" or zero power factor are satisfied at more than one frequency. EMBODIMENT H In this embodiment a primary circuit having more than one resonant capacitor spaced apart from each other (a practice used to extend the length of the track among other reasons) has been restricted to minimize a possible variety of oscillation frequencies. Any pair of L and C can form a resonant circuit, and if one considers the typical manufacturing tolerances and variations in track inductance, it will be apparent that a number of possible resonance frequencies could be adopted, by means of various combinations of adjacent inductance and capacitance. If the capacitors were joined, more particularly at points of amplitude and similar phase, the possible modes of oscillation would be restricted. Zero inductance cables can be used to join nodes spaced from the power supply and therefore to restrict possible modes of oscillation. «00SPA.I93 A zero inductance cable (for example 910 or 924) will typically be one that has a pair of physically symmetrical conductors, electrically isolated from each other, and still tightly coupled magnetically. A close approximation to the ideal is an extension of litz wire with conductors randomly distributed to one group or the other, and therefore intermingled. Multiple conductor cable for telephones, in which color coding facilitates grouping, is a more realistic type of cable. In use a current in one conductor flows against a current in the opposite direction in the other conductor, so that in large part the magnetic fields cancel each other out and to a large extent the conductor appears to have no intrinsic inductance. Figure 9 shows 3 examples of the use of zero inductance cables to join spaced nodes of a circuit and therefore to restrict the oscillation modes. Figure 9a illustrates a single primary conductor module having two capacitors 906 and 907 separated by the intrinsic inductance 905 and 909 within the primary conductors. The zero inductance cable 910 joins the capacitors and a crossover is provided at 911 because the phase of the current at the head on the left side (see the vectors marked V) will be contrary to the phase of the current at the head on the right side , in resonance, but equal to the phase of the current at the bottom of the right side. Preferably the capacitors will be reasonably well matched at the time of assembly, so that the difference currents flowing through the zero inductance cable will be minimized, and the currents remaining in the zero inductance cable will comprise dynamic corrections. to cancel the imbalance. FIGURE 9b illustrates a zero inductance lead wire that joins the ends of a modular primary path such that the capacitor / generator pair 922 is effectively maintained at voltage through the far capacitor 923. Intermediate modules (such as 921) ) are shown with connectors to adjacent modules. Figure 9c illustrates a special case of 9b, in which an almost continuous circuit path 940 forms a Í400SP? .I9J circumambulation and is excited by a power supply 949 (typical manufacturing processes commonly have conveyor belt apparatuses running a closed circuit of this kind). To join the nodes in the capacitors at the beginning (943) and at the end (947), a simple cable or connection that includes a 950 crossover completes the circuit of the conductors of the entire path 941 and 942. The intermediate primary conductor modules do not are shown here Finally, it will be appreciated that various alterations or modifications to the foregoing can be made, without departing from the scope of this invention, by means of the following claims.

C400SPA.I93

Claims (15)

RE.I VI NDI CAC I ONE S

1. A non-contact energy distribution system to cause electrical energy to be transferred from a primary resonant circuit capable of generating an alternating magnetic field to at least one movable object having at least one secondary resonant circuit that incorporates an inductive coil to intercept said magnetic field and therefore generate an electromotive force, characterized in that said power distribution system includes means for maintaining the resonant frequency of the primary resonant circuit and of the resonant circuits secondary to, or close to, a consistent frequency.

2. A non-contact power supply to cause electrical energy to be transferred from a primary resonant circuit to at least one movable object having at least one secondary resonant circuit that incorporates an inductive coil to intercept a magnetic field and therefore generating an electromotive force, said power supply comprising a supply of switching power that generates a high frequency resonant current, characterized in that there are means for maintaining the frequency of the resonant current at or near a predetermined frequency.

3. A non-contact power supply according to claim 2, characterized in that the switching power supply is driven by a stable oscillator.

A non-contact energy distribution system according to claim 1, wherein the primary resonant circuit comprises one or more elongated primary conductors having more than one resonant capacitor for each elongated primary conductor, located at physically separate sites around the elongated primary conductor (s) characterized in that the capacitors are electrically connected in similar phase nodes by means of a zero inductance cable. «S400SPA.I93

5. A non-contact energy distribution system according to claim 1, characterized in that the primary resonant circuit includes means for varying the resonant inductance included in the circuit in such a way that the resonance frequency is largely stable.

6. A non-contact energy distribution system according to claim 5, characterized in that the means for varying the resonant inductance in the primary inductive circuit comprises a first inductance in series with a primary conductor, mutually coupled, by a variable amount , to a second inductance in series with a second primary inductor. A non-contact energy distribution system according to claim 5, characterized in that the means for varying the resonant inductance in the primary inductive circuit comprises one or more discrete inductances in series with each primary conductor, each discrete inductance being capable to be connected to, or disconnected from, the circuit with an associated switch driven by a controlling device. 8. A non-contact energy distribution system according to claim 1, characterized in that the primary resonant circuit includes means for varying the resonant capacitance included in the circuit so that the resonance frequency is largely stable. 9. A non-contact energy distribution system according to claim 8, characterized in that the means for varying the resonant capacitance comprise one or more additional capacitances capable of being connected to the primary resonant circuit by means of a corresponding switch. A non-contact energy distribution apparatus according to claim 1, characterized in that a dedicated secondary resonant circuit having inductance and capacitance is coupled to the primary circuit, and because its resonance frequency is capable of being altered by adjustments to the inductance or capacitance in such a way as to cause, "400IPA." (3) by means of the coupling to the primary circuit, that the resonant frequency of the primary circuit is maintained at a largely constant value 11. A non-contact energy distribution apparatus according to claim 1 , characterized in that the or each secondary resonant circuit is provided with means for detecting the frequency of the primary resonant circuit, and means for altering the resonance frequency of the secondary circuit (s) in such a way as to largely emulate the frequency of the primary circuit 12. A non-contact energy distribution system according to claim 11, characterized in that the secondary circuit is equipped with means to include or exclude additional resonant capacitance 13. A non-contact energy distribution system according to claim 11, characterized in that the secondary circuit is equipped with means to include or exclude inductance reso additional nante. 14. A non-contact energy distribution system according to claim 11, characterized in that the secondary circuit is equipped with means for determining the power factor of the secondary circuit, together with means for altering the resonance that are capable of controlling the Inclusion or exclusion of capacitance or additional resonant inductance. 15. A non-contact energy distribution system according to claim 11, characterized in that the secondary circuit is equipped with means for determining the power factor of the secondary circuit, together with means for altering the resonance that are capable of controlling the Inclusion or exclusion of additional resonant inductance. IN TESTIMONY OF WHICH WE SIGNED THE PRESENT IN MEXICO, D.F. SEPTEMBER 7, 1993. Í4003PA.I93