WO1996039737A1

WO1996039737A1 - Pulsed power rotary amplifier

Info

Publication number: WO1996039737A1
Application number: PCT/US1996/009151
Authority: WO
Inventors: Joseph F. Pinkerton; David B. Clifton
Original assignee: Magnetic Bearing Technologies, Inc.
Priority date: 1995-06-06
Filing date: 1996-06-05
Publication date: 1996-12-12
Also published as: AU6026096A

Abstract

A pulsed power rotary amplifier (100) provides high-magnitude electrical power on-demand by converting stored kinetic energy into a highly controllable electrical signal. The conversion occurs through the use of a composite structure formed by a flywheel (106) attached to a brushless generator (104), such that the rotating electromagnets (112) of the brushless generator (104) are essentially held in place by the flywheel (106). The rotary amplifier (100) produces a large DC output signal from a small DC input signal, or provides an increased AC output signal from a small AC input signal. Additional control of the amplifier output is accomplished through a feedback circuit (200) which adjusts a control signal based primarily on an output signal.

Description

PULSED POWER ROTARY AMPLIFIER

Background of the Invention

This invention relates to devices which provide pulses of electrical energy from stored mechanical energy for short periods of time. More particularly, this invention relates to converting stored kinetic energy into controllable electrical signals. The use of energy storage devices for storing mechanical energy and applying it as electrical energy is well known. For example. Meek et al. U.S. Patent No. 4,034,273 provides a flywheel mounted to an interconnecting driveshaft. The flywheel stores kinetic energy which is delivered through an amplifier to a DC motor to turn a weapons turret. Meek provides the amplification of the kinetic energy through a "conventional high speed rotary amplifier" which, however, may suffer from any one of several deficiencies, including low power density and the use of electrical brushes.

One such conventional rotary amplifier is described in Race U.S. Patent No. 3,020,466. Race discloses an automobile electrical system that includes a control oscillator and a rotary magnetic amplifier to furnish AC current at a desired frequency. The amplifier, however, includes brushes which have a tendency to limit lifespan of the device, as well as requiring frequent maintenance. An additional deficiency of conventional rotary amplifiers is the potential difficulty in compensating for power supply transients due to severe variations in electrical loading on the system (for example, if an air conditioner and headlights are turned on in a car at the same time) .

One attempt at addressing these potential deficiencies has been the replacement of brush amplifiers with brushless amplifiers. In brushless amplifiers (which are often called brushless generators) , an exciter winding is fed a small input signal which induces a much larger signal in a rotating member. The input signal, which may be a DC current or a low frequency AC current, causes an AC current to be induced in the rotating member. The AC current is converted to DC by a rectifier assembly which is typically located within the rotating member. One example of a known rotating rectifier is described in Pinchott U.S. Patent No. 5,065,484. The rectified DC current flows through the main electromagnet windings (on the rotating member) and creates a large rotating magnetic field. The rotating field interacts with the non-rotating main armature to generate a large AC signal in the armature windings. This large AC signal, which is delivered to the external load, may be effectively 10,000 times greater than the signal that was input to the exciter.

Unfortunately, brushless generators also suffer from deficiencies related to friction and wear on the bearings. The potential for increased friction and wear on the bearings becomes even greater as the rotational speed of the generator increases. A desired increase in rotational speed is a growing trend in industry due to the fact that the output of the rotating machine tends to increase as rotational speed increases. Therefore, in order to achieve greater rotational speeds, engineers must design brushless generators that are smaller and more compact than traditional designs (to simplify and reduce the effects of the higher speeds) .

One known method for addressing bearing wear is to replace the conventional bearings with magnetic bearings. Unfortunately, the magnetic instability of the iron core armature would compete with the stabilizing magnetic forces of the magnetic bearing. As such, the magnetic bearing would have to be prohibitively large to overcome the generator's magnetic forces. An additional consideration that may affect the operation of a device such as the drive system of Meek is the mechanical stresses on the system during high speed operation (i.e., when high energy output is required from the flywheel) . The greater the energy requirement, the faster the flywheel must spin and the greater the centrifugal force on the rotary amplifier which is mechanically coupled to the flywheel. It is conceivable that, at a given speed, the rotating electromagnetic could actually be pulled away from the assembly, resulting in a catastrophic failure.

Another known method which attempts to resolve some of the deficiencies of systems such as Meek is the replacement of the rotary amplifier (either the brushless type or the type with brushes) with a permanent magnet generator (PMG) . For example, "A High Efficiency Electromechanical Battery," by Richard F. Post et al., Lawrence Livermore National Laboratory, June 11, 1992 (hereinafter "Post") , describes the use of a flywheel/PMG system which might be used to improve the performance of electric vehicles. Flywheel/PMG systems, however, also have inherent inefficiencies, typically related to the fact that the output of the PMG is not at the proper frequency for use by other electrical components. Therefore, devices such as the one described by Post also require frequency converters to provide usable signals to a user. Unfortunately, to achieve efficient switching, such converters typically include solid- state MOSFET switching transistors which can be prohibitively expensive. In addition, the cost of the permanent magnet material is approximately 100 times the cost of transformer steel. Such switching techniques often function at frequencies five to ten times higher than the highest frequency handled to produce a near-sinusoidal waveform in an efficient manner, and often utilize Pulse Width Modulation (PWM) to perform frequency conversion.

Even though the output signal is produced at the proper frequency in a somewhat efficient manner, the high frequency of the switching operation produces excessive heat and substantial electrical noise. These potential problems are due, at least in part, to the fact that the transistors are switching on and off while large voltages are applied across them. For example, a typical conversion operation requires switching transistors to switch voltages up to 1200 volts in microseconds. The electrical noise from such a device could, for example, make it practically impossible to operate a radio in an automobile. In view of the foregoing, it is an object of this invention to provide improved pulsed power rotary amplifiers which convert mechanical energy into a controllable electrical output without the use of electrical brushes, permanent magnets, or PWM amplifiers. It is also an object of the present invention to provide improved pulsed power rotary amplifiers which provide a high magnitude of electrical power on- demand for short periods of time. It is a further object of the present invention to provide improved pulsed power rotary amplifiers which operate in a stable state at high rpm.

It is a still further object of the present invention to provide improved pulsed power rotary amplifiers which are compact, inexpensive, and efficient to operate.

It is additionally an object of this invention to provide methods for increasing the electrical output of a device which converts stored mechanical energy to electrical energy.

Summary of the Invention

These and other objects of the invention are accomplished in accordance with the principles of the invention by providing pulsed power rotary amplifiers that produce a high rate of conversion of stored mechanical energy to electrical energy. The rotary amplifier or brushless generator is combined with a flywheel in a composite structure which produces an electrical output signal based on a controllable DC or AC input signal and the amount of stored mechanical energy available. Alternate embodiments of a composite structure are disclosed including banding the rotating electromagnets with the flywheel, and connecting the flywheel and generator together via a simple shaft. By combining the flywheel with the rotating amplifier components in at least one of these configurations, the effects of centrifugal force are substantially compensated for, thus allowing the device to efficiently operate at significantly higher rotational speeds.

The pulsed power rotary amplifiers of the present invention include a brushless generator fixed to a composite flywheel mass, a rectification circuit to convert the AC output of the generator to controllable DC, and a feedback signal, coupled to the input circuit of the generator, which adjusts the generator's control signal in response to feedback taken from the generator's output. The brushless generator armature cores may comprise magnetic or non¬ magnetic material, depending on the application. If non-magnetic material is required, air-core coils of non-magnetic wire are rotated through the DC field created by the stationary electromagnets, rather than traditional iron core components. Those skilled in the art will appreciate that the most significant core losses and magnetic forces occur in the main stage of the generator and, therefore, although it may be beneficial to include air-core coils in the exciter stage, it is by no means a requirement of the principles of the present invention to do so. Additionally, for given applications, it may not be necessary to utilize air-core coils in the main stage either, such that both the exciter stage and the main stage are implemented with traditional iron-core elements.

In one preferred embodiment, the composite flywheel/generator mass is contained in a vacuum housing, thereby increasing system performance by the reduction of losses due to aerodynamic drag. Alternatively, the composite mass may be contained in a housing at normal atmospheric pressure (or other pressure as is appropriate) . Whether or not a vacuum is used, the rotating electromagnets are preferably banded together by the flywheel, which acts to relieve a portion of the mechanical stress on the electromagnets. In view of the fact that power output increases approximately to the fourth power of rpm for a given input power, and the fact that the rotary amplifier of the present invention can spin the electromagnets faster, a higher power output is produced (e.g., at twice the rotational speed, the amplified output should increase approximately sixteen times for a given input) .

Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments.

Brief Description of the Drawings

FIG. 1 is a cross-sectional view of a pulsed power rotary amplifier, in accordance with the principles of the present invention; FIG. 2 is a schematic diagram of one embodiment of a control circuit for the pulsed power rotary amplifier of FIG. 1;

FIG. 3 is a graph showing the output signal of the pulsed power rotary amplifier of FIG. 2; FIG. 4 is a graph showing the rectified output signal of the pulsed power rotary amplifier of FIG. 2;

FIG. 5 is a graph showing the rectified and filtered output signal of the pulsed power rotary amplifier of FIG. 2;

FIG. 6 is a schematic diagram of an alternate embodiment of a control circuit for the pulsed power rotary amplifier of FIG. 1; FIG. 7 is a graph showing a sample input signal of the pulsed power rotary amplifier of FIG. 6;

FIG. 8 is a graph showing the output signal of the pulsed power rotary amplifier of FIG. 6, based on the input signal of FIG. 7;

FIG. 9 is a graph showing the rectified output signal of the pulsed power rotary amplifier of FIG. 6, based on the input signal of FIG. 7;

FIG. 10 is a graph showing the rectified ^and filtered output signal of the pulsed power rotary amplifier of FIG. 6, based on the input signal of FIG. 7;

FIG. 11 is a graph showing the output signal of the pulsed power rotary amplifier of FIG. 6, based on the input signal of FIG. 7, taken off the secondary winding of an output transformer;

FIG. 12 is a schematic diagram of a preferred embodiment of a control circuit for the pulsed power rotary amplifier of FIG. 1; FIG. 13 is a graph showing a sample input signal of the pulsed power rotary amplifier of FIG. 12;

FIG. 14 is a graph showing the output signal of the pulsed power rotary amplifier of FIG. 12, based on the input signal of FIG. 13; FIG. 15 is a graph showing the rectified output signal of the pulsed power rotary amplifier of FIG. 12, based on the input signal of FIG. 13;

FIG. 16 is a graph showing the rectified and filtered output signal of the pulsed power rotary amplifier of FIG. 12, based on the input signal of FIG. 13;

FIG. 17 is a graph showing the output signal of the pulsed power rotary amplifier of FIG. 12, based on the input signal of FIG. 13, taken off the output of an H-bridge circuit; and FIG. 18 is a schematic block diagram of an alternate embodiment of a pulsed power rotary amplifier in which a three-phase motor is driven in accordance with the principles of the present invention.

Detailed Description of the Preferred Embodiments

Referring to FIG. 1, a preferred embodiment of a pulsed power rotary amplifier 100 in accordance with the principles of the present invention is described. Rotary amplifier 100 includes housing 102, which is preferably a vacuum sealed enclosure, for containing brushless generator assembly 104, flywheel 106, and bearings 108. Housing 102 may be formed as vacuum sealed unit, of stainless-steel, or it may be formed using multiple pieces of a non-magnetic material such as aluminum or composite material. As described above, although rotary amplifier 100 provides increased performance in a vacuum, the use of a vacuum sealed enclosure is not required to practice the principles of the present invention. Brushless generator assembly 104 comprises two separate stages, exciter stage 110 and main stage 130. The input signal is typically fed into exciter stage 110, while the output signal is typically output from main stage 130. Exciter stage 110 includes a plurality of stationary electromagnets 112 (for example, generator 104 has eight pairs of electromagnets 112) located at equidistant points about the circumference of axis 150. Electromagnets 112 may comprise ferrous core 114 surrounded by windings 116. Windings 116 are coupled to control line 118 which receives the control signals to generator 104, as is described more fully below. Core 114 may be formed from a laminated stack of magnetic material such as soft iron or steel (such that the material is only magnetized in the presence of a magnetic field) . Alternately, core 114 may be formed from a solid magnetic material such as ferrite, or any other suitable material. Electromagnets 112 are arranged in pairs which may be referred to as inner electromagnets 120 and outer electromagnets 122.

Exciter stage 110 also includes a plurality of electrically conductive, non-magnetic, air-core loops 124 embedded within, and extending from, flywheel 106, which forms the armature of the exciter. Loops 124 are mounted such that they extend from hub 152 of flywheel 106 circumferentially about axis 150.

Although it is preferable that the armature of the exciter be formed with air-core loops, the rotary amplifier of the present invention will also be effective with traditional iron-core components in the exciter armature. Loops 124 are fixedly mounted to flywheel 106 such that when flywheel 106 rotates, the plurality of air-core loops 124 are rotated about axis 150 between inner electromagnets 120 and outer electromagnets 122. The rotational axis of flywheel 106 may be connected to a motor or prime mover (not shown) , such as a permanent magnet "brushless motor."

Additionally, brushless generator 104 may itself be used as a motor by simply applying a DC signal to input line 118 which ultimately energizes rotating electromagnet 132. Once energized, a properly timed AC current applied to output line 138 causes a force against rotating electromagnet 132 that increases the rotational speed of the flywheel/brushless generator assembly. Further, if the flywheel/brushless generator assembly is not rotating, an AC input signal applied to line 118, through transformer action, energizes the rotatable electromagnet 132 with DC fields to initialize rotation, at which point a DC signal is then applied as described above to establish brushless generator 104 as a motor.

Main stage 130 includes a plurality of electromagnets 132 which are mounted to, and at equidistant points about, flywheel 106. It is preferable, but not essential, that there be the same number of electromagnets 132 in main stage 130 as there are electromagnets 112 in exciter stage 110. Electromagnets 132 are substantially similar to electromagnets 112 and thus, may also be comprised of a ferrous core 134 surrounded by windings 136. Unlike windings 116, windings 136 are coupled to conversion lines 146 which receive input signals from conversion circuitry 154. Conversion circuitry 154 converts AC signals to DC signals, as described below, and may include any conventional rectification circuit (for example, a full-wave bridge rectifier) . Alternately, conversion circuitry 154 may also include a parallel capacitor (not shown) to condition the pulsating DC signal into a smoother DC signal. Core 134 may also be formed from a laminated stack of magnetic material such as soft iron or steel (such that the material is only magnetized in the presence of a magnetic field) . Alternately, core 134 may be formed from a solid magnetic material such as ferrite, or any other suitable material.

Electromagnets 132 are arranged in pairs which, for reference purposes, may be referred to as inner electromagnets 140 and outer electromagnets 142.

Main stage 130 also includes a plurality of electrically conductive air-core loops 144 fixedly mounted to housing mount 156 in the same manner as loops 124 are mounted to flywheel 106. In main stage 130, when flywheel 106 rotates, the plurality of electromagnets 132 are rotated about axis 150 such that air-core loops 144 are located between inner electromagnets 140 and outer electromagnets 142. Conductive air-core loops 144 are coupled to output line 138, which provides the output signal from generator 104 and thus, from rotary amplifier 100. Although it is preferable that the armature of the main stage be formed with air-core loops, the rotary amplifier of the present invention will also be effective with traditional iron-core components in the main stage armature. FIG. 2 shows a schematic diagram of one embodiment of a control circuit 200 coupled to rotary amplifier 100 of FIG. 1. For the sake of convenience, rotary amplifier 100 of FIG. 2 is substantially identical to rotary amplifier 100 of FIG. 1 and thus, the description above regarding amplifier 100 is equally applicable to FIG. 2.

In FIG. 2, output line 138 is shown as a pair of output lines 202 coupled to a rectification circuit 204. Rectification circuit 204 may be a full- wave bridge rectifier, as shown, or any other convention rectification circuit which provides rectification of the AC output into DC. The output of rectification circuit 204 is coupled to an inductor 206 and a capacitor 208 which act to filter the output of the rectifier into the final output signal V_Q across terminals 210 and 212. Additionally, measurements of voltage, current, or both may be taken from the output signal and fed back to input circuitry 214 via line 216. Or, instead, a feαdback signal may be produced based on rotational speed measurements of a motor (not shown) being driven by amplifier 100 (the speed measurements may be made by any conventional means, e.g., a non-contacting tachometer). Input circuitry 214 receives input signals via line 218 and, based on the feedback signal, sends control signals to rotary amplifier 100 via control line 220 (which is coupled to control line 118 within amplifier 100) .

Each air-core loop (including loops 124 and 144 as shown in FIG. 1) may be a unitary piece of solid electrically conductive material, but preferably air-core loop is made up of turns of wire consisting of a plurality of electrical conductors which are electrically insulated from each other and are electrically connected together in parallel. One such wire, known as litz wire, is constructed of individual film-insulated wires which are bunched or braided together in a uniform pattern of twists and length of lay. This configuration reduces skin effect power losses of solid conductors, or the tendency of radio frequency current to be concentrated at the conductor surface. Properly constructed litz wires have individual strands each positioned in a uniform pattern moving from the center to the outside and back within a given length of the wire. The manner in which conductive air-core loops 124 affect brushless generator 104 is now described. Essentially, when current is applied to windings 116, magnetic fields are generated between inner electromagnets 120 and outer electromagnets 122. As air-core loops 116 rotate (on axis 150) through the fields, the relative motion between air-core loops 124 and electromagnets 112 produces an electromotive force (i.e., a voltage around each of the conductive loops) which induces current in air-core loops 124. Thus, a voltage is induced in exciter stage 110 without the use of iron in the armature (which is the high frequency portion of the exciter) .

Brushless generator 104 operates by providing a small DC input signal or a low frequency (e.g, below 1 khz) AC input signal, such as one watt, to input line 218 while flywheel 106 is rotating about axis 150. The control signal is produced by input circuitry 214 in response to a comparison of the feedback signal on line 216 and the input signal on line 218 (which produces an error signal) . The use of feedback is especially advantageous at frequencies exceeding about 50 hz, the approximate point at which the output may tend to otherwise become somewhat distorted (due to the time constants of the exciter and main electromagnets) . Additionally, in view of the relationship between amplification and rotational speed, it may also be advantageous to provide pre¬ determined corrections for the error signal based on angular velocity of the amplifier (which may be measured by, for example, a non-contacting tachometer) . The control signal is fed to windings 116 which energize stationary electromagnets 112, thereby creating small, radially-directed, DC magnetic fields (or low frequency AC fields) . If AC signals are used for input signals, the AC signals should be limited to about one-tenth the output frequency of air-core loops 124. Otherwise, the amplification effect will be lost (as the input frequency gets closer to the rotating frequency, the amplification factor goes down, eventually reaching a point where no amplification takes place) . At the same time, flywheel 106 rotates air-core loops 124 through the generated DC fields and thus, as described above, AC currents are induced in the air-core loops 124. The induced AC currents are fed, through exciter output lines 126, to conversion circuitry 154. Conversion circuitry 154 converts the AC signal to a DC signal such that the input power is amplified by the exciter stage by a factor of approximately 100. It should be noted that the total amplification factor increases rapidly with respect to rpm (approximately to the fourth power) . For effective amplification, the axial length of core 134 of electromagnet 132 should be at least approximately three times greater than the radial length of air-coil core 144. The greater the ratio, the greater the amplification.

Similarly, the amplified DC signal is fed to the windings 136, through lines 146, of rotating electromagnets 132. The amplified DC signal energizes electromagnets 132, thereby creating a second set of radially-directed DC fields which, in this case, are rotating about axis 150. Because air-core loops 144 are located in the rotating fields, in a manner similar to the interaction between electromagnets 112 and air- core loops 124, AC voltages are induced in air-core loops 144. If an electrical load is placed across terminals 210 and 212, an electrical current will also be induced in air-core loops 144. These induced voltages are provided as outputs from generator 104, and thus amplifier 100, at output line 138. Due to the dual amplification (each stage amplified the power of the signal input to it by a factor of 100) , the power of the final output signal is approximately 10,000 times greater than the small signal which was input to exciter 110.

The rotational frequency of flywheel 106 has a direct relationship to the output power of amplifier 100, such that maximum output power (i.e., where main stage electromagnets 132 have reached magnetic saturation) increases with the square of rotational speed. The added mass of flywheel 106 and its rotation provide kinetic energy which is converted to electrical energy by brushless generator 104. When instantaneous demands for increased power are seen at the output terminals 210 and 212, rotary amplifier 100 converts the kinetic energy stored in rotating flywheel 106 into electrical energy which is output via lines 202 in addition to the average energy supplied by the prime mover or motor (not shown) . Therefore, rotary amplifier 100 provides a high-magnitude of electrical power on-demand for short periods of time (after which, the kinetic energy in the flywheel is depleted) . FIGS. 3-5 are representative graphs showing different signals of the circuit of FIG. 2 based on a DC input signal. FIG. 3 shows a trace 250 of the output signal as seen on lines 202 prior to rectification circuit 204. Trace 250 is essentially the "raw" output signal of rotary amplifier 100.

FIG. 4 shows a trace 260 of the output signal after it has passed through rectification circuit 204. FIG. 5 shows a trace 270 of the final output signal V_Q after rectification by rectification circuit 204 and filtering by inductor 206 and capacitor 208.

FIG. 6 shows an alternate embodiment of a control circuit 600 coupled to rotary amplifier 100 of FIG. 1. For the sake of convenience, rotary amplifier 100 of FIG. 6 is substantially identical to rotary amplifier 100 of FIG. 1 and thus, the description above regarding amplifier 100 is equally applicable to FIG. 6.

The circuitry of FIG. 6 is especially applicable to converting small sine-wave signals into much larger ones. Therefore, unlike control circuit 200 of FIG. 2, which essentially produced a DC output from a DC input, control circuit 600 produces an AC output signal from an AC input signal (albeit a small signal) . Control circuit 600 includes output lines 602, which are coupled to output line 138 of FIG. 1 in the same manner as output lines 202 of FIG. 2 were coupled to output line 138. The output signal of amplifier 100 is rectified by rectification circuit 604, which, as was described above for FIG. 2, may be a full-wave rectifier or any other conventional circuitry which rectifies AC into DC. The rectified signal is then filtered by capacitor 608 to produce the initial output signal (whicn may also be used as a feedback signal) . The initial output signal is applied to the primary winding of transformer 606, which produces the output signal V_Q across terminals 610 and 612.

Measurements of voltage and/or current from the initial output signal are fed back to the input circuitry 614, which compares the feedback signal to an input signal received via line 618 to produce an error signal. Alternately, the feedback signal may be generated from measurements indicative of the speed at which a motor is being driven by amplifier 100. The error signal is used in conjunction with the input signal to produce a control signal' which is input to amplifier 100 via line 620. The remaining operation of control circuit 600 is essentially the same as that described above with regards to control circuit 200, and may be more easily understood by examining the representative graphs of FIGS. 7-11.

FIGS. 7-11 are representative graphs showing different signals of the circuit of FIG. 6 based on a small AC input signal. FIG. 7 shows a trace 640 of the AC control signal as seen on line 620, which represents the input signal from input line 618 after it has been modified by the feedback signal from line 616 (note that the signal has been offset such that it varies in magnitude between zero and one rather than about the zero axis) . FIG. 8 shows a trace 650 of the output signal as seen on lines 602 prior to rectification circuit 604. Trace 650 is essentially the "raw" output signal of rotary amplifier 100. FIG. 9 shows a trace 660 of the output signal after it has passed through rectification circuit 604. FIG. 10 shows a trace 670 of the initial output signal after rectification by rectification circuit 604 and filtering by capacitor 608, which is applied to the primary winding of transformer 606. FIG. 11 shows a trace 680 of final output signal V₀ which is produced on the secondary winding of transformer 606 and across output terminals 610 and 612.

FIG. 12 shows a schematic diagram of a preferred embodiment of control circuit 700 coupled to rotary amplifier 100 of FIG. 1 and additional control components of the control circuit of FIG. 2. For the sake of convenience, rotary amplifier 100 of FIG. 12 is substantially identical to rotary amplifier 100 of FIG. 1 and thus, the description above regarding amplifier 100 is equally applicable to FIG. 12. Additionally, components 202, 204, 206, 208, 214, 216, 218, and 220 are substantially identical to the like- numbered components of FIG. 2 and thus, the description above regarding those components is equally applicable to FIG. 12.

Control circuit 700 differs from control circuit 200 in that a network of switching elements formed into an H-bridge 701 is coupled between the output of the control circuit (as defined in FIG. 2) and the load. The network of switching elements includes semiconductor switches 702, 704, 706, and 708, which are coupled to output terminals 710 and 712. While the switching elements are schematically shown to be silicon-controlled rectifiers, they may alternately be any type of high-power semiconductor switch, such as a MOSFET or an IBGT (insulated gate bipolar transistor) .

Switches 702 and 704 are coupled together in series, as are switches 706 and 708. The two switch pairs are each coupled in parallel to capacitor 208. Each switch pair provides an output at a node formed between the two switches, such that the 702/704 pair provides output terminal 710, while the 706/708 pair provides output terminal 712. A load 711 is typically coupled across output terminals 710 and 712 and an additional feedback line 716 is provided from load 711 to input circuitry 214.

Control circuit 700 is advantageous when compared to previously described control circuits in that control circuit 700 may be operated with either AC or DC input signals. Thus, control circuit 700 performs the same operations as control circuit 200 and control circuit 600. For example, if DC input signals are being utilized, switching elements 702 and 708 are left ON at all times during operation. On the other hand, if AC input signals are being utilized, then switches 702 and 708 are turned ON during the positive part of the cycle and switches 704 and 706 are ON during the negative part of the cycle (the switches are otherwise turned OFF) . Thus, DC output signals are provided from DC input signals and AC output signals are provided from AC input signals without requiring the use of a transformer (i.e., transformer 606 of FIG. 6) . The operation of control circuit 700 may be more easily understood by examining the representative graphs of FIGS. 13-17. FIGS. 13-17 are representative graphs showing different signals of the circuit of FIG. 12 based on a small AC input signal. FIG. 13 shows a trace 740 of the AC input signal as seen on input line 218 (note that unlike trace 640 which shows the offset signal on control line 620, trace 740 shows a representative sample of both the actual AC input signal on input line 218 and the control signal on line 220) . FIG. 14 shows a trace 750 of the output signal as seen on lines 202 prior to rectification circuit 204. Trace 750 is essentially the "raw" output signal of rotary amplifier 100. FIG. 15 shows a trace 760 of the output signal after it has passed through rectification circuit 204. FIG. 16 shows a trace 770 of the initial output signal after rectification by rectification circuit 204 and filtering by capacitor 208, which is applied to the inputs of H-bridge 701 formed by switches 702-708. FIG. 17 shows a trace 780 of the final output signal which is produced by H-bridge 701 across output terminals 710 and 712.

FIG. 18 shows an alternate embodiment of a pulsed power rotary amplifier which drives a three- phase motor in accordance with the principles of the present invention. Pulsed power rotary amplifier 800 includes: a flywheel 806, a prime mover or motor 810, input circuitry 814, a shaft 815 having an axis of rotation 817, a three-phase motor 830, three

H-bridges 831, 841, and 851 (each substantially similar to H-bridge 701 of FIG. 12) , three brushless generators 834, 844, and 854 (each substantially similar to brushless generator 104 of FIG. l) , and three AC-to-DC rectifiers 836, 846, 856 (each substantially similar to rectifier 204 of FIGS. 2 and 12). Additionally, each of rectifiers 836, 846, and 856 preferably includes a filter capacitor similar to capacitor 208 of FIG. 2. Input circuit 814 has three input lines 838,

848, and 858, three main feedback lines 837, 847, and 857, one motor feedback line 807, and three control lines 832, 842, and 852. Generators 834, 844, and 854 and flywheel 806 are all fixedly mounted to shaft 815 such that they all rotate about axis of rotation 817 when driven by prime mover 810. Generators 834, 844, and 854 receive control signals from control lines 832, 842, and 852, respectively, and provide output signals on lines 833, 843, and 853, respectively. The amplifier 800 essentially operates as three independent systems which have been integrated into a single unit. For example, generator 834 is driven by input circuit 814 based on input signals on line 838 and feedback signals on line 837. The output of generator 834 is provided on line 833 to rectifier 836 and subsequently to H-bridge 831. The resultant signal is fed as an output signal to one phase of three-phase motor 830.

Each of the other generators (844 and 854) operate in a similar manner to drive the remaining two phases of motor 830 (with each component for generators 844 and 854 being similarly numbered to those of generator 834, except that the tens digit is changed from 3 to 4 and 5, respectively). The unit integration occurs primarily at input circuit 814, where feedback signals from each of generators 834, 844, and 854, and three-phase motor 830 are coordinated and compensated for. Input circuit 814 adjusts each of the control signals to generators 834, 844, and 854 to maintain three-phase motor 830 at the proper rotational frequency with proper phase offsets.

It will be understood that the foregoing is only illustrative of the principles of the invention, and that various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. For example, additional feedback signals could be used to modify the input to the brushless generator (e.g., the position signal representative of a shaft supported by a magnetic bearing being driven by the rotary amplifier of the present invention) . Additionally, the multiple generator configuration described above may be reconfigured such that the multiple generator outputs are instead coupled together in series to produce a greatly amplified output signal. Thus, the present invention is only limited by the claims which follow.

Claims

I Claim;

1. A pulsed power rotary amplifier having an input and an output, said amplifier comprising: a flywheel which rotates about an axis of rotation; an input circuit coupled to said input, said input circuit providing a control signal in response to an input signal and a feedback signal; a brushless generator mechanically coupled to said flywheel and electrically coupled to said input circuit, said generator providing an amplified output signal to said output in response to said control signal; and a measurement circuit coupled to said input circuit, said measurement circuit measuring selected parameters and producing said feedback signal from said measured selected parameters.

2. The rotary amplifier of claim 1, wherein said measurement circuit is coupled to said generator to measure said amplified output signal, said amplified output signal being said selected parameter, said feedback signal being said measured amplified output signal.

3. The rotary amplifier of claim 2, wherein said measurement circuit measures voltage of said amplified output signal, said voltage being said selected parameter.

4. The rotary amplifier of claim 2, wherein said measurement circuit measures current of said amplified output signal, said current being said selected parameter.

5. The rotary amplifier of claim 2, wherein said measurement circuit measures electrical power of said amplified output signal, said electrical power being said selected parameter.

6. The rotary amplifier of claim 2, wherein said amplifier output is a substantially DC signal and said measurement circuit measures said DC signal, said DC signal being said selected parameter.

7. The rotary amplifier of claim 2, wherein said amplifier output is an AC signal and said measurement circuit measures said AC signal, said AC signal being said selected parameter.

8. The rotary amplifier of claim 1, wherein said measurement circuit is coupled to a motor driven by said generator to measure rotational speed of said motor, said feedback signal being proportional to said motor speed, said rotational speed being said selected parameter.

9. The rotary amplifier of claim 1, wherein said flywheel and said generator are fixedly attached to each other, said generator having rotating electromagnets which are banded together and held in place by said flywheel.

10. The rotary amplifier of claim 1, wherein said flywheel and said generator are fixedly attached to a shaft having an axis, said flywheel and said generator rotating about said axis.

11. The rotary amplifier of claim 1, further comprising an output circuit coupled between said generator output and said amplifier output.

12. The rotary amplifier of claim 11, wherein said input signal is a substantially DC signal, said amplified output signal is a substantially AC signal and said output circuit converts and filters said amplified signal into a substantially DC signal.

13. The rotary amplifier of claim 11, wherein said input signal is a substantially small sinusoidal signal, said amplified output signal is a high-frequency AC signal having modulated amplitude and said output circuit converts and filters said amplified signal into a substantially unmodulated AC signal.

14. The rotary amplifier of claim 1, wherein said generator comprises: a stationary assembly including at least one non-rotating electromagnet and at least one non- rotating armature coil, said non-rotatiπg electromagnet producing at least one non-rotating magnetic field and having windings coupled to said input circuit; a rotating assembly including at least one rotating electromagnet and at least one rotating armature coil, said rotating electromagnet being coupled to said flywheel, rotation of said rotating electromagnet producing at least one rotating magnetic field which travels in a circular path such that said non-rotating armature coil is exposed to said rotating magnetic field, said rotating armature coil travelling in a circular path through said non-rotating magnetic fields, said relative motion of said rotating armature coil and said non-rotating magnetic field inducing an AC current in said rotating armature coil, and said relative motion of said non-rotating armature coil and said rotating magnetic field inducing an AC voltage in said non-rotating armature coil; and a conversion circuit mounted in said rotating assembly, said conversion circuit having an input coupled to said rotating armature coil and having at least one output coupled to windings of said at least one rotating electromagnet, said conversion circuit converting said AC current to a substantially DC current.

15. The rotary amplifier of claim 14, wherein said at least one rotating armature coil is an air-core coil.

16. The rotary amplifier of claim 14, wherein said at least one non-rotating armature coil is an air-core coil.

17. The rotary amplifier of claim 16, wherein: said non-rotating air-core coil has a radial length with respect to said axis of rotation of said rotating assembly; and said rotating electromagnet has a core having an axial length, with respect to said axis of rotation of said rotating assembly, which is at least three times greater than said radial length.

18. The rotary amplifier of claim 16, wherein said at least one rotating armature coil is an air-core coil.

19. The rotary amplifier of claim 14 further comprising a housing which contains said flywheel, said stationary assembly, and said rotating assembly.

20. The rotary amplifier of claim 19, wherein said housing is a substantially vacuum sealed enclosure.

21. The rotary amplifier of claim 14, wherein said conversion circuit comprises a rectifier.

22. The rotary amplifier of claim 16, wherein: said non-rotating electromagnet produces a plurality of magnetic fields which are spaced circumferentially from each other; said rotating electromagnet produces a plurality of magnetic fields which are spaced circumferentially from each other; said at least one non-rotating air-core coil comprises a plurality of air-core coils which are spaced circumferentially from each other; and said at least one rotating coil comprises a plurality of coils which are spaced circumferentially from each other.

23. The rotary amplifier of claim 22, wherein: said plurality of magnetic fields produced by said non-rotating electromagnet which are circumferentially adjacent to each other have oppositely directed magnetic flux; and said plurality of magnetic fields produced by said rotating electromagnet which are circumferentially adjacent to each other have oppositely directed magnetic flux.

24. The rotary amplifier of claim 23, wherein the oppositely directed magnetic fluxes of said non-rotating electromagnet and said rotating electromagnet are directed radially with respect to said axis of rotation of said rotating assembly.

25. The rotary amplifier of claim 1, wherein said generator comprises: an exciter stage coupled to said input circuit for receiving and amplifying said control signal, said exciter stage including at least one stationary electromagnet for producing at least one stationary magnetic field, and at least one rotating coil which rotates about said axis through said stationary magnetic field such that an AC current is induced in said rotating coil; a conversion circuit coupled to said rotating coil for receiving said induced AC current and for converting said induced AC current to a DC current; and a main stage coupled to said conversion circuit, said main stage including at least one rotating electromagnet for producing at least one rotating magnetic field, and at least one non-rotating coil which is exposed to said rotating magnetic field such that an AC voltage is induced in said non-rotating coil.

26. The rotary amplifier of claim 25, wherein said non-rotating coil is an air-core coil.

27. The rotary amplifier of claim 25, wherein said rotating coil is an air-core coil.

28. A rotary amplifier having input means and output means, said rotary amplifier comprising: kinetic energy storage means which rotates about an axis of rotation; stationary field generation means coupled to said input means, said stationary field generating means generating stationary magnetic fields in response to control signals from said input means, said input means producing said control signals from an input signal and a feedback signal; rotating coil means which rotate about an axis through fields produced by said stationary field generation means, said rotation through said stationary fields causing AC currents to be induced in said rotating coil means; conversion means for converting said AC currents to DC currents; rotating field generation means coupled to said kinetic energy storage means and also coupled to said conversion means for receiving said DC currents, said DC currents causing said rotating field generation means to generate rotating fields; stationary coil means which are exposed to said rotating fields, said rotation of said fields across said stationary coil means causing AC voltages to be induced in said stationary coil means, said stationary coil means being coupled to said output means; and measurement means electrically coupled to said input means, said measurement means measuring selected parameters and producing said feedback signal from said measured selected parameters.

29. The rotary amplifier of claim 28, wherein said stationary coil means comprises air-core coil means.

30. The rotary amplifier of claim 28, wherein said rotating coil means comprises rotating air-core coil means.

31. The rotary amplifier of claim 28, further including output processing means coupled between said stationary coil means and said output means, said output processing means comprising: a rectification circuit for rectifying said induced AC voltage; and a filter circuit for filtering said rectified signal into an output signal at said output means.

32. The rotary amplifier of claim 31, wherein said output processing means further comprises a transformer coupled to said filter circuit, said transformer having a primary winding adapted to receive said output signal and a secondary winding coupled to said output means.

33. The rotary amplifier of claim 31, wherein said output processing means further comprises a switch network configured as an H-bridge coupled to said filter circuit, said switch network providing an output signal to said output means.

34. The rotary amplifier of claim 29, wherein said conversion means comprises rectification means.

35. The method of generating an amplified signal using a rotary amplifier, comprising the steps of: rotating a mass about an axis to produce kinetic energy; inputting an input signal and a feedback signal to a control circuit; producing a control signal in response to said input signal and said feedback signal; providing said control signal to at least one stationary electromagnet, said control signal energizing said stationary electromagnet to produce at least one stationary magnetic field; rotating at least one coil about said axis of rotation through said stationary magnetic field to cause an AC current to be induced in said rotating coil; converting said AC current to a DC current; supplying said DC current to at least one rotating electromagnet which is fixedly attached to said rotating mass, said DC current energizing said rotating electromagnet to produce at least one rotating magnetic field; exposing at least one stationary coil to said rotating magnetic field to cause an AC voltage to be induced in said stationary coil; and processing said induced AC voltage into an output signal and into said feedback signal.

36. The method of claim 35, wherein said step of rotating comprises rotating at least one air- core coil about said axis of rotation through said stationary magnetic field to cause an AC current to be induced in said rotating air-core coil.

37. The method of claim 35, wherein the step of exposing comprises exposing at least one stationary air-core coil to said rotating magnetic field.

38. The method of claim 35, wherein said input signal is a DC current.

39. The method of claim 35, wherein said input signal is a low frequency AC current.

40. The method of claim 35, wherein said rotating electromagnet produces magnetic fields which are oriented in a radial direction with respect to said axis of rotation.

41. The method of claim 40, wherein: said stationary air-core coil has a radial length with respect to said axis of rotation; and said rotating electromagnet has a core having an axial length, with respect to said axis of rotation, which is at least three times greater than said radial length.

42. The method of claim 35, wherein said step of converting comprises rectifying said AC current to a DC current.

43. The method of claim 35, wherein: said step of providing produces a plurality of magnetic fields which are spaced circumferentially from each other; said step of supplying produces a plurality of magnetic fields which are spaced circumferentially from each other; said step of exposing comprises the step of exposing a plurality of air-core coils which are spaced circumferentially from each other to said rotating magnetic fields; and said step of rotating comprises the step of rotating a plurality of coils which are spaced circumferentially from each other through said stationary magnetic fields.

44. The method of claim 42, wherein: said step of providing produces said plurality of stationary magnetic fields such that said fields are circumferentially adjacent to each other have oppositely directed magnetic flux; and said step of supplying produces said plurality of rotating magnetic fields such that said fields are circumferentially adjacent to each other have oppositely directed magnetic flux.

45. The method of claim 43, wherein the oppositely directed magnetic fluxes of said providing step and said supplying step are directed radially with respect to said axis of rotation.

46. A pulsed power rotary amplifier for driving a multi-phase motor, said amplifier having a plurality of inputs and a plurality of outputs which are coupled to said motor, said amplifier comprising: a flywheel which rotates about an axis of rotation; an input circuit coupled to said plurality of inputs, said input circuit providing a plurality of control signals in response to a plurality of input signals and a plurality of feedback signals; a plurality of brushless generators mechanically coupled to said flywheel and electrically coupled to said input circuit, each of said generators providing an amplified output signal to one of said plurality of outputs in response to a corresponding one of said control signals; and a plurality of measurement circuits coupled to said input circuit, said measurement circuits measuring selected parameters and producing said feedback signals from said measured selected parameters.

47. The rotary amplifier of claim 46, wherein each of said generators is coupled to one of said measurement circuits, such that one of said feedback signals is generated corresponding to each of said generators.

48. The rotary amplifier of claim 47, wherein said motor is coupled to one of said measurement circuits and one of said feedback signals is representative of motor performance.

49. The rotary amplifier of claim 46, wherein said selected parameters are selected from the group of current, voltage, power, and motor rotational speed.

50. The rotary amplifier of claim 46, further comprising a plurality of output circuits, one of each output circuits being coupled between one of each generators and one of each outputs.

51. The rotary amplifier of claim 50, wherein each of said output circuits comprises: a rectifier circuit; a filter circuit; and an H-bridge circuit.