Patent Description:
Power conversion using the XRAM circuit techniques are known in the prior art for producing a current multiplication of a generator or source output to permit very high current supplied to mainly pulsed electromagnetic loads. These circuits employ a multiplicity of solid state or triggered vacuum switches which quickly reconnect internal energy storage elements within the XRAM generator to reconfigure a circuit by placing series charged energy storage elements in parallel to effect a current multiplication. For example, in a <NUM>-stage XRAM generator if there are <NUM> elements which are charged in series at <NUM> kV input these elements are placed in parallel to yield a <NUM> kV output at <NUM> times the current rating of the individual elements. In one prior art embodiment, the energy storage elements are inductive storage coils. This system has been shown to be effective and implemented in prior art although heavy and of low power density. This prior art requires the energy storage elements to be outside of the main generator or source and consequently require significant extra space and weight for the XRAM generator.

<CIT> discloses an electro-mechanical kinetic energy storage device including an input port, an output port, and a tertiary port separate from and magnetically coupled to the input port and the output port. The input port is configured to receive a first input electrical energy from a first electrical source for inducing mechanical energy into the electro-mechanical kinetic energy storage device. The output port is configured output a first converted electrical energy to a first load in which the outputted electrical energy is generated from the induced mechanical energy. The tertiary port is configured to receive a second input electrical energy from a second electrical source for inducing the mechanical energy, and output a second converted electrical energy to a second load, the second converted electrical energy generated from the induced mechanical energy.

<CIT> discloses a circuit which produces a current pulse through a load element, including a primary energy storage unit and a secondary energy storage unit which can be charged up by the primary energy storage unit an opening switching element which is configured to interrupt or establish a connection between the primary energy storage unit and the secondary energy storage unit and a closing switch which is configured to interrupt or establish a connection between the secondary energy storage unit and the load element; and a counter current element which is connected to the opening switching element such that a counter current flows from the counter current element through the opening switching element when the closing switch is closed.

<CIT> discloses a system including first and second sources configured to provide power to first and second medium-voltage direct current (MVDC) buses, respectively. The system also includes a rotating electrical machine having first and second primary windings and first and second secondary windings. Each primary winding is electrically connected to one of the first and second MVDC buses. The rotating electrical machine is configured to receive the power from the first and second MVDC buses. Each secondary winding is configured to provide output power to a pulsed load. The system further includes at least one battery or ultra-capacitor subsystem electrically connected to the rotating electrical machine. The at least one battery or ultra-capacitor subsystem is configured to receive electrical energy from and provide electrical energy to the rotating electrical machine.

The scope is defined by independent claim <NUM>.

Other objects and advantages of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.

An electrical machine includes as part of its stator XRAM windings for multiplying current output of the machine. The XRAM windings are coupled to switching elements that are configured to produce current multiplication for output to an external load. The XRAM windings may be in slots in the stator, or may be elsewhere in the stator, operatively coupled to other windings in the stator. The stator may be operatively coupled to a rotor and hence to an inertial energy source, such as a flywheel on the same shaft as the elements of the electrical machine. Short circuiting of select windings of the machine can advantageously cause a shifting and concentration of a machine airgap flux of the machine over other windings.

Various embodiments described herein include motoring windings, generating windings, and XRAM or counter-pulse (CP) windings. Alterantively the motoring windings may be considered primary windings, the generating windings may be considered secondary windings, and the XRAM or CP windings may be considered tertiary windings.

In general, an electrical machine has a primary winding, typically on stator, that is distributed in both direct and quadrature axes. The secondary winding also typically on the stator is concentrated on the direct axis. The tertiary winding also on the stator is concentrated on the quadrature axis. During the mode when output system requires the tertiary winding to be used for counter-pulse generation, the airgap flux is shifted by several means from peaking in the direct axis to peaking in the quadrature axis and consequently the voltage induced in the tertiary winding advantageously escalates beyond normal values.

One such means is to short-circuit the primary winding at its terminals (with power source removed) which shifts airgap flux from the peripheral stator segment occupied by the primary winding to the counter-pulse peripheral zone. Another means is to short circuit the terminals of wound polyphase rotor which has the effect of shifting airgap flux to peak in the stator quadrature axis of the tertiary winding. A third means is to employ short-circuiting "null flux" closed loops at various peripheral positions along the stator core which are controlled to create a terminal short circuit on these loops by a set of solid-state switches or vacuum circuit breakers. The magnetic flux through a short-circuited closed loop is low or close to zero and this causes airgap flux to shift peripheral position to where it peaks.

<FIG> shows a synchronous electrical machine <NUM> with two sets of stator windings for providing both a) main pulse output power, and b) integrated inductive storage coils fitted around the stator periphery which serve to function in the XRAM switching circuit for the current multiplication. The two magnetic circuits are functionally decoupled in actual operation since the main and XRAM windings are in use at separate times although share a common magnetic circuit.

The windings include main windings <NUM>, <NUM>, and <NUM>, and secondary windings <NUM>, <NUM>, <NUM>, and <NUM>. The secondary windings <NUM>-<NUM> are shown as part of the electrical machine <NUM>, and also are shown as part of the circuit diagram at the right side of <FIG>. In <FIG> the secondary windings <NUM>-<NUM> are shown both in the left side of the figure as part of the electrical machine <NUM>, and in the right side of the figure, which shows a functional circuit diagram indicating the interconnection between the secondary windings <NUM>-<NUM> in their use for energy storage and current multiplication, as an XRAM circuit.

XRAM circuit techniques can be used for producing a current multiplication of a generator or source output to permit very high current supplied to mainly pulsed electromagnetic loads. Such XRAM circuits use multiple solid state or triggered vacuum switches that quickly reconnect internal energy storage elements within an XRAM generator to reconfigure a circuit by for placing series charged energy storage elements in parallel to effect a current multiplication. The number of stages/elements and the corresponding amont of multiplication of current may take on any of a variety of values. For example, in a ten-stage XRAM generator if there are <NUM> elements that are charged in series at <NUM> kV input, these elements may be placed in parallel to yield a <NUM> kV output at ten times the current rating of the individual elements. The secondary windings <NUM>-<NUM> themselves are configured to function as the individual elements of an XRAM generator.

The main windings <NUM>-<NUM> produce polyphase AC output at a high voltage and low current. This polyphase high-voltage low-current AC output is rectified to high-voltage low-current DC by a rectifier <NUM>. This DC current is used to charge the input stages to the four XRAM stages <NUM>, <NUM>, <NUM>, and <NUM>, each one corresponding to one of the secondary windings <NUM>-<NUM>. The arrangement shown includes inductive storage coils LS1-LS4 (the secondary windings <NUM>-<NUM>) and counter-pulsed by electrostatic capacitors C<NUM>-C<NUM> (reference numbers <NUM>, <NUM>, <NUM>, and <NUM>) for the internal energy storage elements. The four-stage XRAM is shown along with four main reverse conducting thyristors (RCT) <NUM>, <NUM>, <NUM>, and <NUM>, and eight power diodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. The final output switch <NUM> can be a thyristor or similar high current switching device such as a triggered vacuum switch. Output is provided to a load <NUM>, which may be a non-linear load.

In one embodiment the synchronous machine <NUM> is a wound-field electrical generator. The main stator windings <NUM>-<NUM> are energized first by a DC excitation winding. The output from the main stator windings <NUM>-<NUM> is used after AC/DC rectification in the rectifier <NUM> (and capacitive storage capacitor intermediate storage) to inductively charge the "N" (e.g., <NUM>) storage coils <NUM>-<NUM> that are in series connection, with DC current I<NUM>. The thyristors Th<NUM>-Th<NUM> (reference numbers <NUM>-<NUM>) are gated to conduct forward current to charge the inductor elements <NUM>-<NUM> and share the source voltage equally. When the inductors <NUM>-<NUM> reach the steady state value of current, then a load switch thyristor ThL (reference number <NUM>) is closed, and all the "N" storage coils (the secondary coils <NUM>-<NUM>) are in parallel, and output current I<NUM> has been multiplied by a factor of N:<NUM>.

Reference is at times made herein to a machine having N storage coils. In such references it should be appreciated that N represents any integer greater than <NUM>.

This current-multiplication process also works with a permanent-magnet field synchronous AC generator that has a constant airgap flux at all times, and may be superior to a wound-DC field machine, which can have greater variation in magnitude of airgap flux. In such an alternative arrangement the AC/DC rectifier has an intermediate energy storage with an electrostatic capacitor bank. Since the voltage is high at this stage, the capacitor bank is compact and efficient. Energy transfer is from the flywheel through the electrical machine then to the DC rectifier capacitor then routed to the inductive storage coils mounted on the machine periphery.

<FIG> shows a simplified arrangement of using a wound field induction electrical machine <NUM> with two sets of stator windings for providing both main pulse output power, using the main windings <NUM>, <NUM>, and <NUM>, and integrated inductive storage coils <NUM>, <NUM>, <NUM>, and <NUM>, fitted around a stator periphery. The secondary windings (inductive storage coils) <NUM>-<NUM> serve to function in the XRAM switching circuit for the current multiplication. The two magnetic circuits are functionally decoupled in actual operation since the main windings <NUM>-<NUM> and the XRAM windings <NUM>-<NUM> are in use at separate times, although both sets of windings share a common magnetic circuit.

Consider the operation of an induction machine that is a polyphase wound-AC field induction generator and is already up to speed with a significant flywheel for energy storage. The main stator windings <NUM>-<NUM> are energized first by an AC excitation slip-frequency rotor winding <NUM>. The stator-generated output is used after AC/DC rectification (in a rectifier <NUM>), and after capacitive storage capacitor intermediate storage <NUM>, to inductively charge the "N" (e.g. <NUM>) storage coils <NUM>-<NUM>. The coils <NUM>-<NUM> are charged in series connection through thyristors Th<NUM>-Th<NUM> (reference numbers <NUM>, <NUM>, <NUM>, and <NUM>) with DC current. When the inductors reaches the steady-state value of current, then load switch thyristor ThL (reference number <NUM>) is closed and all "N" storage coils Ls<NUM>-LsN (the secondary coils <NUM>-<NUM> in the illustrated embodiment) are in parallel and output current has been multiplied by a factor of N:<NUM>. A variable-voltage variable-frequency (VVVF) power supply <NUM> powering the rotor circuit <NUM> also has the ability to curtail active excitation and short-circuit the rotor winding(s) <NUM> to benefit the overall scheme. This lowers the impedance of the secondary coils, which is advantageous. When the storage inductors (the secondary coils <NUM>-<NUM>) are charged to full rated current and main output winding current is zero, the rotor winding(s) are short circuited at their terminals by either the VVVF drive <NUM> or a separate shorting switch (or vacuum breaker), and the machine airgap flux will peripherally shift and create a DC transient component of current in each storage coil in addition to the first DC current. Energy transfer is from the flywheel through the electrical machine then to the DC rectifier capacitor (for short time period) then routed to the inductive storage coils <NUM>-<NUM> mounted on the machine periphery.

<FIG> shows an embodiment in which a synchronous electrical machine <NUM> has two sets of stator windings that include main windings <NUM>, <NUM>, and <NUM>, for providing both main pulse output power, and integrated inductive storage coils (secondary windings) <NUM>, <NUM>, <NUM>, and <NUM>, fitted around the periphery of a stator of the machine <NUM>. The secondary windings <NUM>-<NUM> serve to function in the XRAM switching circuit for the current multiplication. There are also external polyphase short-circuit switches S1 and S2 (reference numbers <NUM> and <NUM>) on the stator main winding terminals. When the switches S1 and S2 (reference numbers <NUM> and <NUM>) are closed, this reduces the impedance of the pulsed secondary windings <NUM>-<NUM>. The two magnetic circuits on the stator are functionally decoupled in actual operation since the main and XRAM windings are in use at separate times although share a common magnetic circuit.

The synchronous machine may be a permanent magnet (PM) field electrical generator. The main stator windings <NUM>-<NUM> are excited at constant rotor flux by the PM system. Output is used after AC/DC rectification (in a rectifier <NUM>), and after capacitive storage capacitor intermediate storage <NUM>, to inductively charge the "N" (e.g. <NUM>) storage coils <NUM>-<NUM>. The coils <NUM>-<NUM> are charged in series connection with DC current. When the inductors Ls<NUM>-Ls<NUM> (the secondary coils <NUM>-<NUM>) reach the steady state value of current, the switches <NUM> and <NUM> are closed, shorting the main stator output and causing the rotor flux to shift spatially in the airgap by about <NUM> electrical degrees within a few milliseconds. Although the rotor flux remains about constant, it is now concentrated amongst the inductive storage coils <NUM>-<NUM>. The effective magnetic permeance and effective impedance of the main stator winding decreases when the stator short circuit occurs, the magnetic steel is now in a saturation region and the overall terminal impedance of the main stator coils becomes lower. This shifting of radial airgap flux results in a transient component of direct current being induced into the storage coils and enhancing the overall current output multiplication beyond a simple N stage multiplication. The load switch thyristor ThL (reference number <NUM>) is closed and all "N" storage coils (the secondary coils <NUM>-<NUM> in the illustrated embodiment) are in parallel and output current has been multiplied by a factor of greater than N:<NUM>.

A diode D1 (reference number <NUM>) protects the rectifier <NUM> from reverse voltage transients, and ensures that when an air-blast breaker <NUM> opens, that the current I<NUM> is maintained. A flywheel <NUM> is operatively coupled to the machine <NUM>.

<FIG> shows a further embodiment, a machine <NUM> that uses inductive storage for the XRAM generator, and also advantageously uses a set of wound polyphase stator coils placed within the doubly-fed Induction electrical machine (DFIM) <NUM> to store XRAM energy. This arrangement avoids having to use external discrete coils for the XRAM. The machine <NUM> has a rotor <NUM> and a stator <NUM>. the rotor <NUM> has a rotor winding R1 (reference number <NUM>). The stator <NUM> has a main stator winding S2 (reference number <NUM>), and a series of auxiliary windings S3, S4, S5, and S6 (reference numbers <NUM>, <NUM>, <NUM>, and <NUM>).

<FIG> shows three reverse conducting thyristor (RCT) switching devices <NUM>, <NUM>, and <NUM> external to the machine <NUM>, and eight power diodes D1-D8 (reference numbers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) to place the machine coils <NUM>-<NUM> in parallel for creation of a high current pulsed output. The main output thyristor is a unidirectional switching device ThL (reference number <NUM>). The DFIM <NUM> has the wound polyphase rotor (winding R1, reference number <NUM>) that is excited by a variable-voltage variable-frequency power supply (VVVF inverter) <NUM>, which is fed from either a DC or AC auxiliary power source <NUM>. The rotor excitation also contains a polyphase shorting switch <NUM> that completely short circuits the rotor circuit <NUM> at its terminals, so as to enable the XRAM mode. The main power is supplied to the DFIM through the stator motoring winding S1 (reference number <NUM>) from a machine, such as a turbo-generator <NUM>. The DFIM <NUM> is mechanically connected to a flywheel energy storage device <NUM> that contains kinetic energy E1. Shaft speed/energy decrement/increment of DFIM is part of the normal operation.

The main DFIM output winding <NUM> is designated S2 in the illustration, and as shown in drawing is a single-phase stator winding as part of an overall polyphase system. The special XRAM coils on the DFIM stator (for one phase) are designated as same-phase S3, S4, S5 and S6 coils (reference numbers <NUM>, <NUM>, <NUM>, and <NUM>) and are directly connected to RCT circuitry (reference numbers <NUM>-<NUM>), and to a full wave bridge (FWB) main rectifier <NUM>, which supplies the DC charging current I2. The coils S3, S4, S5 and S6 (<NUM>-<NUM>) are wound on the same machine stator magnetic circuit as the main motoring/generating coils (<NUM>), and utilize the machine main airgap flux yet only during a short period of time. In normal generating operation, the rotor is excited by the VVVF supply <NUM>, and initiates the main airgap flux of the machine <NUM>. The RCT thyristors <NUM>-<NUM> connects these four coils <NUM>-<NUM> in series prior to the short circuit mode.

For pulsed power operation, once the main output DC current is rectified and current is circulated into coils S2-S6, the rotor is short circuited which shifts the majority of airgap flux into the coils S2-S6 which boosts this current. Furthermore, upon a rotor short circuit the inductive reactance of coils S2-S6 significantly decreases to what is known as a "bore reactance" which permits high currents to flow with lower reactance. The counter-pulse current I5-I8 provided by electrostatic capacitors C1-C4 (reference numbers <NUM>, <NUM>, <NUM>, and <NUM>) turns OFF the RCT switches <NUM>-<NUM> and the circuit is reconfigured so that Coils S2-S6 are now in parallel to feed the common load. Main output switch <NUM> combines component currents in the diodes <NUM>-<NUM> into a common load <NUM>. The electrostatic capacitors C1-C4 are smaller energy storage devices and the majority of energy storage is from the coils S2-S6 within the electrical machine. The system is compact and advantageously represents a significant reduction in weight and size in comparison with prior approaches.

<FIG> shows a system <NUM> which includes a pair of low-current DFIMs <NUM> and <NUM>, which may be similar to the doubly-fed machine described above in <FIG>. Input power <NUM> may be provided to respective frequency converters <NUM> and <NUM>, and to respective rotor VVVF excitation converters <NUM> and <NUM>. The main frequency converters <NUM> and <NUM> provide power to respective stator inputs <NUM> and <NUM>, and the converters <NUM> and <NUM> provide excitationpower to respective rotors <NUM> and <NUM>. Flywheel energy storage systems <NUM> and <NUM> are also coupled to the respective rotors <NUM> and <NUM>. Stator output main coils <NUM> and <NUM> are coupled to respective full-wave-bridge controlled rectifiers <NUM> and <NUM>. Secondary output coils <NUM> and <NUM> are coupled to respective XRAM-thyristor switch networks <NUM> and <NUM>. Output then goes through respective final pulse shaping networks (PSNs) or pulse forming networks (PFNs) in blocks <NUM> and <NUM>, then on through respective output thyristor switch arrays <NUM> and <NUM>, and then out to a pulsed load <NUM>.

<FIG> shows another embodiment, an electrical machine <NUM> with a four-stage XRAM showing the arrangement of three phases around the stator periphery of the electrical machine <NUM>. The machine <NUM> is a DFIM machine with four poles. Main output windings are in tops of stator slots: <NUM> slots as <NUM>-phases, <NUM> slots per pole per phase arranged as <NUM> separate groups double-layer lap winding each having <NUM> slots/pole. Main motoring winding are in bottom of stator slots: <NUM> coils for a <NUM>-phase system, <NUM> coils per phase, <NUM> coils per pole per phase, as a lap wound double-layer winding. For the XRAM coils there are a total of <NUM> coils in a <NUM>-phase system spaced equally around stator periphery embedded in top of stator slots closest to airgap. In the machine <NUM> the rotor winding is <NUM> pole wound as "skip pole" delta connected winding in typically <NUM> or <NUM> slots.

<FIG> shows an embodiment of a machine <NUM> where the XRAM (N=<NUM>) external storage inductors are eliminated by having the electrical machine provide the magnetic flux to link these inductors to main airgap flux and create a magneto-inductive storage for XRAM coils S3, S4, S5 and S6 (collectively reference number <NUM>). Diodes in some prior arrangements are also eliminated, leaving only four full-wave-bridge power diode assemblies for a four-stage XRAM, shown as an XRAM diode array <NUM>. RCT switching devices are used when very high currents such as <NUM>,<NUM> Amps are involved; otherwise a lower current solid-state switching device such as an IGBT or MOSFET which can commutate its own current by gate turn-off command can be effectively used. In <FIG>, the coils S2-S6 (a stator main AC output <NUM> and the XRAM coils <NUM>) are wound on the electrical machine stator core <NUM> and respond to a sudden short circuit of the rotor circuit R1 (reference number <NUM>) on a rotor <NUM>. An AC or DC excitation source <NUM> and an VVVF excitation inverter <NUM> provide power to the rotor circuit R1 (reference number <NUM>). After the excitation source <NUM> is shut off and when system ready for a high current discharge, the rotor circuit R1 (reference number <NUM>) is short circuited through a line-to-line electronic switch (such as an anti-parallel thyristor combination) <NUM>, which peripherally shifts airgap flux into the stator generating coil <NUM>, or the XRAM coils <NUM>. This consequent shifting of the airgap radial magnetic flux is not nulled but rather accumulates in the XRAM dedicated coils or sector and so reduces their inductive reactance. In certain machine winding layouts, it is also beneficial to short-circuit the stator motoring winding <NUM> after machine <NUM> is up to speed as shown with the two <NUM>-phase vacuum breakers VB and the shorting inductor Lx (collectively reference number <NUM>) connected as line to line. Simultaneously the rotor winding R1 (<NUM>) and stator winding S1 (<NUM>) short circuiting mode results in a high voltage induction into the S2-S6 coils (XRAM coils <NUM>-<NUM>) which is used to reverse bias the set of RCT thyristors <NUM>. The coils S2-S6 are placed closest to the machine airgap to react most effectively with the shifting of stator airgap flux.

In the embodiment shown in <FIG> the counter-pulse capacitors in the embodiment of <FIG> (for example) are eliminated by having the electrical machine auxiliary output winding <NUM> provide the counter-pulse current to effect a commutation of the three RCT thyristor switches <NUM>. The machine counter-pulse circuits CP <NUM> are connected directly across each RCT. RCT switching devices may be used when very high currents such as <NUM>,<NUM> Amps are involved. Otherwise a lower current solid-state switching device such as an IGBT or MOSFET, which can commutate its own current by gate turn-off command, can be effectively used. In <FIG>, the coils S3-S6 (stator XRAM coils <NUM>) and counter pulse coils <NUM> are wound on the common electrical machine stator core and respond (by having high induced voltage) to a sudden short circuit of the rotor circuit. The rotor circuit R1, after excitation inverter VVVF is shut off and when system is ready for a high current discharge, is then short-circuited through a line to line electronic switch (or vacuum breakers) <NUM> which peripherally shifts airgap flux into the stator generating, CP and XRAM coils.

The machine <NUM> is linked to a pulsed DC load <NUM> through diode array <NUM>. Other similar machines, represented in <FIG> by XRAM diode arrays <NUM> and <NUM>, also may be coupled (such as in parallel) to provide power to the load <NUM>.

The special electrical induction machine has an internal space transient effect which produces a non-symmetrical distribution of flux around the airgap periphery in contrast to normal operation where airgap flux is symmetrically distributed. This non-symmetrical distribution of flux is advantageous.

<FIG> shows a spatial distribution of airgap flux when a segment of the machine stator periphery is occupied by a combination of a motoring or generating winding and a specific peripheral sector devoted to both XRAM coil and counter-pulse coils in a <NUM> or <NUM> slot stator of <NUM> or <NUM> poles respectively. The normal flux density for the motoring winding B<NUM> may be <NUM> Tesla, the XRAM flux density B<NUM> may be <NUM> Tesla and the counter-pulse airgap flux density B<NUM> at <NUM> Tesla. These two higher flux densities are a function of short circuiting the motoring winding at its terminals which cause a shifting of the airgap magnetic flux out of the motoring zone and into the XRAM zones. This is a form of flux compression. That is the flux that would normally encircle <NUM> slots is squeezed into a zone of <NUM> slots causing an inherent <NUM>:<NUM> flux compression if the short circuit were perfect. Since there is a leakage inductance in the motoring winding and the short circuit current is limited by the stator to rotor leakage reactance and the end-winding leakage, the inherent flux compression might be a <NUM>:<NUM> ratio which is acceptable. Here it is sent the XRAM and CP coil sector occupies <NUM> slots/<NUM> slots or <NUM>% of the machine periphery. In an alternate embodiment, the XRAM + CP coils occupy <NUM> slots/<NUM> slots or <NUM>% of the machine periphery which is more efficient.

<FIG> shows an example electrical machine coil system. <FIG> show sample layouts of a <NUM>-pole <NUM>-phase machine in <NUM> stator slots showing coil groups for (respectively) XRAM winding (layout <NUM> in <FIG>), motoring winding (layout <NUM> in <FIG>), and generator winding (layout <NUM> in <FIG>) on a common frame. The XRAM winding has <NUM> coils, the motoring winding has <NUM> coils and the generating wining has <NUM> coils. Thus each stator winding can have unique voltage levels and unique power input/output levels. <FIG> shows preferred rotor winding layout <NUM> for a <NUM>-pole DFIM machine in <NUM> rotor slots to match the stator top drawing. The winding layout can be extended to other pole numbers such as <NUM>, <NUM> and <NUM> poles with stator slot numbers starting at <NUM>. The rotor can be excited by a slip-ring assembly or by a brushless exciter, as is well known in the art.

<FIG> shows three different cross sections of stator slots showing three types of configurations for implementing XRAM windings on the stator frame. The arrangements shown in <FIG> may be used as part or in connection with other aspects of the various other embodiments shown therein.

<FIG> shows an approach of combining an XRAM winding into same slot as the generating and motoring windings shown as <NUM> slots/pole/phase, in a machine <NUM> having a stator <NUM>. The stator <NUM> surrounds a rotor <NUM>, and the stator <NUM> has slots <NUM> and <NUM> for receiving the various windings. Only the two slots <NUM> and <NUM> are shown in <FIG> but it will be appreciated that the stator <NUM> may have slots evenly circumferentially spaced around the stator <NUM>. The stator <NUM> and the rotor <NUM> define an airgap <NUM> between them, with the airgap <NUM> radially inward of the stator <NUM> and radially outward of the rotor <NUM>. An XRAM winding <NUM> is located in the slots <NUM> and <NUM> closest to the airgap <NUM> to minimize magnetic permeance/reactance. A motoring winding <NUM> deepest in the slots <NUM> and <NUM>, yielding a highest magnetic permeance/reactance of the group. A main output winding <NUM> is in the slots <NUM> and <NUM>, radially between the XRAM winding <NUM> and the motoring winding <NUM>. All the windings <NUM>, <NUM>, and <NUM> are shown in <FIG> with internal liquid cooling conductor channels. However it will be appreciated that other sorts of conductor cooling may be used instead.

<FIG> shows a cross section of a stator <NUM> of a machine <NUM>. The stator <NUM> surrounds a rotor <NUM>, with an airgap <NUM> between the rotor <NUM> and the stator <NUM>. Various windings of the machine <NUM> are located in slots <NUM>, <NUM>, <NUM>, and <NUM> of the stator <NUM>. The windings include XRAM windings <NUM> that are located in the deepest part of the stator slots <NUM> and <NUM>. The windings <NUM> are only located in select slots (e.g., the slots <NUM> and <NUM>) that are shared with a generating winding <NUM>, and not with a motoring winding <NUM>. The motoring winding <NUM> is confined to slots, such as the slots <NUM> and <NUM>, where the XRAM windings <NUM> are not located. Most of the machine <NUM> is wound with a combination of generating and motoring windings in a common stator slot, and only a small portion of the machine's stator has the combined XRAM and generating windings in common slots. The arrangement for the generating and motor windings can be standard <NUM>-<NUM> slots/pole/phase layout whereas the XRAM winding will generally have a lower number of occupied slots resulting in <NUM>-<NUM> slots/pole/phase. In the configuration shown in <FIG> the method of shorting at the terminals of either the motoring or generating winding (or both) will result in a peripheral shifting of the magnetic flux in the stator core and concentrate this flux around the XRAM windings <NUM>, inducing an electro-magnetic field (EMF) that will result in high voltage generation in the XRAM coils <NUM>.

Here using a larger number of turns (e.g. <NUM> per slot) for the XRAM winding results in a higher voltage induced in the XRAM winding than would be the applied voltage to the motoring winding or the output of the generating winding during a short circuit condition. In addition the larger number of turns for the XRAM winding results in a higher terminal inductance than the generating winding; this inductance L is necessary as an energy storage device since stored energy E= <NUM>*L*I<NUM>. The current I that is induced is proportional to the short circuit current of the combined motoring and generating winding when this mode of operation occurs.

<FIG> shows an embodiment of a machine <NUM> with a stator <NUM> surrounding a rotor <NUM> with an airgap <NUM> therebetween. In the machine <NUM> XRAM coils <NUM> are positioned outside of the standard machine slots <NUM>. The XRAM coils <NUM> have dedicated locations and dedicated magnetic pole pieces <NUM> positioned along the outer part of the magnetic core of the stator <NUM>. The magnetic pole pieces <NUM> are used to confine XRAM magnetics to a specific flux path and increase energy storage of a coil. Special null flux shorting coils <NUM> are located in select of the stator slots <NUM> and enclose the magnetic core back-iron flux to control flux density in the radial dimension shown in <FIG> as Dx. Magnetic flux lines φ1, φ2, φ3 enclose the XRAM coils <NUM> and develop both voltage and inductance of the XRAM coils <NUM>. In normal operation, prior to a pulse duty, the fluxes φ1, φ2, φ3 are at a nominal value. When a pulse duty is being commanded, the array of shorting coils <NUM> are shorted through an electronic switch (e.g., a thyristor or IGBT) and the magnetic flux φ1, φ2, φ3 rapidly increases, and the XRAM output current correspondingly rapidly decreases and is able to store energy. In an embodiment each of the shorting coils has its own shorting electronic switch rather than having multiple shorting coils in series connection.

The machine <NUM> may be a DFIM, as is discussed below in connection of the system shown in <FIG>. Alternatively the machine <NUM> may be another type of rotating electrical machine, including synchronous or reluctance types.

<FIG> shows a system <NUM> that includes the machine <NUM> of <FIG>. <FIG> shows an apparatus <NUM> to short-circuit the null flux loops shown in <FIG>, which causes flux circulating around the XRAM coils to decrease. The machine <NUM> shown in <FIG> is a DFIM. The XRAM current multiplier scheme includes the XRAM coils <NUM>, and the null flux coils <NUM> around the stator core <NUM>, as described above. The machine <NUM> also includes short circuiting switches <NUM> on three null-flux loop windings to concentrate machine flux in XRAM storage coils <NUM> and result in high current output. Reactors X1 and X2 (reference numbers <NUM> and <NUM>) are used to limit short-circuit current to safe values. Generating winding <NUM> is rectified and filtered at DC link <NUM>, then fed into XRAM switching array <NUM>. The XRAM electronic switching array <NUM> is used to create a high current output pulse, in a manner similar to that described above with regard to the embodiments shown in <FIG> and <FIG>. The switching array <NUM> provides current IL to a pulsed load <NUM>, through a switching circuit described further below. There are four types of energy storage as indicated: an electro-kinetic-flywheel E1 (reference number <NUM>), an electrochemical excitation energy source E2 (reference number <NUM>), electrostatic energy sources E2' and E3 (reference numbers <NUM> and <NUM>) and an electromagnetic-XRAM source E4 (reference number <NUM>).

<FIG> shows a specialized load circuit <NUM> for the pulsed load <NUM>, coupled to the XRAM switching array <NUM> (<FIG>). The circuit <NUM> consists of an inductor-capacitor <NUM>-stage pulse forming network. The XRAM switching array <NUM> provides current multiplication and the PFN load circuit <NUM> can provide a lower output impedance and a faster rise time e.g. <NUM> nS than the XRAM into the final load <NUM>, which is shown as resistive element RL. It is a preferred embodiment to have an XRAM high current circuit feed a pulse forming network, such as the circuit or PFN <NUM>, since effective pulse shaping often can require two different types of circuits working in conjunction. A trigger gate pulse <NUM> shown is provided to any number of high current switching devices such as ignitrons, thyristors, thyratrons, or IGBTs.

<FIG> shows the sequence of operation of the system <NUM> (<FIG>) with its five vacuum breakers or similar electronic switches (such as bilateral thyristor pairs), three switches or breakers of which are used for creating short circuiting conditions to shift electrical machine flux within the machine stator core causing buildup of magnetic flux surrounding the XRAM coils and thereby produce an increase in coil inductance/stored energy. The method <NUM> begins in step <NUM>, with when vacuum breakers VB<NUM> and VB<NUM> (reference numbers <NUM> and <NUM> in <FIG>) are closed, and VVVF-<NUM> and VVVVF-<NUM> inverter drives (reference numbers <NUM> and <NUM> in <FIG>) are started.

In step <NUM> a rotor winding R1 (reference number <NUM> in <FIG>) is excited to drive the DFIM <NUM> (<FIG>) to a maximum speed and a maximum kinetic energy. Then, in step <NUM>, there is a transfer of kinetic energy to the electrostatic energy source E3 (reference number <NUM> in <FIG>), charging a capacitor C1 (reference number <NUM> in <FIG>) through a generating winding S2 (reference number <NUM> in <FIG>).

In step <NUM> the system <NUM> (<FIG>) enters into a coast mode, with the breaker VB<NUM> (<NUM>) opened, and the VVVF-<NUM> motoring drive <NUM> shut off. In step <NUM> the XRAM inductors (parts of the XRAM switching array <NUM> (<FIG>)) are charged, through the XRAM windings S3 (the XRAM coils <NUM> of <FIG>) and from a low current from the electrostatic energy source E3 (reference number <NUM> in <FIG>).

In step <NUM> the vacuum breaker VB<NUM> (reference number <NUM> in <FIG>) is opened, and the rotor excitation is turned off at the VVVF-<NUM> motoring drive <NUM>, to wait for all of the electrostatic charge to be transferred from the electrostatic energy source E3 (reference number <NUM> in <FIG>) to the XRAM switching array E4 (reference number <NUM> of <FIG>). Following that, in step <NUM>, shorting vacuum breakers VB<NUM> and VB<NUM> (reference numbers <NUM> and <NUM> in <FIG>) are closed, to start flux shift along the stator slots <NUM> (<FIG>). In step <NUM> vacuum breakers VB<NUM> (reference number <NUM> in <FIG>) are closed, shorting the null flux coils <NUM> (<FIG>) to shift core flux.

Claim 1:
A dynamo-electric machine (<NUM>, <NUM>) comprising:
an electromagnetic structure that includes:
alternating current, AC, primary windings;
polyphase secondary windings (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>); and
N tertiary windings (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) operatively coupled to the primary windings and the polyphase secondary windings;
a rotor;
a flywheel rotating mass on a same shaft as the rotor; and
characterized by further including:
a rectifier (<NUM>, <NUM>) for rectifying high-voltage low-current AC current from the polyphase secondary windings to a high-voltage low-current direct current, DC, current to inductively charge the tertiary windings, wherein the tertiary windings are in series connection with the DC current; and
a XRAM switching circuit comprising an array of switching elements (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), the array of switching elements comprising thyristors (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) and a load switch (<NUM>, <NUM>) comprising a thyristor or a triggered vacuum switch, wherein:
the primary windings provide a motoring torque on the flywheel rotating mass and magnetize the dynamo-electric machine;
the electromagnetic structure provides power to the array of switching elements, with the switching elements configured to produce current multiplication for output to an external load;
the flywheel rotating mass is operatively coupled to the rotor to provide inertial energy storage;
the polyphase secondary windings are energizable by a DC excitation winding to provide output power;
the tertiary windings provide inductive energy storage; and
in operation, the tertiary windings are: configurable, by the array of switching elements by gating the thyristors (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) so as to conduct forward current to charge the tertiary windings and share voltage equally, in a series connection for energy storage; and reconfigurable, by the array of switching elements, in a parallel connection by closing the load switch of the array of switching elements when the N tertiary windings reach a steady state value of current so that all of the tertiary windings are in parallel and an output current is multiplied by a factor of N:<NUM>.