Patent Description:
High-speed switching devices such as bipolar transistors, metal-oxide-semiconductor field-effect transistors (MOSFETs) and insulated-gate bipolar transistors (IGBTs) have enabled increased switching frequencies for voltage-source pulse width modulated (PWM) inverters and direct current-direct current (DC-DC) converters thus leading to improved operating characteristics. High-speed switching techniques, however, present some drawbacks, as a consequence of the faster rate-of-change in the voltage associated with the high-speed switching.

This associated voltage change produces high-frequency oscillatory common-mode voltage and normal-mode voltage when the switching devices change state, for instance from a conducting state to a non-conducting state, at least in part because of parasitic stray capacitance in the load (e.g., a motor). Accordingly, each time an inverter switching event occurs, the voltage of the corresponding inverter output terminal with respect to ground changes rapidly, and a pulse of common-mode current flows in the direct current (DC) link to the inverter, via the capacitance of the motor cable and motor windings, relative to ground. These common-mode voltages and currents due to switching in power converters and inverters introduces numerous well-known problems in electrical systems.

<CIT> relates to a variable frequency drive noise attenuation circuit. The noise attenuation circuit is used in a motor drive system. The motor drive system includes a variable frequency drive having a pulse width modulated inverter converting DC power from a DC bus to three-phase power output on three-phase conductors for driving a motor. The noise attenuation circuit comprises a common-mode transformer including a common mode choke having a core, with first, second and third choke windings on the core, each connected in series with one of the three phase conductors, and a fourth winding on the core. A three-phase iron core transformer creates a neutral point representing common mode voltage. The iron core transformer has three primary windings connected in a "wye" configuration to the three phase conductors. The fourth winding has a start connected to the neutral point and an end operatively connected to the DC bus to force a current, dependent on the voltage of the neutral point relative to the DC bus, in the fourth winding of the common mode transformer in an opposite direction to cancel main common mode current.

<CIT> relates to a circuit device for reducing common-mode interference in a power converter.

<CIT> relates to an output filter and motor drive system.

In one aspect, the present disclosure relates to a common-mode voltage cancellation (CMVC) circuit. The CMVC circuit includes a first set of coupled inductors, each coupled inductor of the first set of coupled inductors having a respective primary winding and a respective secondary winding. Each primary winding of the first set of coupled inductors configured to receive a respective first phase voltage having a common mode voltage component from a corresponding input line. The respective secondary windings of the first set of coupled inductors are electrically coupled in series. The CMVC circuit further includes a second set of coupled inductors comprising at least one primary winding in signal communication with the series connected secondary windings of the first set of coupled inductors to receive a second voltage therefrom, the second set of coupled inductors further comprising secondary windings, each of which is coupled in series with a respective input line and to a respective output line, electrically downstream from the respective input line.

In another aspect, the present disclosure relates to a method of cancelling a common-mode voltage in a circuit. The method includes coupling a respective primary winding of a first set of coupled inductors in signal communication with a respective input line to receive a respective first phase voltage having a common-mode voltage component therefrom, wherein each coupled inductor of the first set of coupled inductors comprises a primary winding and a corresponding secondary winding, and coupling the secondary windings of the first set of coupled inductors electrically in series. The method includes coupling at least one primary winding of a second set of coupled inductors in signal communication with the series-coupled secondary windings of the first set of coupled inductors to receive a second voltage therefrom, wherein the second set of coupled inductors comprises secondary windings, and inducing a respective third voltage at the respective secondary windings of the second set of coupled inductors that is out of phase from the second voltage. The method further includes coupling each secondary winding of the second set of coupled inductors in series with a respective input line to receive the respective first phase voltage having the common-mode voltage component therefrom, and coupling the respective secondary windings of the second set of coupled inductors in series with a respective output line to provide a respective fourth voltage thereto.

These and other features, aspects and advantages of the present disclosure will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate aspects of the disclosure and, together with the description, serve to explain the principles of the disclosure.

A full and enabling disclosure of the present description, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which refers to the appended FIGS. , in which:.

Aspects of the disclosure can be implemented in any environment, apparatus, or method for reducing a common-mode voltage in a circuit regardless of the function performed by the circuit.

As used herein, the term "set" or a "set" of elements can be any number of elements, including only one. Additionally, as used herein, the term "upstream" refers to a direction that is opposite a fluid or an electron flow direction, and the term "downstream" refers to a direction that is in the same direction as the fluid or electron flow. For example, with respect to a device having an input side and an output side, the term "upstream" refers to a direction toward the input side, and the term "downstream" refers to a direction toward the output side. Additionally, while terms such as "voltage", "current", and "power" can be used herein, it will be evident to one skilled in the art that these terms can be interrelated when describing aspects of the electrical circuit, or circuit operations.

Connection references (e.g., attached, coupled, connected, and joined) are to be construed broadly and can include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other. In non-limiting examples, connections or disconnections can be selectively configured to provide, enable, disable, or the like, an electrical connection between respective elements. Non-limiting example power distribution bus connections or disconnections can be enabled or operated by way of switching, bus tie logic, or any other connectors configured to enable or disable the energizing of electrical loads downstream of the bus. Additionally, as used herein, "electrical connection" or "electrically coupled" can include a wired or wireless connection. The exemplary drawings are for purposes of illustration only and the dimensions, positions, order and relative sizes reflected in the drawings attached hereto can vary.

Furthermore, the number of, and placement of, the various components depicted the Figures are also non-limiting examples of aspects associated with the disclosure. For example, while various components have been illustrated with relative position of etc., aspects of the disclosure are not so limited, and the components are not so limited based on their schematic depictions.

With reference to <FIG>, an aspect of a power distribution circuit <NUM> is depicted in block diagram form. The power distribution circuit <NUM> can include at least one power supply <NUM> electrically coupled to an electrical load <NUM>. The power supply <NUM> can comprise a power source <NUM> having an output <NUM>, an inverter <NUM>, having an input <NUM> and an output <NUM>, and a CMVC circuit <NUM> having an input <NUM> and an output <NUM>. The power source <NUM> output <NUM> can be connected to the input <NUM> of the inverter <NUM> by way of transmission lines <NUM>. The inverter output <NUM> can be connected to the input <NUM> of the CMVC circuit <NUM>, via power transmission or input lines <NUM>. The output <NUM> of the CMVC circuit <NUM> can be connected with the electrical load <NUM> via power transmission or output lines <NUM> such as bus bars, to provide electrical power thereto. In an aspect, the output lines <NUM> are coupled electrically in series with the input lines <NUM>. In an aspect, the power supply <NUM> can comprise for example, a conventional DC power source <NUM>, including but not limited to, a battery, photovoltaic panel, DC power supply, any other known source of DC electrical power, or a combination thereof. The DC power from the power source <NUM> can be provided to the transmission lines <NUM>, which ultimately delivers the electrical power to the electrical load <NUM>, coupled to the power supply <NUM>. In other aspects, the power supply <NUM> can comprise a conventional alternating current (AC) power source <NUM>, such as a generator, or the like.

In one non-limiting example, the electrical DC output of the power source <NUM> can be provided via the transmission lines <NUM>, to the input <NUM> of the inverter <NUM>. The inverter <NUM> can include any power inverter adapted or configured to invert the DC power received at the input <NUM> to AC electrical power. The AC electrical power is then provided at the output <NUM> of the inverter <NUM> and transmitted therefrom via power transmission input lines <NUM> to the input <NUM> of the common-mode voltage cancellation circuit <NUM>. For example, in an aspect, the inverter <NUM> can provide a <NUM>-phase AC voltage (hereafter, designated first phase voltages VA1, VB1, VC1, respectively) at the output <NUM> to a respective power transmission input line <NUM>, which in turn can provide the respective phase voltage VA1, VB1, VC1 received from inverter <NUM> to the CMVC circuit <NUM>. The CMVC circuit <NUM> input <NUM> is coupled to the inverter output <NUM> via power transmission or input lines <NUM> to receive the <NUM>-phase AC voltage VA1, VB1, VC1, therefrom. In various aspects, each power transmission input line <NUM> can correspond to a respective AC phase of the inverter output <NUM>.

With continued reference to <FIG>, schematic aspects of the CMVC circuit <NUM> will be described in more detail. The CMVC circuit <NUM> is coupled in signal communication with the inverter <NUM> and can receive the AC electrical power from the output <NUM> of inverter <NUM>, at the input <NUM> of the CMVC circuit <NUM>, via conductors such as the input lines <NUM>. For example, the AC electrical power can be provided as an input to the CMVC circuit <NUM> as a conventional three-phase AC differential mode voltage (phases denoted VA1, VB1, and VC1), with respect to ground (GND) or neutral, and having any desired frequency.

Each first phase voltage VA1, VB1, VC1 can be provided to the CMVC circuit <NUM> on separate respective power transmission lines <NUM>. It will be understood that, while the figures depict the CMVC circuit <NUM> as receiving a conventional three-phase AC voltage VA1, VB1, VC1 from the inverter <NUM> via three input lines <NUM> (i.e., one respective input line <NUM> per phase), aspects of the disclosure are not so limited. It is contemplated that aspects of the CMVC circuit <NUM> can comprise any desired number of AC or DC voltage inputs, receivable at the input <NUM>, and having any desired number of phase and frequency orientations, on any number of desired power transmission lines <NUM> without departing from aspects of the disclosure described herein.

It will be understood that the illustrated aspect of the disclosure of <FIG> is only one non-limiting example of a power distribution circuit <NUM>, and many other possible aspects, configurations, or the like, in addition to that shown are contemplated by aspects of the present disclosure. It will be understood that while aspects of the disclosure are shown, for ease of understanding, in the simple arrangement shown in <FIG>, depicting a single power source <NUM>, the disclosure is not so limited and has general application to electrical power systems or power distribution circuits <NUM> having any number of power sources.

With reference to <FIG>, an aspect of the CMVC circuit <NUM> is depicted in schematic form. The CMVC circuit <NUM> can comprise a first set of coupled inductors <NUM> (for example, a first coupled inductor <NUM>, second coupled inductor <NUM>, and third coupled inductor <NUM>), and a second set of coupled inductors <NUM>. In some aspects, the CMVC circuit <NUM> can optionally include one or more capacitors <NUM>. Each coupled inductor <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> includes respective primary windings <NUM>, <NUM>, <NUM> and corresponding secondary windings <NUM>, <NUM>, <NUM>. In an aspect, the primary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> are arranged to define a first polarity, and the corresponding secondary windings <NUM>, <NUM>, <NUM> are arranged to define second polarity. In an aspect, the first and second respective polarities can be identical. The second set of coupled inductors <NUM> can be at least partially disposed downstream of the input <NUM> and proximate to the output <NUM>. In one non-limiting aspect, the second set of coupled inductors <NUM> can include at least one primary winding <NUM> and at least one secondary winding, shown as windings <NUM>, <NUM>, <NUM>. In an aspect, the at least one primary winding <NUM> of the second set of coupled inductors <NUM> is arranged to define a third polarity, and the corresponding secondary windings <NUM>, <NUM>, <NUM> are arranged to define a respective fourth polarity. In one non-limiting aspect, the third and fourth polarities are identical. In the aspect shown, the third polarity is opposite the second polarity. Each secondary winding <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> can be associated with a respective input line <NUM> and a respective output line <NUM>. For example, in an aspect, each secondary winding <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> can be coupled electrically in series between a respective input line <NUM> (providing a respective phase voltage VA1, VB1, VC1), and a respective output line <NUM>.

The secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> are coupled in series with each other, and are further coupled in signal communication (for example, are coupled in parallel) with the at least one primary winding <NUM> of the second set of coupled inductors <NUM> to provide a respective voltage thereto.

Aspects of the CMVC circuit <NUM> receive the respective first phase voltages VA1, VB1, VC1 from the inverter <NUM> at the CMVC circuit <NUM> input <NUM> via the input lines <NUM>. The input lines <NUM> provide the respective first phase voltages VA1, VB1, VC1 to respective primary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM>. When received by the CMVC circuit <NUM>, the respective first phase voltages VA1, VB1, VC1 provided by the inverter <NUM> can additionally comprise a common mode voltage component (hereinafter, Vcm).

For example, the input <NUM> of the CMVC circuit <NUM> can be conductively connected with the set of first coupled inductors <NUM>. Each respective AC input phase voltage VA1, VB1, VC1, or input line <NUM> thereof, is connected with a respective coupled inductor <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> in signal communication to provide the respective AC phase voltage VA1, VB1, VC1 thereto. For example, as shown, the first voltage phase (VA1) is connected with the first coupled inductor <NUM>, the second voltage phase (VB1) is connected with the first coupled inductor <NUM>, and the third voltage phase (VC1) is connected with the first coupled inductor <NUM>. In an aspect, each primary winding <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> can be coupled to a respective input line <NUM> at a corresponding node, designated <NUM>, <NUM>, <NUM>. As depicted in <FIG>, primary winding <NUM> can be coupled to a respective input line <NUM> associated with phase voltage VA1 at node <NUM>, primary winding <NUM> can be coupled to a respective input line <NUM> associated with phase voltage VB1 at node <NUM>, and primary winding <NUM> can be coupled to a respective input line <NUM> associated with phase voltage VC1 at node <NUM>. In one non-limiting aspect of the disclosure, each respective primary winding <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> is configured to receive a single respective first phase voltage VA1, VB1, VC1 between the input <NUM> and electrical ground (GND) or neutral. Additionally, or alternatively, in non-limiting aspects of the disclosure, each respective secondary winding <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> can be coupled electrically in series.

In an aspect, the respective secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> can be coupled in series with a respective input line <NUM> and downstream of a respective node <NUM>, <NUM>, <NUM>. The input lines <NUM> can thus additionally provide the received first phase voltages VA1, VB1, VC1 to respective secondary winding <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM>.

When provided to the respective primary winding <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM>, the received first phase voltages VA1, VB1, VC1 (including the respective common mode component Vcm) result in an induced second phase voltage VA2, VB2, VC2 at the corresponding secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM>. It can be seen that since the secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> are coupled electrically in series, the induced second phase voltages VA2, VB2, VC2 at the secondary windings <NUM>, <NUM>, <NUM> are summed (hereinafter, VSUM) and provided to the at least one primary <NUM> of the second set of coupled inductors <NUM>.

The summed voltage VSUM, when provided to the at least one primary winding <NUM> of the second set of coupled inductors <NUM>, results in a respective induced third voltage VA3, VB3, VC3 at the corresponding secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM>. Additionally, since the secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> are coupled in series with respective power transmission input lines <NUM> downstream of nodes <NUM>, <NUM>, <NUM> to receive respective first phase voltage VA1, VB1, VC1 therefrom, a fourth phase voltage VA4, VB4, VC4 can be defined at the respective secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> that is a sum of the respective received first phase voltage VA1, VB1, VC1, including the common mode voltage component Vcm, and the respective induced third voltage VA3, VB3, VC3.

It will be understood that an AC voltage applied to a coil (e.g., a coupled inductor primary winding) will induce a voltage in a second coil (e.g., a coupled inductor secondary winding) where the two are linked by a magnetic path (e.g., the coupled inductor core). The phase relationship of the two sinusoidal AC voltages (i.e., the primary and secondary voltages) will depend upon the polarity of the respective windings, and can be arranged to be either in-phase with each other, or displaced by <NUM> degrees. For example, as described herein, a "first polarity" winding matching with a second "first polarity" winding can be arranged such that the phase relationship of the two sinusoidal AC voltages at the primary and secondary voltages are in-phase with each other. In contrast, as described herein, a "first polarity" winding matching with a second "second polarity" winding can be arranged such that the phase relationship of the two sinusoidal AC voltages at the primary and secondary voltages are out of phase, or displaced by <NUM> degrees, relative to each other. The magnitude of the induced secondary voltage will depend on the turns or winding ratio of the primary winding to the secondary winding. For ease of understanding and explanation, the aspect depicted in <FIG> is described herein as each coupled inductor <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> having a primary to secondary winding ratio of <NUM>:<NUM>. It will be appreciated that each coupled inductor <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> may comprise any desired winding ratio without departing from the scope of the aspects herein.

As noted hereinabove, the secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> are magnetically coupled to the corresponding primary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM>. It will thus be understood that the mutual inductance of the corresponding primary windings <NUM>, <NUM>, <NUM> and secondary windings <NUM>, <NUM>, <NUM> will cause the respective first phase voltages VA1, VB1, VC1 (including the common mode voltage component Vcm) received at the primary winding <NUM>, <NUM>, <NUM> to be induced on the corresponding secondary windings <NUM>, <NUM>, <NUM> as the respective second phase voltage VA2, VB2, VC2.

It will be understood that in a conventional three phase AC system, a common mode voltage is typically a voltage difference between the power source and ground or the neutral point of a three-phase load. A common-mode voltage component appears on each line of the multi-line circuit, in-phase and with an amplitude that is an average of the voltages from each line. For example, the common-mode voltage component Vcm of a three-phase AC system having a balanced load, comprising three phase voltages VA1, VB1, VC1 (e.g., the phase to ground voltages, such as, voltage between phase A and ground, etc.) at the output of an inverter with respect to electrical ground, can be expressed as: Vcm = (VA1 + VB1 + VC1) / <NUM>.

With continued reference to <FIG>, and as noted above, it will be appreciated that because the secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> are electrically coupled in series, the respective induced second phase voltages VA2, VB2, VC2 (that is, the induced differential mode phase voltages VA2, VB2, VC2) will effectively be added or summed together to define a summed voltage designated VSUM. This can be expressed as the sum of the differential mode phase voltages (i.e., VA2, VB2, VC2) and the common mode voltages (designated VA1cm, VB1cm, VC1cm) for each phase:
<MAT>.

However, it will additionally be appreciated that since the three sinusoidal first phase voltages VA2, VB2, VC2 are <NUM> degrees out of phase with respect to each other, the sum of the three-phase voltage differential mode component VA2, VB2, VC2 will, by definition, equal zero. Thus, the summed voltage VSUM, may be alternatively be expressed as:
<MAT>
<MAT>
<MAT>.

The summed voltage VSUM at the secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> can thus be considered to be in phase with, and having a magnitude that is three times that of the common mode voltage Vcm.

In an aspect, the voltage VSUM can be provided to the at least one primary winding <NUM> of the second set of coupled inductors <NUM>. The summed AC voltage VSUM provided to the at least one primary winding <NUM> of the second set of coupled inductors <NUM> will likewise be transferred (i.e., based on the mutual inductance of the corresponding primary and secondary windings) to the respective secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> to define an induced respective third phase voltage VA3, VB3, VC3.

As noted above, each at least one primary winding <NUM> of the second set of coupled inductors defines a third polarity that can be opposite the first and second polarity, and is electrically coupled in signal communication with the series-connected coupled inductor secondaries <NUM>, <NUM>, <NUM> of the first set of first coupled inductors <NUM> to receive the summed AC voltage VSUM therefrom.

The magnitude of the induced secondary voltage at the respective secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> will depend on the turns or winding ratio of the at least one primary winding <NUM> to the respective secondary winding <NUM>, <NUM>, <NUM>. For ease of understanding and explanation, the aspect depicted in <FIG> is described herein with respect to the second set of coupled inductors <NUM> as having a respective primary to secondary winding ratio of <NUM>:<NUM>. In various aspects, the second set of coupled inductors <NUM> may comprise any desired winding ratio without departing from the scope of the aspects herein.

For example, in some aspects, the turns ratio of the at least one primary winding <NUM> to the respective secondary windings <NUM>, <NUM>, <NUM> can be selected based on the number of AC phases in the CMVC circuit <NUM> when the CMVC circuit <NUM> is a polyphase AC circuit. In aspects, the turns ratio (i.e. the ratio of the number of primary winding turns to number of secondary winding turns) of the at least one primary <NUM> to the respective secondary winding <NUM>, <NUM>, <NUM> can be designated as the ratio T:<NUM>, where T is the number of turns of the primary winding <NUM>. In an aspect, the value of T may be selected to equal the number of electrical phases in the CMVC circuit <NUM>. For example, in an aspect comprising a <NUM>-phase AC circuit, the turns ratio of the second set of coupled inductors <NUM> can be selected to be <NUM>:<NUM>. That is, the respective induced third voltage VA3, VB3, VC3 at the respective secondary windings <NUM>, <NUM>, <NUM> will be <NUM> times the voltage VSUM at the at least one primary winding <NUM>.

For ease of understanding, as shown in the drawings, a conventional "dot" depicted adjacent to a conventional coupled inductor winding symbol is used to indicate the polarity of a given winding. As will be understood, the term "polarity" refers to the relative direction of the induced voltages between the primary and secondary windings at any given moment in the AC cycle, and the voltage drop from polarity to non-polarity across one winding is essentially in phase with the voltage drop from polarity to non-polarity across the other winding(s). Thus, a positively increasing current in the dotted terminal of one winding induces a positive voltage at the dotted terminal of the other corresponding winding. When so arranged, (i.e., having the same polarity orientation, following left to right on their respective secondary windings <NUM>, <NUM>, <NUM>), the set of first coupled inductors <NUM> can be considered to have additive polarity. It will be understood that for a coupled inductor having additive polarity, the voltage across the secondary windings of the coupled inductor will be the sum of the voltages at the secondary winding side of the coupled inductor. Conversely, for a coupled inductor having subtractive polarity, the voltage across the secondary windings will be the difference of the voltages at secondary side of the coupled inductor.

Aspects of the disclosure can be included wherein the first set of coupled inductors <NUM> are arranged to cooperate with the second set of coupled inductors <NUM> to modify or adjust the respective first, second, and third phase voltages VA1, VB1, VC1, VA2, VB2, VC2, VA3, VB3, VC3 to operatively cancel or reduce the common mode voltage component Vcm from the input phase voltage (e.g. due to the opposite relative polarity of the windings of the first set of coupled inductors <NUM> relative to the relative polarity of the second set of coupled inductors <NUM>), resulting in the fourth phase voltage VA4, VB4, VC4. That is, the respective fourth phase voltages VA4, VB4, VC4 are equal to the respective first phase voltages VA1, VB1, VC1 with the common mode voltage component Vcm cancelled or subtracted therefrom. The respective fourth phase voltage VA4, VB4, VC4 can then be provided downstream from the corresponding secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> for additional filtering (for example by an LC filter <NUM>, not shown) or directly to the electrical load <NUM>, via respective transmission output lines <NUM>.

As noted above, each at least one primary winding <NUM> of the second set of coupled inductors <NUM> defines a third polarity opposite the first and second polarity, and is electrically coupled in signal communication with the series-connected coupled inductor secondaries <NUM>, <NUM>, <NUM> of the first set of first coupled inductors <NUM> to receive the summed AC voltage VSUM therefrom. Since the second set of coupled inductors <NUM> is arranged to have a subtractive polarity with respect to the first set of coupled inductors <NUM>, the voltage induced at the secondary windings, <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> will be subtractive, or <NUM> degrees out of phase with the voltage provided to the first set of coupled inductors <NUM>.

For example, with continued reference to <FIG>, as noted above, the first phase voltages VA1, VB1, VC1 are provided to the to the respective primary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> from respective transmission lines <NUM> and include the common mode voltage component equal to 3Vcm (that is, three times the common mode voltage Vcm), in phase with the first phase voltages VA1, VB1, VC1. The respective first phase voltages VA1, VB1, VC1 (including the common mode voltage component Vcm) are also provided via respective transmission lines <NUM> to respective secondary winding <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM>.

The induced second phase voltages VA2, VB2, VC2 are summed at the series-connected secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> resulting in a summed voltage, VSUM, which is essentially equal to <NUM> times the common mode voltage Vcm = (VA1 +VB1 +VC1)/<NUM>. The summed voltage VSUM is provided to the at least one primary winding <NUM>, thereby resulting in an induced third phase voltage VA3, VB3, VC3 at the respective secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM>. The induced third phase voltages VA3, VB3, VC3 will be subtractive, or <NUM> degrees out of phase with the common mode voltage component Vcm of the corresponding first phase voltages VA1, VB1, VC1. The combination of the respective first phase voltage VA1, VB1, VC1, including and in phase with the common mode voltage component Vcm, with the respective third phase voltage VA3, VB3, VC3, at the respective secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> operably defines a respective fourth phase voltage VA4, VB4, VC4. Because the respective third phase voltage is equal to but out of phase with the common mode voltage component Vcm, the common mode voltage component Vcm, will operatively be cancelled or reduced. Consequently, the respective fourth phase voltage VA4, VB4, VC4 will be equal to and in phase with the corresponding first phase voltage VA1 VB1, VC1 but with the common mode component subtracted, or cancelled. The "clean" respective fourth phase voltage VA4, VB4, VC4 can then be provided via power transmission or output line <NUM> to an additional LC filter <NUM> (not shown), or to the electrical load <NUM> (not shown).

It will be understood that, while <FIG> depicts the CMVC circuit <NUM> being in signal communication with respective power transmission output lines <NUM> to provide a respective fourth phase voltage VA4, VB4, VC4 thereto, other aspects are not so limited. It is contemplated that other aspects of the CMVC circuit <NUM> can comprise any desired number of power output lines <NUM>, having any desired number of phase and frequency orientations, without departing from the scope of the disclosure herein.

In various aspects of the disclosure, other electrical components and devices can be added to the CMVC circuit <NUM> without departing from the scope of the disclosure. For example, as depicted in <FIG>, a first set of capacitors <NUM> can optionally be included in the CMVC circuit <NUM>. The first set of capacitors <NUM> can comprise any desired number or type of capacitor, including only one. In an aspect, the first set of capacitors <NUM> comprises a high-pass capacitor. In an aspect the first set of capacitors <NUM> can be coupled electrically in series between the respective series-coupled secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> and the at least one primary winding <NUM> of the second set of coupled inductors <NUM>. In another aspect, the first set of capacitors can be isolated from system ground to reduce a common mode current flow to ground.

It will be appreciated that in various aspects still other additional components can be added to enhance the functionality of the CMVC circuit <NUM> without departing from the scope of the disclosure herein. For example, aspects can optionally include a resistor <NUM>. With reference to <FIG>, an alternative aspect of the CMVC circuit <NUM> is shown in accordance with various aspects described herein. The CMVC circuit <NUM> is similar to the CMVC circuit <NUM> illustrated in <FIG>; therefore, like parts will be identified with like numerals, with it being understood that the description of the like parts of the first example CMVC circuit <NUM> of <FIG> applies to the second example CMVC circuit <NUM> of <FIG>, unless otherwise noted. One difference is that aspects of the disclosure included in <FIG> can include for example, resistor <NUM>.

Another notable difference is that as indicated by the polarity dot notation of the coupled inductors, the respective polarities of the various coupled inductors of the aspect depicted in <FIG> are essentially opposite those as depicted in <FIG>. However, in both aspects, the relative polarities of the respective primary windings <NUM>, <NUM>, <NUM> and secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM>, and the relative polarities of the respective primary windings <NUM> and secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM>, are arranged with respect to each other such that at high frequencies the common mode voltage Vcm present on the respective input lines <NUM> will be canceled or reduced at the respective output lines <NUM>.

For example, in some aspects such as depicted in <FIG>, the first polarity (defined by the primary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM>) and second polarity (defined by the secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM>) can be identical relative to each other, and the third polarity (defined by primary windings 611of the second set of coupled inductors <NUM>) and fourth polarity (defined by the secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM>), can be identical to each other, yet the first and second polarities can be opposite the third and fourth polarities. Conversely, in other aspects such as depicted in <FIG>, the first polarity and second can be opposite relative to each other, and the third polarity and fourth polarity can be opposite relative to each other, yet the second polarity can be identical to the third polarity.

While <FIG> depicts a single resistor <NUM> disposed in series with capacitor <NUM> can comprise any desired number or type of resistor. In an aspect, the resistor <NUM> can be used as damping for potential oscillation between the inductors and capacitors in CMVC circuit <NUM>. In an aspect, the optional resistor <NUM> can be coupled electrically in series between the respective series-coupled secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> and the at least one primary winding <NUM> of the second set of coupled inductors <NUM>. In another aspect, the resistor <NUM> can be coupled electrically in series with the first set of capacitors <NUM>.

With continued reference to <FIG>, the CMVC circuit <NUM> can comprise the first set of transformers <NUM> (for example, the first transformer <NUM>, second transformer <NUM>, and third transformer <NUM>), and a second set of transformers <NUM>. As depicted, the CMVC circuit <NUM> includes the first capacitor <NUM> and the resistor <NUM> coupled in series. Each transformer <NUM>, <NUM>, <NUM> of the first set of transformers <NUM> includes respective primary windings <NUM>, <NUM>, <NUM> and corresponding secondary windings <NUM>, <NUM>, <NUM>. The primary windings <NUM>, <NUM>, <NUM> of the first set of transformers <NUM> are arranged to define the first polarity, and the corresponding secondary windings <NUM>, <NUM>, <NUM> are arranged to define the second polarity. However, in contrast to the aspect of <FIG>, the first and second respective polarities are shown opposite each other. The second set of transformers <NUM> can be at least partially disposed downstream of the input <NUM> and proximate to the output <NUM>. In an aspect, the second set of transformers <NUM> can include at least one primary winding <NUM> and at least one secondary winding, shown as windings <NUM>, <NUM>, <NUM>. The at least one primary winding <NUM> of the second set of transformers <NUM> is arranged to define the third polarity, and the corresponding secondary windings <NUM>, <NUM>, <NUM> are arranged to define the respective fourth polarity, and associated with one of each respective output lines <NUM>. As can be seen, the third and fourth polarities are opposite (in contrast to the aspect of <FIG>). As shown, the third polarity is identical to the second polarity.

As described hereinabove (with respect to the CMVC circuit <NUM> of <FIG>), the non-limiting aspect of the CMVC circuit <NUM> will likewise result in a summed voltage VSUM at the secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> that can have a magnitude that is three times that of the common mode voltage Vcm.

The voltage VSUM can be provided to the at least one primary winding <NUM> of the second set of coupled inductors <NUM>. The summed AC voltage VSUM provided to the at least one primary winding <NUM> of the second set of coupled inductors <NUM> will likewise be transferred (i.e., based on the mutual inductance of the corresponding primary and secondary windings) to the respective secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> to define the induced respective third phase voltage VA3, VB3, VC3. As noted above, each at least one primary winding <NUM> of the second set of coupled inductors defines a third polarity that is identical to the second polarity, and is electrically coupled in signal communication with the series-connected coupled inductor secondaries <NUM>, <NUM>, <NUM> of the first set of first coupled inductors <NUM> to receive the summed AC voltage VSUM therefrom.

For example, in some aspects, the turns ratio of the at least one primary winding <NUM> to the respective secondary windings <NUM>, <NUM>, <NUM> can be selected based on the number of AC phases in the CMVC circuit <NUM> when the CMVC circuit <NUM> is a polyphase AC circuit. In aspects, the turns ratio (i.e. the ratio of the number of primary winding turns to number of secondary winding turns) of the at least one primary <NUM> to the respective secondary winding <NUM>, <NUM>, <NUM> can be designated as T: <NUM>, where T is the number of turns of the primary winding <NUM>. In an aspect, the value of T may be selected to equal the number of electrical phases in the CMVC circuit <NUM>. For example, in an aspect comprising a <NUM>-phase AC circuit, the turns ratio of the second set of coupled inductors <NUM> can be selected to be <NUM>:<NUM>. That is, the respective induced third voltage VA3, VB3, VC3 at the respective secondary windings <NUM>, <NUM>, <NUM> will be <NUM> times the voltage VSUM at the at least one primary winding <NUM>.

Aspects of the disclosure can be included wherein the first set of coupled inductors <NUM> are arranged to cooperate with the second set of coupled inductors <NUM> to modify or adjust the respective first, second, and third phase voltages VA1, VB1, VC1, VA2, VB2, VC2, VA3, VB3, VC3 to operatively cancel or reduce the common mode voltage component Vcm therefrom (e.g. due to the opposite polarity of the windings), resulting in the fourth phase voltage VA4, VB4, VC4. That is, the respective fourth phase voltages VA4, VB4, VC4 are equal to the respective first phase voltages VA1, VB1, VC1 with the common mode voltage component Vcm cancelled or subtracted therefrom. The respective fourth phase voltage VA4, VB4, VC4 can then be provided downstream from the corresponding secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> for additional filtering (for example by an LC filter <NUM>, not shown) or directly to the electrical load <NUM>, via respective power transmission or output lines <NUM>.

As noted above, in the aspect depicted in <FIG>, each at least one primary winding <NUM> of the second set of coupled inductors <NUM> defines a third polarity opposite the second polarity, and is electrically coupled in signal communication with the series-connected coupled inductor secondaries <NUM>, <NUM>, <NUM> of the first set of first coupled inductors <NUM> to receive the summed AC voltage VSUM therefrom. Since the second set of coupled inductors <NUM> is arranged to have a subtractive polarity with respect to the first set of coupled inductors <NUM>, the voltage induced at the secondary windings, <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> will be subtractive, or <NUM> degrees out of phase with the voltage provided to the first set of coupled inductors <NUM>.

For example, as noted above, the first phase voltages VA1, VB1, VC1 are provided to the to the respective primary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> from respective transmission lines <NUM> and include the common mode voltage component equal to 3Vcm, in phase with the first phase voltages VA1, VB1, VC1. The respective first phase voltages VA1, VB1, VC1 (including the common mode voltage component Vcm) are also provided via respective transmission lines <NUM> to respective secondary winding <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> downstream of nodes <NUM>, <NUM>, <NUM>.

The induced second phase voltages VA2, VB2, VC2 are summed at the series-connected secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> resulting in a summed voltage, VSUM, which is essentially equal to <NUM> times the common mode voltage Vcm = (VA1 +VB1 +VC1)/<NUM>. The summed voltage VSUM is provided to the at least one primary winding <NUM>, thereby resulting in an induced third phase voltage VA3, VB3, VC3 at the respective secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM>. The induced third phase voltages VA3, VB3, VC3 will be subtractive, or <NUM> degrees out of phase with the common mode voltage component Vcm of the corresponding first phase voltages VA1, VB1, VC1. The combination of the respective first phase voltage VA1, VB1, VC1, including and in phase with the common mode voltage component Vcm, with the respective third phase voltage VA3, VB3, VC3, at the respective secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> operably defines a respective fourth phase voltage VA4, VB4, VC4. Because the respective third phase voltage is equal to but out of phase with the common mode voltage component Vcm, the common mode voltage component Vcm, will operatively be cancelled or reduced. Consequently, the respective fourth phase voltage VA4, VB4, VC4 will be equal to the corresponding first phase voltage VA1 VB1, VC1 but with the common mode component subtracted, or cancelled. The "clean" respective fourth phase voltage VA4, VB4, VC4 can then be provided via output lines <NUM> to an optional LC filter <NUM> (not shown), or to the electrical load <NUM> (not shown).

With reference to <FIG>, a non-limiting aspect of a CMVC circuit <NUM> is shown in accordance with various aspects described herein. The CMVC circuit <NUM> is similar to the CMVC circuit <NUM> illustrated in <FIG>; therefore, like parts will be identified with like numerals, with it being understood that the description of the like parts of the first example CMVC circuit <NUM> of <FIG> applies to the second example CMVC circuit <NUM> of <FIG>, unless otherwise noted. One difference is that aspects of the disclosure included in <FIG> can include for example, a second set of capacitors <NUM>.

For example, as depicted in <FIG> the optional second set of capacitors <NUM> can comprise a respective capacitor <NUM>, <NUM>, <NUM> coupled electrically in series between the respective primary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors and the at respective input lines <NUM> (e.g. capacitor <NUM> is coupled between VA1 and the primary winding <NUM> of coupled inductor <NUM>, capacitor <NUM> is coupled between VB1 and primary winding <NUM> of coupled inductor <NUM>, and capacitor <NUM> is coupled between VC1 and primary winding <NUM>). In an aspect, each capacitor <NUM>, <NUM>, <NUM> of the second set of capacitors <NUM> is a high frequency band pass capacitor.

The CMVC circuit <NUM> can be coupled in signal communication with the inverter <NUM> (not shown) and can receive the AC electrical power from the output <NUM> of inverter <NUM> via power transmission lines <NUM>. For example, in the non-limiting aspect of <FIG>, the AC electrical power can be provided to the CMVC circuit <NUM> as a conventional three-phase first AC voltage (VA1, VB1, VC1) having any desired frequency. Each phase voltage VA1, VB1, VC1 can be provided to the CMVC circuit <NUM> on separate respective input lines <NUM>.

It will be understood that the aspect depicted in <FIG> will operate in essentially the same way as the aspect depicted in <FIG>, with like parts having the same function and arrangement. For example, as depicted in <FIG>, the respective first phase voltages VA1, VB1, VC1 are provided to respective capacitors <NUM>, <NUM>, <NUM> of the second set of capacitors <NUM> (e.g., a respective high frequency band-pass filter capacitor) and to the respective primary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM>. The resultant, induced second phase voltages VA2, VB2, VC2 at the respective secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> are summed to define a voltage VSUM that is equal to the common mode voltage component Vcm = (VA1 +VB1 +VC1)/<NUM>. The summed voltage VSUM is provided to the at least one primary winding <NUM> of the second set of coupled inductors <NUM> thereby resulting in an induced third phase voltage VA3, VB3, VC3 at the respective secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM>. The induced third phase voltages VA3, VB3, VC3 will be subtractive or <NUM> degrees out of phase with the corresponding first phase voltages VA1, VB1, VC1 provided via respective transmission lines <NUM> to the respective secondary winding <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM>. The combination of the respective first phase voltage VA1, VB1, VC1 with the respective third phase voltage VA3, VB3, VC3, at the respective secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> operably defines a respective fourth phase voltage VA4, VB4, VC4 that is equal to and in phase with the corresponding first phase voltage VA1 with the common mode component removed or cancelled. The respective fourth phase voltage VA4, VB4, VC4 can then be provided via transmission line <NUM> to an optional LC filter <NUM> (not shown), or to the electrical load <NUM>. In this way, the voltage provided to each respective output line <NUM> by the respective secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> is equal to the respective first phase voltage VA1, VB1, VC1 with the common mode voltage component reduced therefrom.

It will be understood that, while <FIG> depicts the CMVC circuit <NUM> being in signal communication with respective power transmission lines <NUM> to provide a respective fourth phase voltage VA4, VB4, VC4 thereto, other embodiments are not so limited. It is contemplated that other embodiments of the CMVC circuit <NUM> can comprise any desired number of AC voltage outputs, having any desired number of phase and frequency orientations, provided to any number of desired power transmission lines <NUM> without departing from the scope of the claims herein.

In various aspects of the CMVC circuit, <NUM>, the first and second set of coupled inductors <NUM>, <NUM> can comprise any respective number of coupled inductors having any desired turns ratio without departing from aspects of the disclosure. Further, in additional or alternative aspects of the disclosure, coupled inductors may be arranged as individual inductors, such as coupled inductors, without departing from aspects of the disclosure.

In an aspect, the number of coupled inductors comprising the first or second set coupled inductors <NUM>, <NUM> can be selected based on the number of phases in the CMVC circuit <NUM>. For example, in an aspect, the number of coupled inductors in the first or second set coupled inductors <NUM>, <NUM> can be set to N, where N is the number of phases in the CMVC circuit <NUM>.

With reference to <FIG>, an alternative aspect of the CMVC circuit <NUM> is shown in accordance with various aspects described herein. The CMVC circuit <NUM> is similar to the CMVC circuit <NUM> illustrated in <FIG>; therefore, like parts will be identified with like numerals, with it being understood that the description of the like parts of the first example CMVC circuit <NUM> of <FIG> applies to the second example CMVC circuit <NUM> of <FIG>, unless otherwise noted. One difference is that aspects of the disclosure included in <FIG> can include for example, a second set of resistors <NUM>.

Another notable difference is that as indicated by the polarity dot notation of the coupled inductors, the respective polarities of the various coupled inductors of the aspect depicted in <FIG> are essentially opposite those as depicted in <FIG>. However, in both aspects, the relative polarities of the respective primary windings <NUM>, <NUM>, <NUM> and secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM>, and the relative polarities of the respective primary windings <NUM> and secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM>, are arranged with respect to each other such that at high frequencies the common mode voltage Vcm present on the respective input lines <NUM> will be canceled or reduced at the secondary respective output lines <NUM>.

For example, as depicted in <FIG> the optional second set of resistors <NUM> can comprise a respective resistor <NUM>, <NUM>, <NUM> coupled electrically in series between the respective primary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors and the at respective input lines <NUM> (e.g. resistor <NUM> is coupled between VA1 and the primary winding <NUM> of coupled inductor <NUM>, resistor <NUM> is coupled between VB1 and primary winding <NUM> of coupled inductor <NUM>, and resistor <NUM> is coupled between VC1 and primary winding <NUM>). In an aspect, each resistor <NUM>, <NUM>, <NUM> of the second set of capacitors <NUM> is a damping resistor.

<FIG> illustrates another power distribution circuit <NUM> including a CMVC circuit <NUM> according to another aspect of the present disclosure. The power distribution circuit <NUM> is similar to the power distribution circuit <NUM>; therefore, like parts will be identified with like numerals, with it being understood that the description of the like parts of the power distribution circuit <NUM> applies to the power distribution circuit <NUM>, unless otherwise noted. One difference is that non-limiting aspects of the CMVC circuit <NUM> can be utilized in conjunction with a conventional common-mode voltage filtering circuit <NUM>. For example, the conventional common-mode voltage filtering circuit <NUM> can comprise a conventional LC filter. The LC filter <NUM> can be in signal communication with the CMVC circuit <NUM>, and further arranged to provide an output voltage to the electrical load <NUM>. For example, the LC filter <NUM> can be coupled electrically in series between the CMVC circuit <NUM> and the electrical load <NUM>.

<FIG> illustrates a flow chart demonstrating a method <NUM> of reducing or cancelling a common-mode voltage by way of utilizing aspects of the CMVC circuits described herein. The method begins by coupling a respective primary winding <NUM>, <NUM>, <NUM> of a first set of coupled inductors <NUM> in signal communication with a respective input line <NUM> to receive a respective first phase voltage VA1, VB1, VC1 having a common mode voltage component therefrom, at <NUM>. Each primary winding <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> can define a first polarity. In some aspects, the corresponding secondary winding <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> can define a second polarity identical to the first polarity. In other aspects, the second polarity can be opposite the first polarity.

The method includes coupling the secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> electrically in series, at <NUM>. Next, the method includes coupling at least one primary winding <NUM> of a second set of coupled inductors <NUM> in signal communication with the series-coupled secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM> to receive a second summed voltage VSUM therefrom, at <NUM>. The second voltage VSUM can be a sum of the voltages across the series-coupled secondary windings <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM>. In an aspect, the at least one primary winding <NUM> of the second set of coupled inductors <NUM> can define a third polarity opposite the second polarity. In another aspect, the at least one primary winding <NUM> of the second set of coupled inductors <NUM> can define a third polarity identical to the second polarity. The respective secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> can define a fourth polarity identical to the third polarity. In other aspects, the respective secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> can define a fourth polarity identical to the third polarity. The method includes inducing a respective third voltage VA3, VB3, VC3 at respective secondary winding <NUM>, <NUM>, <NUM> that is out of phase from the respective first voltage VA1, VB1, VC1, at <NUM>. The method includes coupling the respective secondary windings <NUM>, <NUM>, <NUM> of the second set of coupled inductors <NUM> in series with a respective input line <NUM> to receive the respective first phase voltage therefrom, at <NUM>. Next, the method includes coupling the at least one secondary winding <NUM>, <NUM>, <NUM> of the at least one second coupled inductor <NUM> in series with a respective output line <NUM> to provide a respective fourth voltage VA4, VB4, VC4 thereto, at <NUM>. In an aspect, the respective fourth voltage VA4, VB4, VC4 is equal to the first phase voltage VA1, VB1, VC1 with the common mode voltage reduced therefrom.

Other aspects can include coupling a capacitor <NUM> electrically in series between the series-coupled first coupled inductor secondary windings <NUM>, <NUM>, <NUM> and the at least one primary winding <NUM> of the second set of coupled inductors <NUM>. Yet other aspects can comprise coupling a respective capacitor <NUM>, <NUM>, <NUM> electrically in series between each respective input line and the respective primary winding <NUM>, <NUM>, <NUM> of the first set of coupled inductors <NUM>.

The sequence depicted is for illustrative purposes only and is not meant to limit the method <NUM> in any way as it is understood that the portions of the method can proceed in a different logical order, additional or intervening portions can be included, or described portions of the method can be divided into multiple portions, or described portions of the method can be omitted without detracting from the described method.

The aspects disclosed herein provide a common-mode voltage cancellation circuit and method. The technical effect is that the above described aspects enable the cancelling or reduction of the common-mode voltage in a power supply system. One advantage that can be realized in the above aspects is that the above described aspects enable the use of smaller, lighter, and less expensive LC filters compared with conventional systems.

To the extent not already described, the different features and structures of the various aspects can be used in combination with each other as desired. That one feature cannot be illustrated in all of the aspects is not meant to be construed that it cannot be, but is done for brevity of description. Thus, the various features of the different aspects can be mixed and matched as desired to form new aspects, whether or not the new aspects are expressly described. Combinations or permutations of features described herein are covered by this disclosure.

Further aspects are provided by the subject matter of the following clauses:
A common-mode voltage cancellation (CMVC) circuit, comprising a first set of coupled inductors, each coupled inductor of the first set of coupled inductors having a respective primary winding, and a respective secondary winding, each primary winding of the first set of coupled inductors configured to receive a respective first phase voltage having a common mode voltage component from a corresponding input line, wherein the respective secondary windings of the first set of coupled inductors are electrically coupled in series; and a second set of coupled inductors comprising at least one primary winding in signal communication with the series connected secondary windings of the first set of coupled inductors to receive a second voltage therefrom, the second set of coupled inductors further comprising at least one secondary winding, each at least one secondary winding coupled in series with a respective input line and to a respective output line, electrically downstream from the respective input line.

The CMVC circuit of the preceding clause wherein a relative polarity of the primary and secondary windings of the first set of coupled inductors is opposite a relative polarity of the primary and secondary windings of the second set of coupled inductors.

The CMVC circuit of any preceding clause, wherein the respective first phase voltage having a common mode voltage component is also received by the respective secondary windings of the second set of coupled inductors.

The CMVC circuit any preceding clause, wherein a summed voltage across series connected secondary windings of the first set of coupled inductors is proportional to the common mode voltage component.

The CMVC circuit of any preceding clause, wherein an induced voltage at the respective secondary windings of the second set of coupled inductors is out of phase with the common mode voltage component.

The CMVC circuit of any preceding clause, wherein the voltage across each respective secondary winding of the second set of coupled inductors is proportional to a sum of the respective first phase voltages and the common mode voltage component.

The CMVC circuit of any preceding clause, wherein the voltage provided to each respective output line by the respective secondary windings of the second set of coupled inductors is equal to the respective first phase voltage with the common mode voltage component reduced therefrom.

The CMVC circuit of any preceding clause, wherein the CMVC circuit is a polyphase AC circuit, and wherein the second set of coupled inductors comprises at least N coupled inductors, wherein N is equal to the number of electrical phases in the CMVC circuit.

The CMVC circuit of any preceding clause, further comprising at least one of a capacitor and a resistor electrically coupled in series between the series-connected first coupled inductor secondaries and the at least one primary of the second set of coupled inductors.

The CMVC circuit any preceding clause, further comprising at least one of a set of capacitors and a set of resistors, each respective capacitor and resistor coupled electrically in series with a primary winding of a respective coupled inductor of the first set of coupled inductors.

The CMVC circuit of any preceding clause, wherein each respective output line is in signal communication with an LC filter.

A method of cancelling a common-mode voltage in a circuit, comprising: coupling a respective primary winding of a first set of coupled inductors in signal communication with a respective input line to receive a respective first phase voltage having a common-mode voltage component therefrom, wherein each coupled inductor of the first set of coupled inductors comprises a primary winding and a corresponding secondary winding; coupling the secondary windings of the first set of coupled inductors electrically in series; coupling at least one primary winding of a second set of coupled inductors in signal communication with the series-coupled secondary windings of the first set of coupled inductors to receive a second voltage therefrom, wherein the second set of coupled inductors comprises at least one secondary winding; inducing a respective third voltage at the respective secondary windings of the second set of coupled inductors that is out of phase from the second voltage; coupling the at least one secondary winding of the second set of coupled inductors in series with a respective input line to receive the respective first phase voltage having the common-mode voltage component therefrom; and coupling the respective secondary windings of the second set of coupled inductors in series with a respective output line to provide a respective fourth voltage thereto.

The method of the preceding clause, wherein a relative polarity of the primary and secondary windings of the first set of coupled inductors is opposite a relative polarity of the primary and secondary windings of the second set of coupled inductors.

The method of any preceding clause, wherein the respective first phase voltage having the common-mode voltage component is also received by the respective secondary windings of the second set of coupled inductors.

The method of any preceding clause, wherein a voltage across the series connected secondary windings of the first set of coupled inductors is proportional to the common mode voltage component.

The method of any preceding clause, wherein the induced respective third voltage at the respective secondary windings of the second set of coupled inductors is out of phase with the common mode voltage component.

The method of any preceding clause, wherein the voltage across each respective secondary winding of the second set of coupled inductors comprises a sum of the respective first phase voltage with the common mode voltage component, and the induced voltage at the respective secondary windings of the second set of coupled inductors.

The method of any preceding clause, further comprising, providing to each respective output line a fourth respective voltage that is equal to the respective first phase voltage with the common mode voltage component reduced therefrom.

The method of any preceding clause, further comprising coupling a capacitor electrically in series between the series coupled secondary windings of the first set of coupled inductors and the at least one primary winding of the second set of coupled inductors.

The method of any preceding clause, further comprising coupling a capacitor electrically in series between each respective input line and the respective primary winding of the first set of coupled inductors.

Claim 1:
A common-mode voltage cancellation (CMVC) circuit (<NUM>), comprising:
a first set of coupled inductors (<NUM>), each coupled inductor (<NUM>, <NUM>, <NUM>) of the first set of coupled inductors (<NUM>) having a respective primary winding (<NUM>, <NUM>, <NUM>), and a respective secondary winding (<NUM>, <NUM>, <NUM>), each primary winding of the first set of coupled inductors (<NUM>, <NUM>, <NUM>) configured to receive a respective first phase voltage (VA1, VB1, VC1) having a common mode voltage component (Vcm) from a corresponding input line (<NUM>), wherein the respective secondary windings (<NUM>, <NUM>, <NUM>) of the first set of coupled inductors (<NUM>) are electrically coupled in series; and
a second set of coupled inductors (<NUM>) comprising at least one primary winding (<NUM>) in signal communication with the series connected secondary windings (<NUM>, <NUM>, <NUM>) of the first set of coupled inductors (<NUM>) to receive a second voltage therefrom (VA2, VB2, VC2) , the second set of coupled inductors (<NUM>) further comprising secondary windings (<NUM>, <NUM>, <NUM>), each of which coupled in series with a respective input line (<NUM>) and to a respective output line (<NUM>), electrically downstream from the respective input line (<NUM>).