Abstract: A multiphase interleaved forward power converter includes an inductor and first and second subconverter comprising respective transformers. The converter also includes first and second drives configured to respectively operate the first and second subconverters with cycling periods comprising a conduction period, a reset period, and an idle period. The first and second drives are also configured to phase shift the cycling periods in each subconverter such that the conduction period of the subconverter is at least partially complementary to the idle period of the other subconverter. The second drive also clamps a voltage across a winding of the transformer of the first subconverter to substantially prevent a first resonance voltage from propagating in the first subconverter during the idle period of the first subconverter.

Abstract: An apparatus for conversion between AC power and DC power. The apparatus includes: a first power conversion circuit having a first AC side and a DC side, at least one second power conversion circuit each having a second AC side and sharing the DC side with the first power conversion circuit, and at least one choke having a first terminal, a second terminal and at least one third terminal, wherein: the first terminal is arranged to be electrically coupled to a phase of the AC power, and the second terminal and the at least one third terminal are electrically coupled to respective same phases of the first AC side of the first power conversion circuit and the second AC side of the at least one second power conversion circuit.

Abstract: A voltage source converter comprises a converter arm extending between two terminals each terminal being connectable to a or a respective electrical network, the converter arm including a valve that includes at least one module, the or each module being operable to selectively provide a voltage source; and a controller programmed to selectively operate the valve to clamp a voltage at either or both of the two terminals and thereby operate the valve as a current limiter to limit a selected current flowing in the converter arm at or below a fixed or variable current threshold.

Abstract: A modular power converter includes first and second terminals to connect to electrical networks and at least one module connected between the first and second terminals, the module(s) including at least one switching element and at least one energy storage device, the switching element(s) and the energy storage device(s) combining to selectively provide a voltage source, the switching element(s) being switchable to transfer power between the first and second terminals. The converter further includes a control unit configured to selectively control switching of the switching element(s) to store energy from or release energy to either or both of the first and second terminals so as to decouple respective power flows at the first and second terminals and thereby inhibit a modulation of power flow at one of the first and second terminals from modifying a power flow at the other of the first and second terminals.

Abstract: According to the embodiments provided herein, power and data transfer system may include a primary inductive, a secondary inductive coupler, a power source, and a controller. The primary inductive coupler may forms a flat front face. The primary inductive coupler may include a primary winding wound around a primary core. The primary core may be adjacent to the flat front face. The secondary inductive coupler may be separated from the flat front face of the primary inductive coupler by a fluid. The secondary inductive coupler may include a secondary winding. The power source may generate a current in the primary winding of the primary inductive coupler and a magnetic field in the secondary winding of the secondary inductive coupler. The controller may execute machine readable instructions to receive charging data via a feedback loop and adjust the current based upon the charging data.

Abstract: A resonant circuit includes first, second, and third input nodes configured to receive a three phase input power and is formed as a delta circuit including a first leg connected between a first corner node and a second corner node, a second leg connected between the second corner node and a third corner node, and a third leg connected between the third corner node and the first corner node. A first outer resonant device is connected between the first input node and the first corner node, a second outer resonant device connected between the second input node and the second corner node, and a third outer resonant device connected between the third input node and the third corner node. Each leg of the delta circuit includes an inner resonant device connected in series with a corresponding transformer.

Abstract: A three phase step-up autotransformer construction is discussed herein. The passive 12-pulse AC-DC converter offers simplicity, high reliability and low cost solution to AC-DC power conversion. The autotransformer is a component of the passive 12-pulse AC-DC converter. The autotransformer converts three-phase AC power into six-phase AC power. With appropriate vector design, the autotransformer may be configured to draw a near sinusoidal 12-pulse current waveform from the three-phase voltage source. The six-phase output may be configured to drive a rectifier (non-linear) load.

Abstract: A non-isolated symmetric self-coupling 18-pulse rectifier power supply system comprises a phase-shifting autotransformer, three circuits of output devices, a time sequence controller and a power output end. The phase-shifting autotransformer is provided with three groups of output ends and one group of input ends, and the output device in each circuit comprises a zero-sequence suppression reversing inductor, a three-phase uncontrolled rectifier bridge and a bidirectional switch BUCK converter, which are connected to each other in turn. The time sequence controller is provided with three groups of control ends which are respectively connected to the control end of the bidirectional switch BUCK converter in each circuit. The output end of the bidirectional switch buck converter in each circuit is connected to the power output end.

Abstract: An electromagnetic connector is disclosed that is configured to form a first magnetic circuit portion comprising a first core member and a first coil disposed of the first core member. The electromagnetic connector is configured to mate with a second electromagnetic connector, where the second electromagnetic connector is configured to form a second magnetic circuit portion comprising a second core member and a second coil disposed of the second core member. The first core member and the second core member are configured to couple the first coil to the second coil with a magnetic circuit formed from the first magnetic circuit portion and the second magnetic circuit portion when the electromagnetic connector is mated with the second electromagnetic connector. The magnetic circuit is configured to induce a signal in the first coil when the second coil is energized.

Abstract: A coldplate for use with electronic components in an electric vehicle (EV) or a hybrid-electric vehicle (HEV). The coldplate includes a main portion having multiple raised features on a surface thereof. The raised features are configured for attaching the main portion to a printed circuit board having multiple electronic components attached thereto. The raised features are further configured for maintaining the printed circuit board in a spaced relation relative to the main portion to facilitate air flow between the printed circuit board and the main portion for dissipating heat generated by the plurality of electronic components. The coldplate also includes a protrusion extending from the surface of the main portion. The protrusion is configured for contacting one of the plurality of electronic components attached to the printed circuit board for dissipating heat generated by the electronic component.

Abstract: A series-connected multi-level power conversion device according to an aspect of embodiments includes a multi-winding transformer and a power conversion unit. The multi-winding transformer has a relationship that n secondary windings respectively connected to n single-phase power converters in the same output phase have a voltage phase difference of 60/n degrees and a relationship that the m secondary windings respectively connected to the m single-phase power converters corresponding to the m output phases have a voltage phase difference of 60/m degrees.

Abstract: A coldplate for use with a transformer in an electric vehicle (EV) or a hybrid-electric vehicle (HEV). The coldplate includes a main portion having a recess formed therein, the recess having a floor configured for contacting a bottom surface of a transformer for dissipating heat generated by the transformer. The main portion includes a raised feature configured for contacting a winding of the transformer for dissipating heat generated by the transformer. The coldplate also includes a bracket member for use in securing the transformer in the recess of the main portion, the bracket member configured for contacting the main portion and the transformer for dissipating heat generated by the transformer. The bracket member includes a contact surface for contacting a top surface of the transformer, the contact surface having an area sufficient to contact substantially all of the top surface of the transformer.

Abstract: Design of a T-connected autotransformer based 20-pulse ac-dc converter is presented in this invention. The 20-pulse topology is obtained via two paralleled ten-pulse ac-dc converters each of them consisting of a five-phase (five-leg) diode bridge rectifier. For independent operation of paralleled diode-bridge rectifiers, a zero sequence blocking transformer (ZSBT) is designed and implemented. Connection of a tapped inter-phase transformer (IPT) at the output of ZSBT results in doubling the number of output voltage pulses to 40. Experimental results are obtained using the designed and constructed laboratory prototype of the proposed converter to validate the design procedure and the simulation results under varying loads. The VA rating of the magnetic in the proposed topology are calculated to confirm the savings in space, volume, weight, and cost of the proposed configuration.

Abstract: A power conversion device is provided which includes a plurality of series circuits each formed of a voltage source and a controlled current source. At least two of said series circuits formed of the voltage source and the controlled current source are connected in parallel. Further, parallel connection points of the series circuits connected in parallel form output terminals.

Abstract: A 24-pulse and 18-pulse composite AC-to-DC converter is a converter using two or more conversion methods in parallel. The converter may include a main rectifier receiving at least a portion of an input AC signal, an autotransformer having an output voltage with lower amplitude than the input AC signal, and a plurality of auxiliary bridge rectifiers, each receiving the output from each leg of the autotransformer. In one embodiment of the invention, the main rectifier may receive a substantial portion of the load current, allowing each of the auxiliary bridge rectifiers to be generally smaller than the main rectifier.

Abstract: An AC/DC converter system comprises an input circuit for connection to a 3-phase AC source. An autotransformer is coupled to the input circuit for developing first and second phase shifted AC supplies. A first AC/DC converter has a first rectifier connected to the first phase shifted AC supply converting AC power to DC power across a first DC bus having a first DC bus capacitor. A second AC/DC converter has a second rectifier connected to the second phase shifted AC supply converting AC power to DC power across a second DC bus having a second DC bus capacitor. First and second sets of switches are connected between the respective first and second DC buses and a main DC bus having a main DC bus capacitor. The first and second sets of switches are controlled so that only one of the first and the second DC buses is connected to the main DC bus to charge the main DC bus capacitor.

Abstract: A signal transmission arrangement includes a transformer with a first and a second winding. A damping circuit has an input terminal for receiving an input signal. The damping circuit is coupled to the first winding and is configured to have an electrical resistance that is dependent on the input signal. An oscillator circuit includes the second winding and is configured to provide an oscillating signal. An evaluation circuit is configured to receive the oscillating signal and to provide an output signal that is dependent on an amplitude of the oscillating signal.

Abstract: A nearly 2 to 1 boosting mufti-phase AC-to-DC converter may include a main rectifier, an auxiliary rectifier; and an autotransformer connected to the main rectifier and the auxiliary rectifier. The autotransformer may include a plurality of interconnected windings arranged in a plurality of legs, with one of the legs for each phase and with each leg including a plurality of windings, wherein all but one of the windings of each leg have equal turns ratios and one of the windings of each leg has a turns ratio that is less than the turns ratio of all of the other windings of the respective leg.

Abstract: Energy management of an electronic device using multiple electric power sources. The electric power sources may include a parasitic electric power source, a rechargeable electric power source, an intermittent electric power source, and a continuous electric power source. The electronic device further may include a power supply for receiving the electric power from the source(s) and supplying electric power to the various components of the electronic device that require power. The electronic device may include a source selector for controlling which power source supplies electric power to the power supply. Energy management of the electronic device may be configured to use a permanently exhaustible power source such as a battery only when other power sources are unavailable.

Abstract: A dual-input 18-pulse autotransformer rectifier unit for more electric aircraft AC-DC converter uses an autotransformer with a nine-phase output to condition AC power prior to DC rectifying the AC power.

Abstract: A multiphase transformer rectifier unit for converting a three-phase alternating current supplied from a power distribution system to direct current supplied to at least one load. The multiphase transformer rectifier unit includes a magnetic core having a primary winding set and secondary winding set, and a rectifier circuit. The secondary winding set is arranged to generate N substantially equally distributed output phases, wherein N is an odd number multiple of 3, and N>3, and the primary winding set (17) is arranged to provide a positive or negative phase shift equal substantially to 360 ( 8 × N ) degrees of said output phases. Also an arrangement of two inventive multiphase transformer rectifier units for reducing current distortion in the power distribution system.

Abstract: A composite power conversion method using a WYE asymmetrical autotransformer that converts electrical power from AC to DC uses two or more conversion methods in parallel and provides a passive technique that “splits” the input 3-phase voltages into additional phases, so that the number of DC rectification pulses is increased to improve AC line current THD The WYE asymmetric autotransformer topology provides a potential improvement in size/weight and efficiency compared to former asymmetric autotransformers.

Abstract: An electromagnetic connector is disclosed that is configured to form a first magnetic circuit portion comprising a first core member and a first coil disposed of the first core member. The electromagnetic connector is configured to mate with a second electromagnetic connector, where the second electromagnetic connector is configured to form a second magnetic circuit portion comprising a second core member and a second coil disposed of the second core member. The first core member and the second core member are configured to couple the first coil to the second coil with a magnetic circuit formed from the first magnetic circuit portion and the second magnetic circuit portion when the electromagnetic connector is mated with the second electromagnetic connector. The magnetic circuit is configured to induce a signal in the first coil when the second coil is energized.

Abstract: A composite-like AC-to-DC converter has boosting capabilities. The term “composite AC-to-DC converter” has been coined to distinguish a converter using two or more conversion methods in parallel. All the autotransformer designs for the boost topology composite-like system begin with vector diagrams constructed using the tips of the line-to-line voltage vectors. A constructor arc is swung between these tips equal to the length of the line-to-line voltage vector span. The number of autotransformer three-phase outputs is then determined by the number of equally spaced rays drawn from the opposite vector tip to the arc. The intersection of points of these rays with the arc are used to design the composite-like autotransformer's winding's voltage ratios and interconnections.

Abstract: A signal transmission arrangement includes a transformer with a first and a second winding. A damping circuit has an input terminal for receiving an input signal. The damping circuit is coupled to the first winding and is configured to have an electrical resistance that is dependent on the input signal. An oscillator circuit includes the second winding and is configured to provide an oscillating signal. An evaluation circuit is configured to receive the oscillating signal and to provide an output signal that is dependent on an amplitude of the oscillating signal.

Abstract: A 24-pulse and 18-pulse composite AC-to-DC converter is a converter using two or more conversion methods in parallel. The converter may include a main rectifier receiving at least a portion of an input AC signal, an autotransformer having an output voltage with lower amplitude than the input AC signal, and a plurality of auxiliary bridge rectifiers, each receiving the output from each leg of the autotransformer. In one embodiment of the invention, the main rectifier may receive a substantial portion of the load current, allowing each of the auxiliary bridge rectifiers to be generally smaller than the main rectifier.

Abstract: A multiphase power converter includes a plurality of subconverters and a control circuit. Each subconverter has an input circuit, an output circuit, and a magnetic core coupling the input circuit to the output circuit. The magnetic core of at least one of the plurality of subconverters has a core section that is shared by the magnetic core of another one of the plurality of subconverters. The control circuit is configured to operate the input circuits of the plurality of subconverters with different phases. The magnetic cores may be cores of a transformer, a coupled inductor, etc.

Abstract: A dual-input nine-phase autotransformer converts first and second three-phase AC inputs to a nine-phase AC output. The autotransformer includes input terminals for connection to a first three-phase AC input and a second three-phase AC input smaller than the first three-phase AC input. The autotransformer includes a first plurality of coils, a second plurality, and a third plurality of coils wound on respective phase legs of the autotransformer. The autotransformer includes a plurality of output terminals for providing a plurality of AC output voltages, and a plurality of internal terminals for connecting the first, second, and third plurality of coils in a configuration that provides a 40° phase shift in the AC outputs provided by the dual-input nine-phase autotransformer.

Abstract: Embodiments of the present invention provide novel techniques for using multiple 18-pulse rectifier circuits in parallel. In particular, each rectifier circuit may include an autotransformer having 15 inductors coupled in series, joined by 15 nodes interposed between pairs of the inductors. The inductors may be represented as a hexagon in which alternating sides of the hexagon have two and three inductors, respectively. Each rectifier circuit may also include three inputs for three-phase AC power coupled to alternating vertices of the hexagonal representation and nine outputs for AC power coupled between each node that is not a vertex of the hexagonal representation and a respective diode bridge. Outputs of the diode bridges for the rectifier circuits may be coupled to a DC bus. In addition, a means for reducing circulating current between the parallel rectifier circuits and for promoting load sharing between the parallel rectifier circuits is also provided.

Abstract: A 24-pulse composite AC-to-DC converter is a converter using two or more conversion methods in parallel. The converter may include a main rectifier receiving at least a portion of an input AC signal, an autotransformer having an output voltage with lower amplitude than the input AC signal, and a plurality of auxiliary bridge rectifiers, each receiving the output from each leg of the autotransformer. In one embodiment of the invention, the main rectifier may receive a substantial portion of the load current, allowing each of the auxiliary bridge rectifiers to be generally smaller than the main rectifier.

Abstract: In a method for reducing load dump overvoltages during operation of a synchronous rectifier for a polyphase alternating current having a number of inputs which correspond to the number of alternating current phases of the alternating current, and having at least two outputs for providing a direct current, an alternating current phase is connected to each of the inputs, and each of the inputs are electrically optionally connected via active switching elements to either the first or the second output in accordance with a control unit.

Abstract: Techniques for using multiple 18-pulse rectifier circuits in parallel are described herein. In particular, each rectifier circuit may include an autotransformer having 15 inductors coupled in series, joined by 15 nodes interposed between pairs of the inductors. The inductors may be represented as a hexagon in which alternating sides of the hexagon have two and three inductors, respectively. Each rectifier circuit may also include three inputs for three-phase AC power coupled to alternating vertices of the hexagonal representation and nine outputs for AC power coupled between each node that is not a vertex of the hexagonal representation and a respective diode bridge. Outputs of the diode bridges for the rectifier circuits may be coupled to a DC bus. In addition, a means for reducing circulating current between the parallel rectifier circuits and for promoting load sharing between the parallel rectifier circuits is also provided.

Abstract: A current supply arrangement (A, B) for rectifying three-phase current into multi-pulse DC current with at least one three-phase AC current transformer with a transformer core or three single-phase AC current transformers, each having a transformer core, wherein the three-phase AC current transformer includes three first secondary-side coils (L21, L22, L23), each of which is arranged on a corresponding leg of the transformer core, wherein each secondary side coil is arranged on a leg of the transformer cores, with at least one first rectifier having first converter valves (D1, D2, D3). The first converter valves (D1, D2, D3) are connected with the first secondary-side coils (L21, L22, L23) to form the first rectifier, wherein the current supply arrangement (A, B) includes means (S1, S2, S3) for changing the transformer ratio of the three-phase AC current transformer or the transformer ratios of the three single-phase AC current transformers.

Abstract: A converter cell module and a voltage source converter system. The converter cell module includes at least two switching elements, means for energy storage and an autotransformer. The autotransformer is arranged to bypass the converter cell module in the case of failure occurring in the converter cell module.

Abstract: A device for inverting an electric parameter in the field of power transmission and distribution has a converter that can be connected between an alternating current grid and a DC circuit and having power semiconductor valves extending between an alternating current connection and a DC voltage connection. Each power semiconductor valve has a series circuit of bipolar submodules, each with an energy storage device and a power semiconductor circuit in parallel with the energy storage device, and a grid connection unit connected to the alternating current connection for connecting to the alternating current grid. Simple, effective, and inexpensive symmetrization of the voltages in the DC voltage circuit relative to ground potential is brought about. A star point reactor is connected between the grid connection unit and the inverter with a potential node, including throttle coils connected to a grounded star point.

Abstract: A bus centering device for use in an aircraft electrical power distribution system that includes a positive bus rail, a negative bus rail, and a ground is described. The device includes a central node, a first and second switching component configured to couple the central node to the positive rail and the negative rail for a first and second predetermined duty cycle, respectively. The device includes an inductive component coupled between the central node and ground, and is configured to maintain a voltage at the central node substantially equal to ground, wherein a voltage between the positive rail and the central node is maintained substantially equal to a voltage between the negative rail and the central node. The device includes a first and second current limiting device configured to maintain a continuity of current from the inductive component when the first and second switching components are turned off.

Abstract: A power-factor correction circuit for a three-phase power supply is provided. The correction circuit comprises a filtering unit at the input receiving the three phases of the current, at least one inductor per phase placed downstream of the filtering unit, a rectifying bridge powering a current-chopping stage, wherein the filtering unit comprises a differential-mode filtering cell comprising at least one inductive circuit formed of a single magnetic material in a double E, each leg of the E being surrounded by a winding. The invention applies notably to the field of power electronics, in particular to the production of three-phase power supply units.

Abstract: A power conversion system comprises: a source of multiphase high frequency alternating current (AC) electrical input power; a high frequency controlled magnetics transformer for each phase of the multiphase high frequency AC input power, with each transformer having a primary winding coupled to its respective phase of the multiphase high frequency AC input power, at least one secondary winding that produces high frequency AC output power and at least one control winding responsive to a direct current (DC) control signal that changes the high frequency output power in proportion to the amplitude of the DC control signal; a power converter that receives the multiphase high frequency AC output power from each high frequency transformer secondary and converts it to system output power without the high frequency AC content; and a system controller responsive to the system output power that produces a DC control signal for each control winding that changes in amplitude in response to changes in a measured parameter

Abstract: The invention relates to the electrical power supply of aircraft and notably of large commercial aircraft. According to the invention, the aircraft is equipped with an AC-DC converter that distributes power over a DC network starting from a three-phase alternating voltage of 230 volts applied to its main inputs (E1, E2, E3). The converter comprises an autotransformer which preferably has nine outputs (A1, A2, A3, B1, B2, etc.) for a nine-phase rectification. These outputs are applied to a rectifier bridge with 18 diodes. When the aircraft is on the ground, the AC power is delivered at 115 volts from a ground generator; it is applied via a three-phase connector (CAUX) to auxiliary inputs (M1, M2, M3) connected to intermediate taps of the three-phase windings forming the AC-DC converter.

Abstract: A polygon connected three-phase autotransformer using nine windings per phase provides a reduced power rating fifteen-phase power source suitable for 30-pulse AC to DC power converters. The windings are selected and connected in a manner that accommodates zero-sequence currents, such as the third harmonic, and minimizes total kVA rating. When the autotransformer is used to power a 15-phase AC to DC converter its kVA rating is typically less than 51% of the DC load kW. AC line current distortion is negligible and can satisfy the most exacting practical harmonic specifications. Additional isolated windings can provide means for the invention to operate as an efficient double-wound transformer.

Abstract: A device for converting an electrical current includes at least one phase module with an AC connection and at least one DC connection. A phase module branch is provided between each DC connection and each AC connection. Each phase module branch has a series connection made of sub-modules, which in turn include an energy accumulator each and at least one power semiconductor. Measuring sensors provide actual values and there are provided control means connected to the measuring sensors. The control can be easily adapted to any arbitrary number of sub-modules in each phase module branch. The control means include a current regulating unit and control units associated with a phase module branch each, wherein the current regulating unit is configured to provide branch target values for the control units. The control units are designed to produce control signals for the sub-modules.

Abstract: Three single-phase interphase transformers are connected to a three-phase transformer. The three single-phase interphase transformers each contain a component for efficiently dissipating heat.

Abstract: There is provided a power supply for AC/DC and DC/DC conversion which receives the DC power supplied from airplanes, vehicles and vessels as well as normal AC power, and converts the power to DC power and supplies it to portable electronic products. The power supply for AC/DC and DC/DC conversion includes an AC input 10, a DC input 20, a switch 30 for selecting AC input power or DC input power, a DC output 40, and a circuit used for AC/DC and DC/DC conversion 100 which converts the power input from the AC input or the DC input to DC power having predetermined values of current and voltage, and a secondary side of a transformer (TL) for AC/DC conversion inside the circuit for conversion serves as an inductor for performing DC/DC conversion.

Abstract: A power conversion system includes two three-level converters, and a phase shifted transformer coupled to the converters.

Abstract: Three coils, each having several serial windings, have selected windings connected in a delta. Input AC power is applied through outrigger windings at the delta apices. At least two strategically located, direct tap, natural output points are provided at each side of the delta. For 6-phase output, only the six natural output points are required. For 9-phase output, an additional central output terminal connects to each side of the delta through a stub winding. The 6-phase or 9-phase output is passed to a rectifier circuit.

Abstract: The present invention provides a wireless power feeding system which achieves a configuration enabling effective reception of electrical energy wirelessly transmitted from a wireless power feeding device, and which contributes to the improvement of the power reception efficiency. For the above purpose, the wireless power feeding system includes a power transmitting coil for wirelessly transmitting the electrical energy, a power supply connected to the power transmitting coil, a control unit for controlling the power supply, a power receiving coil portion for receiving the electrical energy transmitted from the power transmitting coil, a power receiving circuit for supplying a load member with the electrical energy received by a power receiving coil, and a magnetic member for collecting a magnetic flux generated by the power transmitting operation of the power transmitting coil to the power receiving coil.

Abstract: A power supply includes a direct converter provided in the form of a two-phase or three-phase bridge circuit. The bridge branche of the direct converter includes a serial connection of any number of identical two-terminal networks, each having the following characteristics: The two-terminal networks each have at least one switching state, in which their terminal voltage takes on positive values independent of the magnitude and polarity of the terminal current; the two-terminal networks each have at least one switching state, in which their terminal voltage takes on negative values independent of the magnitude and polarity of the terminal current; the two-terminal networks have at least one internal energy store.

Abstract: A multi-phase transformer system is provided having a main transformer fed by an N-phase voltage and a separate auxiliary transformer fed by the N-phase voltage. Windings in the main transformer are connected to secondary windings in the auxiliary transformer to provide pairs of connected windings. Each pair of connected windings has one of the windings of the main transformer and one of the secondary windings of the auxiliary transformer. The windings in such connected pair are arranged to produce voltages having different phases with each pair of windings producing an output voltage equal to the vector sum of the voltages produced by the such connected pair of windings. With such an arrangement, by having two separate transformers, i.e., the main transformer and the auxiliary transformer, fabrication of a multi-phase transformer system is simplified.

Abstract: A polyphase generator for medical diathermy apparatus comprises a ferromagnetic ring core bearing two primary windings each of which has two winding portions positioned diametrically opposite one another. The winding portions in each case are connected in series and are wound such that they create opposing magnetic effect which substantially cancel one another. Two primary windings are positioned substantially at right angles to one another. A plurality of secondary windings are arranged on the core to supply output terminals. A direct current supply may be connected via switching means to induce a resonant signal within the primary windings to generate a polyphase output at the terminals for use in application to electrodes of diathermy apparatus operating in excess of 200 kHz.

Abstract: Harmonic distortion in a multiple phase power system is controlled by enabling different phase relationships to be set, and changed, in the field, between the devices being energized and the power source providing the energization. This has particular application, for example, in canceling harmonics caused by multiple six-pulse variable frequency drives used for controlling connected three-phase induction motors that operate electric submersible pumps. A transformer used to achieve this has two winding groups, each with two sets of contacts at different phase relationships.