A capacitor has a parasitic inductance component and is electrically connected between a positive line and a negative line. A converter includes a reactor provided in the positive line and performs voltage conversion of a DC voltage smoothed by a capacitor. An inverter performs DC-AC conversion between the converter and an AC motor by switching control. A path of the positive line which connects a DC power supply and the capacitor has an inductance smaller than an inductance of a path of the negative line which connects the DC power supply and the capacitor. A difference between the inductance of the path and the inductance of the path is less than twice the parasitic inductance component.

Unique systems, methods, techniques and apparatuses of a power converter are disclosed. One exemplary embodiment is a resonant power converter comprising a DC bus, a primary leg, an auxiliary leg, and an LC resonant circuit. The auxiliary leg is coupled between DC bus and includes a first auxiliary switch and a second auxiliary switch coupled at an auxiliary midpoint connection. The LC resonant circuit includes an air-core resonant inductor and a resonant capacitor coupled between the auxiliary midpoint connection and a primary midpoint connection of the primary leg. A controller is structured to control the first and second auxiliary switch and the first and second primary switch so as to provide resonant operation of the LC resonant circuit effective to provide a substantially zero voltage condition across the first and second primary switch while toggling the switches.

A power converter includes: input terminals for inputting a DC voltage; output terminals for outputting an AC voltage; a switch; a first resonant capacitance connected between both ends of the switch; a first LC resonance circuit connected in series with the switch between the output terminals; and a second LC resonance circuit connected between the input terminals and the switch. The first LC resonance circuit includes an inductance and a capacitance in series. When the input terminals are shorted, frequency characteristics of an impedance of the second LC resonance circuit include first to fourth resonant frequencies. The first resonant frequency is higher than a switching frequency of the switch. The second and fourth resonant frequencies are around double and four times the switching frequency. The impedance has local maxima at the first and third resonant frequencies and local minima at the second and fourth resonant frequencies.

A power converter includes: input terminals for inputting a DC voltage; output terminals for outputting an AC voltage; a switch; a first resonant capacitance connected between both ends of the switch; a first LC resonance circuit connected in series with the switch between the output terminals; and a second LC resonance circuit connected between the input terminals and the switch. The first LC resonance circuit includes an inductance and a capacitance in series. When the input terminals are shorted, frequency characteristics of an impedance of the second LC resonance circuit include first to fourth resonant frequencies. The first resonant frequency is higher than a switching frequency of the switch. The second and fourth resonant frequencies are around double and four times the switching frequency. The impedance has local maxima at the first and third resonant frequencies and local minima at the second and fourth resonant frequencies.

An electrical motor system and a method for operating the electrical motor system are disclosed. The electrical motor system comprises a direct current (DC) source, a filter connected in parallel with the DC source and an electric motor with at least two sets of windings. A voltage signal is provided from the DC source to the inverter circuit where the signal is modulated. The modulated signal is then supplied from the inverter circuit to each set of windings with a respective time offset between each set of windings respectively, providing a very efficient DC bus ripple reduction. Hereby, it is e.g. possible to use small filter capacitors/capacitor banks in electrical motor systems.

An electrical motor system and a method for operating the electrical motor system are disclosed. The electrical motor system comprises a direct current (DC) source, a filter connected in parallel with the DC source and an electric motor with at least two sets of windings. A voltage signal is provided from the DC source to the inverter circuit where the signal is modulated. The modulated signal is then supplied from the inverter circuit to each set of windings with a respective time offset between each set of windings respectively, providing a very efficient DC bus ripple reduction. Hereby, it is e.g. possible to use small filter capacitors/capacitor banks in electrical motor systems.

A power supply, including a primary pre-converter, coupled to supplying mains, configured to receive an AC voltage at low frequency and output a high DC voltage, and further configured to receive the high DC voltage and to output the alternating current; a primary converter, disposed on a primary side of the power supply, coupled to the high DC voltage from the primary pre-converter; an isolating transformer to receive the high frequency AC voltage and output a high frequency secondary AC voltage, and to receive a high frequency secondary AC current and to output primary high frequency AC current; and an output converter, on a secondary side of the power supply, wherein the output converter is configured to receive high frequency AC voltage from the isolating transformer and to output a DC voltage of a first or second polarity to an output, and wherein the output converter is configured to receive DC current of a first or second direction from the output and to output a high frequency AC current to the isolating transformer.

A power supply, including a primary pre-converter, coupled to supplying mains, configured to receive an AC voltage at low frequency and output a high DC voltage, and further configured to receive the high DC voltage and to output the alternating current; a primary converter, disposed on a primary side of the power supply, coupled to the high DC voltage from the primary pre-converter; an isolating transformer to receive the high frequency AC voltage and output a high frequency secondary AC voltage, and to receive a high frequency secondary AC current and to output primary high frequency AC current; and an output converter, on a secondary side of the power supply, wherein the output converter is configured to receive high frequency AC voltage from the isolating transformer and to output a DC voltage of a first or second polarity to an output, and wherein the output converter is configured to receive DC current of a first or second direction from the output and to output a high frequency AC current to the isolating transformer.

A power conversion apparatus includes: DC input terminals for inputting a DC voltage; AC output terminals for outputting an AC voltage; a switching element; a first resonant capacitance connected across the switching element; a first LC resonance circuit that has an inductance and a capacitance connected in series and is connected together with the switching element between the AC output terminals; and a second LC resonance circuit connected in series together with the switching element between the DC input terminals. The second LC resonance circuit includes a first connector portion connected to one DC input terminal and a second connector portion connected to the switching element, and has a first current path, which includes an inductance, and a second current path, which includes a series circuit with an inductance and a capacitance, formed between the first connector portion and the second connector portion.

A power conversion apparatus includes: DC input terminals for inputting a DC voltage; AC output terminals for outputting an AC voltage; a switching element; a first resonant capacitance connected across the switching element; a first LC resonance circuit that has an inductance and a capacitance connected in series and is connected together with the switching element between the AC output terminals; and a second LC resonance circuit connected in series together with the switching element between the DC input terminals. The second LC resonance circuit includes a first connector portion connected to one DC input terminal and a second connector portion connected to the switching element, and has a first current path, which includes an inductance, and a second current path, which includes a series circuit with an inductance and a capacitance, formed between the first connector portion and the second connector portion.