Method and Apparatus for Reducing Radiated Emissions in Switching Power Converters

A power conversion section configured to convert a direct current (DC) voltage to an alternating current (AC) voltage, wherein the AC voltage is conducted from the power conversion section by at least two first electrical conductors and wherein each of the first electrical conductors includes a capacitance between the first electrical conductor and a first ground connection, the power conversion section comprising:

• a direct current (DC) bus having a positive rail and a negative rail, wherein the DC bus is operable to have the DC voltage present between the positive rail and the negative rail;
• an output configured to receive each of the at least two first electrical conductors conducting the AC voltage from the power conversion section;
• a plurality of switching devices, each switching device configured to selectively connect one of the positive rail and the negative rail to the output;
• a plurality of second electrical conductors, wherein each of the second electrical conductors is connected within the power conversion section between at least one of the plurality of switching devices and the output;
• and
• a plurality of capacitors, wherein each capacitor is electrically connected between one of the plurality of second electrical conductors and a common electrical connection.

A power converter for a motor drive having a filter for reducing radiated emissions, the power converter comprising:

• an input configured to receive a direct current (DC) voltage, the input having a positive terminal and a negative terminal;
• a direct DC bus having a positive rail and a negative rail, wherein the positive rail is electrically connected to the positive terminal of the input, the negative rail is electrically connected to the negative terminal of the input, and the DC voltage from the input is present between the positive rail and the negative rail;
• an output including a plurality of terminals, wherein each of the plurality of terminals is configured to conduct one phase of a multi-phase alternating current (AC) voltage;
• a plurality of switching devices, wherein a pair of the plurality of switching devices corresponds to each of the plurality of terminals on the output and wherein each pair is connected in series between the positive rail and the negative rail;
• a plurality of electrical conductors, wherein each of the plurality of electrical conductors is connected between one of the pairs of the plurality of switching devices and one of the plurality of terminals on the output, wherein a first switching device of each pair of switching devices selectively connects the positive rail to the corresponding electrical conductor and a second of each pair of switching devices selectively connects the negative rail to the corresponding electrical conductor;
• and
• a plurality of capacitors, each of the plurality of capacitors is electrically connected between one of the plurality of electrical conductors and a common electrical connection.