EMI filter topology for power inverters

An EMI filter for an electric vehicle propulsion system including a power source, an electronic switch having first and second terminals, and first and second power conductors electrically connecting the first and second terminals, respectively, to the power source, comprising:

• a first capacitive element electrically connected in parallel with the first and second power conductors, the first capacitive element comprising an electrolytic capacitor having a capacitance of about 3500 microfarads;
• a second capacitive element comprising a plurality of film capacitors, first and second terminals, an intrinsic inductive component, and an internal capacitance component, the first and second terminals being electrically connected to the first and second power conductors, respectively;
• an inductive element electrically connected in series with the power conductor, the inductive element separating the first and second capacitive elements and having an inductance of about 10 microhenries;
• and
• first and second junctions electrically connecting the first and second terminals of the second capacitive element to the first and second terminals of the electronic switch, respectively, the first and second junctions having first and second intrinsic inductive components, respectively;
• wherein a sum of inductances of the first and second internal inductive components of the first and second junctions is less than 10 nanohenries, an inductance of the internal inductive component of the second capacitive element is less than 10 nanohenries, and a capacitance of the internal capacitance component is about 45 microfarads.

An EMI filter for a multiphase electric vehicle propulsion system including a power source, a plurality of electronic switches having first and second terminals, and first and second power conductors electrically connecting the first and second terminals of the plurality of electronic switches, respectively, to the power source, comprising:

• a first capacitive element electrically connected in parallel with the first and second power conductors;
• a second capacitive element associated with each of the plurality of electronic switches, each of the second capacitive elements having first and second terminals and an intrinsic inductive component, the first and second terminals of each of the second capacitive elements being electrically connected to the first and second power conductors, respectively;
• a first inductive element electrically connected in series with the first power conductor, the first inductive element separating the first capacitive element and the plurality of second capacitive elements;
• and
• a first and second junction associated with each of the second capacitive elements, each of the first and second junctions connecting the first and second terminals of associated second capacitive elements to the first and second terminals of associated electronic switches, respectively, each of the plurality of first and second junctions having first and second intrinsic inductive components;
• wherein a sum of inductances of the first and second intrinsic inductive components associated with each first and second junctions is less than an inductance of the intrinsic inductive component of the associated second capacitive element.