A device includes an EMC (electromagnetic compatibility) filter, a frequency converter coupled to the EMC filter, and a motor coupled to the frequency converter via a motor cable. A leakage current compensator includes a leakage current detector and a compensation current generator configured to generate a compensation current that is directed against the leakage current and is overlaid on the leakage current in such a way that the leakage current is reduced.

A common mode filter for reducing differential mode signal converting to common mode signal comprising: a core-cylinder, a first coil, and a second coil; wherein two ends of the core-cylinder respectively extend and set with a first flange and a second flange; wherein m.sub.1, m.sub.2, and m.sub.3 turns and n.sub.1, n.sub.2, and n.sub.3 turns are respectively and sequentially wound and set on the first winding portion, the second winding portion, and the third winding portion of the first winding area, the second winding area, and the third winding area of the first coil and the second coil. Therefore, the present invention can effectively reduce the mode conversion characteristic (Scd), and can also improve the noise reduction performance of the product; thereby greatly upgrading the practicality of the present invention; and the present invention has a simple process, therefore the product yield can be further upgraded to achieve the effect.

A balun includes an unbalanced terminal; balanced terminals; first and second main lines; and first and second sub-lines. The first main line has an end connected to the unbalanced terminal. The second main line has an end connected to the first main line and an end that is open. Each of the first and the second sub-lines is connected between the balanced terminal and a reference potential, respectively. The second sub-line includes a first partial line connected to the balanced terminal, and a second partial line connected between the first partial line and the reference potential. The second main line includes a third partial line connected to the first main line, and a fourth partial line connected to the third partial line. The distance between the first partial line and the third partial line is shorter than the distance between the second partial line and the fourth partial line.

A balun includes an unbalanced terminal; balanced terminals; first and second main lines; and first and second sub-lines. The first main line has an end connected to the unbalanced terminal. The second main line has an end connected to the first main line and an end that is open. Each of the first and the second sub-lines is connected between the balanced terminal and a reference potential, respectively. The second sub-line includes a first partial line connected to the balanced terminal, and a second partial line connected between the first partial line and the reference potential. The second main line includes a third partial line connected to the first main line, and a fourth partial line connected to the third partial line. The distance between the first partial line and the third partial line is shorter than the distance between the second partial line and the fourth partial line.

A balun includes: an unbalanced terminal; a first and a second balanced terminals; a first and a second main lines; a first and a second sub-lines; and a first line. The first main line has a first end connected to the unbalanced terminal. The second main line has a first end connected to a second end of the first main line, and a second end that is open. The first sub-line is connected between the first balanced terminal and a reference potential, and is coupled to the first main line. The second sub-line is connected between the second balanced terminal and the reference potential, and is coupled to the second main line. The first line has a first end connected to the midpoint of the first sub-line, and a second end that is open. The first line is coupled to the first main line and the first sub-line.

Radio frequency filtering circuitry blocks certain frequencies in an outgoing signal so that the signal may be transmitted over a desired frequency. The radio frequency filtering circuitry includes a first inductor having a first coil and a second inductor coupled to and disposed within the first coil. The second inductor has a second coil and a third coil symmetrical to the second coil. When current is applied to the radio frequency filtering circuitry, the current in the second coil causes a first induced current in the first coil and the current in the third coil causes a second induced current in the first coil, wherein the second induced current is approximately equal in magnitude and opposite in direction to the first induced current. As such, the second induced current may compensate for the first induced current.

An electric compressor includes a compression part, an electric motor, an inverter device, and a housing. The inverter device includes an inverter circuit, a noise reduction unit, and a circuit board. The noise reduction unit includes a common mode choke coil and a smoothing capacitor. The common mode choke coil includes an annular core, a pair of winding wires, and an annular electrical conductor. The electrical conductor is split into a first metal plate and a second metal plate in a circumferential direction. The first metal plate is thermally coupled to the housing. The second metal plate is electrically connected to the first metal plate. An electrical resistance value of the first metal plate is larger than that of the second metal plate.

A filter device includes an unbalanced terminal, balanced terminals, and first and second resonant circuits. The first resonant circuit is connected to the unbalanced terminal. The second resonant circuit is connected to the balanced terminals and electromagnetically coupled with the first resonant circuit. The first resonant circuit includes a resonator in which an inductor and a capacitor are connected in parallel between the unbalanced terminal and a reference potential. The second resonant circuit includes a resonator including an inductor connected between the balanced terminals and capacitors connected in series between the balanced terminals.

A filter device includes an unbalanced terminal, balanced terminals, and first and second resonant circuits. The first resonant circuit is connected to the unbalanced terminal. The second resonant circuit is connected to the balanced terminals and electromagnetically coupled with the first resonant circuit. The first resonant circuit includes a resonator in which an inductor and a capacitor are connected in parallel between the unbalanced terminal and a reference potential. The second resonant circuit includes a resonator including an inductor connected between the balanced terminals and capacitors connected in series between the balanced terminals.

An inductor device, a filter device, and a steering system. The inductor device includes first to third cores and first and second wires. The first core, a portion of the first wire passing through the first core, and a portion of the second wire passing through the first core are provided as a first inductor. The second core and another portion of the first wire passing through the second core are provided as a second inductor. The third core and another portion of the second wire passing through the third core are provided as a third inductor.