Electric wire, coil, device for designing electric wire, and electric motor
An electric wire includes a conductive portion 11 made of a material having a volume resistivity higher than that of copper, wherein the volume resistivity of the conductive portion is specified so that, in a frequency range in which the electric wire is used, a ratio of AC resistance of the conductive portion 11 to AC resistance of reference copper wire is less than 1.
1. An electric wire, comprising:
a conductive portion made of a material having a volume 5 resistivity higher than that of copper, wherein
an AC resistance value of the electric wire has a first frequency equal to an AC resistance value of a copper wire having the same diameter and length as the conductive portion, and a second frequency which is larger than the first frequency and has an AC resistance value of the electric wire equal to the AC resistance value of the copper wire between the first frequency and the second frequency,
the AC resistance value of the electric wire is smaller than the AC resistance value of the cooper wire between the first frequency and the second frequency,
a frequency range in which the electric wire is used between 1 kHz to 1 MHz and a volume resistivity of the conductive portion is specified so that the frequency in which th electric wire is used is set within a frequency range of between the first frequency and the second frequency, and
a DC resistance value of the conductive portion per unit length obtained by dividing the volume resistivity of the conductive portion per unit length obtained by dividing the volume resistivity of the conductive portion by a cross-sectional area so that the second frequency is not less than the upper limit of the frequency in which the electric wire is used is specified by a relationship of
0.7×10 (0.925×log 10 Rdc+2.24) ≦f 2 ≦1.3×10 (0.925×log 10 Rdc+2.24) [Equation 1]
where Rdc (mΩ/cm) is the DC resistance value and f 2 (kHz) is the second frequency.
2. The electric wire according to claim 1 , wherein the conductive portion is made of any one of a copper alloy selected from brass, phosphor bronze, silicon bronze, copper-beryllium alloy and copper-nickel-silicon alloy, aluminum, and copper-clad aluminum.
3. The electric wire according to claim 1 , wherein the frequency in which the electric wire is used includes a fundamental frequency of the alternating current used for the electric wire to 20th order harmonic frequencies.
4. The electric wire according to claim 1 , wherein diameter of the conductive portion is between 0.005 mm and 0.6 mm.
5. A coil, comprising an electric wire as a strand, wherein
the electric wire includes a conductive portion made of a material having a volume resistivity higher than that of copper, and
an AC resistance value of the electric wire has a first frequency equal to an AC resistance value of a copper wire having the same diameter and length as the conductive portion, and a second frequency which is larger than the first frequency and has an AC resistance value of the electric wire equal to the AC resistance value of the copper wire,
the AC resistance value of the electric wire is smaller than the AC resistance value of the copper wire between the first frequency and the second frequency,
a frequency range in which the coil is used is between 1 kHz and 1 MHz and a volume resistivity of the conductive of the conductive portion is specified so that the frequency in which the electric wire is used is set within a frequency range of between the first frequency and the second frequency, and
a DC resistance value of the conductive portion per unit length obtained by dividing the volume resistivity of the conductive portion by a cross-sectional area so that the second frequency is not less than the upper limit of the frequency in which the coil is used is specified by a relationship of
0.7×10 (0.925×log 10 Rdc+2.24) ≦f 2 ≦1.3×10 (0.925×log 10 Rdc+2.24) {Equation 2]
where Rdc (mΩ/cm) is the DC resistance value and f 2 (kHz) is the second frequency.
6. The coil according to claim 5 , wherein the conductive portion is made of any one of a copper alloy selected from brass, phosphor bronze, silicon bronze, copper-beryllium alloy and copper-nickel-silicon alloy, aluminum, and copper-clad aluminum.
7. The coil according to claim 5 , wherein the frequency in which the coil is used includes a fundamental frequency of the alternating current used for the coil to 20th order harmonic frequencies.
8. The coil according to claim 5 , wherein diameter of the conductive portion is between 0.05 mm and 0.6 mm.