| 摘要 |
PURPOSE: To prevent an excitation coil from generating an excessive resistance power loss by wrapping the excitation coil directly around an arc tube envelope and forming it using a conductor made of a metal with a high melting point, a low resistivity, and a low vapor pressure. CONSTITUTION: A ribbon of a high temperature metal with a resistivity of less than 50×10<-16>Ωcm at 1000 deg.C is spirally rolled directly around an arc tube 12 as an excitation coil 16 of a lamp. Metals used for the excitation coil 16 are refractory metals such as tungsten and molybdenum. Moreover, a diameter of the excitation coil 16 is very small compared with an induction coil used in a traditional lamp. When the resistivity of the excitation coil 16 is high, a skin thickness increases and the resistance of the coil becomes low. Overall efficiency rises due to the small diameter achieved by the coil 16. Therefore, a coil current and a coil loss decrease.
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