To provide a composite wire capable of rapidly detecting abnormality in the temperature of a discharge lamp.
An insulator 4 is a thermoplastic resin with temperature that is higher than the normal temperature of the discharge lamp 1 as a melt point and is exposed so that external temperature is transferred directly. The composite wire 3 for detecting temperature is wound around the discharge lamp 1 so that the temperature of the discharge lamp 1 is easily transferred to the insulator 4. When the temperature of the discharge lamp 1 rises due to abnormal discharge and the melt point of the insulator 4 is reached, the temperature of the discharge lamp 1 is instantly transferred to the insulator 4, thus dissolving the insulator 4 and short-circuiting a current wire 5 and a detection wire 6.
Ishibashi Masayuki
Masaaki Ogata
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