Abstract: In a chopper circuit, output power is controllable with a direct current power source as a power source, and a smoothing capacitor is connected between output terminals of the chopper circuit. A polarity inversion circuit applies an alternating voltage to a high pressure discharge lamp with a voltage across the smoothing capacitor as a power source. The output power of the chopper circuit and an inversion frequency of the polarity inversion circuit are controlled by a control circuit based upon a terminal voltage of the smoothing capacitor, which is detected by a voltage detecting circuit. In the control circuit, a switch voltage is set for defining a range of voltages detected by the voltage detecting circuit, and the inversion frequency is changed in plural stages according to the magnitude relation between the detected voltage and the switch voltage.

Abstract: In a chopper circuit, output power is controllable with a direct current power source as a power source, and a smoothing capacitor is connected between output terminals of the chopper circuit. A polarity inversion circuit applies an alternating voltage to a high pressure discharge lamp with a voltage across the smoothing capacitor as a power source. The output power of the chopper circuit and an inversion frequency of the polarity inversion circuit are controlled by a control circuit based upon a terminal voltage of the smoothing capacitor, which is detected by a voltage detecting circuit. In the control circuit, a switch voltage is set for defining a range of voltages detected by the voltage detecting circuit, and the inversion frequency is changed in plural stages according to the magnitude relation between the detected voltage and the switch voltage.

Abstract: A core for blow-forming the lining of a vessel for molten metal, which core is provided with a main body having blow-in holes and an exhaust port, the side face and the lower faces of said body having the same dimensions and shapes as those of the inside of the lining of said vessel for molten metal, a flange mounted approximately horizontally in the outer direction at the periphery of the upper end of said main body, a plurality of supports which are actuated downwardly from said flange, and airtight and shock absorbers mounted beneath said flange, a lining method which uses said core, and a lining composition used in said lining method.