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Low Voltage AC Hg Arc Lamp Power Supply

IP.com Disclosure Number: IPCOM000083815D
Original Publication Date: 1975-Jul-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Davis, JB: AUTHOR [+2]

Abstract

A low-voltage power supply for operating an AC mercury-arc lamp is provided that greatly improves the efficiency of operation of such arc lamp.

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Low Voltage AC Hg Arc Lamp Power Supply

A low-voltage power supply for operating an AC mercury-arc lamp is provided that greatly improves the efficiency of operation of such arc lamp.

A mercury-arc lamp, when it has not been lighted for awhile, is "cold". As a consequence, it has a very low-internal resistance, the latter making it necessary to use a current that is between 150 to 200 percent that of normal operating current to light the lamp. Such low resistance is also maintained for approximately ten minutes, and a return to normal operating current occurs as the lamp approaches normal operating temperatures.

To compensate for the above-noted large starting current for the lamp, a conventional power supply for such lamp used a large ballast resistor in series with the mercury-arc lamp as well as a voltage of the order of 230 volts. This high-voltage supply source is needed to increase the conduction angle of the lamp, by exceeding the lamp's firing potential early in the operating cycle. Such conventional power supply is inefficient because about 10,000 watts are consumed during lamp operation, while the arc lamp itself consumes only 3600 watts.

The figure is a schematic drawing of an efficient power supply for a mercury- arc lamp 2. A step-down transformer 4 provides a lamp voltage of approximately 65 volts, because mercury-arc lamp brightness is determined by lamp voltage, and a voltage of 65 volts is optimally suited for such a lamp. A first ballast resisto...