High-pressure sodium lamp lighting device

A method for reducing an acoustic resonance phenomenon of a high-pressure sodium lamp lighting device fed with a high frequency AC voltage from an electronic ballast, the method comprising the steps of:

• preparing a lamp of arc length AL within the scope of 142.8 mm≤AL≤167 mm, conforming to the electronic ballast;
• changing a lamp voltage VL when the lamp is lit to acquire lighting frequency characteristics VL-f of the electronic ballast, the electronic ballast wherein a lighting frequency f [kHz] varies depending on the lamp voltage;
• provisionally determining an initial lamp voltage from the lamp voltage—lighting frequency characteristics VL-f to determine an initial lighting frequency of the electronic ballast,
• acquiring a range of an arc tube inner diameter with which the initial lighting frequency does not fall within a range of a first and a second acoustic resonance occurrence bands f1 kHz and f2 kHz, respectively, by using a first equation (Equation 1) and a second equation (Equation 2), and
• creating a lamp having a lamp voltage VL with a lighting frequency higher than a second acoustic resonance occurrence band maximum value f2max, with an inner diameter within a range of an acquired arc tube inner diameter to operate the high-pressure sodium lamp lighting device,
• wherein Equation 1 for the first acoustic resonance occurrence band f1 kHz is f1min to f1max=(−7.4 D+130) to (−8.3 D+156),
• wherein Equation 2 for the second acoustic resonance occurrence band f2 kHz is f2 min to f2max=(−11.5 D+200) to (−10.0 D+197));
• and
• wherein D is the arc tube inner diameter in millimeters.