The high pressure sodium lamp starts, in the initial stage, is the mercury vapour and the xenon gas pressure discharge. At this time, the lamp working voltage is very low, the current is very big; as the discharge process continues, the arc temperature rises gradually, mercury, sodium vapor pressure is determined by the most cold end temperature of the discharge tube, when the discharge tube cold end temperature is stable, the discharge tends to be stable, the luminous flux, working voltage, working current and power of the bulb are also in normal working state. Under normal operating conditions, the whole start-up process takes about 10 minutes.
The fluctuation of power supply voltage will cause light bulb, the change of electrical parameters; if the power supply voltage rises will cause the bulb working current to increase, causes the arc tube cold end temperature enhancement, the mercury, the sodium vapor pressure increases, the work voltage, the bulb power increases, causes the lamp life to reduce greatly; conversely, the power supply voltage decreases, the light does not work The luminous efficiency is reduced and may cause the bulb to not start or extinguish itself. Therefore, the demand for customers in the light bulb use, the power supply voltage fluctuations should not be too large, the general requirements in the rated value of +6% ~-8% range of changes.