REGULATING POWER SUPPLIES PS2R & PS-600R

Why is voltage regulation/compensation important?

Lamp manufacturers design lamps to operate at a designated voltage. Lamps rated to operate at a nominal 12 volts give optimum overall performance if operated between 11.5 and 12 volts. Within this range, the lamp delivers the optimum color temperature(light output) and operates for the rated lamp life. Operating a lighting system at the correct voltage is very important because too much voltage(overvoltage) causes premature lamp burnout; and too little voltage(undervoltage) causes reduction in the quality of light output.

What are the causes of overvoltage and undervoltage?

Overvoltage:

1. Underloaded transformer: If a transformer is not fully loaded, the lamps on the system will be operating at a higher voltage than if the transformer is a fully loaded. A 12 volt transformer that is underloaded by as little as 50 watts could increase its operating voltage by as much as 1/4(.25) of a volt.

2. Lamp Burnout: Lamp burnout essentially causes the "underloaded transformer" problem. As lamps burnout on the system, the voltage is increased to the remaining lamps causing their early burnout. A system, initially operating at 11.8 volts, could "overvolt" with just one lamp burn out!

3. Primary Overvoltage: In some cases, especially older buildings, the primary supply may surge or operate at voltages substantially higher than 120 volts. Since transformers usually step down the input voltage by a ratio(120v-12v = Ratio 10:1), the secondary voltage increases as the primary voltage increases.

Undervoltage:

1. Undersized Power Feed: If the power feed wire from the transformer to the lighting system is undersized, because of the increased resistance, the voltage will drop significantly by the time it reaches the system.
   
2. Primary Undervoltage: In some cases, especially older buildings, the primary supply may operate at voltages substantially lower the 120 volts. Since transformers usually step down the input voltage by a ratio (120v:12v = Ratio 10:1), the secondary voltage decreases as the primary voltage decreases.

The potential cost of overvoltage illustrated:

A retail store has a low voltage lighting system with eighty lamps. The store s lights are on 14 hours a day, 7 days a week(5,096 hours/year). The lamps have a lamp life of 3600 hours.

Unfortunately, the lamps are burning at an average of 3% over 12 volts(12.36v). This was caused because the transformers were underloaded when the system was installed and because maintenance has not been replacing the lamps as they burn out. Consequently, the average lamp life is reduced by 25% to 2700 hours!

If the cost of a lamp and the labor to replace it is $20, then the overvoltage is costing the store $704 a year! If the over-voltage is at 6% (12.76v), then the cost of overvoltage to the store is $2256 a year!!

Specification Guide

POWER SUPPLIES