MAX DROP is load. the voltage drop at full output and full MIN LOAD is the smallest load for satisfactory operation LOAD REG is change In output voltage as the load varies from full load to 1 6 of full load. LINE REG IS ratiO of the change in output voltage ior a change in input voltage. The value at the light of the vertical bar gives the output voltage level for which the specification was written or test conducted. CURVE is the specified control curve of the dimmer. ACOUSTIC NOISE (lamp) is the noise output at a lamp filament caused by the rapid turn-on of the SCR. I 2 3 4 6 MAX DROP S'-' SV 7V 3V 5V MIN LOAD S5W 75W 600W 40W 100W I.SV 3.6V LINE REG us I60 1.~5160 CURVE ±5% 10-6 ACOUSTIC NOISE (LAMPl YES LOAD REG l Fig. 4: 6V 1.4 V 1.4 V 16 160 4~160 5-212 10-3 10-2 6-3 YES YES YES YES 1 40 160 A more serious load-related problem is the poor performance of all dimmers at small loads. It would seem desirable for any dimmer to be connected to any load within its rating without resorting to special "ghost" loading. If this property is missing, the load and the dimmer must be fitted together. Such rearrangements lead to extensive and time consuming alterations of the bank configuration, and the necessity of maintaining an elaborate bookkeeping system. All of the dimmers in this test series exhibited sharp overshoots, and often continued high frequency ringing when the dimmer was driving a small load. This overshoot and the remainder of the transient contain very high frequency energy which is a serious interference hazard to audio radio and video service nearby. Any unbalanced loading of the three phase input feed will cause the line voltage to a dimmer to vary. In addition the normal pattern of power demand by the community will result in changes in line level. These line voltage changes will cause unscheduled alteration of the lighting design unless the dimmer circuitry provides an output voltage which is constant over the normal range of line variations. Tabular Results for Five Designs Tested Figure 4 displays the results of our tests. The designation curve ±. 5 % refers to the part of the range of the manual controller (scale of 0-10 which stayed within + 5% of the specified curve. The MIN LOAD measurement is that value of load which produced an output voltage having a leading edge containing an overshoot transient of less than 5% of instantaneous voltage. Some dimmer designs also exhibited instability in trigyering with very small loads (less than 100 watts) and one unit became so unstable it would turn on to full voltage and then not respond to manual control. It could be said that in the areas of control curve, lamp noise and internal losses, most manufacturers had a somewhat optimistic idea of their unit's performance. 65 W 64 2 ~ ~ --l o > 63 t; 62 5 0... f- 4 6 :::) o 61 3 60 Another way of evaluating the test results is to look at the comparative and absolute performance of the five dimmer designs. The load regulation of the dimmers was tested at 50V rms with a maximum load of 5 KW. The load was then reduced in steps to 2 KW while the output voltage was monitored. The results of this routine are plotted in Figure 5. The ideal performance would be to have no change over the full range of loading. Since most setting of light levels by the lighting designer is done by eye and the circuit loading of each dimmer is constant except when some catastrophic failure occurs, it is questionable whether good load regulation is required. The necessary readjustments made by the lighting operator to maintain adequate visability are so much larger in scope than those caused by any changes in the dimmer that it does not seem that load regulation is an important attribute of an effective lighting system. OCTOBER 1966 2KW 3KW 4KW 6KW LOAD Fig. 5: Load Regulation 'of 60V In this test series, Iine regulation measurements were made at the 50 volt, the 90 volt and the full voltage output levels. The output level was monitored as the input to the dimmer was varied through a range of -15 volts to + 5 volts from nominal line voltage. The results are level, three of regulation while regulation. The shown in Figure 5. At the sixty volt the designs responded with nearly ideal the other two units showed little or no sixty volt level is the output at which 17http://www.I.SV