PD IEC/TR 62750:2011 pdf download – Unified fluorescent lamp dimming standard calculations.
Dimming of fluorescent lamps is becoming increasingly important as a strategy for conserving global energy resources. This report is the result of many years of effort by global experts to understand and test fluorescent dimming systems with the objective of standardizing these systems to grow confidence and reliability in the marketplace. Two theoretical frameworks have been merged to create this unified dimming standardization method: the SoS (sum of squares of lead-in-wire currents) and CV (cathode voltage) models. The application of dimming to actual fluorescent lamp and electronic controlgear (ECG) systems is the primary concern for reliability in the application and end-user confidence. Characteristics of the dimming parameter limits described in this report and observed in real system applications such as in situ field diagnostics are offered as informative. The practical need to use substitution resistors for ECG qualification is described in this report and also given as normative parameters in the lamp and ECG standards. No attempt to treat the informative real lamp-ECG system parameters as normative will be made in either the lamp or the controlgear standards.
Therefore, at low currents, or to describe the upper boundary of acceptable cathode heating, the CV’ becomes a preferred approach to standardizing the cathode-heating requirement. In the region of dimming where the lamp current is lowered below I D30 , values for the minimum cathode voltage, CV’ min , are set to prevent premature cathode destruction by sputtering. Excessive additional heating will result in overheating of the cathode and thereby accelerated end blackening of the lamp. To protect the cathode from overheating, resulting in excessive barium evaporation (end-blackening) and possible mercury starvation in the lamp, a maximum heating level should be set for the cathode voltage. This maximum cathode voltage, CV’ max , is set to limit the cathode temperature below a temperature typically corresponding to a cathode resistance ratio of R h /R c < 5,2. The uncoated part of the cathode can be overheated by the combination of high additional heating and the discharge current itself (mainly in the higher dimming region). Setting a maximum, I LHmax , to the higher lead-in wire current, I LH , will protect these parts of the cathodes. For controlgear design guidance, a target line SoS’ tgt is also defined. It is a best setting for the cathode heating to be sufficiently far away from the critical minimum and maximum.
3.4.2 Electronic controlgear qualification limits – CV max The calculation of the normative maximum cathode voltage for ECG qualification on the specified resistor substitution network (R test2 , R L1 0min , R L1 0max , R L30 and R L60 ) is done by transforming the informative maximum cathode voltage limit, CV’ max for lamp-ECG systems into a cathode voltage limit for the substitution resistor networks, CV max . As in 3.3.2, the cathode heating characteristics (see 3.2.1 ) are used to determine the maximum cathode power, P’ max0 , with no lamp current, P’ max0 = [CV’ max / a2] (1 /b2) This heating power is then applied to the specified substitution resistor R test2 and the resulting maximum cathode voltage for the substitution resistor is calculated, CV max = [R test2 × P’ max0 ] (1 /2) This value is specified as normative for ECG qualification at I D = I Dmin , I D30 and I D60 in the lamp datasheets. This normative CV max limit shall also apply to all ECG that, by design (e.g. step-dimming ECG), are required to be tested at other I D levels. The substitution resistor network (R test2 , R L1 0min , R L1 0max , R L30 and R L60 or R L ) shall use the same lamp substitution resistor as employed in ECG qualification testing for SoS min or CV min specifications. 4 Example of calculation for 54W HO lamps 4.1 General The example given in this clause is intended to illustrate the calculation methodology of this technical report. Parameter values for the 54W T5 HO lamps are selected from the best available data at the time of publication of this technical report. Future modifications to the IEC 60081 datasheets will not necessitate revision of this report clause. Further, this clause is not intended as informative or normative for 54W T5 HO lamps. The calculation begins with the following input parameters (see Table 4).