NEMA LSD 73-2015 Energy Savings with Fluorescent and LED Dimming.pdf

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1、NEMA Standards PublicationNational Electrical Manufacturers AssociationNEMA LSD 73-2015 Energy Savings withFluorescent and LEDDimmingA NEMA Lighting Systems Division Document LSD 73-2015 Energy Savings with Fluorescent and LED Dimming Prepared by: NEMA Ballast and Lighting Controls sections National

2、 Electrical Manufacturers Association 1300 North 17th Street, Suite 900 Rosslyn, Virginia 22209 Approved: June 18, 2015 Published: July 14, 2015 www.nema.org The requirements or guidelines presented in this document, a NEMA Lighting Systems Division white paper, are considered technically sound at t

3、he time they are approved for publication. They are not a substitute for a product sellers or users own judgment with respect to the particular product discussed, and NEMA does not undertake to guarantee the performance of any individual manufacturers products by virtue of this document or guide. Th

4、us, NEMA expressly disclaims any responsibility for damages arising from the use, application, or reliance by others on the information contained in these white papers, standards, or guidelines. The opinions expressed in this statement represent the consensus views of the member companies of the Lig

5、hting Systems Division of the National Electrical Manufacturers Association. The members of the Lighting Systems Division manufacture traditional technology lamps and ballasts, light-emitting diodes (LEDs and OLEDs), LED lamps and modules, LED drivers and power supplies, luminaires, lighting control

6、s, and management systems. NEMA LSD 73-2015 2015 National Electrical Manufacturers Association 2 Contents 1 Scope 3 2 Purpose 3 3 References . 3 4 Definitions 3 5 0-10 V Dimming . 3 5.1 Background . 3 5.2 0-10 V Variation 4 5.3 Conclusion . 4 6 Dimming Fluorescent Systems 4 6.1 Control and Dimming L

7、inearity 4 6.2 Control and Input Wattage Linearity . 6 6.3 NEMA LL 9 Compatibility 7 7 Dimming LED Systems . 9 7.1 LED Drivers Operation 9 7.2 LED Drivers Dimming Operation . 11 7.3 LED Luminaire Dimming Efficiency and Light Output . 12 7.4 Dimming LED Systems Conclusions. 13 8 Conclusions . 13 Figu

8、res Figure 1 Lamp Current versus Dimming Volts . 5 Figure 2 Input Power versus Dimming Volts . 6 Figure 3 Cathode Heat Requirements for Deep Dim Operation 7 Figure 4 NEMA LL 9compliant Ballast Cathode Voltage versus Lamp Current 8 Figure 5 Non-NEMA LL 9compliant Ballast Cathode Voltage versus Lamp C

9、urrent 8 Figure 6 LED Driver, Constant Voltage Type 9 Figure 7 LED Driver, Constant Current Type 10 Figure 8 LED Driver Operating Range . 10 Figure 9 LED Drivers 0-10 V Dimming 11 Figure 10 LED Driver Input Power as a Function of the Dimming Control Voltage . 11 Figure 11 LED Luminaire Dimming Examp

10、le: Relative Lumens versus Power. 12 Figure 12 LED Luminaire Dimming Example: Efficacy versus Lumens 12 Figure 13 LED Driver Efficiency as a Function of the Dimming Control Voltage. 13 NEMA LSD 73-2015 2015 National Electrical Manufacturers Association 3 1 Scope The scope of this paper includes dimm

11、able fluorescent ballast and Light Emitting Diode (LED) drivers that are controlled by 0-10 V (1-10 V) control input. This paper explains the relationship between the control input voltage and overall energy consumed by these ballasts and drivers. 2 Purpose Dimmable fluorescent ballasts and LED driv

12、ers consume less power when dimming. However, determining the energy savings at different output levels can be challenging because several components comprise lighting systems: control, control wiring, power source, and light source. This paper describes the signal path from the user control input t

13、hrough the control wiring, ballast or driver, and lamp or LED module. It also explains factors that affect energy consumption and savings, efficacy, and user experience at each stage. This paper is written for stakeholders interested in energy-efficient lighting, including manufacturers, specifiers,

14、 facility managers, and consultants. 3 References ANSI C82.11-2011, American National Standard for Lamp Ballast: High Frequency Fluorescent Lamp Ballast ANSI C82.13-2002, American National Standard for Lamp BallastsDefinitions for Fluorescent Lamps and Ballasts IEC 60929, Edition 4.0, AC- and/or DC-

15、supplied electronic control gear for tubular fluorescent lampsPerformance requirements NEMA LL 9-2011, Dimming of T8 Fluorescent Lighting Systems 4 Definitions All definitions in this white paper are consistent with the definitions provided in ANSI standards. Refer to ANSI C82.13. 5 0-10 V Dimming 5

16、.1 BACKGROUND For close to 30 years, general lighting control by DC voltage has been used throughout the US to control brightness of fluorescent lighting. Called 0-10 V dimming in the US, in other parts of the world it is referred to as 1-10 V dimming. It is used today to control light sources such

17、as LEDs. Throughout this paper, references to ballasts also include drivers for LEDs or other sources. The ANSI standard is C82.11-2011, American National Standard for Lamp Ballast: High Frequency Fluorescent Lamp Ballast, Annex A, and the IEC standard is IEC 60929, AC- and/or DC-supplied electronic

18、 control gear for tubular fluorescent lampsPerformance requirements, Appendix E2. Both standards are similar and define a minimal set of requirements: Current is always sourced at the ballast (10A to 2mA). This allows very simple devices, such as potentiometers, to control dimming. Note that most mo

19、dern control devices are capable of sourcing current; in general lighting, however, the ballast is always the source. (0-10 V is different for theatrical lighting and generally not compatible). The only requirement for control signal voltage in ANSI C82.11 is value of lamp power: 1 V = minimum value

20、 of lamp power NEMA LSD 73-2015 2015 National Electrical Manufacturers Association 4 1 V to 10 V = lamp power rising from minimum to maximum value 0 V to 11 V = stable lamp operation 0 V to 1 V = minimum light output Included in the standard is a requirement for an overall voltage limit of 15 VDC, a

21、s well as polarity protection. 5.2 0-10 V VARIATION The 0-10 V dimming method is not precise and is prone to differences in control voltage versus light output for various reasons: a) The standards referenced above loosely define the requirements for this control method; however, they do not specify

22、 the actual operation of the light source over the range of voltage. As a result, ballasts and drivers have various dimming curves (brightness versus control voltage), such as Linear, Square Law, Logarithmic, and many variations. Since the ballast determines the dimming curve, controls generally foc

23、us on linear control voltage output versus the control position. b) The current is sourced by the ballast or driver, meaning that the more ballasts or drivers connected in a circuit, the more current and voltage difference between control and ballast. c) The wiring practice is not specified and vari

24、es greatly. The size and length of wire will make a great difference. For example: 1) Control set to min (1 V) 2) 1000 ft 20 AWG wire (2 wires = 20 ohms) 3) 25 ballasts = .05A control current (at min setting) 4) Voltage difference between control and ballast = 1 V 5) Voltage at ballast = 2 V This vo

25、ltage drop is worst at the lower settings. Because of differences in control voltage versus light output, many types of ballast flatten the top and bottom of the dimming curve to make reaching minimum and maximum brightness possible with most controls. Many controls also allow trimming minimum and m

26、aximum settings. For example, a particular ballast might reach full brightness at 8.5 V and minimum brightness at 2.5 V. This flattening is not usually a problem for the user, since the brightness is normally adjusted to the desired level by operating the control and observing the lighting. The user

27、 is generally unaware of control voltage variations. 5.3 CONCLUSION Many factors affect the accuracy of brightness and energy use in response to the control voltage. Consequently, control voltage should not be used for determining energy use unless it has been calibrated for a specific installation.

28、 Since energy use is directly related to light output level, the relationship of light output versus power input should be the primary method to accurately determine lighting system energy consumption. 6 Dimming Fluorescent Systems 6.1 CONTROL AND DIMMING LINEARITY All fluorescent dimming systems ar

29、e inherently energy saving. The ability to lower a light level brings an associated reduction in energy consumption. It is important to consider that not all ballasts are as efficient during dimming or respond to the 0-10 VDC control signal in the same way. The difference in control response is less

30、 noticeable when all ballasts in a site are the same model by the same manufacturer. The NEMA LSD 73-2015 2015 National Electrical Manufacturers Association 5 light level, in most applications, is set via a monitor photocell that looks for a specific amount of light on a scene. This is common in “bi

31、g box” retail and other stores that use sky lighting and daylight harvesting. With respect to the 0-10 VDC control input, some ballasts have a nonlinear response curve that has larger dead zone areas where the ballast does not respond linearly to a change in the control voltage. The ideal ballast wi

32、ll have a dead zone between 0 and 1 VDC, then respond linearly from full dim at 1 VDC, to the maximum output at 9 VDC, and having a top-end dead zone between 9 and 10 VDC. While the control is between 1 and 9 VDC, the response of the ballast should be linear. In Figure 1, the pink and blue traces re

33、present the dimming input response to the 0-10 V input control voltage for two different manufacturers dimming ballasts. The blue trace seems to exhibit a larger dead band at the upper end, staying constant output from 0 V through 8 V, then starts to linearly dim as the control voltage is reduced. F

34、or this ballast, the user can adjust the control downward but not see or measure any reduction in light or energy level for some portion of the control rotation. The pink trace shows an abbreviated dead zone from 10 VDC to about 9.5 VDC, where the output is constant. Once decreased below the 9 VDC a

35、rea, the dimming is linear. In this case, if the customer adjusts the dimming control down, a light level and energy level reduction occur in the first few degrees of control rotation. The preferred case is to have a dimming ballast that closely responds to the established ANSI dimming control chara

36、cterization found in ANSI C82.11-2011. That way, every change of the dimming control will translate into a linear light level and energy level reduction. Figure 1 Lamp Current versus Dimming Volts NEMA LSD 73-2015 2015 National Electrical Manufacturers Association 6 6.2 CONTROL AND INPUT WATTAGE LIN

37、EARITY The previous case showed the relationship between control voltage and lamp current or light output. Figure 2 shows the relationship between control voltage and input power for the same two ballasts as seen in Figure 1. Pink and blue represent the same ballasts in Figure 1. Similar to the blue

38、 trace in Figure 1, there seems to be an extra dead zone in the dimming response of the blue ballast. The input wattage stays at maximum until the control voltage is reduced to below 8 VDC when the ballast begins its dimming action and is linear with dimming voltage to down to 1 VDC per the ANSI-def

39、ined dead zone. Lack of response at the high end can cause the user to turn the dimming control knob and not see any reduction of light or energy for many degrees of rotation of the control. While this ballast still saves energy, the user becomes concerned about the reduced dimming range of the cont

40、rol, since some of the rotation has no visible effect. The pink trace shows dimming results as the dimming voltage comes below 9 VDC, giving linear dimming performance. As the dimming level is reduced, around 6 VDC, a bump in the wattage curve is noticeable where the wattage slightly increases, then

41、 begins to fall again as the control voltage is reduced. The ballast with the pink trace employs cathode cut-off circuitry, where the cathode heating is turned on only for deep dimming, as defined by NEMA LL 9. At discharge currents greater than 155mA, no additional cathode heating is required to ke

42、ep the lamp cathodes in thermionic emission. When the ballast is asked to deliver discharge current greater than 155mA, the ballast will switch the cathode heating off, resulting in energy savings, since no energy is wasted to heat cathodes that are already warm from the arc discharge. This can be s

43、een in Figure 2 in the range of about 9 to 6 VDC, where the input wattage for the pink ballast is considerably lower than that that for the blue ballast. In the blue ballast, cathode heating is applied for the entire dimming cycle and does not have a cathode cut-off characteristic. The pink ballast

44、will turn the cathode heat on and off as needed, in response to the control voltage and the discharge current. As mentioned earlier, the trip point is about 155mA. Below 155mA, cathode heating is on; above 155mA, cathode heating is off. Figure 2 Input Power versus Dimming Volts NEMA LSD 73-2015 2015

45、 National Electrical Manufacturers Association 7 6.3 NEMA LL 9 COMPATIBILITY Figure 3, from NEMA LL 9, defines the need for cathode heat during deep dim operation. LL 9 was developed to define how much cathode heating was required at various points during the dimming curve. Ballasts that are complia

46、nt with NEMA LL 9 will help the lamp maintain a full lamp life rating and minimize early failures due to end darkening and cathode depletion. Figure 3 Cathode Heat Requirements for Deep Dim Operation The measured cathode heating voltages for each lamp should be within the limits shown in order to be

47、 compliant with NEMA LL 9. Examples of compliant and noncompliant ballasts follow. NEMA LSD 73-2015 2015 National Electrical Manufacturers Association 8 Figure 4 NEMA LL 9compliant Ballast Cathode Voltage versus Lamp Current Figure 4 shows a ballast that is NEMA LL 9compliant in terms of cathode hea

48、ting voltage supplied versus lamp discharge current. At currents above 160 mA, no additional heating is required. Below 160 mA, the heating voltages should be within the limit lines to ensure sufficient heating, but not so much heating that the emission mix boils off the cathode. Figure 5 Non-NEMA L

49、L 9compliant Ballast Cathode Voltage versus Lamp Current NEMA LSD 73-2015 2015 National Electrical Manufacturers Association 9 Figure 5 shows a ballast that is not compliant with NEMA LL 9. In this example, some of the voltages on the respective lamp leads are not sufficient to ensure proper cathode heating, since some traces fall below the defined lower limits. If the lamp cathode is not sufficiently heated during deep dimming, then it is possible the cathode will not be as emissive as it should be, and cathode sputtering will occur. Sputtering will prematurel