Lawrence Berkeley Laboratory

1 Cyclotron Road Berkeley, California
Attention: Isaac Turiel From Thomas E. Hagen 

### Subiect: Ballast Life Estimates for both Electromagnetic and Electronic Ballast. A full-blown MIL HDBK-217F reliability analysis was deliberately deferred because it would not yield an accurate number. For the electromagnetic ballast there are no equivalent failure rates that can be applied to the numerous manufacturing processes and designs that are already in the field. If there were, it would be difficult to figure out what the various percentages of the market place each manufacturer's design represented. Some manufacturers actually performed an accelerated life test on their products. Their processes were then tuned to give each of their products a 45,000 hour half life. To the best of our knowledge there were no comprehensive field life studies of magnetic ballast As for electronic ballast there are some ongoing studies that will yield a better picture of field half-life. A MIL HBK-217F reliability study of electronic ballast can yield a number that is meaningful only in comparing one design strategy versus another. Such as comparing passive versus active power factor designs or potted versus unpotted designs. In general the life numbers that "217F" predicts are quite a bit shorter than what is experienced in fact (from the minutes of the IEEE Reliability Working Group of September 4, 1997). This is because commercial parts have improved dramatically and this is not reflected in "217F." The actual experience of some manufacturers that have made a significant effort at getting a quality product to the field yield actual projected half life in excess of 1,000,000 hours across their entire electronic ballast product line. Obviously, there is some other mechanism such as component wear out, corrosion, mechanical fatigue, or others that ultimately cut short this long life. A look at the warranty periods of the major ballast manufacturers reveals some insight into what they anticipate is their projected half-life. See Figure 1-1 for a chart or warranty period versus percentage of returns. The manufacturers all specify a 5 year warranty period for electronic ballast and 3 year period for energy efficient magnetic ballast. Figure 1-1 of this report, shows the impact of various warranty periods with anticipated total returns has on half life for either type of ballast. Currently one major manufacturer (GE reselling other vendors Ballast) is sending out data that supports a .1% per year return rate on their electronic ballast over the last five years. Other manufacturers have privately disclosed similar numbers. There is however, an opposing force that will come into to play, that will drastically reduce the 1,000,000 hour half lives. That is the wear out mechanism associated with the capacitors internal to the ballast. The electronic ballast uses electrolytic capacitors that will be the initial life-limiting component. This component can be purchased at several different quality and temperature levels. Each of these parameters has a drastic effect on the life of the capacitor. Temperature rise, voltage stress, and current stress negatively impact the life of this component. A preliminary analysis indicates that these components if they are run near 60C with 80% of their rated voltage and near their rated ripple currents will yield a life of 3 years for an 85C unit rated at 1000 hour life to 22 years for a 105C unit rated at 2000 hour life. In discussions with electrolytic capacitor manufacturers, they design in a factor between 1.5 and 2 times their rated life for their production cycle. See Table 1-1 This factor gives them good yields on their production lines. It was also revealed that once the components get to the end of their lives they start to deteriorate rapidly ("run away" as result of their increasing "equivalent series Resistance," ESR). However, this failure is not a catastrophic failure in the sense that it will cause the ballast to "short out" causing the internal fuse within the ballast to open. The most likely indication of this deterioration is that quality of the light decreases, as the capacitor dries out from the excessive heat caused by the increasing ESR and the ripple current. In addition, the lamp life will decrease as the crest current factor increases. Some ballast may show flickering while some Lawrence Berkeley Laboratory 1 Cyclotron Road Berkeley, California
Attention: IsaacTuriel
From Thomas E. Hagen Subject: Ballast Life Estimatesfor both Electromagneticand Electronic Ballast. 

# \

A full-blown MIL HDBK-217F reliability analysis was deliberately deferred because itwould not yield an accurate number. Forthe electromagnetic ballastthere are no equivalent failure ratesthat can be applied to the numerous manufacturing processes and designsthat are already in the field. If there were, itwould be difficultto figure out whatthe various percentages ofthe market place each manufacturer's design represented. Some manufacturers actually performed an accelerated life test on their products. Their processes were then tuned to give each oftheir products a 4S,000 hour half life. To the best ofour knowledge there were no comprehensive field life studies of magnetic ballast As for electronic ballast there are some ongoing studies thatwill yield a better picture offield half-life. A MIL HBK-217F reliability study ofelectronic ballast can yield a number that is meaningful only in comparing one design strategy versus another. Such as comparing passive versus active power factor designs or potted versus unpotted designs. In general the life numbersthat "217F" predicts are quite a bit shorterthan what is experienced in fact (from the minutes ofthe IEEE Reliability Working Group ofSeptember 4, 1997). This is because commercial parts have improved dramatically and this is not reflected in "217F." The actual experience of some manufacturersthat have made a significant effort at getting a quality productto the field yield actual projected half life in excess of 1,000,000 hours acrosstheir entire electronic ballast product line. Obviously, there is some other mechanism such as component wear out, corrosion, mechanical fatigue, or othersthat ultimately cut shortthis long life.
A look at the warranty periods ofthe major ballast manufacturers reveals some insight into what they anticipate is their projected half-life. See Figure 1-1 for a chart orwarranty period versus percentage of returns. The manufacturers all specify a Syearwarranty period for electronic ballast and 3 year period for energy efficient magnetic ballast. Figure 1-1 ofthis report, shows the impact ofvarious warranty periods with anticipated total returns has on half life for eithertype of ballast. Currently one major manufacturer (GE reselling othervendors Ballast) is sending out data that supports a .1% per year return rate on their electronic ballast overthe last five years. Other manufacturers have privately disclosed similar numbers. There is however, an opposing force that will come into to play, thatwill drastically reduce the 1,000,000 hour half lives. That is the wear out mechanism associated with the capaCitors internal to the ballast. The electronic ballast uses electrolytic capacitors thatwill be the initial life-limiting component. This component can be purchased atseveral differentquality and temperature levels. Each ofthese parameters has a drastic effect on the life ofthe capacitor. Temperature rise, voltage stress, and current stress negatively impactthe life ofthis component. A preliminary analysis indicates thatthese components ifthey are run near 60C with 80% oftheir rated voltage and neartheir rated ripple currents will yield a life of 3 years for an 8SC unit rated at 1000 hour life to 22years for a 10SC unit rated at 2000 hour life.
In discussions with electrolytic capacitor manufacturers, they design in a factor between 1.S and 2 times their rated life fortheir production cycle. See Table 1-1 This factor givesthem good yields on their production lines. Itwas also revealed that oncethe components gettothe end oftheir lives they startto deteriorate rapidly ("run away· as result oftheir increasing "equivalent series Resistance," ESR). However, this failure is not a catastrophic failure in the sense that itwill cause the ballast to "short out" causing the internal fuse within the ballastto open. The most likely indication ofthis deterioration is that quality ofthe light decreases, asthe capacitor dries outfrom the excessive heat caused by the increasing ESR and the ripple current. In addition, the lamp life will decrease as the crest current factor increases. Some ballast may showflickering while somemay not light at all. In all it will be a "soft " fail that may extends its life in the field

. This is a wear out

type of failure

. In environments that have large number of ballast being used the same number of hours the ballast would all fail at about the same time

. Thus in this type of situation reballasting should be used as a preventive program.
Rated Max Temp 105C 105C 85C 85C Rated Life 2000 hours 1000 hours 2000 hours 1000 hours Ambient Temp 60C 60C 60C 60C Calculated life 22 years 10 years 6 years 3 years Expected Life 32 years 15 years 9 years 4 years
Table 1-1 The energy efficient magnetic ballast has an internal capacitor that is used to regulate the current in the lamp and provide some power factor correction also. This component also has wear out mechanism. These units have microscopic defects that cause micro arcing (clearing") between their deposited electrodes. (The electrodes are actually metal films vaporized or plated on the surfaces of the dielectric film.) The micro arcing causes the metal film in the area of the arc to vaporize

. This has several effects; it clears the faults, it minutely reduces the capacitance, it increases the effective series resistance , and it initiates other deteriorating effects such as ozone contamination. The result of these changes is the unit continues to be operational but it has slightly lower light output

. Over a period of time the light will be significantly lower and the lamp life will be shorter due to non-optimum current shapes

. The capacitance change over time is dependent upon the voltage, temperature, humidity, and protective coating type, and current stress. The capacitance can decrease at a rate of .5% to 1. 5% per 1000 hours of operation . After 12 years (44,000 hours) of use the lamps will be lighted to somewhere between 59 % to 75% of their light potential

. This is significant loss of light output

. Again this a wear out type of mechanism that would lend itself well to a preventative program such as reballasting

. It is also a subjective type of failure

. It is expected that they would stay in the field longer if replaced on a random basis. Based upon this study of the life of ballast, the life Is not going to be limited by the random failures that is the basis of MIL HDBK 217. The ballast lives are going to be limited by the wear out mechanism associated with critical capacitors in their constrOuction. For the electronic ballast the capacitorthat will come into play first will be the electrolytic capacitor that is used for providing the DC Rail Voltage for the output section

. Based upon our calculations we estimate that most electronic ballast will last approximately 15 years before they start to rapidly deteriorate. This failure will be a soft failure in that it will be seen as reduced light output, some flickering, and reduced lamp life. The magnetic ballast will also last about 15 years before the output capacitor deteriorates enough to give similar soft failure modes. Both of these ballast lives could be greatly extended by buying higher quality capacitors at modest increase in cost (less than 50 cents per ballast to double the useful life of the electronic ballast).

The expected life of the ballast were calculated based upon the combined effects on ballast replacements of the failure rate (based upon warranty period and 1.5% max returned to the manufacturer), the reduction in performance forthe film capacitors , and the loss of the electrolytic capacitor (for the electronic ballast only). See Figure 1-2 for the plot of the calculations. Illustrated in figure 1-2 are the following: 

### Magnetic ballast replacement rate. may not light at all. In all it will be a "solt" fail that may extends its life in the field. This is a wear out type offailure. In environments that have large number of ballast being used the same number of hours the ballast would all fail at aboutthe sametime. Thus in thistype ofsituation reballasting should be used as a preventive program. Rated Max Temp 105C 105C 85C 85C Rated Life 2000 hours 1000 hours 2000 hours 1000 hours AmbientTemp 60C 60C 60C 60C Calculated life 22 years 10 years 6 years 3 years Expected Life 32 years 15 years 9 years 4 years
Table 1-1
The energy efficient magnetic ballast has an internal capacitorthat is used to regulate the current in the lamp and provide some power factor correction also. This component also has wear out mechanism. These units have microscopic defectsthat cause micro arcing (clearing") between theirdeposited electrodes. (The electrodes are actually metal films vaporized or plated on the surfaces ofthe dielectric film.) The micro arcing causes the metal film in the area ofthe arcto vaporize. This has several effects; it clears the faults, it minutely reduces the capacitance, it increases the effective series resistance, and it initiates other deteriorating effects such as ozone contamination. The result ofthese changes is the unit continues to be operational but it has slightly lower light output. Over a period oftime the light will be significantly lower and the lamp life will be shorter due to non-optimum current shapes. The capacitance change over time is dependent upon the voltage, temperature, humidity, and protective coating type, and current stress. The capacitance can decrease at a rate of .5%to 1.5% per 1000 hours of operation. After 12 years (44,000 hours) of use the lamps will be lighted to somewhere between 59%to 75% oftheir light potential. This is significant loss of light output. Again this a wear outtype of mechanism that would lend itselfwell to a preventative program such as reballasting. It is also a subjective type of failure. It is expected thatthey would stay in the field longer if replaced on a random basis.
Based upon this study ofthe life of ballast, the life is not going to be limited by the random failures that is the basis of MIL HDBK 217. The ballast lives are going to be limited by the wear out mechanism associated with critical capacitors in their constrOuction. Forthe electronic ballast the capacitorthat will come into play first will be the electrolytic capacitorthat is used for providing the DC Rail Voltage for the output section. Based upon our calculations we estimate that most electronic ballast will last approximately 15 years beforethey startto rapidly deteriorate. This failure will be a softfailure in that it will be seen as reduced light output, some flickering, and reduced lamp life. The magnetic ballast will also last about 15years before the output capacitor deteriorates enough to give similar soft failure modes. Both ofthese ballast lives could be greatly extended by buying higher quality capacitors at modest increase in cost (less than 50 cents per ballast to doublethe useful life ofthe electronic ballast).

The expected life ofthe ballast were calculated based upon the combined effects on ballast replacements ofthe failure rate (based upon warranty period and 1.5% max returned to the manufacturer), the red,uction in performance forthe film capacitors, and the loss ofthe electrolytic capacitor (for the electronic ballast only). See Figure 1-2 forthe plot ofthe calculations. Illustrated in figure 1-2 arethe following: Magnetic ballast replacement rate.Electronic Ballast replacement rate with an electrolytic capacitor rated at 105 C for 1000 hours.



### Electronic Ballast replacement rate with an electrolytic capacitor rated at 105 C for 2000 hours.

Note that the life of the electronic ballast is nearly doubled if a 2000 hour electrolytic capacitor is used.



### Figure 1-1

Half We Versus Wa Pe

250 .......................................................................................................................................................

04.5%Total Failed Urrts 13 3.00/0 Total Failed Urals 01.5% Total Failed Units

4 5 Electronic Ballast replacement rate with an electrolytic capacitor rated at 105 C for 1000 hours.
Electronic Ballast replacement rate with ali electrolytic capacitor rated at 105 C for 2000 hours.

Note thatthe life ofthe electronic ballast is nearly doubled ifa 2000 hour electrolytic capacitor is used.

Figure 1-1

HalfUfeVersusWarrantyPeriod**~T"""""'."""'."""""""""."""** ..""" .••••••••••••.•••••••.••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••..••••••.••••••••, 229**xot---~-------------------------------------**

I!! 

### al > 150 .5 04.5%Total Failed 

## .e Units :J l1li3.0%Total Failed lI:: Units


# .. l1li1.5%Total Failed ::t 

### 'i Units

### ~ 100

# elL

50

2 3 4 5 YeaIS OfWamlnty

## Cumulative Probability of Ballast Lifetime

100

80+

60+

C) 20 -I1 Magnetic Ballast EB 105C @ 1000 Hrs -A- EB 105C @ 2000 Hrs

4 7 10 13 16 

## Years 19 22 25 28

Figure 1-2 

## Cumulative Probability of Ballast lifetime**100~==============~--------------------------------1** 

# ! 80 

## ::s 

# .-**~** 

## ca_ 

# u..:: 60 

# CDn**.~** 

## ca 

## -.c**~** 

# e 40 

# en.

::So 

# o 20 -+- Magnetic Ballast



## -- EB 105C @ 

## 1000Hrs -Ir- 

## EB 105C @ 

## 2000 Hrs

1 

## 4 7 

## 10 13 

### 16 19 

## 22 25 28 

## Years

Figure 1-2