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

EE-RM-97-500 COMMENT 20J

Lawrence Berkeley Laboratory 

1 Cyclotron Road 

Berkeley, California 

Attention: Isaac Turiel 

From Thomas E. Hagen 

Subject: 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 4S,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 offield 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 S 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 8SC unit rated at 1000 hour life to 22 years 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 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 oftheir 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 
may 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

capacitor that 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.

EE-RM-97-500 COMMENT 20J

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 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 

capacitor that 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 red,uction 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. 
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

EE-RM-97-500 COMMENT 20J

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

used. 

Figure 1-1 

Half Ufe Versus Warranty Period 

~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

EE-RM-97-500 COMMENT 20J

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