5 to 9 watt CFL ballast test

[JohnR66]

Testing a 5 to 9 watt CFL PLS ballast with different lamps, from the test
below, it appears it is designed for 9w bulbs and overdrives the 5 watt
ones, using more power as well. It would seem designing a special ballast
for 5 watt lamps would make more since. Thoughts?

Lamp Supply current* Lamp Current Lamp voltage Lamp power System
power
5w .123 .195 39
7.61 14.76
9w .090 .133 68
9.04 10.80

*with 2 uf PF correction

 

[Andrew Gabriel]

Testing a 5 to 9 watt CFL PLS ballast with different lamps, from the test
below, it appears it is designed for 9w bulbs and overdrives the 5 watt
ones, using more power as well. It would seem designing a special ballast
for 5 watt lamps would make more since. Thoughts?

Lamp Supply current* Lamp Current Lamp voltage Lamp power System
5w .123 .195 39 7.61 14.76
9w .090 .133 68 9.04 10.80

*with 2 uf PF correction

I presume this is on a 120V mains supply?
In this case there is too little voltage headroom to run
both lamps at near their correct power rating from the
same untapped series ballast. This is commonly done with
240V mains supplies, but the extra voltage headroom means
they all operate nearer their design power rating.

 

[JohnR66]

I presume this is on a 120V mains supply?
In this case there is too little voltage headroom to run
both lamps at near their correct power rating from the
same untapped series ballast. This is commonly done with
240V mains supplies, but the extra voltage headroom means
they all operate nearer their design power rating.

Yes, it is 120 volts. Other than offering an array of wattages, 5, 7 and 9,
it seems pointless to run lower wattage lamps since the power used is
actually greater.
John

 

[Andrew Gabriel]

Yes, it is 120 volts. Other than offering an array of wattages, 5, 7 and 9,
it seems pointless to run lower wattage lamps since the power used is
actually greater.

Yes, but it's not _quite_ as bad as you calculate.
Your System Power column is wrong because you have
assumed Power Factor = 1 which will not be the case.
When running the 5W tube, it looks like it needs a
3µF capacitor. However, the resistive losses in the
ballast will double, so the System Power in the 5W
lamp case is probably fractionally higher than for
the 9W lamp (I calculate 11.13W from your data, but
this is making assumptions as I don't have enough
data to produce an accurate figure).

It would indeed seem silly to run lower wattage tubes
with this ballast. These lamps were designed to run
this way in 230V countries, but that doesn't work
very well in 120V countries where the lack of voltage
headroom causes a much more marked change in lamp
current with different lamp lengths/voltages.

 

[JohnR66]

Yes, but it's not _quite_ as bad as you calculate.
Your System Power column is wrong because you have
assumed Power Factor = 1 which will not be the case.
When running the 5W tube, it looks like it needs a
3µF capacitor. However, the resistive losses in the
ballast will double, so the System Power in the 5W
lamp case is probably fractionally higher than for
the 9W lamp (I calculate 11.13W from your data, but
this is making assumptions as I don't have enough
data to produce an accurate figure).

It would indeed seem silly to run lower wattage tubes
with this ballast. These lamps were designed to run
this way in 230V countries, but that doesn't work
very well in 120V countries where the lack of voltage
headroom causes a much more marked change in lamp
current with different lamp lengths/voltages.

Indeed, adding more PF correction (3.7 uf) dropped the current to .096 for a
11.52 VA rating with the 5 watt tube

I tested an Advance 4 to 9 watt ballast and got current down to .085 for a
VA of 10.2. Adjusting capacitance I got the same for a 9w tube. Dissapating
only 1.2 watts in the ballast is pretty good with the 9w tube. The ballast
does not get very warm after a while of operation. 115 Deg F measured on the
ballast itself after temp stabilized.

I probably could do a bit better at 5 watts, but I don't have capacitors of
small enough values to fine tune.
John