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Electronic ballast w/ preheat lamp

A

AP

Jan 1, 1970
0
I am an computer engineer but have never had any prior experience with
ballasts and lighting system.

I currently have a preheat type (germicidal) flouricent lamp with is being
operated with a magnetic ballast and a glow starter. I want to change to an
electronic ballast using the IRPLLNR2E reference design by International
Rectifiers (http://www.irf.com/technical-info/refdesigns/lnr2.pdf)

My problem arises because the documentation for this design says it is
suitable for any rapid start lamp. However, would this design work for my
lamp? From my research on the net I understand that the only difference
between the preheat and rapid start lamps is that the magnetic rapid start
ballasts always run a current through the lamp filaments. I have not been
able to determine if this design would also do this, effectively burning out
my lamp.

I would appreciate any help on this matter.

Thanks in advance.

Anks

ps. While researching on the net I have got 2 different interpretations of
what the term 'preheat' is used for. Does it refer to the type of lamp, or
the process by which a rapid start ballast starts a lamp? What is the
official use of this term?
 
V

Victor Roberts

Jan 1, 1970
0
I am an computer engineer but have never had any prior experience with
ballasts and lighting system.

I currently have a preheat type (germicidal) flouricent lamp with is being
operated with a magnetic ballast and a glow starter. I want to change to an
electronic ballast using the IRPLLNR2E reference design by International
Rectifiers (http://www.irf.com/technical-info/refdesigns/lnr2.pdf)

My problem arises because the documentation for this design says it is
suitable for any rapid start lamp. However, would this design work for my
lamp? From my research on the net I understand that the only difference
between the preheat and rapid start lamps is that the magnetic rapid start
ballasts always run a current through the lamp filaments. I have not been
able to determine if this design would also do this, effectively burning out
my lamp.

I would appreciate any help on this matter.

Thanks in advance.

Anks

ps. While researching on the net I have got 2 different interpretations of
what the term 'preheat' is used for. Does it refer to the type of lamp, or
the process by which a rapid start ballast starts a lamp? What is the
official use of this term?

First, the easy part. The term "preheat" is used differently by
different people or in different situations. There seems to be a
difference in the use of the term in the US and the UK (and perhaps
all of Europe) and I will use the US definition here.

Preheat operation is a starting mode for fluorescent lamps in which
the electrodes are first heated, usually to a temperature above their
normal operating temperature, with a relatively high current while
there is no voltage across the lamp. This current is usually high
enough to cause a discharge from one end of the electrode to the
other, and causes the ends to glow "white". (This means the phosphor
is being excited and the glow is not just from a hot electrode.) In
all preheat systems I have ever seen, the electrode heating current is
limited ONLY by the same inductor used to control lamp current. Hence
the high heating current. At the end of the electrode heating cycle,
the electrode heating current is removed from the lamp and voltage is
applied across the lamp (from one end to the other). The combination
of hot electrodes and voltage across the lamp starts the discharge. No
external heating power is applied to the electrodes during operation
after starting. They are heated only by the discharge.

The term "preheat" is also used in rapid start mode to say that the
electrodes are preheated by the ballast before the lamp starts. I
would prefer that people say "the electrodes are heated to their
normal operating temperature by the ballast" and thus avoid the
confusion over the term "Preheat."

The terms Preheat and Rapid Start are defined in ANSI Standard
C78.81-2001, American National Standard For Electric Lamps - Double
Capped Fluorescent Lamps. I believe this is available for download at
now charge from www.nema.org.

Now, about using Preheat lamps on Rapid Start ballasts. Preheat lamps
are indeed different than Rapid Start lamps because they have higher
resistance electrodes. While not specified by the lamp manufacturers,
Preheat lamps can be used as "high resistance rapid start" lamps
according to ANSI C78.81-2001. Most rapid start lamps have an
electrode heating voltage of 3.6 volts. Preheat start lamps can be
used in Rapid Start mode if the electrode heating voltage is changed
from 3.6 volts to 8.0 volts. The ballast you are considering is
probably designed to heat the electrodes with 3.6 volts. This value
would have to be changed to 8.0 volts in order to use preheat lamps.

I suggest you get a copy of ANSI C78.81-2001 and look up your lamp to
confirm what I have said.
 
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