The High Pressure Sodium Lamp (HPS)

Here we have another interesting light source
its high pressure sodium
its a light source that s commonly use today
for street and lightning large areas
pretty much everybody is pretty familiar
with it now because of its orangish glow
some of the newer lamps has pinkish or purplish color
but pretty much has an orange color.
This lamp was actually developed at GE,
the ceramic was developed right in Niskayuna,
around 1958 and the first lamps
And the first lamps which I have a prototype of
it was actually built here in Schenectady
and they started to experiment with this lamp around 1959
they start to make a lamp with lucalox ceramic
and what it is is a ceramic is a polycrystalline aluminum oxide ceramic
basically its aluminum oxide is what it is, made in to a ceramic
and the reason why they use it in high pressure sodium is because
the high temperatures at which this lamps operate
quartz or glass or even ceramic ordinary ceramic
could not withstand the heat,
so they have to make a special aluminum oxide ceramic
to withstand the heat that the lamps generate.
Basically all the lamp is a discharge lamp,
has one electrode at each end at the arc tube
and the current goes thru a gas to fill gas inside the xenon gas
and is an amalgam of mercury and sodium in the arc tube
the reason why there is the mercury and sodium is for two reasons:
number one it controls the vaporization rate of the sodium during the warm up,
number two, mercury vapor lens it's blue rays to the light
to make the light less monochromatic is more full spectrum because it got
blue rays as well as yellow and red and orange rays
so is technically a white light source
even know it doesn't look like white.
it is a type of white light source.
Objects lighted by it at least you can tell the color of them
not that well but you can
so that's was the advantage of high pressure sodium design
plus they are more compact and longer lasting that the old low pressure sodium lamps were.
though they are not that efficient as low pressure sodium
but the advantages out way the disadvantages obviously.
There are interesting lamp it that to start the lamp when
is cold they have to pulse it with a high voltage pulse.
to start the arc thru the lamp so to do that they use
an external electronic circuit built in to the ballast
to start the lamp that work almost like a coil on a car
how it fire's a spark plug it just hits the lamp
with a high voltage spike and that s what s start s the arc.
Once the arc starts is thru xenon first
so the lamp will light up almost a sky blue color then
it turn s blue because the mercury vapor
the mercury rather vaporizes first
then when the mercury generates enough heat the sodium vaporizes
last and then the color all finally shift over to orangish color
as the sodium vaporizes in to the mercury arc stream
and the true colors combine the blue and the orange combine
and then you get that purplish orange or whatever color
the lamps varies by brand by color
so they are not all exactly the same
but the lamp has pretty good efficiency
it didn’t turn out to be as high efficiency
as they originally thought the lamp itself is very efficient
but the auxiliary equipment used with it the ballast
have to be very lossy because the arcs run at low voltage
so they got to step that voltage down in the ballast
Here's another high pressure sodium lamp
but this one has a little bit different design
is actually a kind of a home owner brand name
like for the average consumer Lights of America
and they did things a little differently
instead of using an electronic circuit to pulse the lamp
to start it like as they previously said
this lamp has and you can see it there
running along the arc tube there's a flat strip
then there's a little wire that runs down along side the arc tube.
And what that does is it just set's up a capacitance
or a stray voltage between the arc tube
and the other side of the circuit the return side of the circuit
so that the amount of voltage it takes to strike the arc thru the lamp
is lower and it doesn't require a pulse to start it
in fact the fill gas in the arc tube may be different to
and maybe neon or argon instead of xenon
which strikes at a lower voltage
so you combined that with the starting strip
and the lamp doesn’t require an external lamp igniter
it will start on a voltage set the ballast puts out
this was used for the Lights of America homeowner light fixture
which makes fining replacement lamps difficult unfortunately
but they do make larger versions of this lamp
to retrofit in to existing mercury vapor fixtures
it uses the same basic principle as this
and it will start and operate on mercury vapor ballast
without any external starting gear being necessary
to be added to the fixture
in fact one type this strip is actually a heater
and there's a starter in it like a florescent lamp uses
that blinks the current on and off to the heater
and it gains heat each time until heats up the arc tube and off
and that helps it to strike plus every time the starter opens
it creates a pulse from the ballast by the induction of the ballast
and that helps start the lamp.
so, some of the HPS conversion lamps
to convert existing older fixtures uses this principle as well.
this is just another way to start an HPS lamp
without having igniter on a ballast
it works ok but it has its issues to like
sometimes the lamp don’t like to start on cold weather
and things like that, so is not perfect
but it is another way to start an HPS lamp