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PostPosted: Sat Jul 18, 2015 10:10 pm 
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Hi All,

I just thought I would share with you a photograph of a lovely old 140W sodium Parmar ballast. I do like the options for mounting.

I'm not exactly sure where in Cumbria this came from but it must have been used somewhere.

I didn't realise Parmar did old gear, how old are Parmar?

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Here is a photograph of how the Philips 90W SOX ballasts have changed over the years. The first one on the left is a leak transformer. The other 5 all form part of a ballast/ignitor circuit. The ignitor is an SX76.

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An interesting point about the SX76 ignitor is it shows a strike voltage of 0.9KV.


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PostPosted: Fri Jul 24, 2015 8:07 pm 
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Hi All,

I'm just going through a few ballasts and 90W SOX tubes which I acquired last week when an interesting situation arose. I was testing some tubes on a Parmar transformer and all was ok until I plugged in an older tube. The tube lit up, but very faintly and you could see rings of red flowing up and down the tube. I then tested the same tube on a ballast/Ignitor circuit, the tube struggled at first but then illuminated correctly.

The ignitor circuit must be "harsher" on start up than a leak transformer which "kicks" the tube into life.

I do remember a while back a discussion about running 140w SLI/h lamps on a transformer rather than an ignitor circuit as the ignitor circuit is harsh. Is it the fact the ignitor circuit appears to produce 0.9Kv on start up?  Does anyone have a technical explanation of why this would happen?

Regards,

Andrew.


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PostPosted: Sat Jul 25, 2015 7:21 am 
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Leak transformers work as resonant circuits. The voltage rises at 50Hz until it is enough to strike the lamp. Its quite a "gentle" start.

Ignitor circuits switch the ballast at frequencies greater than 50Hz (often KHz). The higher switching frequency is more efficient when using the inductance of the ballast to create the striking voltage. This results in the striking voltage rising more rapidly, and to a higher value which strikes the lamp more rapidly - in effect a pulse start. The lamp is "jolted" into life.

A similar analogy is the old style fluorescent tube gear. The 1960s "InstaStart"/starterless gear was resonant, glow starters produce a rapid pulse start - although in this case still at 50Hz.


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PostPosted: Sat Jul 25, 2015 7:36 pm 
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Removed during the local SOX for LED street lighting replacement scheme, I managed to save this 1960s Parmar 140w SO ballast just in the nick of time.

http://www.ipernity.com/doc/324907/39035710


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