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Thread: Flourescent Lighting Fixture Starters

  1. #11
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    Quote Originally Posted by kwired View Post
    Did they make "preheat" style systems that operate on 277 volts? ...
    I have no idea. I'm not a lamp historian and I never say "never". It's just a generally-applicable caution.

    Quote Originally Posted by kwired View Post
    ... the ballast is going to have whatever difference there is from the input voltage across it. ...
    Um, not quite. The ballast is almost purely inductive and the lamp is not. The vector voltage sum will equal the line voltage, of course, but if you measure each one with a voltmeter, without considering the phase angle, you may find that the two voltages add up to quite a bit more than line voltage.

  2. #12
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    I'm a little confused. I am reading that the OP is talking about 1 starter in a multiple lamp fixture. The OP stated that at the time of the incident none of the lamps lit until the one starter was replaced. I have never seen a fixture that didn't have one starter per lamp.

    Was it 277? I don't know either if there were "preheat" ballasts for 277 but one of the first things the OP should have determined is the operating voltage of the fixture and his maintenance people should have been aware of it if it is indeed 277.

    Another thought is that when you insert a starter in a live fixture it will buzz or vibrate as the bi-metallic switch operates. You can feel that with your fingers as you twist it.

    For what it's worth, new starters available today have plastic cans.

    -Hal

  3. #13
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    The ballast, a series inductor, is there as a current limiter, because fluorescents drop impedance as they warm up.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  4. #14
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    And the inductive kick from the inductance because of the initial on/off action of the starter results in a high voltage, enough to strike the arc within the lamp.

    -Hal

  5. #15
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    Quote Originally Posted by drcampbell View Post

    Um, not quite. The ballast is almost purely inductive and the lamp is not. The vector voltage sum will equal the line voltage, of course, but if you measure each one with a voltmeter, without considering the phase angle, you may find that the two voltages add up to quite a bit more than line voltage.
    Quote Originally Posted by LarryFine View Post
    The ballast, a series inductor, is there as a current limiter, because fluorescents drop impedance as they warm up.
    So what voltage does the lamp operate at? Same lamp but with 277 volt supply obviously needs something to reduce voltage to similar level it would operate on with 120 volt supply.
    I live for today, I'm just a day behind.

  6. #16
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    I believe they only operate at 120v. 277 would require a transformer as part of the ballast.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  7. #17
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    Quote Originally Posted by kwired View Post
    So what voltage does the lamp operate at? ...
    I made a statistically-significant measurement of one antique T12 fixture. 123 volts on the lamp itself. Magnetic ballast, but without an external starter.

  8. #18
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    From an old Advance troubleshooting guide, for a preheat ballast using starters the minimum open circuit voltage is 176V for a F30T12 or a F40T12 lamp. Then you have the voltage kick from the starter circuit opening.

    A Low Power Factor Rapid Start ballast for the same F40T12 lamp has a open circuit voltage of 220V

    Advance-fluorescent-ballast-troubleshooting-guide1.pdf

    Another link to a European paper describing the starter function.

    Quote Originally Posted by hbiss View Post
    And the inductive kick from the inductance because of the initial on/off action of the starter results in a high voltage, enough to strike the arc within the lamp.

    -Hal

  9. #19
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    180703-0745 EDT

    The article

    http://www.ecospecifier.com/media/72...t%20Lights.pdf

    referenced by MTW in the previous post is very good. I have read only a portion, but the basics of the operation of a fluorescent light are provided.

    .

  10. #20
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    180703-1046 EDT

    I have limitedly looked at a two bulb rapid start 4 ft fixture.

    The open circuit filament voltage is about 4.2 V, open circuit across both bulbs about 280 V. Clearly the ballast is a transformer with several secondaries. Three isolated from each other filament secondaries. Possibly a single high voltage secondary with high leakage inductance, or could have an external inductor.

    The voltage across both bulbs at initiation of conduction is about 250 V and drops to about 100 V where I think conduction stops. I only have a two channel scope. These are used in diffrence mode to measure voltage.

    .

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